Metabolomics for Empirical Delineation of the Traditional Korean Fermented Foods and Beverages

Trends in Food Science & Technology 61 (2017) 103e115

Contents lists available at ScienceDirect

Trends in Food Science & Technology journal homepage: http://www.journals.elsevier.com/trends-in-food-science- and-technology

Review Metabolomics for empirical delineation of the traditional Korean fermented foods and beverages

* Digar Singh 1, Sunmin Lee 1, Choong Hwan Lee

Department of Bioscience and Biotechnology, Konkuk University, 05029, Seoul, South Korea article info abstract

Article history: Background: The umpteen varieties of traditional Korean fermented foods, condiments, seasonings, and Received 12 August 2016 beverages deliver a wallop of savor, aroma, nutrients, probiotics, and functional bioactives. However, our Received in revised form surprisingly limited comprehensions of the associated metabolomes, related phenotypes, and health 21 October 2016 effects maneuvered through the perplexing interplay of fermentative microﬂora turns their empirical Accepted 3 January 2017 analyses a non-trivial undertaking. Available online 5 January 2017 Scope and approach: The economy data indicates that the shipment values for traditional Korean fermented foods per se stood a miraculous 4 billion USD in 2013 with burgeoning 71% increase in domestic Keywords: Metabolomes food industries in last decade (statistical yearbook, Korea Food and Drug Administration, 2014). Quin- Fermented soy-foods tessentially, the consumers now expect the highest possible standards of food manufacturing with in- Vegetables sights of their molecular contents and associated health effects. A range of analytical platforms, based on Seafood chromatographic separation coupled with spectrometric or spectroscopic detection, enables the Bioprocesses metabolomic snapshots for fermentative bioprocesses and underlying biotransformation mechanisms. However, a technological void still exist which restrict the generic use of analytical methodologies owing to the complexity of diverse metabolomes. Key ﬁndings and conclusions: This review outlines the metabolomic perspectives for the traditional Korean fermented foods and beverages. We discuss the current trends towards the application of metabolomics and related methodologies to probe their metabolite contents and functionality. Moreover, the crucial bottlenecks associated with fermentative bioprocess and microbial transformations are also addressed in the context of artisanal and industrial manufacturing processes. Further, the article pro- poses a rational metabolomic approach towards the discernment of palatability and insalubrities associated with fermented foods. © 2017 Elsevier Ltd. All rights reserved.

1. Introduction studies have suggested the cultural trends of intentional fermentation practices by the early Neolithic civilizations in East Asia, The prehistoric civilizations of the Korean peninsula instru- ascertaining its traditional hegemony in pre-historic times mented the artisanal fermentative practices to gain the nutritive (McGovern et al., 2004). However, the earliest text reference to and functional diets, besides surviving the meagerness. Unwit- fermented soybeans was found in a Chinese dictionary “Shuo-wen tingly, our ancestors became the first biotechnologists to harness Chiehtzu” by Hsu Shen (121 AD) during the Kokan dynasty (25e220 beneficial microbes and their metabolites to enhance the palat- CE), which describes “Shi (soybean nuggets) as the bean products ability, shelf life, and savory of foods. Immediately henceforth, the made by placing the beans in the dark room for natural fermen- Far East civilizations excelled the art of turning every piece of na- tation to occur” (Steinkraus, 1983). Another important compilation ture's bounty into fermented stuffs, including grains, soybeans, from the medieval Korean history “Dongui Bogam” (1613 CE), by the vegetables, and seafood. Modern mass spectrometry (MS)-based royal physician, Heo Jun, during the rule of the Joseon (synonym: Chosun) dynasty of Korea, described the curative applications of doenjang. In recent times, the scientific reports with empirical de- * Corresponding author. lineations for the perplexing metabolomes for traditional fer- E-mail address: [email protected] (C.H. Lee). 1 These authors contributed equally to this work. mented foods and beverages are soaring high, both, in academia as http://dx.doi.org/10.1016/j.tifs.2017.01.001 0924-2244/© 2017 Elsevier Ltd. All rights reserved. 104 D. Singh et al. / Trends in Food Science & Technology 61 (2017) 103e115 well as industry. Translational metabolomics has incontrovertibly analytical platforms with case selective targeted or untargeted unfolded the functional aspects of a variety of fermented foods viz., approaches become indispensable to standardize the quality con- fermented soy, cereal, milk products, vegetables and herbs, sau- trol for promoting the widespread consumer acceptance of arti- sages, fish-based products, and health beverages, among others (Hu sanal or commercial fermented products. & Xu, 2013). Yet another perplexing, but intriguing, aspect of fermentative bioprocess includes a correlative assessment of the 3. Metabolomics: trends and neoteric approaches microbial consortia and their plethora of associated metabolites influencing the overall functional or deleterious aspects of desired Among the various 'omics' cascades, only metabolomics repre- end products. The aforementioned correlations are vital for sents the generic harbinger of genomic expressions carried by ensuring the desired health effects and nutrition, as well as the transcriptome as well as proteome together, and hence offers a characteristic taste, aroma, and consumption safety of fermented more tractable option for metabolome studies (Kell et al., 2005). foods produced using artisanal or industrial methods (Jung, Cho, Metabolomics is inconsistently defined as the analysis of the et al., 2015; Ray, Ghosh, Singh, & Chandra Mondal, 2016). Hence, quantitative complements of low molecular weight metabolites the neoteric metabolomic approaches, in conjunction with other (<1800 Da) present in a cell, tissue, or organism under a given set of 'omics' cascades (transcriptomics, proteomics, or genomics), can physiological conditions (Zhou, Xiao, Tuli, & Ressom, 2012). Bio- potentially transmogrify our classical perspectives towards fer- chemically, metabolites are the metabolic pathway intermediates mented foods and beverages. or the end products driving essential cellular functions i.e., bio- energetics and cell signaling. Besides their endogenous production 2. Socioeconomic trends, globalization, and metabolomics in the host, metabolites are also obtained exogenously through the critique of technological hurdles diet (Johnson, Ivanisevic, & Siuzdak, 2016). Hence, the food metabolomics typically encompasses the assessment of untargeted Fermented foods and condiments are often considered as the metabolite profiles coupled with statistical analyses as well as the primary components of the most prominent traditional cuisines in targeted identification of functional metabolites or the food safety Far-East Asian countries including China, Japan, and Korea. Aside biomarkers associated with metabolite toxins or contaminants from its role in food storage alone, the artisanal fermentation (Fig. 1). methods might have also been adapted to achieve the desired fla- vors, aroma, and health effects in diet. In the modern age, an esti- 3.1. Sampling, extraction, and instrumentations: methodologies mated one-third of the human diet comes from fermented foods and beverages (Borresen, Henderson, Kumar, Weir, & Ryan, 2012). A range of analytical platforms viz., nuclear magnetic resonance The rapid industrialization and consumer demands have bolstered (NMR), gas chromatography-mass spectrometry (GCÀMS), liquid the large scale production of traditional fermented foods and chromatography-mass spectrometry (LCÀMS), capillary beverages across the world. The data from the 'Ministry of Agri- electrophoresis-mass spectrometry (CEÀMS), 2D-NMR, and matrix culture, Food and Rural Affairs, the Republic of Korea, indicate that assisted laser desorption ionization - time of flight - mass spec- the national food export stood a miraculous 59 billion USD in the trometry (MALDI-TOF-MS) has recently been applied to probe the year 2014, with over 71% increase in the domestic food industries in functional metabolomes of traditional Korean fermented foods a decade. Additionally, the traditional fermented foods including (Kim, Cho, et al., 2012; Lee, Lee et al., 2016; Lee, Kim et al., 2012). Jang, Kimchi, and Jeotgal production witnessed a record figure of The present technologies allow the study of tens to hundreds of approximately 3.72 million tons in 2013 with a shipment value of metabolites in complex biological samples (Patti, Yanes, & Siuzdak, about 4 billion USD (statistical yearbook, Korea Food and Drug 2012). However, the complex fermentation matrix rich in dynamic Administration, 2014). A recent surge in the number of patents and microbial assortments makes their unbiased metabolomic evalua- literature describing the functional metabolites and health effects tion a non trivial undertaking. The first important step towards an associated with traditional fermented foods and beverages further unbiased metabolomic study involves temporal design based indicates their growing vogue among consumers (Table 1). sampling. In foodomics, the temporal fermentation dynamics, mi- The quality and safe consumption standards for fermented foods crobial successions, as well as the in vitro and in vivo evaluation of and beverages in the Republic of Korea are primarily governed by phenotypes and health biomarkers, respectively, involves the time Korea food and drug administration (KFDA) which has established dependent sampling. Immediately following the sampling, any the strict guidelines (amended 2009) for risk assessment. Specif- residual biological activities or enzymatic transformations must be ically, the levels of aflatoxins (a potent carcinogen) in jangryu quenched using liquid nitrogen, cold storage (À40 C), or sample (fermented soy foods), kimchi, and jeot-gal are recommended lyophilization under aseptic conditions (Hu & Xu, 2013). Unlike below the level of 10 ppb (parts per billion) for commercial pro- targeted analysis, the untargeted or comprehensive metabolomics duction (Lee, Lee, & Lee, 2012). Buoyed by the consumer's cogni- aims the extraction of widest possible classes of metabolites which zance for the nutritional and functional components of diet, often results in compromised analytical sensitivity. However, the metabolomics has emerged as an important tool to unravel the choice of suitable internal standard (IS) while extraction normalize scientific details. Moreover, the specter of potential food in- the errors while subsequent acquisition and analyses. To a larger toxications and related insalubrities associated with fermentative extent, the sample extraction and purification procedures deter- stages, processing, or storage of end products can effectively be mine the degree of biasness in the metabolic profiling data. In case addressed using neoteric analytical methods under the purview of of fermented food matrices, a number of studies have substantiated metabolomics. The comprehensive untargeted metabolomics the successful application of polar and non-polar solvents viz., enable the unbiased characterizations for health effects of dietary methanol, ethanol, acetonitrile, or isopropanol in different pro- components on animal subjects demarcating the subsidiary factors portions (Lee, Jung, Jeon, 2014a, Lee, Jung, Jeon, 2014b; Lee, Lee viz., age, gender, physiological state with discriminatory metabolic et al., 2014; Oh, Jang, Woo, Kim, & Lee, 2016; Suh et al., 2016). patterns (Cevallos-Cevallos, Reyes-De-Corcuera, Etxeberria, Dany- These liquid-liquid extraction procedure are effectively carried out luk, & Rodrick, 2009; Scalbert et al., 2009). In contrast, the targeted under continues agitation condition unto varying periods of time to approaches allow the characterization of known toxins or nutrients obtain the optimal extraction yield for metabolites. These simple with established health effects. Hence, the high throughput extraction procedures critically reduce the pretreatment steps and D. Singh et al. / Trends in Food Science & Technology 61 (2017) 103e115 105

Table 1 A list of traditional Korean fermented foods and beverages with associated health effects and functional metabolomes. The data collected from patent information and literature search.

