* ViewManuscript metadata, withcitation Line and similarNumbers papers at core.ac.uk brought to you by CORE Click here to view linked References provided by Digital.CSIC 1 2 3 Food phenolics and lactic acid bacteria 4 5 6 Héctor Rodríguez a, José Antonio Curiel a, José María Landete a, Blanca de 7 las Rivas a, Félix López de Felipe b, Carmen Gómez-Cordovés a, José 8 Miguel Mancheño c, Rosario Muñoz a,* 9 10 11 12 a Departamento de Microbiología, Instituto de Fermentaciones Industriales, CSIC, Juan 13 de la Cierva 3, 28006 Madrid, Spain 14 b Grupo en Biotecnología de Bacterias Lácticas de Productos Fermentados, Instituto del 15 Frío, CSIC, José Antonio de Novaís 10, 28040 Madrid, Spain 16 c Grupo de Cristalografía Macromolecular y Biología Estructural, Instituto Rocasolano, 17 CSIC, Serrano 119, 28006 Madrid, Spain 18 19 20 21 *Corresponding author. Tel.: +34-91-5622900; fax: +34-91-5644853 22 E-mail address: [email protected] (R. Muñoz) 23 24 1 25 Abstract 26 27 Phenolic compounds are important constituents of food products of plant 28 origin. These compounds are directly related to sensory characteristics of foods 29 such as flavour, astringency, and colour. In addition, the presence of phenolic 30 compounds on the diet is beneficial to health due to their chemopreventive 31 activities against carcinogenesis and mutagenesis, mainly due to their antioxidant 32 activities. Lactic acid bacteria (LAB) are autochthonous microbiota of raw 33 vegetables. To get desirable properties on fermented plant-derived food products, 34 LAB has to be adapted to the characteristics of the plant raw materials where 35 phenolic compounds are abundant. Lactobacillus plantarum is the commercial 36 starter most frequently used in the fermentation of food products of plant origin. 37 However, scarce information is still available on the influence of phenolic 38 compounds on the growth and viability of L. plantarum and other LAB species. 39 Moreover, metabolic pathways of biosynthesis or degradation of phenolic 40 compounds in LAB have not been completely described. Results obtained in L. 41 plantarum showed that L. plantarum was able to degrade some food phenolic 42 compounds giving compounds influencing food aroma as well as compounds 43 presenting increased antioxidant activity. Recently, several L. plantarum proteins 44 involved in the metabolism of phenolic compounds have been genetically and 45 biochemically characterized. The aim of this review is to give a complete and 46 updated overview of the current knowledge among LAB and food phenolics 47 interaction, which could facilitate the possible application of selected bacteria or 48 their enzymes in the elaboration of food products with improved characteristics. 49 2 50 Contents 51 52 1. Introduction 53 2. Lactic acid bacteria in fermented food products of plant origin 54 3. Influence of phenolics on the growth and viability of lactic acid bacteria 55 3.1. Lactobacillus plantarum 56 3.2. Other lactic acid bacteria species 57 4. Metabolism of food phenolics by lactic acid bacteria 58 4.1. Lactobacillus plantarum 59 4.1.1. Tannase 60 4.1.2. Phenolic acid decarboxylase 61 4.1.3. Benzyl alcohol dehydrogenase 62 4.2. Other lactic acid bacteria species 63 5. Treatment of food by-products by lactic acid bacteria 64 6. Conclusions 65 Acknowledgments 66 References 67 68 69 3 70 1. Introduction 71 72 In the last years, researchers and food manufacturers have become increasingly 73 interested in phenolic compounds. The reason for this interest is the recognition of their 74 antioxidant properties, their great abundance in our diet, and their probable role in the 75 prevention of various diseases associated with oxidative stress, such as cancer, and 76 cardiovascular and degenerative diseases (Manach et al., 2004). 77 The term “phenolic compound” described several hundred molecules found in 78 edible plants that possess on their structure a benzenic ring substituted by, at least, one 79 hydroxyl group. These compounds may be classified into different groups as a function 80 of the number of phenol rings that they contain and of the structural elements that bind 81 these rings to one another. Distinctions are thus made between phenolic acids (benzoic 82 or hydroxycinnamic acid derivatives), flavonoids, stilbenes, and lignans. The flavonoids 83 may themselves be divided into flavonols, flavones, isoflavones, flavanones, 84 anthocyanidins, and flavanols (catechins and proanthocyanidins). In addition to this 85 diversity, polyphenols may be associated with various carbohydrates and organic acids 86 (Manach et al., 2004). 