Iranian Journal of Fisheries Sciences 18(4) 1101-1114 2019 DOI: 10.22092/ijfs.2019.118094 Chemical compositions, volatile compounds and sensory property of salted shrimp paste (Kapi) produced from Acetes vulgaris and Macrobrachium lanchesteri Pongsetkul J.1; Benjakul S.1*; Sumpavapol P.1; Vongkamjan K.1; Osako K.2 Received: March 2017 Accepted: October 2017 Keywords: Acetes vulgaris, Macrobrachium lanchesteri, Kapi, Volatile compounds, Sensory properties 1-Department of Food Technology, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai, Songkhla, Thailand, 90112 2-Department of Food Science and Technology, Tokyo University of Marine Science and Technology, 5-7 Konan 4, Minato-ku, Tokyo 108-8477, Japan *Corresponding author's Email: [email protected] Introduction orientalis). Since the last decade, krill Salted or fermented krill or shrimp stocks have drastically dropped by 3% pastes are widely consumed in many per year (Meland and Willassen, 2007). Asian countries including Thailand Two species of small shrimps: Acetes (Kapi), Indonesia (Terasi Udang), vulgaris and Macrobrachium Malaysia (Belacan), Philippines lanchesteri became potentially (Bagoong-alamang) or Vietnam (Mam alternative sources for Kapi production, ruoc), etc (Hajeb and Jinab, 2015). It is because their high availability often used to enhance palatability of throughout the years, especially in the many foods by providing desirable southern part of Thailand. To produce flavor and salty or umami taste. In salted shrimp paste, shrimps are mixed general, raw material, shrimp or with salt and ground into a fine paste. krill/salt ratio, fermentation process and Then, salted shrimps are sun-dried to time can be varied, depending on reduce their moisture content, followed regions or countries. The different by fermentation at room temperature characteristics and properties of those for approximately for 1 month products were reported (Peralta et al., (Pongsetkul et al., 2014). During 2008). fermentation, the protein hydrolysis Kapi, traditional salted shrimp paste occurs and is mediated by the action of of Thailand, is traditionally made from indigenous and microbial proteases. planktonous krill (Mesopodopsis These phenomena yield short chain 1102 Pongsetkul et al., Chemical compositions, volatile compounds and sensory property of… peptides and free amino acids, which Furthermore, relationship between enhance the flavor and taste of final volatile compounds and sensory product (Pongsetkul et al., 2015a, b). properties of both Kapi, and Kim et al. (2014) reported that short commercial Kapi was also studied chain peptides and free amino acids of using principal component analysis Korean shrimp paste significantly (PCA). increased during the fermentation period and could be responsible for the Materials and methods unique flavor of the product. The Sample collection formation of Maillard reaction products Shrimps (A. vulgaris and M. (MRPs) was also observed throughout lanchesteri) were caught from the coast fermentation of Philippine salt- in Ko-yo and The-Pha in Songkhla fermented shrimp paste and related with province, Thailand, respectively. After the darker/browner color of the final capture, shrimp were transported in ice product (Peralta et al., 2008). with a shrimp/ice ratio of 1:2 (w/w) in a Moreover, some fermented shrimp polystyrene container to the Department products exhibited the strong of Food Technology, Prince of Songkla antioxidant activities (Faithong et al., University, Hat Yai, Thailand, within 2010; Kleekayai et al., 2015). approximately 2 h. Flavor or aroma is one of the most important factors in Kapi quality Preparation of Kapi (Phithakpol, 1993). The characteristic Shrimps were mixed with salt at the flavor and aroma are primarily due to ratio of 5:1 (w/w) and transferred into protein and lipid degradation by the basket, covered with the cheese autolytic and bacterial enzymes during cloth. The mixture was kept at room fermentation, governed by different raw temperature (28-32°C) overnight. Then, material, process employed, as well as the drained samples were mashed or strains of microorganism involved pounded thoroughly and spread out on (Saisithi et al., 1966). Several volatile fiberglass mats to dry with sunlight. components of shrimp paste products The drying step was continued until were associated with their flavors (Cha samples disintegrate and turned from and Cadwallader, 1995; Wittanalai et pink to dark purplish brown (with the al., 2011; Kang and Baek, 2014; moisture content of 35-40%). Pongsetkul et al., 2014). Nevertheless, Subsequently, samples were transferred a little information regarding chemical into earthen jars, covered with plastic compositions, especially volatiles as bag tightly (close system), and allowed well as sensory property of Kapi, to ferment at room temperature. After produced from A. vulgaris and M. 30 days of fermentation, Kapi were lanchesteri has been reported. collected and referred to as KA (Kapi Therefore, this investigation aimed to produced from A. vulgaris) and KM comparatively characterize Kapi (Kapi produced