S. Traditional Korean fermented foods and beverages No. Patent information Metabolomes

Applicant and PCT No. Patent summary/Health effects Functional metabolites/enzymes/health References effects

Category I: Fermented soy-based foods 1 J9 Bio Agricultural Association Corp. (2013) - PCT/ Cheonggukjang containing Pediococcus acidilactici surfactins A and B, antimicrobial Lee, Shim, et al., KR2013/010180 j9 co-culture with Bacillus for increased shelf-life. lipopeptides, and bacteriocins 2016 2 Kim, Y.K and others (2011) - Postech Academy- Extracellular vesicles isolated from doenjang (soy- trypsin inhibitors, isoflavone, Jung, Park, & Industry Foundation - PCT/KR2011/002837 paste) with potential anti-inflammatory diseases aglyconated genistein, vitamin E, and Park, 2006 and anti-cancers effects. linoleic acid 3 Kwon, T.S (2010) - PCT/KR2010/009462 Doenjang, gochujang, and Ganjang with potential purines - xanthine and hypoxanthine; Kim,Choi, et al., curative effects viz., gouty arthritis, diabetes, and capsaicin 2012 prostatic pain management etc. 4 C.J. Corp. (2005) - PCT/KR2005/002067 Lactobacillus plantarum Strain PL62 KCCM-10655P ee used in doenjang manufacturing was shown to have anti-obesity. 5 Shin, H.J. and others (2010) - Amorepacific Ganjang derived microbial inoculations to make ee Corporation -PCT/KR2010/007092 fermented tea with functional properties. 6 Korea Food Research Institute and SNU RandDB Ganjang with maillard peptide relates to the hydrolyzed amino acids and Shin & Jeong, Foundations - Rhyu, M.R and others (2010) - PCT/ modulation of trpv1 activity and inflammation- saccharides 2015 KR2010/007845 related diseases. 7 Kikkoman Corporation (2010) - PCT/JP2010/073342 Ganjang with hypotensive effects and its method of ee production. 8 C.J. Corp and Jeon, M and others (2006) - PCT/ Ganjang and Gochujang production process with ee KR2006/005662 increased g-aminobutyric acid (GABA) contents. 9 Han, K.Y. and others (2007) C.J. Corp. Pusan National Fucoidan added gochujang (korean red pepper lipolytic enzymes Koo et al., 2008 University, Industry-University Cooperation soybean paste) having increased anti-obesity Foundation Park - PCT/KR2007/000035 effects 10 Kim, J.Y (2012) Byung-Hoon han esbiotech co., ltd. - Capsanthin components in gochujang possess anti- capsaicin and its hydrolytic products Lee, Cho, et al., 13481995 obesity effects. 2015 11 Hwang, I. H (2013) - 25006088 A reusable fibrous carrier to retain Bacillus subtilis ee strain in soy-fermentation for providing culture constancy. 12 Giuliani S.P.A. (2011) - PCT/IT2011/000240 LAB fermented soya functional metabolites ee (isoflavones, aglycones, equol, lunasil) with applications in food, medical, and cosmetic. 13 Societe Des Produits Nestle S.A (2001) - PCT/EP2001/ Koji molds for cholesterol-lowering fermented ee 007908 products. Category II: Fermented vegetable 14 Probionic Co. Ltd and Park, Yong-Ha and others - PCT/ Kimchi isolated microflora used for the vitamin, functional terpenoid, and Cheigh & Park, KR2011/003522 fermentation of substrates (rice) with enhanced bioactive organic acids (lactic acids, 1994; Park et al., antibacterial, antiviral bioactives. succinic acid, and isocitric acid) 2016 Category III: Fermented fish and seafood 15 Nippon Suisan Kaisha, Ltd. Doumoto, Nobuhiko Mori, Fermented fish LAB (Leuconostoc, Lactobacillus, alanine, aspartate, glutamate, and Jung, Jung, et al., Takashi Masu, Masayuki (2002) - PCT/JP2002/007951 Lactococcus and Pediococcus) with improved flavor glycine 2016 and texture. 16 Unilever N.V. Unilever PLC Hindustan Lever Ltd Reduced foul fishy smell for long term storage. ee (2003) - PCT/EP2003/012027 Category IV: Fermented beverages 17 Bae, K.H (2015) - PCT/KR2015/003806 Fermented beverage made with Acorus gramineus immunomodulation, anti-obesity, aid in Kim, Cho, & Shin, and persimmon vinegar with improved bioprocess digestion, and regulates blood glucose 2012; Sugiyama steps. levels et al., 2003 18 Purac Biochem B.V (2015) - PCT/NL2015/050187 Methods for obtaining neutralized concentrated ee vinegar. 19 Kim, J.W and others (2010) - Not Available Rice wine (Makgeolli) manufacturing using the anti-oxidant, immunomodulatory, and Lee et al., 2010; whole ginseng anticancer activities Nile, 2015 20 Park and others and Amorepacific corp. (2010) - PCT/ Composition having antioxidant and whitening anti-oxidant Nile, 2015 KR2010/005207 effects containing a concentrate of Korean rice wine (Makgeolli).

thus probably ensure the recovery of a widest array of metabolite methods, which have been successfully employed for the delinea- classes for analyses using different high throughput instruments tion of metabolomic aspects of fermented foods and beverages, are (Cajka & Fiehn, 2016). The primary areas utilizing the applications brieﬂy described below. of quantitative and qualitative metabolomics include plant metabolomes (Chen et al., 2013), medicine (Guo et al., 2015), human chemometrics, and pathophysiology (Madsen, Lundstedt, & 3.1.1. GC-MS/LC-MS Trygg, 2010; Medina, Dominguez-Perles, Gil, Ferreres, & Gil- The MS based chromatographic systems (LC or GC) are the most Izquierdo, 2014), as well as food and nutritional research prevalent methods in contemporary metabolomic research (Cajka (Gibbons, O'Gorman, & Brennan, 2015). Several of these robust & Fiehn, 2016). GCeMS is usually employed for the evaluation of primary metabolites viz., amino acids, fatty acids, carbohydrates, 106 D. Singh et al. / Trends in Food Science & Technology 61 (2017) 103e115

deciphered. The choice of separation methods (GC or LC) for the analyses of metabolites depends upon the physico-chemical nature of the analytes. Both methods have their own associated drawbacks and beneﬁts. The GC system is usually preferred for the analysis of volatile metabolites or compounds amenable to chemical deriva- tization, and mainly includes primary metabolites viz., fatty acids, amino acids, sugar or sugar alcohols, and esters. Yamamoto et al. (2012) have described GC-TOF-MS-based metabolic proﬁles for soy sauce in order to decipher its components and brewing processes. On the other hand, the thermally labile polar secondary metabolites in a variety of fermented foods have been extensively studied using LC systems (Lee, Lee et al., 2014). The polarity of metabolites determines the type of stationary (reverse phase or normal phase) and mobile phases (isocratic or gradient) employed towards the resolution of metabolite peaks in LC- analysis. How- ever, the GC-TOF-MS system is generally considered superior in terms of chromatographic resolution of metabolites with ease of peak deconvolution for overlapping spectra (Begley et al., 2009; Jonsson et al., 2004). Nevertheless, the MS hyphenated GC/LC systems together provide a robust instrumentation towards the holistic delineation of complex metabolomes.

