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Papain, chymotrypsin and related proteins—a comparative study of their beer chill-proofing abilities and characteristics

1981; Elsevier BV; Volume: 3; Issue: 1 Linguagem: Inglês

10.1016/0141-0229(81)90037-5

1879-0909

John F. Kennedy, Victor W. Pike,

Proteins in Food Systems

The role of proteolysis in the beer chill-proofing action of the proteolytic enzyme papain (EC 3.4.22.2) has been investigated by comparing the chill-proofing ability of papain with that of a proteolytically inactive derivative, S-carboxymethylpapain. The latter was prepared by treating papain with bromoacetic acid to carboxymethylate selectively the single essential sulphydryl group of the enzyme, that of l-cysteine-25. Both papain and S-carboxymethylpapain were found to exhibit increasing chill-proofing ability with increasing concentration in beer; at a protein concentration in beer of 30 μg/ml the chill-proofing effect of each protein proved to be substantial. Papain, either in the presence or absence of sodium bisulphite, was, however, found to be more effective than S-carboxymethylpapain at all protein concentrations. It is concluded that the chill-proofing action of papain originates largely, but not wholly, from its proteolytic action. Similarly, the chill-proofing ability of the proteolytic enzyme chymotrypsin (EC 3.4.21.1) has been compared with that of its proteolytically inactive zymogen, chymotrypsinogen A. Both proteins were found to exhibit increasing chill-proofing ability with increasing concentration in beer. The chill-proofing effect of chymotrypsin was, however, found to be greater than that of chymotrypsinogen A at all protein concentrations in beer. On the basis of these results and the close similarities in the molecular structures of chymotrypsin and chymotrypsinogen A, it is concluded that the chill-proofing action of chymotrypsin also originates largely, but not wholly, in its proteolytic action. The results from this study collectively demonstrate that no straightforward correlation exists between the proteolytic activity added to beer and its resistance to chill-haze formation.