ReviewFormation of taste-active amino acids, amino acid derivatives and peptides in food fermentations – A review
Graphical abstract
Overview on the generation of taste compounds from proteins during food fermentation. Proteolysis generates taste active peptides and amino acids; glutathione reductase generates the kokum-active glutathione. Enzymatic conversions to taste active derivatives were proposed to be catalysed by lactoyl-transferase [2], succinyl transferase [3], pyroglutamyl cyclase [4], or by γ-glutamyl-transferase [5]. Maillard/Amadori products [6] are formed by chemical conversion during heating.
Introduction
Taste determines food selection, intake, absorption, and digestion, and thus contributes to the nutritional status as well as to decisions on food purchase (Barylko-Pikielna and Kostyra, 2007, Beksan et al., 2003). Six basic tastes, salt, sweet, and umami, sour, bitter, and oleogustus, are detected by taste receptors in taste buds on the tongue and palate epithelium (Running, Craig, & Mattes, 2015). Sweet, umami and bitter tastes are particularly related to food acceptance or rejection (Barylko-Pikielna & Kostyra, 2007). Sweet taste allows to identify carbohydrate-rich foods as a source of energy (Behrens, Meyerhof, Hellfritsch, & Hofmann, 2011); sweet taste receptors are absent in carnivores (Jiang et al., 2012). Umami molecules impart savory taste and increase other taste intensities (Jinap & Hajeb, 2010). Umami taste is linked to meat intake and umami taste receptors are typically absent in herbivores (Zhao, Yang, Xu, & Zhang, 2010). L-Glu and 5′-ribonucleotides elicit umami taste (Jinap & Hajeb, 2010). Humans reject bitter tasting foods, however, a limited level of bitterness in food may be desirable. Moreover, bitter taste reception in humans is highly variable (Meyerhof et al., 2010). Saltiness often determines the sensory acceptance of savory foods, such as soups, sauces, snacks, and bakery products (Schindler et al., 2011). However, salt intake in industrialized nations exceeds by 80–100% the amount recommended by WHO. Sodium reduction, achieved through partial replacement of sodium chloride with potassium chloride, a combination of different taste enhancers, such as glutamate, peptides or modified physical properties of food, has been investigated (Blesa et al., 2008, Schindler et al., 2011, Zhao et al., 2015). Kokumi-active compounds are not taste active but enhance the taste intensity of other compounds by modulation of the signal transduction from the taste receptors to the brain (Kuroda and Naohiro, 2015, Maruyama et al., 2012). The kokumi taste activity imparts mouthfulness, complexity, and long lasting taste (Ueda et al., 1997, Toelstede and Hofmann, 2008b, Toelstede et al., 2009).
Food fermentation is one of the oldest methods for food processing and traditional fermented foods are highly valued for their rich and complex taste and odour (Hutkins, 2006). The metabolic activity of food-fermenting microorganisms determines food quality, generates flavour, and enhances palatability. This communication aims to review the current knowledge related to taste active compounds in fermented foods, focussing on taste-active amino acids, amino acid derivatives, and peptides. The established or putative pathways of the generation of taste-active compounds are discussed for soy sauce, cheese, fermented meats, and bread. While these foods do not represent the diversity of fermented foods, they provide a cross-section of the different fermentation procedures, raw materials, and fermentation organisms that are employed in food fermentations (Hutkins, 2006, Gänzle, 2015). The conversion of sugars to organic acids is common to all food fermentations with lactic acid bacteria and is therefore not considered.
Section snippets
Generation of taste-active amino acids and peptides during food fermentation
Taste compounds are generated through primary proteolysis of the raw material by proteases from endogenous enzymes or microorganisms (Fig. 1 and Table 1), followed by secondary proteolysis, and enzymatic or chemical conversion of amino acids into derivatives. An overview on enzymes with putative or known contribution to the formation of taste active peptides or amino acids in fermented foods is provided in Table 2. Taste active peptides, amino acids, and amino acid derivatives are the
Soy sauce
Soy sauce is used as a condiment because of its umami and salty taste. The umami taste is attributed to amino acids, particularly Glu, Ala, and Asp (Kaneko et al., 2011, Lioe et al., 2004, Lioe et al., 2006). Although some small peptides including pGlu-Asp, pGlu-Val, and lac-Glu exhibit umami taste, their direct contribution is negligible due to their low concentration in soy sauce. However, these compounds provide the taste background and enhance other tastes (Noguchi et al., 1975, Oka and
Interaction between taste active amino acids and peptides and salt
NaCl tastes salty, masks metallic and bitter tastes, and enhances umami taste. Conversely, amino acids and peptides may enhance the salty taste and thus allow reducing salt levels in food. The salty taste of dry cured meat correlated to the concentrations of glutamate and aspartate (Careri et al., 1993). Omission tests with cheese indicated that arginine at subthreshold concentration significantly enhanced salty taste (Toelstede and Hofmann, 2008a, Toelstede et al., 2009). Perception of salty
Debittering in food fermentations
Bitterness limits the acceptance and marketing of food and is of particular concern in cheese production. Physical or chemical methods of debittering include the adsorption of bitter peptides on suitable resins, their extraction, or rely on masking agents including cyclodextrin and poly-γ-glutamate (Ley, 2008, Saha and Hayashi, 2001). Enzymatic debittering is achieved with transglutaminase or peptidases (FitzGerald & O'Cuinn, 2006). Unbalanced proteolysis is responsible for the formation of
Conclusions and perspectives
The generation of taste active compounds in food fermentation results from proteolysis and peptide hydrolysis in combination with amino acid conversion and formation of taste-active amino acid derivatives. Proteolysis in food fermentations is well understood, however, the elucidation of enzymes and metabolic pathways converting peptides or amino acids to taste-active derivatives is still in its infancy. The use of isogenic mutant strains in food fermentations in combination with chemical and
References (125)
- et al.
Study of taste-active compounds in the water-soluble extract of mature cheddar cheese
International Dairy Journal
(2010) - et al.
Effect of selected strains of Debaryomyces hansenii on the volatile compound production of dry fermented sausage “salchichón”
Meat Science
(2010) - et al.
Sensory interaction of umami substances with model food matrices and its hedonic effect
Food Quality and Preference
(2007) - et al.
Hydrolytic activity of Penicillium chrysogenum Pg222 on pork myofibrillar proteins
International Journal of Food Microbiology
(2003) - et al.
Microbiology and physico-chemical changes of dry-cured ham during the post-salting stage as affected by partial replacement of NaCl by other salts
Meat Science
(2008) Sourdough products for convenient use in baking
Food Microbiology
(2007)- et al.
Evaluation of bitterness in Ragusano cheese
Journal of Dairy Science
(2005) - et al.
Enzymatic debittering of food protein hydrolysates
Biotechnology Advances
(2006) - et al.
Comparison of different IlvE aminotransferases in Lactobacillus sakei and investigation of their contribution to aroma formation from branched chain amino acids
Food Microbiology
(2012) - et al.
Proteolysis in sourdough fermentations: Mechanisms and potential for improved bread quality
Trends in Food Science & Technology
(2008)