3.1.2. NMR The recent surge in the number of publications describing NMR- based metabolomics in food, beverages, herbal products, animal tissue bio-fluids, and plants undoubtedly demonstrate its growing field of applications (Larive, Barding, & Dinges, 2015). NMR spectroscopy is often considered most advanced for its ability to unravel the dynamics of biological molecules down to atomic resolution with stereochemical details (Ha, Paulsen, Sun, Song, & Ham, 2014; Seger, Sturm, & Stuppner, 2013). However, efforts are being made to miniaturize the bulky NMR setups (magnets and electronics) in order to simplify their application in conjunction with chromatography systems viz., GC, LC, or CE (Diekmann et al., 2011; Ha et al., 2014; McDowell & Fukushima, 2008). In recent years, NMR spectroscopy has extensively been applied to decipher the traditional food metabolomes viz., soybean (Harrigan et al., 2015), doenjang or fermented soybean paste (Yang et al., 2009), fermented fish sauce or myeolchi-aekjeot (Lee, Jung, & Jeon, 2015), fermented shrimp or saeu-jeot (Lee et al., 2014b), soy sauce (Li et al., 2014), cheonggukjang (Choi, Yoon, Kim, & Kwon, 2007), and various koji preparations (Okutsu et al., 2015). Despite their lower sensitivity, NMR-based metabolomics approaches are usually considered superior than MS-based methods as the data in latter case is significantly biased by the modes of ionization and instrumentations (Forseth & Schroeder, 2011). Moreover, the relatively simpler methods of sample preparation without involving chemical extraction procedures establish its hegemony in detection of the compounds prone to chemical destruction. Quintessentially, the non- Fig. 1. An archetypal scheme of metabolomics approach to study the related metab- destructive nature of NMR enables the real time analyses of me- olomes associated with fermentative bioprocess and products. tabolites in the samples providing an insight into their natural in- teractions. The recent advancements in 2D-NMR spectroscopy have and organic acids, whereas LCeMS systems are commonly used for further enhanced its spectral resolution capabilities many-fold, secondary metabolites viz., alkaloids, flavonoids, saponins, phenolic revolutionizing its application for interpretations in complex & acids, phenylpropanoids, glucosinolates, and polyamines (t'Kindt, metabolomic and stereochemical data (Guennec, Giraudeau, Morreel, Deforce, Boerjan, & Van Bocxlaer, 2009; Lee, Lee et al., Caldarelli, 2014). 2014). Recently, metabolite profiles for the characteristic phenotypes (antioxidant activities) and functional properties (anti- 3.1.3. CE-MS obesity and anti-osteoporosis in mice models) of fermented soy- Yet another methodology in metabolomics, CE-MS, is applied fi bean mixtures (Suh et al., 2016), and traditional vinegar types (Jang speci cally for the separation of highly polar and ionogenic me- et al., 2015; Lee, Kim, et al., 2016), have been highlighted using tabolites based on their varying charge - to - mass ratios (Ramautar, & various chromatography-linked MS methods followed by multi- Somsen, de Jong, 2015). Hence, the neutral metabolites are also variate analyses. Similarly, the metabolite profiles of cheonggukjang separated from the charged ones. Kim, Choi, et al. (2012) have fi (Baek et al., 2010), and doenjang (Lee, Lee et al., 2014) have been successfully determined comprehensive metabolite pro les for cheonggukjang (fermented cooked soybean paste) as a function of D. Singh et al. / Trends in Food Science & Technology 61 (2017) 103e115 107 fermentation time using CE-MS and GC-MS in a complementary generate homogenous parametric outputs for retention times (RT), way. Furthermore, they have described an enhanced repertoire of mass - to - charge ratio (m/z), MSn spectra, and relative intensities 123 metabolites, with 45% of them selectively recovered using CE- of the peaks identified using the hyphenated MS-systems. MS. Recent developments in CE-MS instrumentation have allowed Although, the alignment of CE-MS data can be more complicated the simultaneous identification of cationic as well as anionic me- on account of its lower reproducibility for migration time (Baran tabolites through meticulous modification of the key parameters et al., 2006). On the other hand, the NMR data for metabolites viz., pH of background electrolyte (BGE), direction of electro- based on the unique pattern of chemical shifts are comparatively osmotic force (EOF), or the use of capillary tubes with cationic more suitable for identification using a compound library search coatings (Hirayama, Igarashi, Tomita, & Soga, 2014). However, CE- (Zheng, Zhang, Ragg, Raftery, & Vitek, 2011). A myriad of free or MS still lags behind other methods like LC-MS and GC-MS on ac- commercially available data processing (baseline correction/noise count of its lower detection sensitivity and observed variations in filtering, peak detection, peak alignment, normalization) tools are migration times for ions resulting in lower reproducibility (Lubbe, being used by researchers viz., XCMS, MetaboAnalyst, MetAlign, Ali, Verpoorte, & Hae Choi, 2013, pp. 209e238). However, the Mzmatch, Mzmine2, Galaxy-M, R project, with a variety of peak application of CE-MS as a complement to the classical methods processing and annotation capabilities (Smith, Want, O'Maille, (GC-MS, LC-MS, or NMR) can certainly enhance the detection Abagyan, & Siuzdak, 2006; Lommen, 2009; Pluskal, Castillo, spectrum of metabolites many fold. Villar-Briones, & Oresic, 2010; Scheltema, Jankevics, Jansen, Swertz, & Breitling, 2011; Davidson, Weber, Liu, Sharma-Oates, & 3.1.4. Electronic nose Viant, 2016; Di Guida et al., 2016). The MS data is usually subjected Another important technological advancement with the po- to further parametric time warping and m/z calibration using the tential to revolutionize applications in metabolomics research, is data from co-injected IS (internal standard) compounds and the electronic mimic of the biological olfactory mechanism i.e., reference libraries (Sugimoto, Kawakami, Robert, Soga, & Tomita, electronic nose (E-nose). Although initially developed as a non- 2012). Data redundancy and systemic biases (instrumentation, invasive tool to correlate human breath profiles with disease bio- chromatography column variation, or variation in sample concen- markers, recent developments in E-nose technology have initiated trations etc.) are subsequently eliminated through comparative its use in a multitude of applications, including metabolomics analysis with the IS data or through employing various statistical (Wilson, 2015). In addition to its wieldy operations, the E-nose operations viz., data transformation (logarithmic or power trans- instrumentation also offers a low cost alternative compared to the formations), median, quantile, and pareto scaling etc. (Scholz, conventional high-throughput analytical setups. Although, the E- Gatzek, Sterling, Fiehn, & Selbig, 2004; van den Berg, Hoefsloot, nose technology can still be considered to be at the juvenile stage, Westerhuis, Smilde, & van der Werf., 2006; Brodsky, Moussaieff, the futuristic versions are rapidly gaining ground in the field of Shahaf, Aharoni, & Rogachev, 2010; Kohl et al., 2012; Sugimoto metabolite biomarker analysis and metabolomics. Various sophis- et al., 2012). The metabolomics has further proven its eminence ticated versions of future E-nose instruments at different stages of by providing a broad overview of the metabolic states for complex development include surface acoustic wave (SAW), quartz crystal biological systems or related bioprocesses envisaged using statis- microbalance (QMB), metal oxide semiconductors (MOS), con- tical methods i.e., univariate or multivariate (MVA) analyses. An ducting polymers (CP), and DNA-carbon nanotubes (Wilson & overwhelming number of reports have highlighted the successful Baietto, 2009; Wilson, 2015) etc. Recently, Santini et al. (2016) interpretation of metabolomics data for fermentation bioprocesses have described the successful application of E-nose technology in using various MVA methods (Jeong, Lee, Jung, Choi, & Jeon, 2013; complementation to the conventional methods (GC-MS and NMR) Kim, Choi, et al., 2012; Lee, Lee et al., 2014). The principal compo- to fathom the breath component metabolomics for respiratory nent analysis (PCA) is an unsupervised, multivariate method that ailments. Furthermore, the effects of varying nuruk (starter culture) analyzes a data table using underlying mathematical principles and process parameters on the overall composition of organic acids (eigen values and vectors) to transform a large number of corre- and volatiles for brown rice vinegar were effectively delineated lated datasets into a limited number of variables, termed principal using the E-nose technology in comparison with the GC-MS (Lee, components (Abdi & Williams, 2010). On the other hand, partial Yoon, et al., 2012). In recent years, the E-nose conjugated with least squares discriminant analysis (PLS-DA) is commonly applied MS-system has successfully been employed to discriminate the to evaluate clear distinctions between the groups (variables) within quality, aromas, and origins of food products, including cider vin- datasets (Gromski et al., 2015). However, when data with very high egar and doenjang (Hong, Noh, & Kim, 2015; Jo et al., 2013). Recent systemic variations are encountered, the interpretation becomes advancements in operational ease and sensitivity have further difficult, compelling the use of another extension of the PLS- enhanced the scope of E-nose technologies in rapid metabolite algorithm i.e., OPLS-DA (orthogonal partial least squares discrimi- profiling without involving intermediate steps of sample nant analysis). The OPLS-DA enables easier interpretation of an preparation. analytical model through the subtraction of the predictive variables from the non-predictive ones (Bylesjo€ et al., 2006). Hence, the 3.2. Data analyses and interpretations statistical analyses of multivariate metabolomic datasets allows a comprehensive model visualization for its functional, biological, The vast array of datasets generated with any of the metabolite and molecular coherence in an unbiased fashion (Weckwerth & detection methods need an efficient analysis and interpretation Morgenthal, 2005). approach (Fig. 1). The combined methods viz., GC-MS/GC-NMR, LC- MS/LC-NMR, or NMR alone, result in relatively complex data with 4. Traditional Korean fermented foods and beverages: a one or more added dimensions. Hence, the metabolomics data metabolomics cognizance must be interpreted in terms of the corresponding phenotypes justifying the hypotheses of an experiment. Prior to the analyses, Ushering in the omics- epoch, the foodomics has witnessed the the raw metabolomics data must be converted to an appropriate unprecedented advancements in the areas of food processing as format i.e., NetCDF or mzXML, for the efficient preprocessing of data well as its nutritional and functional make outs regarding the hu- with respect to the available online databases (Pedrioli et al., 2004). man health in toto. In particular, the application of metabolomics in Complex data alignment procedures are then performed to deciphering the health effects of fermented foods have witnessed a 108 D. Singh et al. / Trends in Food Science & Technology 61 (2017) 103e115 recent surge with bottom-up approaches integrating the dietary to nearly 2000 BCE in peninsular Korea and Manchuria (Shin & biomolecules with host's physiological states. Among the various Jeong, 2015). In recent years, besides being nutritious, fermented fermented foods consumed in East Asian countries, perhaps, soy- soy foods are also reported to help building resistance against bean represents the most ubiquitously employed component (Yang, diseases like cancers, osteoporosis, and cardiovascular ailments Kwon, Chung, Park, & Pak, 2011). The fermented soybeans with (Toro-Funes, Bosch-Fuste, Latorre-Moratalla, Veciana-Nogues, & blends of indigenous berries have recently been reported to alle- Vidal-Carou, 2015). There is a perplexing interplay of microbial viate the high fat diet (HFD) induced obesity in rat models using the communities viz., Bacillus spp., Enterococcus faecium, Leuconostoc MS-based metabolomic characterization of altered obesity bio- lactis, and Aspergillus species as well as their associated metab- markers in plasma i.e., lysoPCs (Suh et al., 2016). The primary olomes while meju (solid cubical molds of fermented soybeans) functional components reported from fermented soy based foods fermentation which specifically transforms it to a most suitable include soy isoflavones viz., aglycone forms of genistein, daidzein, starter material for some of the world's most relished soy foods and glycetein, with curative effects against the ailments like (Lee, Kim, et al., 2012). obesity, diabetes, cardiovascular diseases, inflammatory disorders, and cancer, etc., (Gupta et al., 2015). Intriguingly, the isoflavones 4.1.1. Cheonggukjang acts both as estrogenic as well as anti-estrogenic metabolites and The Bacillus subtilis short-term fermented (2e3 days), whole or ergo regulates the blood cholestrol levels either through reduced coarsely ground steamed soybean, cheonggukjang, represents one cholestrol (LDL - low density lipoprotein) uptake while intestinal of the most delectable soy foods of the region with both nutritional absorption or enhanced bile acid secretions which in turn reduces and functional properties. A number of studies have repeatedly the blood cholestrol, and hence ameliorates the cardiovascular highlighted the functional aspects of cheonggukjang viz., anti- diseases. On the other hand, the anti-oxidative nature of soy iso- obesity (Kim et al., 2013; Lee & Koh, 2006), antioxidant (Shin lflavones is believed to effect the decreased lipid peroxidation and et al., 2014), neuroprotective effects (Go et al., 2016), immune associated DNA damage and thus helps preventing cancer (Omoni function-enhancing (Lee, Paek, et al., 2016), and anti-osteoporotic & Aluko, 2005). Nevertheless, a holistic approach is still needed effects (Wu, Lee, Lee, Chae, & Ahn, 2014). The GC-MS and CE-MS to link the functional aspects of fermented soy foods with charac- profiles of cheonggukjang fermented using Bacillus strains teristic health effects. Regarding the health beverages, the potential revealed significantly enhanced purine (xanthine and hypoxan- pathophysiological effects of dietary vinegar made using Rubus thine) levels during the later stages of fermentation, depending coreanus (Korean black raspberries) on ovariectomized rat models upon the choice of microbial inocula i.e., Bacillus amyloliquefaciens were described using MS-based metabolomic approaches (Lee, and B. licheniformis (Kim, Choi, et al., 2012). A number of antimi- Kim, et al., 2016). The authors have comprehensively correlated crobial compounds have been reported in traditionally manufac- the MS-based plasmatic metabolite profiles and discriminant me- tured cheonggukjang inoculated using the natural microflora from tabolites, particularly the amino acids viz., Phe & Trp, with bone rice straw (jip), which includes surfactins A and B, antimicrobial osteoclast activity and histomorphometry. Among the prime lipopeptides, and bacteriocins (Lee, Shim, et al., 2016; Son et al., components of vinegar, acetic acid is particularly known to affect 2011). Hence, the taste, flavor, texture, and nutritional as well as the intestinal absorption of calcium and osteoblast activity in bones functional properties of cheonggukjang vary markedly depending (Kishi et al., 1999). on the type of starter substance (soybean) and the inoculated The majority of traditional fermented foods and beverages in microflora, which together determine its quality and appraisal. East Asia, including Korea, are primarily made using cereals, soybeans, vegetables, fish, and seafood. A common start-up material 4.1.2. Doenjang (also called Toenjang) for various fermented products is koji, which serves as a biological The Korean traditional soybean paste, doenjang, is prepared source of microbes producing hydrolytic enzymes, and brings about using brined doenjang-meju spontaneously fermented with natu- the breakdown of complex nutrients into simpler ones. Koji, a word rally transferred microbial communities for 3e12 weeks incubation now popular beyond its homeland, described as the partially (Jung, Lee, & Jeon, 2014b). Hence, it is commonly understood that cooked soybeans or grains enrobed with microbial inocula i.e., the diverse microbial variety in doenjang-meju brings about the Aspergillus oryzae or Monascus purpureus, under fermentative enzymatic hydrolysis of a variety of complex nutrients enhancing conditions. It has conventionally been used in Far East Asia towards its overall organoleptic, nutritious, and health beneficial properties. the preparation of a myriad of cuisine delicacies viz., doenjang Jeong et al. (2014) have suggested the potential attenuating effects (analogous to Japanese miso), ganjang (analogous to Japanese of doenjang, manufactured with selectively inoculated probiotic shoyu), cheonggukjang (analogous to Japanese natto), gochujang (a microflora viz., A. oryzae, B. subtilis-SKm, and L. lactis-GAm on colon red pepper meju paste), sake, and sikhye (a rice beverage analogous cancer using mice models. Additionally, The anticancer effects re- to Japanese amazake). Some other fermented foods like kimchi ported for doenjang are primarily correlated with secondary me- (fermented cabbage) or sikhae (fermented fish) also involve lactic tabolites viz., trypsin inhibitors, isoflavone, aglyconated genistein, acid bacteria (LAB) inoculations viz., Leuconostoc, Lactobacillus, and vitamin E, and linoleic acid (Jung, Park, & Park, 2006; Kwon et al., Pediococcus (Rhee, Lee, & Lee, 2011). The complex interplay of mi- 2011). Moreover, the anti-mutagenic functional metabolites are crobial communities and metabolites together defines the ultimate also reported in doenjang which primarily include genistein, lino- taste, flavor, texture, shelf life, and the functional properties of leic acid, b-sitosterol glucoside, and soyasaponin (Park, Jung, Rhee, fermented foods. Among the numerous scrumptious foods, condi- & Choi, 2003). The fermentative manufacturing steps for doenjang ments, and beverages of Korea, a few of the most relished ones typically involves; (1) steaming (110 C & 1 h) and crushing of raw including their health beneficial effects and rare but equivocal soybeans, (2) molding of crushed soybeans to meju blocks and safety issues are discussed below under the paradigm of drying (1 day), (3) meju fermentation (15 days) with natural metabolomics. microflora, followed by (4) meju brining through soaking in salt water (21e24%, w/v), and finally (5) aging (141 days) depending 4.1. The fermented soy-based foods upon the processes (Lee, Lee et al., 2014). The temporal MS-based metabolite profiling has indicated an increase in the relative pro- Fermented soy foods have been an irreplaceable components of portions of primary metabolites (monosaccharides, amino acids, daily cuisines in East Asian societies, and their relevance dates back and fatty acids) during the later stages (steps 3e5). On the other D. Singh et al. / Trends in Food Science & Technology 61 (2017) 103e115 109 hand, the levels of functional secondary metabolites viz., iso- Gochujang, in particular, is reported to have numerous beneficial flavones (glycosides and aglycones, which vary reciprocally) and health effects viz., anti-mutagenic (Choo, 2000), anti-tumor (Park, soyasaponins (which decrease from step 2, onwards) are reportedly Kong, Jung, & Rhee, 2001), anti-cancer (Kim et al., 2005), and varied during the bioprocess (Lee, Kim, et al., 2012, Lee, Lee et al., anti-obesity (Ahn et al., 2006; Shin et al., 2016). Unsurprisingly, the 2014). The doenjang fermentation process is primarily affected by characteristic taste and functionality of gochujang are greatly a myriad of prokaryotic genera viz., Bacillus, Enterococcus, Lactoba- influenced by its fermentative microflora and common raw in- cillus, Clostridium, Staphylococcus, Corynebacterium, Oceanobacillus, gredients viz., gochu (Korean red pepper), meju (soybean powder), and Tetragenococcus, each differentially affecting the fermentation and glutinous rice or wheat. The majority of the microbial popu- bioprocess and production of functional metabolites. In one report, lation in soy-based fermented foods is derived from meju. Jang, Lactobacillus and Tetragenococcus were primarily correlated with Kim, Park, and Park (2011) have described the 16S rDNA-based the production of g-aminobutyric acid (GABA) and biogenic relative proportions of the microflora in different gochujang sam- amines, respectively, during doenjang fermentative production ples, with an average of 96% Bacillus spp., Oceanobacillus (1.6%), (Jung, Jung, Lee, & Jeon, 2016). Adding to an exception, a few reports Serratia (1%), Candida (0.8%), and Zygosaccharomyces (0.4%). have also highlighted the food safety issues associated with doen- Further, approximately 93.10% of the bacterial population of jang samples fermented using artisanal methods with coliform gochujang typically belongs to the phylum Firmicutes, exemplifying contaminations and detectable levels of harmful aflatoxins (Kim & their high salt tolerance and hydrolytic enzyme activities necessary Kim, 2012; Park, Shukla, Lee, Kim, & Kim, 2014). Nevertheless, the for the fermentative manufacturing of gochujang (Nam, Park, & Lim, aflatoxin or biogenic amines levels for artisanal doenjang samples 2012). Gochujang is well known for its anti-obesogenic and anti- were indicated below the critical safety limits, the renewed efforts atherogenic effects, reducing both the rate of fat deposition and are needed to standardize its manufacturing and safety circulatory levels of cholesterol and triglycerides through modu- management. lation of the levels of lipogenic and lipolytic enzymes (Koo, Seong, Kwon, Sohn, & Cha, 2008). Further, the microbial conversion of 4.1.3. Ganjang (also called Kanjang) capsaicin (a key functional metabolite in gochujang) to its de- Ganjang (regular soy sauce), along with its variants guk-ganjang rivatives, vanillylamine and trans-8-methyl-6-nonenoic acid is also (soup soy sauce) and wae-ganjang (comparatively sweeter and less reported in koji-based fermented foods (Cho et al., 2014; Romano, salty), represents the most favored umami seasoning with overseas Gandolfi, Guglielmetti, & Molinari, 2011). Lee, Jung, & Jeon, et al. consumption in all of its forms. Ganjang is traditionally manufac- (2015) have elaborated the bioconversion process of capsaicin by tured through an extended fermentation of the liquid portion, A. oryzae resulting in the production of novel metabolites viz.,N- remaining after doenjang-meju fermentation, in solar salt for 3e6 vanillylcarbamoylbutyric acid, N-vanillyl-9-hydroxy-8- months (Ham et al., 2004). The characteristic dark brown texture of methyloctanamide, u-hydroxycapsaicin, 8-methyl-N-vanillylcar- ganjang is due to the chemical combination of hydrolyzed amino bamoyl-6(E)-octenoic acid, and 2-methyl-N-vanillylcarbamoyl- acids and saccharides forming malanoidin compounds (Shin & 6(Z)-octenoic acid, using NMR and MS-based metabolite profiling. Jeong, 2015). The soy sauce is often considered as a health food They have further verified the capsaicin bioconversion from on account of its associated antioxidant and anti-mutagenic activ- gochujang samples. The resulting metabolites from capsaicin ities, and its potential curative effects for ulcerative colitis (Aoshima bioconversion are also reported to have the characteristic func- & Ooshima, 2009; Song, Choi, Seo, Lim, & Park, 2014; Wang et al., tional properties of the parent compounds (Onozaki, Sasaoka, & 2007). The primary microflora predominating during the different Ezaki, 1976). Hence, the evaluation of the metabolic plethora stages of ganjang fermentation include Weissella cibaria, Lactoba- associated with gochujang would further help in ensuring its mass cillus fermentum, Staphylococcus gallinarum, S. kloosii, S. arlettae, production and quality control. Bacillus and halotolerant Chromohalobacter spp. (Jung, Chun, & Jeon, 2015; Tanaka, Watanabe, & Mogi, 2012). Jung, Chun, et al. 4.2. Kimchi (fermented vegetables) (2015) have further investigated the fermentative dominance of halotolerant species, besides the usually present Bacillus species The climatic extremes of winter in the region (Far East, including effecting the production of functional amino acids and organic Korea) compelled the ancient peoples to develop the art of storing acids as well as the putrescine traces (a biogenic amine). The soy nutritious vegetables to ensure their availability throughout the sauce is also reported for the occasional untoward production of year. Kimchi is the Korean name for preserved vegetables, often carcinogenic ethyl carbamates (EC) owing to the faulty fermenta- seasoned with spices and fermented seafood. The Gimjang (Kimchi- tions or storage conditions i.e., using diethyl dicarbonate (DEDC) as making season), in the Republic of Korea (South), and traditional art anti-microbial agents (Hasegawa et al., 1990; Park et al., 2007). The of Kimchi making in the Democratic Republic of Korea (North), were EC mediated genotoxicity is correlated with the epoxides leading to included in the “UNESCO's Intangible Cultural Heritage Lists” in the the formation of DNA adducts and hence the mutations in vital years 2013 and 2015, respectively (http://www.unesco.org). Hence, organs (Forkert, 2010). Hence, the metabolomic characterization of it would perhaps not be an exaggeration to label kimchi as the the fermentation bioprocess and end products becomes necessary epitome of Korean fermented foods. It is not only served as a side to track the incursion of deleterious components in soy sauce. dish (Banchan), but is also an inextricable component of the traditional meal, Bapsang. The basic components of the traditional 4.1.4. Gochujang (also called Kochujang) kimchi usually include cabbage (baechu), white radish, red pepper, The Korean fermented red pepper condiment with a toothsome ginger, garlic, and other components of choice. Here, the red pepper piquant savor is globally renowned for its spectrum of functional (gochu) controls the growth of putrefactive microflora and pro- and bioactive metabolites. In medieval Korea, contemporary en- motes only those beneficial to health; therefore, the overall mi- cyclopedias of medicine, namely “Euibangyuchi” and “Hyangyak- crobial diversity is expected to be higher in kimchi without red jipsongbang III”, both describe the curative properties of gochujang pepper i.e., white (or baek) kimchi (Jeong, Lee, et al., 2013; Kwon for patients with certain stomach ailments (Kwon, Chung, Yang, & et al., 2015). Kimchi, as a vegetable-based fermented foodstuff, Jang, 2015). In recent times, the prominence of traditional fer- serves as a rich source of dietary fibers, vitamins, and functional mented foods in oriental societies has gained an impetus on ac- terpenoid bioactives (b-carotene and b-sitosterol), along with count of the metabolomic delineation of their functional aspects. probiotic microflora (Cheigh & Park, 1994). The principal microflora 110 D. Singh et al. / Trends in Food Science & Technology 61 (2017) 103e115 associated with kimchi is lactic acid bacteria (LAB), which pivotally putrefying microbes. The fermentative preparation is accompanied governs its shelf life, taste, nutrition, and organoleptic properties. A by the growth of the rich microflora, affecting the biotransforma- variety of LABs reported in kimchi include Lactobacillus, Lactococcus, tion of the raw components into palatable products rich in nutri- Pediococcus, Leuconostoc, and Weissella, besides the few yeast tion. Pyrosequencing analyses of different saeu-jeot samples at genera found exclusively during the long term storage period (>2 different stages of fermentation reveal the microbial community moths) viz., Saccharomyces, Pichia, and Candida (Hong, Choi, Lee, dynamics, where Firmicutes (Psychrobacter, Staphylococcus, Salimi- Yang, & Lee, 2016; Jeong, Lee, et al., 2013). Recently, Park et al. crobium, Alkalibacillus, and Halanaerobium) gradually replace Pro- (2016) have isolated the Lactobacillus strains, L. plantarum, and teobacteria (Pseudoalteromonas, Photobacterium, Vibrio, Aliivibrio, L. sakei, from white kimchi samples, which have potential con- and Enterovibrio) during the later stages. Moreover, 1H NMR based sumption safety and in vivo anti-obesity effects based on diet metabolite profiling has shown that the levels of amino acids and induced obesity (DIO) mouse model studies. LAB mediated glucose remain significantly unaltered during the later stages of fermentation is accompanied by an increase in organic acid levels fermentation on account of the increased salinity unsuitable for the viz., lactic acids, succinic acid, and isocitric acid, creating the low pH action of enzymes (Lee et al., 2014a). Thus, the endogenous pro- environment suitable for the growth of the necessary probiotic teases and lipases in shrimp play a pivotal role during fermentation, microflora. However, the area of synbiotic formulation of kimchi contributing to its organoleptic properties and palatability. still remains a terra incognita for food scientists and requires further investigative efforts. 4.4. Health beverages