from M. lanchesteri). produced from both shrimps. Iranian Journal of Fisheries Sciences 18(4) 2019 1103 The obtained samples were subjected to Browning products analyses. Preparation of water extract Kapi (1 g) was mixed with 25 ml of Characterization of Kapi produced distilled water. The mixtures were from A. vulgaris and M. lanchesteri homogenized at a speed of 11,000 rpm pH and water activity (Aw) for 2 min, followed by centrifugation at The pH of samples was measured 8,500 ×g for 15 min at room according to the method of Nirmal and temperature. The supernatant was Benjakul (2009) using a pH meter collected and adjusted to 25 mL using (Sartorius, Gottingen, Germany). Aw of distilled water before analyses. Kapi was determined using a water activity analyzer (Thermoconstanter, Measurement of browning products Novasina, Switzerland). After being diluted, the water extracts were measured for browning intensity Proximate composition (A420) and Maillard reaction products Moisture, ash, fat, protein and (A280 and A295) using the UV-1601 carbohydrate contents of Kapi were spectrometer (Shimadzu, Kyoto, Japan). determined according to AOAC method The fluorescence intensity at an (2000) with the analytical No. of excitation wavelength of 347 nm and 35.1.13, 35.1.14, 35.1.25, 35.1.15 and emission wavelength of 415 nm was 35.1.16, respectively. also determined using a fluorescence spectrophotometer RF-1501 (Shimadzu, Salt content Kyoto, Japan). Salt content was determined as per AOAC (2000) with the analytical Volatile compounds number of 35.1.18 and was expressed To extract volatile compounds, samples as %NaCl. (5 g) were mixed with 10 mL of deionized water. The mixture was Color homogenized at a speed of 13,000 ×g The color of samples was determined for 1 min to disperse the sample. The using a colorimeter (ColourFlex, homogenate was placed in a 20-mL Hunter Lab Reston, VA) with the CIE headspace vial (Supelco, Bellefonte, system. L* (lightness), a* PA, USA) and determined using a (redness/greenness), b* solid-phase micro-extraction gas (yellowness/blueness), ΔE* (total chromatography mass spectrometry difference of color) and ΔC* (the (SPME GC-MS) as per the method of difference in chroma) were recorded as Iglesias and Medina (2008) as detailed described by Pongsetkul et al. (2014). by Takeungwongtrakul and Benjakul (2013). Volatile compounds were identified and expressed in the terms of relative abundance. 1104 Pongsetkul et al., Chemical compositions, volatile compounds and sensory property of… Sensory evaluation 1998). For PCA (Principal Component The 50 untrained panelists, who Analysis), the XLSTAT Software consumed Kapi regularly, were used for (XLSTAT, 2008, Addinsoft, New York, evaluation. The samples were wrapped NY, USA) was used. with aluminium foil and heated in hot air oven at 60°C for 30 min. After Results and discussion cutting into small pieces (2×2×1 cm2), Characteristics and properties of Kapi samples were placed in 15-mL plastic pH, water activity (Aw) and proximate cup, covered with lids and left at room composition temperature for 30 min before serving. As shown in Table 1, Kapi produced The panelists were asked to open the lid from A. vulgaris (KA) and M. and sniff. Between the samples, lanchesteri (KM) had the neutral pH. panelists rinsed their mouth with water KM had the slightly higher basic pH or cracker. Scores for appearance, (7.27), compared with KA (7.16) color, odor, flavor, texture and overall (p<0.05). The slightly basic pH might likeness using a 9-point hedonic scale be caused by the basic degradation were recorded. products generated during postmortem storage of raw material or the formation Principal component analysis (PCA) of volatile base compounds such as PCA was performed to access the ammonia during fermentation of relationship between volatile samples (Pongsetkul et al., 2014). The compounds, odor-liking, flavor-liking pH of Korean dried shrimp paste was in and overall-liking score of Kapi the range of 6.83-7.23 (Cho and Kim, produced from A. vulgaris and M. 2010), while Fillipino fermented shrimp lanchesteri, as well as commercial Kapi paste had pH of 7.50 (Montano et al., produced from krill (Mesopodopsis 2001). The pHs of those shrimp pastes orientalis) obtained from different were similar to those of Kapi in the provinces in Thailand, including Krabi, present study. Both samples had no Samut Sakhon and Rayong. differences in water activity (Aw) (p>0.05). Aw of both Kapi was in the Statistical analysis range of 0.6-0.7, which could be Completely randomized design (CRD) classified as an intermediate moisture was used throughout the study. All food (Fennema, 1996). This was experiments were run in triplicate. Data associated with the prolonged shelf-life were subjected to analysis of variance of this product due to the lowered (ANOVA), and mean comparisons growth of food pathogens and spoilage were carried out by the Duncan’s microorganisms (Chirife, 1989). Low multiple range test. Independent T-test Aw of Kapi samples were in agreement was performed for pair comparison with the low moisture content.