87 Traditionally, and from a basic knowledge, phenolic compounds have been 88 considered nutritionally undesirable because they precipitate proteins, inhibit digestive 89 enzymes and affect the utilization of vitamins and minerals, reducing the nutritional 90 values of foods. However, the recent recognition of their antioxidant properties reduced 91 the investigations of their adverse health effects. The presence of phenolic compounds 92 on the diet is beneficial to health due to their chemopreventive activities against 93 carcinogenesis and mutagenesis. The health effects of phenolic compounds depend on 4 94 the amount consumed and on their bioavailability (Chung et al., 1998; Shen et al., 95 2007). 96 In addition to having nutritional and antioxidant properties, phenolic compounds 97 influence multiple sensorial food properties, such as flavour, astringency, and colour. 98 Phenolic compounds contribute to the aroma and taste of numerous food products of 99 plant origin. The contribution of phenolic compounds to aroma is mainly due to the 100 presence of volatile phenols. Volatile phenols could be produced by the hydrolysis of 101 superior alcohols or by the metabolism of microorganisms, yeast and LAB. In addition, 102 food phenolics also contribute to food astringency. Some phenolic substances, mostly 103 tannins, present in foods are able to bring about a puckering and drying sensation 104 referred to as astringency which is related to the ability of the substance to precipitate 105 salivary proteins (Lea and Arnold, 1978). Moreover, phenolic compounds are natural 106 food pigments that greatly influence the colour of vegetable food products. Among 107 flavonoids, the anthocyanins are responsible for the pink, scarlet, red, mauve, blue and 108 violet colors of vegetables, fruits, fruit juices and wine (Harborne, 1988). Most 109 flavonoids are present in plant cells in the form of glycosides. 110 Fruits, vegetables and beverages, such as tea, are the main sources of phenolic 111 compounds in the human diet (Kapur and Kapoor, 2001). The Mediterranean diet 112 includes fermented vegetable food products, such as wine and table olives, for which 113 phenolic compounds are responsible of some of their sensorial and nutritional 114 characteristics. 115 116 2. Lactic acid bacteria in fermented food products of plant origin 117 5 118 Vegetables are strongly recommended in the human diet since they are rich in 119 antioxidant, vitamins, dietary fibres and minerals. The major part of the vegetables 120 consumed in the human diet are fresh, minimally processed, pasteurized or cooked by 121 boiling in water or microwaving. Minimally processed and, especially, fresh vegetables 122 have a very short-life since subjected to rapid microbial spoilage and the above cooking 123 processes would bring about a number of not always desirable changes in physical 124 characteristics and chemical composition of vegetables. Among the various 125 technological options, fermentation by lactic acid bacteria (LAB) may be considered as 126 a simple and valuable biotechnology for maintaining and/or improving the safety, 127 nutritional, sensory and shelf-life properties of vegetables. Lactic acid fermentation of 128 vegetables has nowadays an industrial significance for cucumbers, cabbages and olives. 129 Several other varieties of vegetables (e.g., carrots, French beans, marrows, artichokes, 130 capers and eggplants) also increase their safety, nutritional, sensory and shelf-life 131 properties through lactic acid fermentation under standardized industrial conditions. 132 Composition of microbiota and its development are important factors 133 influencing fermentation and final product quality. Overall, LAB are a small part of the 134 autochthonous microbiota of raw vegetables. To get desirable properties of fermented 135 vegetable food products, LAB has to be adapted to the intrinsic characteristics of the 136 raw materials. Spontaneous fermentations typically result from the competitive 137 activities of a variety of autochthonous and contaminating microorganisms. Those best 138 adapted to the conditions during the fermentation process will eventually dominate. 139 Initiation of a spontaneous process takes a relatively long time, with a high risk for 140 failure. Failure of fermentation processes can result in spoilage and/or the survival of 141 pathogens, thereby creating unexpected health risks in food products. Thus, from both a 142 hygiene and safety point of view, the use of starter cultures is recommended, as it would 6 143 lead to a rapid acidification of the product and thus inhibit the growth of spoilage and 144 pathogenic bacteria, and to a product with consistent quality. Although a large number 145 of LAB starters are routinely used in dairy, meat and baked food fermentations, only a 146 few cultures have been used for vegetable fermentations. Lactobacillus plantarum is the 147 commercial starter most