4.3. Jeot (fermented fish and seafood) The Korean lexicon of traditional beverages is rich in a number of health beverages. Sikhye, a traditional non-alcoholic beverage The salt-fermented seafood called 'jeot' is one of the most made with glutinous rice fermented using malt water, is usually scrumptious of the Korean side-dishes and sauces. A variety of taken after a meal to aid digestion. Although, a lack of sufficient seafood are used in the long term salt-fermentative preparation of studies could limit our discussion about sikhye, it has been studied jeot including shrimp, oyster, shellfish, fish (anchovies), fish eggs, as an essential component of the Korean diet from the perspective and fish intestines among other things, depending upon the of weight loss and anti-obesity (Fuller et al., 2012). However, a few regional availability and climate (Do, Lee, & Chang, 1993). There are reports also suggest the Bacillus cereus spore induced toxicity in estimated 150e160 types of jeot prepared in Korea, using both frozen commercial products upon thawing and during storage, thus traditional and modern methods, with an average of 30 commercial fresh sikhye can be considered best for safe and healthy con- variants (Guan, Cho, & Lee, 2011). However, the reportedly higher sumption (Kim, Kim, et al., 2012). proportions of biogenic amines owing to the rich animal protein Another customary, non-alcoholic beverage consumed world- contents make their bio -safety consideration a necessity. Mah, wide, including Korea, is vinegar, which is manufactured using a Kim, and Hwang (2009) have discussed the production of variety of raw materials like cereals, wheat, rice, or fruits depending biogenic amines and their management implications below the upon the regional taste, culture, and expertise. Vinegar has many hazardous levels in jeot-gal using different blends of garlic and beneficial health effects including, immunomodulation, appetite glycine rich components. Here we describe the most important suppression, and anti-obesity; it aids digestion and regulates blood ones studied with the scientific evidences. glucose as well as cholesterol levels (Kim, Cho, & Shin, 2012; Sugiyama, Saitoh, Takahara, Satoh, & Hashimoto, 2003). In recent 4.3.1. Myeolchi-aekjeot years, traditionally manufactured vinegars using Rubus coreanus This traditional fermented fish sauce is prepared by fermenting (Korean black raspberry or bokbunja) have been investigated for anchovies in high concentrations of salt (~25%) for 6e9 months' their potential nutraceutical properties including anti-obesity, anti- duration at 20e30 C, promoting the spontaneous growth of hal- cancer, and postmenopausal anti-osteoporotic effects (Jung et al., otolerant and halophilic microbial species (Fukui et al., 2012). 2009, Jung, Cho et al., 2015; Lee, Kim, et al., 2016). Jang et al. Among the various microbial communities appearing spontane- (2015) have described in detail the MS-based metabolite profiles ously viz., Chromobacter, Bacillus, Halomonas, Micrococcus, Brevi- for traditional vinegars made using Korean black raspberry and bacterium, Halobacterium, Vibrio, Flavobacterium, Staphylococcus, lacquer rice, compared with commercial ones, and have deter- and Tetragenococcus, only a few emerge as the dominant species mined the target metabolites viz., cyanidin-3-xylosylrutinoside, during the later stages of fermentation, namely Staphylococcus, cyanidin-3-rutinoside, and quercetin with higher antioxidant ac- Tetragenococcus, and Halanaerobium (Lee, Jung, & Jeon, 2015). The tivities. Biochemically, the aerobic conversion of starchy materials salt-fermentative hydrolysis of protein components in anchovy is into acetic acid is accompanied by a variety of gram negative acetic accompanied by amino acid release through enzymatic hydrolysis acid bacteria viz., Acetobacter aceti, A. pasteurianus, A. polyxygenes, mediated by exogenous and endogenous proteases. The 1H NMR A. xylinum, A. malorum, and A. pomorum, besides a few yeast vari- profiles for myeolchi-aekjeot during the course of fermentative eties (Haruta et al., 2006; Tamang, Watanabe, & Holzapfel, 2016). ripening indicate that alanine, aspartate, glutamate, and glycine During the course of alcoholic fermentation, followed by aerobic levels steadily increase, determining its characteristic umami savor conversion of the raw substrates to vinegar, microbial metabolism (Jung et al., 2016). Fermented anchovies are therefore another brings about the synthesis of numerous metabolites altering the choice of condiment or seasoning used in Korean cuisine aroma, taste, and functionality of the final product. Hence, one can throughout the ages. tout vinegar as an elixir of life on account of its beneficial health effects. 4.3.2. Saeu-jeot Our discussion seems incomplete without any reference to the The shrimp (saeu) sauce 'saeu-jeot' is another traditionally rel- other popular fermented and low-alcohol beverages of the region, ished condiment made using the salt-fermentation of tiny shrimp makgeolli and omegisool, which have deep-rooted traditional (Acetes japonicus). The fermentative preparation of saeu-jeot is values. Makgeolli, commonly known as rice wine, is made using carried out in a similar fashion to that of myeolchi-aekjeot under barley, wheat, or malts in addition to rice, resulting in a nutritious high salt concentrations (25e30% solar salt) but at contrastingly and slightly alcoholic (~6%) beverage. The nutritious components, low incubation temperatures (0e10 C) to prevent the growth of including organic acids, vitamin B, glutathione, and live yeast in D. Singh et al. / Trends in Food Science & Technology 61 (2017) 103e115 111 makgeolli, confers it potential antioxidant, immunomodulatory, and reported for the ganjang fermentative bioprocess (Jung, Chun, et al., anticancer activities (Lee et al., 2010; Nile, 2015). The nuruk sup- 2015). The authors have effectively correlated the denaturing plemented LAB genera viz., Lactobacillus, Pediococcus, and Entero- gradient gel electrophoresis (DGGE)-detected microbial commu- coccus in traditional makgeolli serve as probiotics and reportedly nities and 1H-NMR-based metabolite profiles using multivariate possess anti-diabetic and anti-obesity effects (Kadooka et al., 2010; redundancy analysis (MVRDA). In particular, the Bacillus spp. were Moon, Baik, & Cha, 2014; Yadav, Jain, & Sinha, 2007). Hence, the reportedly linked to the metabolism of sugars and sugar alcohols microbiological and metabolite blend in makgeolli makes it a health (glucose, fructose, galactose, and glycerol), while the Chromohalo- beneficial beverage, provided the alcoholic percentage and daily bacter spp. were effecting the production of putrescine and organic consumptions are regulated. Yet another traditional low-alcohol acids (acetate, lactate, pyruvate, a-aminobutyrate, g-amino- beverage, a particular specialty of the Jeju island region of Korea, butyrate, and formate). Similarly, a number of correlative studies omegisool, is recently reported to contain probiotic LAB microflora, linking the different microbial communities and their corre- like Lactobacillus and Pediococcus, with potential gut health effects sponding metabolomic outcomes during the fermentative bio- (Oh & Jung, 2015). Recent findings related to the functional aspects processes for a variety of traditional foods and beverages viz., of traditional hermetic beverages have indisputably provided an myeolchi-aekjeot, saeu-jeot, kimchi, and makgeolli have been re- impetus to expanding nutritional research. ported (Jeong et al., 2013b; Lee et al., 2014b, 2014a; Lee, Jung et al., 2015; Ponnusamy, Lee, & Lee, 2013). 5. Microbiomes: minutiae for microbial transformations and The complementary multi-omics approaches viz., meta- metabolomes genomics, proteomics, and metabolomics together underscores the microbial transformations in a fermentation matrix which further The artisanal manufacturing bioprocesses for indigenous fer- requires ingenious systems biology based interactive outlooks to- mented foods in different parts of the world are inherited as the wards their mechanistic comprehensions. Hence, outlining the ef- wisdom of tradition. However, the cryptic ancient lore is now being fects of fermented food microbiome, dietary components, and deciphered to explain the underlying minutiae of microbial enzyme associated metabolomes per se on sculpting the human gut mediated raw substrates transformations and the resulting microbiota and health are essential stepping stones for establishing metabolomes with characteristic savor and health effects. Metab- the worldwide consumer acceptance of traditional Korean fer- olomics can potentially be employed to elucidate the perplexing mented foods and beverages. Although, an increasing number of microbial transformations of substrates during fermentative bio- scientific reports highlight the importance of microbial community processes, and thus find applications in commercial production of dynamics and their effects on the resulting metabolome and phe- fermented foods and beverages. Moreover, an insight of the dy- notypes, the field still remains a Gordian-knot of food biotechnology namic correlations for metabolite intermediates and associated owing to the lack of generalized methodologies. microbial communities while a fermentative bioprocess helps envisaging the corresponding microbiome model applicable in food 6. Conclusions quality and safety evaluations. The fermentation matrix of foods and beverages can also be The artisanal practices of making traditional Korean fermented viewed as a complex ecosystem, harboring a variety of microflora foods and beverages have undergone a remarkable transformation carrying out the hydrolysis of nutrient ingredients and causing the in recent times. A number of soy, vegetable, and seafood-based release of a myriad of metabolites viz., amino acids, organic acids, condiments, as well as local malt or fruit beverages, have attrac- active metabolites, and aglycones as shown Fig. 2 (Jung, Lee, & Jeon, ted global attention owing to their beneficial health effects. 2014a; Lee, Kim, et al., 2012). Besides the raw substrate ingredients, Metabolomics, in conjugation with other conventional approaches, a wide variety of environmental variables viz., pH, incubation have revealed a number of beneficial health effects associated with temperature, salinity, water activity (aw), and aeration etc., also traditional fermented foods of the peninsula. The present scenario influence the overall microbial communities in a fermentative regarding the scientific interpretation of global fermented foods bioprocess. In case of meju, a major ingredient of fermented soy seems rather discriminative, and considerably less attention is foods, the high performance liquid chromatography (HPLC) anal- being paid to the most generic aspect of food biotechnology i.e., the ysis of isoflavone metabolism inferred a reciprocal correlation be- food metabolome. Recent advancements in the precision and tween total isoflavones and glycoside levels, where the latter was robustness of metabolomic instrumentation have enabled us to converted to aglycones during the course of fermentation (Jung address the critical bottlenecks of artisanal fermentative food et al., 2014b). Further, the enzymatic transformation of isoflavone production viz., processing, health benefits, functional aspects, glycosides to isoflavone aglycones (daidzein and genistein) through quality control, and safety. In recent times, a food is considered microbial b-glucosidase activity was primarily observed during the much more than the source of basic nutrients. In particular, fer- cheonggukjang fermentation process and determines its functional mented foods are globally recognized for their concomitant pro- properties (Lee, Kim, et al., 2012; Park, Jeong, Kim, & Lee, 2012). biotic microbial assortments, functional metabolomes, and dietary Recently, Lee, Lee, et al. (2014) have comprehensively described the nutrients. In this context, the comprehensive evaluation and char- levels of discriminant metabolites at different stages of the acterization of the associated metabolomes becomes an essential fermentative bioprocess of doenjang, using complementary GC-MS step. and LC-MS metabolite profiles followed by multivariate analyses. Besides perceived complications, the cryptic metabolomes and Similarly, metabolomic approaches in conjugation with the enzy- their functional effects are progressively been studied using the matic activity assays has successfully been applied to reveal the sophisticated analytical and data mining approaches. This usually dynamics of amino acid levels during cheonggukjang fermentation involves the identification of biomarker compounds or the overall with different garlic components (Oh et al., 2016). Kim, Choi, et al. metabolomes influenced under a selected fermentative bioprocess. (2012) have elucidated the tendency in the levels of metabolite Hence, the procedural ambiguities in the artisanal manufacturing intermediates viz., carbohydrates, purines, and pyrimidines during of traditional foods and beverages must be standardized to obtain the different steps in cheonggukjang fermentation. the consistent desired quality products. A number of high An another correlative study highlighting the process specific throughput analytical platforms viz., GC-MS, LC-MS, or NMR are microbial community dynamics and metabolite production was largely been employed in the field of food metabolomics, which has 112 D. Singh et al. / Trends in Food Science & Technology 61 (2017) 103e115

