Benzaldehyde, enzymatic formation from

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],... 

The recycling of the undesired enantiomer from the enzymatic resolution is of crucial importance particularly on an industrial scale [107]. The classical chemical method consists of the thermal racemization of an amino acid ester at about 150-170°C. Milder conditions can be employed for the racemization of the corresponding amides via intermediate formation of Schiff bases with aromatic aldehydes such as benzaldehyde or salicylaldehyde (Scheme 2.14). More recently, intense research has been devoted to the use of isomerase enzymes (such as amino acid racemases [108]) aiming at the development of dynamic resolution processes. 

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