Hydrolysis of amylopectin by amylolytic enzymes: level of inner chain attack as an important analytical differentiation criterion

Abstract

Differences in amylase action pattern on amylopectin were demonstrated by the relation between the decrease in potassium iodide–iodine binding of waxy maize starch and the increase in reducing value during hydrolysis, as expressed by the RV 80 value (i.e., the reducing value for a potassium iodide–iodine binding value of 80% of that of the starting material). In the initial stages of the hydrolysis, the ratio of the increase in the level of reducing polysaccharides to the increase in the total level of reducing sugars formed during amylolysis of amylopectin can be considered as a measure of the level of inner chain attack (LICA) in the overall hydrolysis of the amylopectin structure and correlated with the respective RV 80 value. Bacillus amyloliquefaciens α-amylase and Aspergillus oryzae α-amylase, with the lowest RV 80 and the highest LICA values, hydrolysed the inner chains of amylopectin to a greater extent than did porcine pancreatic α-amylase. In the initial stages of hydrolysis, Bacillus stearothermophilus maltogenic amylase, like the Bacillus cereus β-amylase, did not display any significant degree of internal hydrolysis of amylopectin, in line with the high RV 80 and very low LICA values for these enzymes. However, at the later stages of hydrolysis, the maltogenic amylase probably exhibited a significant degree of internal hydrolysis of amylopectin, which itself seems to depend on temperature. The temperature dependence of the hydrolysis pattern of this enzyme is relevant for interpretation of its action as antifirming enzyme in bread-making applications.