Fig. 2. The correlative networks for different metabolites transformed by microbial assortments in major classes of fermented foods and beverages of the Korean peninsula. Color codes and figure geometries: Gray boxes for microorganism; White circles for metabolites; Ellipses (differently colored) for fermented food and beverages. The metabolite classes indicated here includes: Purines (xanthine, hypoxanthine), Amino acids (arginine, glutamate), Organic acids (acetate, lactate, pyruvate, a-aminobutyrate, formate), and Isoflavones (daidzein, genistein). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) enabled a holistic delineation of the physiological, microbiological, flight mass spectrometry analysis for large-scale nontargeted metabolomic e and functional aspects of traditional fermented products. studies of human serum. Analytical Chemistry, 81, 7038 7046. Borresen, E. C., Henderson, A. J., Kumar, A., Weir, T. L., & Ryan, E. P. (2012). Fer- mented foods: Patented approaches and formulations for nutritional supple- Acknowledgements mentation and health promotion. Recent Patents on Food, Nutrition & Agriculture, 4,134e140. Brodsky, L., Moussaieff, A., Shahaf, N., Aharoni, A., & Rogachev, I. (2010). Evaluation This work was supported by the National Research Foundation of peak picking quality in LCÀ MS metabolomics data. Analytical Chemistry, 82, of Korea (NRF) grant funded by the Korea government (MSIP) (No. 9177e9187. Bylesjo,€ M., Rantalainen, M., Cloarec, O., Nicholson, J. K., Holmes, E., & Trygg, J. NRF-2014R1A2A1A11050884) and by the Strategic Initiative for (2006). OPLS discriminant analysis: Combining the strengths of PLS-DA and Microbiomes in Agriculture and Food, Ministry of Agriculture, Food SIMCA classification. Journal of Chemometrics, 20,341e351. and Rural Affairs, Republic of Korea (as part of the (multi-ministe- Cajka, T., & Fiehn, O. (2016). Toward merging untargeted and targeted methods in rial) Genome Technology to Business Translation Program) (grant mass spectrometry-based metabolomics and lipidomics. Analytical Chemistry, 88, 524e545. number 916005-2). This study was also supported by grant from Cevallos-Cevallos, J. M., Reyes-De-Corcuera, J. I., Etxeberria, E., Danyluk, M. D., & the Korea Food Research Institute (E0164503-01). Rodrick, G. E. (2009). Metabolomic analysis in food science: A review. Trends in Food Science & Technology, 20,557e566. Cheigh, H. S., & Park, K. Y. (1994). Biochemical, microbiological, and nutritional References aspects of kimchi (Korean fermented vegetable products). Critical Reviews in Food Science and Nutrition, 34,175e203. Abdi, H., & Williams, L. J. (2010). Principal component analysis. Wiley Interdisci- Chen, W., Gong, L., Guo, Z., Wang, W., Zhang, H., Liu, X., et al. (2013). A novel in- fi fi plinary Reviews: Computational Statistics, 2, 433e459. tegrated method for large-scale detection, identi cation, and quanti cation of Ahn, I. S., Do, M. S., Kim, S. O., Jung, H. S., Kim, Y. I., Kim, H. J., et al. (2006). Anti- widely targeted metabolites: Application in the study of rice metabolomics. e obesity effect of kochujang (Korean fermented red pepper paste) extract in 3T3- Molecular Plant, 6,1769 1780. L1 adipocytes. Journal of Medicinal Food, 9,15e21. Cho, S., Moon, H., Hong, G. E., Lee, C. H., Kim, J. M., & Kim, S. K. (2014). Biodegra- Aoshima, H., & Ooshima, S. (2009). Anti-hydrogen peroxide activity of fish and soy dation of capsaicin by Bacillus licheniformis SK1230. Journal of the Korean Society e sauce. Food Chemistry, 112,339e343. for Applied Biological Chemistry, 57,335 339. fi Baek, J. G., Shim, S. M., Kwon, D. Y., Choi, H. K., Lee, C. H., & Kim, Y. S. (2010). Choi, H. K., Yoon, J. H., Kim, Y. S., & Kwon, D. Y. (2007). Metabolomic pro ling of Metabolite profiling of cheonggukjang, a fermented soybean paste, inoculated cheonggukjang during fermentation by 1H NMR spectrometry and principal e with various Bacillus strains during fermentation. Bioscience Biotechnology and components analysis. Process Biochemistry, 42, 263 266. Biochemistry, 74, 1860e1868. Choo, J. J. (2000). Anti-obesity effects of kochujang in rats fed on a high-fat diet. The e Baran, R., Kochi, H., Saito, N., Suematsu, M., Soga, T., Nishioka, T., et al. (2006). Korean Nutrition Society, 33, 786 793. MathDAMP: A package for differential analysis of metabolite profiles. BMC Davidson, R. L., Weber, R. J., Liu, H., Sharma-Oates, A., & Viant, M. R. (2016). Galaxy- fl Bioinformatics, 7, 530. m: A Galaxy work ow for processing and analyzing direct infusion and liquid Begley, P., Francis-McIntyre, S., Dunn, W. B., Broadhurst, D. I., Halsall, A., Tseng, A., chromatography mass spectrometry-based metabolomics data. Gigascience, 5, et al. (2009). Development and performance of a gas chromatography-time-of- 10. D. Singh et al. / Trends in Food Science & Technology 61 (2017) 103e115 113

