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Hydrolytic enzyme activities as indicators of fungal spoilage in bakery products



Cake analogues were prepared at different aw (0.80, 0.85 and 0.90) and pH (6 and 7.5) levels and inoculated with a range of seven representative moulds of spoilage mycoflora of bakery products. The responses recorded were colony radii after 1, 2, 3 and 4 weeks as well as microbial counts and total and specific activities of six hydrolytic enzymes after 4 weeks. Multivariate analysis was applied in order to determine correlations among the responses and thus assess the suitability of using enzyme activities as estimators for fungal growth. The results showed that enzyme activities correlated with growth parameters for Aspergillus and Penicillium isolates, although the useful enzymes were not the same for the three isolates tested. The correlation was poor, however, for Eurotium isolates. In general, specific activities of some enzymes showed better correlation with growth parameters, with α-D-galactosidase, β-D-galactosidase, β-D-glucosidase and N-acetyl-β-D-glucosaminidase being the more useful enzymes among those assayed.

© 2003 Society of Chemical Industry