Cheese protein degradation

Clegg, K. M., Lee, Y. K., and McGilligan, J. F. (1982). Trinitrobenzene sulfonic acid and ninhydrin reagents for the assessment of protein degradation in cheese samples. /. Food Technol. 17, 517-520. 

Cheese becomes progressively firmer (i.e., requires a higher compression force to induce fracture), more cohesive, mealier, and drier, and the structure of the protein matrix becomes coarser and more compact (fused), with increasing concentration factor. The reduced rates of protein degradation result in slower softening and flavor development during maturation. 

Degradation of proteins by proteases has important implications for the quality of many foods. These include beneficial effects in the development of desirable attributes, such as texture and flavor, e.g. in cheese manufacturing, meat tenderization, beer brewing, soy and fish sauce manufacturing, and production of protein hydrolysates of various origins for different functional or nutritional purposes. The proteases involved may be endogenous to the foods or they may be added for specific pur-... 

Production and processing of many food products (e.g. cheese, soya sauce and beer) involves enzymatic degradation of the proteins. This has increased the scientific interest in proteases which in turn has led to new applications. Proteases catalyse the degradation of food proteins originate from three sources ... 

Table 1 shows the taste profile obtained for crude cheese, reconstituted cheese made vnth homogenized proteins, fat with and without WSE, and WSE. Their comparison allowed the impact of each fiaction on the taste of the cheese to be evaluated. The omission of WSE led to a tasteless product, showing that WSE contained all the taste-active compounds. In reconstituted cheese where the structure of die matrix was almost totally degraded, bitterness was weaker and saltiness higher than in crude cheese (Table 2). The omission of fat and proteins from the reconstituted cheese caused an increase of saltiness and a decrease of bitterness compared to crude cheese. These data demonstrated that, in the crude cheese, the matrix structure partially masked the saltiness and increased the bitterness due to taste-active compounds. In addition, the comparison with results obtained with grated cheese in which the destructuring was intermediate between crude and reconstructed cheese for the same taste descriptors (Table 2) confirmed that the more die matrix was destructured, the more the bitterness increased and die saltiness decreased. Thus, cheese taste might be explained by the taste of die WSE containing the taste-active compounds modulated by the masking effect of both fat and proteins but also by an effect linked to the cheese mafrbc structure.

Traditionally fermented dairy products have been used as beverages, meal components, and ingredients for many new products [60], The formation of flavor in fermented dairy products is a result of reactions of milk components lactose, fat, and casein. Particularly, the enzymatic degradation of proteins leads to the formation of key-flavor components that contribute to the sensory perception of the products [55], Methyl ketones are responsible for the fruity, musty, and blue cheese flavors of cheese and other dairy products. Aromatic amino acids, branched-chain amino acids, and methionine are the most relevant substrates for cheese flavor development [55]. Volatile sulfur compounds derived from methionine, such as methanethiol, dimethylsulflde, and dimethyltrisul-fide, are regarded as essential components in many cheese varieties [61], Conversion of tryptophan or phenylalanine can also lead to benzaldehyde formation. This compound, which is found in various hard- and soft-type cheeses, contributes positively to the overall flavor [57,62]. The conversion of caseins is undoubtedly the most important biochemical pathway for flavor formation in several cheese types [62,63]. A good balance between proteolysis and peptidolysis prevents the formation of bitterness in cheese [64,65],... 

Tyramine is formed in foods such as cheese by the bacterial degradation of milk and other proteins, firstly to tyrosine and other amino acids, and the subsequent deearboxylation of the tyrosine to tyramine. This interaction is therefore not associated with fresh foods, but with those which have been allowed to over-ripen or mature in some way, or if spoilage occurs. Tyramine is an indirectly-acting sympathomimetic amine, one of its actions being to release noradrenaline (norepinephrine) from the adrenergic neurones associated with blood vessels, which causes a rise in blood pressure by stimulating their constriction. ... 

Proteolytic enzymes. Proteolytic enzymes produced by starter organisms usually play a key role in the degradation of milk caseins to oligopeptides, smaller peptides and amino acids in fermented dairy products and cheese. Besides being necessary for normal growth of lactococci in milk, this degradation of proteins is important for the development of flavour and texture in cheese. 

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