Di Guida, R., Engel, J., Allwood, J. W., Weber, R. J., Jones, M. R., Sommer, U., et al. fermentation. International Journal of Food Microbiology, 160, 252e259. (2016). Non-targeted UHPLC-MS metabolomic data processing methods: A Jeong, S. H., Lee, S. H., Jung, J. Y., Choi, E. J., & Jeon, C. O. (2013b). Microbial succession comparative investigation of normalisation, missing value imputation, trans- and metabolite changes during long-term storage of kimchi. Journal of Food formation and scaling. Metabolomics, 12,1e14. Science, 78,763e769. Diekmann, J., Adams, K. L., Klunder, G. L., Evans, L., Steele, P., Vogt, C., et al. (2011). Jeong, D. W., Kim, H. R., Jung, G., Han, S., Kim, C. T., & Lee, J. H. (2014). Bacterial Portable microcoil NMR detection coupled to capillary electrophoresis. community migration in the ripening of doenjang, a traditional Korean fer- Analytical Chemistry, 83, 1328e1335. mented soybean food. Journal of Microbiology and Biotechnology, 24,648e660. Do, S. D., Lee, Y. M., & Chang, H. G. (1993). The study on kinds and utilities of jeot-kal Jo, D., Kim, G. R., Yeo, S. H., Jeong, Y. J., Noh, B. S., & Kwon, J. H. (2013). Analysis of (fermented fish products). Korean Society of Food and Cookery Science, 9, aroma compounds of commercial cider vinegars with different acidities using 222e229. SPME/GC-MS, electronic nose, and sensory evaluation. Food Science and Forkert, P. G. (2010). Mechanisms of lung tumorigenesis by ethyl carbamate and Biotechnology, 22, 1559e1565. vinyl carbamate. Drug Metabolism Reviews, 42, 355e378. Johnson, C. H., Ivanisevic, J., & Siuzdak, G. (2016). Metabolomics: Beyond biomarkers Forseth, R. R., & Schroeder, F. C. (2011). NMR-spectroscopic analysis of mixtures: and towards mechanisms. Nature Reviews: Molecular Cell Biology, 17,451e459. From structure to function. Current Opinion in Chemical Biology, 15,38e47. Jonsson, P., Gullberg, J., Nordstrom, A., Kusano, M., Kowalczyk, M., Sjostrom, M., Fukui, Y., Yoshida, M., Shozen, K., Funatsu, Y., Takano, T., Oikawa, H., et al. (2012). et al. (2004). A strategy for identifying differences in large series of metab- Bacterial communities in fish sauce mash using culture-dependent and -inde- olomic samples analyzed by GC/MS. Analytical Chemistry, 76,1738e1745. pendent methods. Journal of General and Applied Microbiology, 58,273e281. Jung, K. O., Park, S. Y., & Park, K. Y. (2006). Longer aging time increases the anti- Fuller, N. R., Lau, N. S., Denyer, G., Simpson, A. E., Gerofi, J., Wu, M., et al. (2012). cancer and antimetastatic properties of doenjang. Nutrition, 22, 539e545. A 12-week, randomised, controlled trial to examine the acceptability of the Jung, J., Son, M. Y., Jung, S., Nam, P., Sung, J. S., Lee, S. J., et al. (2009). Antioxidant Korean diet and its effectiveness on weight and metabolic parameters in an properties of Korean black raspberry wines and their apoptotic effects on Australian overweight and obese population. Obesity Research & Clinical Prac- cancer cells. Journal of the Science of Food and Agriculture, 89,970e977. tice, 6,1e90. Jung, J. Y., Lee, S. H., & Jeon, C. O. (2014a). Kimchi microflora: History, current status, Gibbons, H., O'Gorman, A., & Brennan, L. (2015). Metabolomics as a tool in nutri- and perspectives for industrial kimchi production. Applied Microbiology and tional research. Current Opinion in Lipidology, 26,30e34. Biotechnology, 98, 2385e2393. Go, J., Kim, J. E., Kwak, M. H., Koh, E. K., Song, S. H., Sung, J. E., et al. (2016). Neu- Jung, J. Y., Lee, S. H., & Jeon, C. O. (2014b). Microbial community dynamics during roprotective effects of fermented soybean products (Cheonggukjang) manufac- fermentation of doenjang-meju, traditional Korean fermented soybean. Inter- tured by mixed culture of Bacillus subtilis MC31 and Lactobacillus sakei 383 on national Journal of Food Microbiology, 185,112e120. trimethyltin-induced cognitive defects mice. Nutritional Neuroscience, 19, Jung, J. Y., Chun, B. H., & Jeon, C. O. (2015). Chromohalobacter is a causing agent for 247e259. the production of organic acids and putrescine during fermentation of ganjang, Gromski, P. S., Muhamadali, H., Ellis, D. I., Xu, Y., Correa, E., Turner, M. L., et al. (2015). a Korean traditional soy sauce. Journal of Food Science, 80, 2853e2859. A tutorial review: Metabolomics and partial least squares-discriminant anal- Jung, M. A., Cho, S. H., Lee, S., Kim, J., Kim, Y. S., Oh, K., et al. (2015). Anti-obesity ysis-a marriage of convenience or a shotgun wedding. Analytica Chimica Acta, effects on unripe Rubus coreanus miquel extract in high fat diet-induced obese 879,10e23. mice. International Journal of Biochemistry Research & Review, 5,20e26. Guan, L., Cho, K. H., & Lee, J. H. (2011). Analysis of the cultivable bacterial com- Jung, W. Y., Jung, J. Y., Lee, H. J., & Jeon, C. O. (2016). Functional characterization of munity in jeotgal, a Korean salted and fermented seafood, and identification of bacterial communities responsible for fermentation of doenjang: A traditional its dominant bacteria. Food Microbiology, 28,101e113. korean fermented soybean paste. Frontiers in Microbiology, 7,1e10. Guennec, A. L., Giraudeau, P., & Caldarelli, S. (2014). Evaluation of fast 2D NMR for Jung, J. Y., Lee, H. J., Chun, B. H., & Jeon, C. O. (2016). Effects of temperature on metabolomics. Analytical Chemistry, 86, 5946e5954. bacterial communities and metabolites during fermentation of myeolchi-aek- Guo, L., Milburn, M. V., Ryals, J. A., Lonergan, S. C., Mitchell, M. W., Wulff, J. E., et al. jeot, a traditional korean fermented anchovy sauce. PLoS One, 11,1e20. (2015). Plasma metabolomic profiles enhance precision medicine for volunteers Kadooka, Y., Sato, M., Imaizumi, K., Ogawa, A., Ikuyama, K., Akai, Y., et al. (2010). of normal health. Proceedings of the National Academy of Sciences U S A, 112, Regulation of abdominal adiposity by probiotics (Lactobacillus gasseri SBT2055) 4901e4910. in adults with obese tendencies in a randomized controlled trial. European Gupta, S. K., Dongare, S., Mathur, R., Mohanty, I. R., Srivastava, S., Mathur, S., et al. Journal of Clinical Nutrition, 64, 636e643. (2015). Genistein ameliorates cardiac inflammation and oxidative stress in Kell, D. B., Brown, M., Davey, H. M., Dunn, W. B., Spasic, I., & Oliver, S. G. (2005). streptozotocin-induced diabetic cardiomyopathy in rats. Molecular and Cellular Metabolic footprinting and systems biology: The medium is the message. Na- Biochemistry, 408,63e72. ture Reviews: Microbiology, 3,557e565. Ha, D., Paulsen, J., Sun, N., Song, Y. Q., & Ham, D. (2014). Scalable NMR spectroscopy Kim, M., & Kim, Y. S. (2012). Detection of foodborne pathogens and analysis of with semiconductor chips. Proceedings of the National Academy of Sciences U S A, aflatoxin levels in home-made doenjang samples. Preventive Nutrition Food 111, 11955e11960. Science, 17,172e176. Ham, S. S., Choi, K. K., Cui, C. B., Lee, B. G., Joo, D. S., & Lee, D. S. (2004). Quality Kim, J. Y., Park, K. W., Yang, H. S., Cho, Y. S., Jeong, C. H., Shim, K. H., et al. (2005). characteristics of soy sauce fermented by Bacillus licheniformis NH20 isolated Anticancer and Immuno-activity of methanol extract from onion kochujang. The from traditional meju and Aspergillus oryzae. Food Science and Biotechnology, 13, Korean Society of Food Preservation, 12,173e178. 537e543. Kim, H., Kim, H., Bang, J., Kim, Y., Beuchat, L. R., & Ryu, J. H. (2012). Reduction of Harrigan, G. G., Skogerson, K., MacIsaac, S., Bickel, A., Perez, T., & Li, X. (2015). Bacillus cereus spores in sikhye, a traditional Korean rice beverage, by modified Application of (1)h NMR profiling to assess seed metabolomic diversity. A case tyndallization processes with and without carbon dioxide injection. Letters in study on a soybean era population. Journal of Agricultural and Food Chemistry, Applied Microbiology, 55,218e223. 63, 4690e4697. Kim, J. Y., Choi, J. N., John, K. M., Kusano, M., Oikawa, A., Saito, K., et al. (2012). GC- Haruta, S., Ueno, S., Egawa, I., Hashiguchi, K., Fujii, A., Nagano, M., et al. (2006). TOF-MS- and CE-TOF-MS-based metabolic profiling of cheonggukjang (fast- Succession of bacterial and fungal communities during a traditional pot fermented bean paste) during fermentation and its correlation with metabolic fermentation of rice vinegar assessed by PCR-mediated denaturing gradient gel pathways. Journal of Agricultural Food Chemistry, 60,9746e9753. electrophoresis. International Journal of Food Microbiology, 109,79e87. Kim, S. H., Cho, H. K., & Shin, H. S. (2012). Physicochemical properties and antiox- Hasegawa, Y., Nakamura, Y., Tonogai, Y., Terasawa, S., Ito, Y., & Uchiyama, M. (1990). idant activities of commercial vinegar drinks in Korea. Food Science and Determination of ethyl carbamate in various fermented foods by selected ion Biotechnology, 21,1729e1734. ® monitoring. Journal of Food Protection ,53, 1058e1061. Kim, J. Y., Choi, J. N., Choi, J. H., Cha, Y. S., Muthaiya, M. J., & Lee, C. H. (2013). Effect of Hirayama, A., Igarashi, K., Tomita, M., & Soga, T. (2014). Development of quantitative fermented soybean product (Cheonggukjang) intake on metabolic parameters in method for determination of gamma-glutamyl peptides by capillary electro- mice fed a high-fat diet. Molecular Nutrition & Food Research, 57, 1886e1891. phoresis tandem mass spectrometry: An efficient approach avoiding matrix Kishi, M., Fukaya, M., Tsukamoto, Y., Nagasawa, T., Takehana, K., & Nishizawa, N. effect. Journal of Chromatography A, 1369,161e169. (1999). Enhancing effect of dietary vinegar on the intestinal absorption of cal- Hong, Y., Noh, B. S., & Kim, H. Y. (2015). Discrimination of doenjang samples using a cium in ovariectomized rats. Bioscience, Biotechnology, and Biochemistry, 63, mass spectrometry-based electronic nose and human sensory preference 905e910. testing. Food Science and Biotechnology, 24,31e36. Kohl, S. M., Klein, M. S., Hochrein, J., Oefner, P. J., Spang, R., & Gronwald, W. (2012). Hong, S. W., Choi, Y. J., Lee, H. W., Yang, J. H., & Lee, M. A. (2016). Microbial com- State-of-the art data normalization methods improve NMR-based metabolomic munity structure of korean cabbage kimchi and ingredients with denaturing analysis. Metabolomics, 8,146e160. gradient gel electrophoresis. Journal of Microbiology and Biotechnology, 26, Koo, B. S., Seong, S. H., Kwon, D. Y., Sohn, H. S., & Cha, Y. S. (2008). Fermented 1057e1062. kochujang supplement shows anti-obesity effects by controlling lipid meta- Hu, C., & Xu, G. (2013). Mass-spectrometry-based metabolomics analysis for foo- bolism in C57BL/6J mice fed high fat diet. Food Science and Biotechnology, 17, domics. TRAC Trends in Analytical Chemistry, 52,36e46. 336e342. Jang, S. J., Kim, Y. J., Park, J. M., & Park, Y. S. (2011). Analysis of microflora in Kwon, D. Y., Hong, S. M., Ahn, I. S., Kim, M. J., Yang, H. J., & Park, S. (2011). Iso- gochujang, Korean traditional fermented food. Food Science and Biotechnology, flavonoids and peptides from meju, long-term fermented soybeans, increase 20, 1435e1440. insulin sensitivity and exert insulinotropic effects in vitro. Nutrition, 27, Jang, Y. K., Lee, M. Y., Kim, H. Y., Lee, S., Yeo, S. H., Baek, S. Y., et al. (2015). Com- 244e252. parison of traditional and commercial vinegars based on metabolite profiling Kwon, D. Y., Chung, K. R., Yang, H. J., & Jang, D. J. (2015). Gochujang (Korean red and antioxidant activity. Journal of Microbiology and Biotechnology, 25,217e226. pepper paste): A Korean ethnic sauce, its role and history. Journal of Ethnic Jeong, S. H., Lee, H. J., Jung, J. Y., Lee, S. H., Seo, H. Y., Park, W. S., et al. (2013a). Effects Foods, 2,29e35. of red pepper powder on microbial communities and metabolites during kimchi Larive, C. K., Barding, G. A., Jr., & Dinges, M. M. (2015). NMR spectroscopy for 114 D. Singh et al. / Trends in Food Science & Technology 61 (2017) 103e115

