Sensory property, amino acid

Besides all the sensory and texturizing properties, GA has interesting antioxidant properties such as an efficient capacity for deactivation of excited electronic states and moderated radical scavenging capacity. There is increasing experimental evidence that associate the antioxidant function with its protein fraction, mainly by amino acid residues such as histidine, tyrosine and lysine, which are generally considered as antioxidants molecules (Marcuse, 1960,1962 Park et al., 2005). 

Proteins are important food components mainly due to their nutritional and functional value. Dietary proteins provide amino acids and nitrogen necessary for organisms. They also play a major role in determining the sensory and textural characteristics of food products. The functional properties are related to their ability to form viscoelastic networks, bind water, entrap flavors, emulsify fat and oil, and form stable foams [105]. 

Hernandez-Orte, R, Ibarz, M.J., Cacho, J., Ferreira, V. (2005). Effect of the addition of ammo-mum and amino acids to musts of Airen variety on aromatic composition and sensory properties of the obtained wine. Eood Chem., 89, 163-174. 

The protein efficiency ratio (PER) of sesame seed protein is 1.86 (35). The PER value can be raised to 2.9 when sesame seed protein is supplemented with lysine (36). El-Adawy (37) added sesame products including sesame meal, sesame protein isolate, and protein concentrate to red wheat flour to produce flour blends. It was found that water absorption, development time, and dough weakening were increased as the protein level increased in all blends however, dough stability decreased. Sesame products could be added to wheat flour up to 16% protein without any detrimental effect on bread sensory properties. The addition of sesame products to red wheat flour increased the contents of protein, minerals, and total essential amino acids the in vitro protein digestibility also increased significantly. 

Many microbial metabolites are volatile compounds and in terms of their sensory properties can be broken into two broad categories odorants and tastants (Table 1). Tastants include salty, sour, sweet, and bitter compounds such as amino acids, peptides, and sugars. Primary odorants typically are quite volatile and include carbonyl compounds, esters, and terpenes. There is considerable overlap between the two categories lactones, for example, have both taste and odor properties. In keeping with the theme of this symposium, volatile aroma substances will be the primary focus. 

This chapter deals with protein structure-function relationships resulting from proteolytic modification, covalent amino acid incorporation, and the effects of these enzymatic modifications on sensory and nutritional quality, on the functional properties, and on the biological activities of proteins and peptides. 

A proteinase-catalyzed reaction including splitting and synthesis of peptide bonds is a process also suitable for covalent amino acid incorporation into peptide chains. This type of enzymatic modification reaction of food proteins is useful for different purposes alteration of sensory properties, solubility, nutritional quality, functional properties, antifreeze character, and different biological activities. Recently, special proteinase-catalyzed reactions have been elaborated by which proteins can be modified with particular respect to their primary structure and conformation. 

A Tokyo group [46] was the first to propose a combined process of enzymatic protein hydrolysis and resynthesis for producing a product with improved sensory properties and modified amino acid composition. An enzymatic reaction was used also for the removal of bound impurities [108,109], for debittering of hydrolysates [47,110], and for decolorization of proteins of particular origin [111]. 

The main importance of lipids is their influence on sensory properties. They affect the texture (Chapter 4) and increase the viscosity of the morsel after mixing with saliva high viscosity is appreciated by most consumers. Their interaction products with amino acids, proteins, and sugars (see Chapter 17) have favorable effects on the color of food surfaces. Coating foods with a layer of oil produces glossy aspect and improves the appearance of the food product. 

Proteins affect several sensory properties such as appearance, color, texture, and flavor. Although most proteins have little flavor, they influence perceived flavor because they may contain bound off-flavors modify flavor by selective binding produce off-flavors or act as precursors of flavors through the Strecker degradation of amino acids [79]. 

Organoleptic Properties. Stereochemical differences of enantiomeric excipients may influence perception by sensory organs. Kutti [17] reported as early as 1886 that the interaction of stereoisomer with chiral receptors led to chiral discrimination as a consequence of the formation of diastereomers. He observed that the dextrorotatory asparagine has a sweet taste whereas the levorotatory form is tasteless. Greenstein and Winitz [18] and Solms et al. [19] reported such differences for many amino acids. Shallenberger et al. [20] reported that for some monosaccharides, both isomers have similar sweetness. In contrast, aspartame (A-aspartylalanine methyl ester) is marketed as the l,l isomer because it is more than 100 times as sweet as sucrose. However, the l,d diastereomer of aspartame is bitter [11], It should be noted that the individual differences of perception of these properties could vary. 

More detailed analysis has been conducted regarding the influence of capsaicin on the electrical properties of various types of neurons. God-fraind et al. (1980), recording from rat and chick sensory neurons in culture, found that capsaicin prolongs the duration of action potentials evoked by intracellular current injection. Salt and Hill (1980) investigated the effect of microiontophoretically applied capsaicin on trigeminal nucleus caudalis and cerebellar neurons in the rat and cat. The predominant response in the trigeminal nucleus was one of excitation or potentiation of amino acid-induced excitation while cerebellar neurons were either inhibited or unaffected. 

Hansen and Lund, 1987). In rye bread, compounds such as alcohols, esters and carbonyls have been identified (Hansen et al., 1989). Choice of fermentation temperature, dough yield, flour quality and starter culture all influence the sensory properties of the final bread. Free amino acids formed during fermentation increase Maillard reaction products, thus intensifying the taste. Sensory analysis has shown that sour dough rye breadcrumbs had the most intense and bread-like flavour compared with chemically acidified doughs (Hansen et al., 1989). 

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