The mechanism and effects of collagen amide group hydrolysis during liming

An important reaction during liming is the hydrolysis of the amide side-cha ins of asparagine and glutamine. There are two mechanisms by which the reac tion can proceed: direct hydrolysis, with hydroxyl catalysis, or intramolec ular catalysed hydrolysis. A consequence of the intramolecular mechanism is that the naturally occurring L-asparagine is racemised to:D-aspartic acid. It was found that there is no initial rise in the amount of D-aspartic acid during the first 24 hours of liming. Therefore, hydrolysis is dominated by the direct mechanism. Because the intramolecular mechanism depends on the protein conformation at the site of the reaction, it is concluded that, wit hin the conventional period of liming, collagen remains intact; that is, th ere is no appreciable breakdown of the structure, to alter the collagen con formation, which would allow the intramolecular hydrolysis mechanism to ope rate effectively.