metabolomics and metabolic profiling. Analytical Chemistry, 87,133e146. Cheonggukjang (fermented soybean paste) fermentation. Food Research Inter- Lee, C. U., & Koh, J. B. (2006). Effects of cheonggukjang on lipid metabolism in female national, 82,86e94. rats fed cholesterol diet. Journal of Life Science, 16, 932e937. Okutsu, K., Yoshizaki, Y., Ikeda, N., Kusano, T., Hashimoto, F., & Takamine, K. (2015). Lee, M. Y., Sung, S. Y., Kang, H. K., Byun, H. S., Jung, S. M., Song, J. H., et al. (2010). Antioxidants in heat-processed koji and the production mechanisms. Food Quality characteristics and physiological functionality of traditional rice wines Chemistry, 187, 364e369. in chungnam province of Korea. Korean Journal of Microbiology and Biotech- Omoni, A. O., & Aluko, R. E. (2005). Soybean foods and their benefits: Potential nology, 38,177e182. mechanisms of action. Nutrition Reviews, 63,272e283. Lee, G. I., Lee, H. M., & Lee, C. H. (2012). Food safety issues in industrialization of Onozaki, H., Sasaoka, K., & Ezaki, H. (1976). Hydrolytic degradation of capsaicin by traditional Korean foods. Food Control, 24,1e5. Aspergillus niger and Aspergillus oryzae. Journal of Fermentation Technology, 54, Lee, S. W., Yoon, S. R., Kim, G. R., Woo, S. M., Jeong, Y. J., Yeo, S. H., et al. (2012). Effect 297e301. of nuruk and fermentation method on organic acid and volatile compounds in Park, K. Y., Kong, K. R., Jung, K. O., & Rhee, S. H. (2001). Inhibitory effects of brown rice vinegar. Food Science and Biotechnology, 21, 453e460. kochujang extracts on the tumor formation and lung metastasis in mice. The Lee, S. Y., Kim, H. Y., Lee, S., Lee, J. M., Muthaiya, M. J., Kim, B. S., et al. (2012). Mass Korean Society of Food Science and Nutrition, 6,187e191. spectrometry-based metabolite profiling and bacterial diversity characteriza- Park, K. Y., Jung, K. O., Rhee, S. H., & Choi, Y. H. (2003). Antimutagenic effects of tion of Korean traditional meju during fermentation. Journal of Microbiology and doenjang (Korean fermented soypaste) and its active compounds. Mutation Biotechnology, 22, 1523e1531. Research/Fundamental and Molecular Mechanisms of Mutagenesis, 523,43e53. Lee, S. H., Jung, J. Y., & Jeon, C. O. (2014a). Effects of temperature on microbial Park, S. K., Kim, C. T., Lee, J. W., Jhee, O. H., Om, A. S., Kang, J. S., et al. (2007). Analysis succession and metabolite change during saeu-jeot fermentation. Food Micro- of ethyl carbamate in Korean soy sauce using high-performance liquid chro- biology, 38,16e25. matography with fluorescence detection or tandem mass spectrometry and gas Lee, S. H., Jung, J. Y., & Jeon, C. O. (2014b). Microbial successions and metabolite chromatography with mass spectrometry. Food Control, 18,975e982. changes during fermentation of salted shrimp (saeu-jeot) with different salt Park, M., Jeong, M. K., Kim, M., & Lee, J. (2012). Modification of isoflavone profiles in concentrations. PLoS One, 9,1e12. a fermented soy food with almond powder. Journal of Food Science, 77, Lee, S. Y., Lee, S., Lee, S., Oh, J. Y., Jeon, E. J., Ryu, H. S., et al. (2014). Primary and C128eC134. secondary metabolite profiling of doenjang, a fermented soybean paste during Park, H. K., Shukla, S., Lee, J. S., Kim, J. K., & Kim, M. (2014). Reduction of foodborne industrial processing. Food Chemistry, 165,157e166. pathogens and aflatoxins in doenjang samples using defined meju. Journal of Lee, M. Y., Cho, J. Y., Lee, Y. G., Lee, H. J., Lim, S. I., Park, S. L., et al. (2015). Biocon- Food Safety, 34,161e167. version of capsaicin by Aspergillus oryzae. Journal of Agricultural and Food Park, S., Ji, Y., Park, H., Lee, K., Park, H., Beck, B. R., et al. (2016). Evaluation of Chemistry, 63,6102e6108. functional properties of lactobacilli isolated from Korean white kimchi. Food Lee, S. H., Jung, J. Y., & Jeon, C. O. (2015). Bacterial community dynamics and Control, 69,5e12. metabolite changes in myeolchi-aekjeot, a Korean traditional fermented fish Patti, G. J., Yanes, O., & Siuzdak, G. (2012). Innovation: Metabolomics: The apogee of sauce, during fermentation. International Journal of Food Microbiology, 203, the omics trilogy. Nature Reviews: Molecular Cell Biology, 13, 263e269. 15e22. Pedrioli, P. G., Eng, J. K., Hubley, R., Vogelzang, M., Deutsch, E. W., Raught, B., et al. Lee, J. H., Paek, S. H., Shin, H. W., Lee, S. Y., Moon, B. S., Park, J. E., et al. (2016). Effect (2004). A common open representation of mass spectrometry data and its of fermented soybean products intake on the overall immune safety and application to proteomics research. Nature Biotechnology, 22, 1459e1466. function in mice. Journal of Veterinary Science (in press). Pluskal, T., Castillo, S., Villar-Briones, A., & Oresic, M. (2010). MZmine 2: Modular Lee, J. Y., Shim, J. M., Yao, Z., Liu, X., Lee, K. W., Kim, H. J., et al. (2016). Antimicrobial framework for processing, visualizing, and analyzing mass spectrometry-based activity of Bacillus amyloliquefaciens EMD17 isolated from cheonggukjang and molecular profile data. BMC Bioinformatics, 11, 395. potential use as a starter for fermented soy foods. Food Science and Biotech- Ponnusamy, K., Lee, S., & Lee, C. H. (2013). Time-dependent correlation of the mi- nology, 25, 525e532. crobial community and the metabolomics of traditional barley nuruk starter Lee, M. H., Lee, J., Nam, Y. D., Lee, J. S., Seo, M. J., & Yi, S. H. (2016). Characterization of fermentation. Bioscience Biotechnology and Biochemistry, 77, 683e690. antimicrobial lipopeptides produced by Bacillus sp. LM7 isolated from chung- Ramautar, R., Somsen, G. W., & de Jong, G. J. (2015). CE-MS for metabolomics: De- kookjang, a Korean traditional fermented soybean food. International Journal of velopments and applications in the period 2012-2014. Electrophoresis, 36, Food Microbiology, 221,12e18. 212e224. Lee, M. Y., Kim, H. Y., Singh, D., Yeo, S. H., Baek, S. Y., Park, Y. K., et al. (2016). Ray, M., Ghosh, K., Singh, S., & Chandra Mondal, K. (2016). Folk to functional: An Metabolite profiling reveals the effect of dietary Rubus coreanus vinegar on explorative overview of rice-based fermented foods and beverages in India. ovariectomy-induced osteoporosis in a rat model. Molecules, 21,1e19. Journal of Ethnic Foods, 3,5e18. Li, Y., Teng, Z., Parkin, K. L., Wang, Q., Zhang, Q., Luo, W., et al. (2014). Identification Rhee, S. J., Lee, J. E., & Lee, C. H. (2011). Importance of lactic acid bacteria in Asian of bioactive metabolites dihydrocanadensolide, kojic acid, and vanillic acid in fermented foods. Microbial Cell Factories, 10,1e13. soy sauce using GC-MS, NMR spectroscopy, and single-crystal x-ray diffraction. Romano, D., Gandolfi, R., Guglielmetti, S., & Molinari, F. (2011). Enzymatic hydrolysis Journal of Agricultural and Food Chemistry, 62, 8392e8401. of capsaicins for the production of vanillylamine using ECB deacylase from Lommen, A. (2009). MetAlign: Interface-driven, versatile metabolomics tool for Actinoplanes utahensis. Food Chemistry, 124, 1096e1098. hyphenated full-scan mass spectrometry data preprocessing. Analytical Chem- Santini, G., Mores, N., Penas, A., Capuano, R., Mondino, C., Trove, A., et al. (2016). istry, 81, 3079e3086. Electronic nose and exhaled breath NMR-based Metabolomics applications in Lubbe, A., Ali, K., Verpoorte, R., & Choi, H. Y. (2013). NMR-Based metabolomics airways disease. Current Topics in Medicinal Chemistry, 16,1610e1630. Analysis. In Metabolomics in practice : Successful strategies to generate and Scalbert, A., Brennan, L., Fiehn, O., Hankemeier, T., Kristal, B. S., van Ommen, et al. analyze metabolic data. (2009). Mass-spectrometry-based metabolomics: Limitations and recommen- Madsen, R., Lundstedt, T., & Trygg, J. (2010). Chemometrics in metabolomics-a re- dations for future progress with particular focus on nutrition research. view in human disease diagnosis. Analytica Chimica Acta, 659,23e33. Metabolomics, 5(4), 435e458. Mah, J. H., Kim, Y. J., & Hwang, H. J. (2009). Inhibitory effects of garlic and other Scheltema, R. A., Jankevics, A., Jansen, R. C., Swertz, M. A., & Breitling, R. (2011). spices on biogenic amine production in Myeolchi-jeot, Korean salted and fer- PeakML/mzMatch: A file format, Java library, R library, and tool-chain for mass mented anchovy product. Food Control, 20,449e454. spectrometry data analysis. Analytical Chemistry, 83, 2786e2793. McDowell, A., & Fukushima, E. (2008). Ultracompact NMR: 1H spectroscopy in a Scholz, M., Gatzek, S., Sterling, A., Fiehn, O., & Selbig, J. (2004). Metabolite finger- Subkilogram magnet. Applied Magnetic Resonance, 35,185e195. printing: Detecting biological features by independent component analysis. McGovern, P. E., Zhang, J., Tang, J., Zhang, Z., Hall, G. R., Moreau, R. A., et al. (2004). Bioinformatics, 20,2447e2454. Fermented beverages of pre- and proto-historic China. Proceedings of the Na- Seger, C., Sturm, S., & Stuppner, H. (2013). Mass spectrometry and NMR spectros- tional Academy of Sciences U S A, 101, 17593e17598. copy: Modern high-end detectors for high resolution separation techniques - Medina, S., Dominguez-Perles, R., Gil, J. I., Ferreres, F., & Gil-Izquierdo, A. (2014). state of the art in natural product HPLC-MS, HPLC-NMR, and CE-MS hyphen- Metabolomics and the diagnosis of human diseases-a guide to the markers and ations. Natural Products Reports, 30, 970e987. pathophysiological pathways affected. Current Medicinal Chemistry, 21, Shin, D., & Jeong, D. (2015). Korean traditional fermented soybean products: Jang. 823e848. Journal of Ethnic Foods, 2,2e7. Moon, Y. J., Baik, S. H., & Cha, Y. S. (2014). Lipid-lowering effects of Pediococcus Shin, E. C., Lee, J. H., Hwang, C. E., Lee, B. W., Kim, H. T., Ko, J. M., et al. (2014). acidilactici M76 isolated from Korean traditional makgeolli in high fat diet- Enhancement of total phenolic and isoflavone-aglycone contents and antioxi- induced obese mice. Nutrients, 6,1016e1028. dant activities during cheonggukjang fermentation of brown soybeans by the Nam, Y. D., Park, S. L., & Lim, S. I. (2012). Microbial composition of the Korean potential probiotic Bacillus subtilis CSY191. Food Science and Biotechnology, 23, traditional food “kochujang” analyzed by a massive sequencing technique. 531e538. Journal of Food Science, 77, 250e256. Shin, H. W., Jang, E. S., Moon, B. S., Lee, J. J., Lee, D. E., Lee, C. H., et al. (2016). Anti- Nile, S. H. (2015). The nutritional, biochemical and health effects of makgeolli -a obesity effects of gochujang products prepared using rice koji and soybean meju traditional Korean fermented cereal beverage. Journal of the Institute of Brewing, in rats. Journal of Food Science and Technology, 53,1004e1013. 121,457e463. Smith, C. A., Want, E. J., O'Maille, G., Abagyan, R., & Siuzdak, G. (2006). XCMS: Oh, Y. J., & Jung, D. S. (2015). Evaluation of probiotic properties of Lactobacillus and Processing mass spectrometry data for metabolite profiling using nonlinear Pediococcus strains isolated from Omegisool, a traditionally fermented peak alignment, matching, and identification. Analytical Chemistry, 78, 779e787. millet alcoholic beverage in Korea. LWT e Food Science and Technology, 63, Son, G. H., Kim, J., Muthaiya, M. J., Lee, S., Kim, H. Y., & Lee, C. H. (2011). Antimi- 437e444. crobial compounds profile during cheonggukjang fermentation against Xan- Oh, D. G., Jang, Y. K., Woo, J. E., Kim, J. S., & Lee, C. H. (2016). Metabolomics reveals thomonas oryzae pv. oryzae (Xoo). Journal of Microbiology and Biotechnology, 21, the effect of garlic on antioxidant- and protease-activities during 1147e1150. D. Singh et al. / Trends in Food Science & Technology 61 (2017) 103e115 115

