Amino acids organoleptic properties

For us to remain perfectly healthy, the protein in our diet must supply suffident quantities of amino acids. We prefer to eat our protein in particular forms, that is in foods having particular textures, tastes and smells (these are called organoleptic properties). Conventional sources of protein are plants, mainly as cereals and pulses, and animals, mainly as meat, eggs and milk. The proportions of such proteins eaten in various parts of the world differ widely (Figure 4.1). 

Proteins are one of the most important ingredients in food production for both animals and humans. Besides having nutritional properties, protein contributes to the functional and organoleptic properties of food. The nutritional value of a protein depends on the total essential amino acid content. However, the availability of amino acids is conditioned by some protein attributes, mainly digestibility. 

In 1981 a study was undertaken in Poland on 680 samples of rubber products used in food processing plants. In 35% of the samples migration of metals/ metalloids into 3% acetic acid was reported (14% of the samples contained lead, 2.6% arsenic and 3% barium). The known carcinogen phenyl-feeto-naphthylamine was found in 15.1% of the compounds, with amino type antioxidants being detected in 23% of the compounds in total. Poor organoleptic properties were found in 22.1% of the samples. Migration of accelerators... 

It has been demonstrated that tocopherols in hnoleic safflower oil were more stable than tocopherols in oleic safflower oil (150). The USDA did room odor studies that showed that oleic safflower did well compared with all other oils used in the study (151). A broad study was conducted of the effects of various substances on the oxidation of safflower oil in deep frying (152) of high temperature reactions in the presence of amino acids (153) and of the effect of amino acids on emulsions (154), dried emulsions (155, 156), and chemical and organoleptic properties (155, 156). 

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. 

The following sections deal with important amino acids, peptides and proteins, their structure, occurrence, properties, fate in the human organism, nutritional aspects and important interactions and reactions that fundamentally affect the nutritional value, organoleptic properties (odour, taste, colour and texture) and the hygienic-toxicological quahty of food commodities. 

The process of protein biosynthesis is called translation. Post-translational oxidation, alkylation and esterification of some amino acids that are bound in proteins yield modified proteinogenic amino acids (see Section 2.2.1.1.2). Non-proteinogenic (non-encoded, non-standard or secondary) amino acids do not function as building blocks of proteins, as they have other roles in organisms. Amino acids also have an influence on the organoleptic properties of food, especially on their taste. Products of reactions of amino acids are often important compounds influencing odour, taste and colour of foods. 

Some amino acids are sensorially active substances, which can therefore influence the organoleptic properties of food. For example, glycine has a sweet taste (70% of the sweetness of sucrose) and is sometimes mixed with saccharin as a sweetening agent. According to their organoleptic properties, the proteinogenic amino acids can be classified as ... 

Table 8.9 Organoleptic properties of aldehydes arising from amino acids and fatty acids.

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