Song, J. L., Choi, J. H., Seo, J. H., Lim, Y. I., & Park, K. Y. (2014). Anti-colitic effects of Wang, H., Jenner, A. M., Lee, C. Y., Shui, G., Tang, S. Y., Whiteman, M., et al. (2007). kanjangs (fermented soy sauce and sesame sauce) in dextran sulfate sodium- The identification of antioxidants in dark soy sauce. Free Radical Research, 41, induced colitis in mice. Journal of Medicinal Food, 17, 1027e1035. 479e488. Steinkraus, K. H. (1983). Traditional food fermentations as industrial resources. Acta Weckwerth, W., & Morgenthal, K. (2005). Metabolomics: From pattern recognition Biotechnologica, 3,3e12. to biological interpretation. Drug Discovery Today, 10, 1551e1558. Sugimoto, M., Kawakami, M., Robert, M., Soga, T., & Tomita, M. (2012). Bioinfor- Wilson, A. D., & Baietto, M. (2009). Applications and advances in electronic-nose matics tools for mass spectroscopy-based metabolomic data processing and technologies. Sensors (Basel), 9, 5099e5148. analysis. Current Bioinformatics, 7,96e108. Wilson, A. D. (2015). Advances in electronic-nose technologies for the detection of Sugiyama, A., Saitoh, M., Takahara, A., Satoh, Y., & Hashimoto, K. (2003). Acute volatile biomarker metabolites in the human breath. Metabolites, 5,140e163. cardiovascular effects of a new beverage made of wine vinegar and grape juice, Wu, W. J., Lee, H. Y., Lee, G. H., Chae, H. J., & Ahn, B. Y. (2014). The antiosteoporotic assessed using an in vivo rat. Nutrition Research, 23, 1291e1296. effects of cheonggukjang containing vitamin k2 (menaquinone-7) in ovariecto- Suh, D. H., Jung, E. S., Park, H. M., Kim, S. H., Lee, S., Jo, Y. H., et al. (2016). Comparison mized rats. Journal of Medicinal Food, 17, 1298e1305. of metabolites variation and antiobesity effects of fermented versus non- Yadav, H., Jain, S., & Sinha, P. R. (2007). Antidiabetic effect of probiotic dahi con- fermented mixtures of Cudrania tricuspidata, Lonicera caerulea, and soybean taining Lactobacillus acidophilus and Lactobacillus casei in high fructose fed rats. according to fermentation in vitro and in vivo. PLoS One, 11,1e15. Nutrition, 23,62e68. Tamang, J. P., Watanabe, K., & Holzapfel, W. H. (2016). Review: Diversity of micro- Yamamoto, S., Bamba, T., Sano, A., Kodama, Y., Imamura, M., Obata, A., et al. (2012). organisms in global fermented foods and beverages. Frontiers in Microbiology, 7, Metabolite profiling of soy sauce using gas chromatography with time-of-flight 1e28. mass spectrometry and analysis of correlation with quantitative descriptive Tanaka, Y., Watanabe, J., & Mogi, Y. (2012). Monitoring of the microbial communities analysis. Journal of Bioscience and Bioengineering, 114,170e175. involved in the soy sauce manufacturing process by PCR-denaturing gradient Yang, S. O., Kim, M. S., Liu, K. H., Auh, J. H., Kim, Y. S., Kwon, D. Y., et al. (2009). gel electrophoresis. Food Microbiology, 31,100e106. Classification of fermented soybean paste during fermentation by 1H nuclear t'Kindt, R., Morreel, K., Deforce, D., Boerjan, W., & Van Bocxlaer, J. (2009). Joint GC- magnetic resonance spectroscopy and principal component analysis. Bioscience MS and LC-MS platforms for comprehensive plant metabolomics: Repeatability Biotechnology and Biochemistry, 73, 502e507. and sample pre-treatment. Journal of Chromatography B, 877, 3572e3580. Yang, H. J., Kwon, D. Y., Chung, K. R., Park, S., & Pak, V. (2011). Fermented soybean Toro-Funes, N., Bosch-Fuste, J., Latorre-Moratalla, M. L., Veciana-Nogues, M. T., & products and their bioactive compounds. INTECH Open Access Publisher. Vidal-Carou, M. C. (2015). Biologically active amines in fermented and non- Zheng, C., Zhang, S., Ragg, S., Raftery, D., & Vitek, O. (2011). Identification and fermented commercial soybean products from the Spanish market. Food quantification of metabolites in 1H NMR spectra by Bayesian model selection. Chemistry, 173, 1119e1124. Bioinformatics, 27, 1637e1644. van den Berg, R. A., Hoefsloot, H. C., Westerhuis, J. A., Smilde, A. K., & van der Zhou, B., Xiao, J. F., Tuli, L., & Ressom, H. W. (2012). LC-MS-based metabolomics. Werf, M. J. (2006). Centering, scaling, and transformations: Improving the Molecular BioSystems, 8,470e481. biological information content of metabolomics data. BMC Genomics, 7,1e15.