Observations on the alpha-amylolysis pattern of some waxy maize starches from inbred line Ia453
2000
Maize starches of the endosperm mutants waxy (wx), dull:waxy (duwx), and amylose-extender:dull:waxy (aeduwx) from inbred line Ia453 lack amylose. However, in addition to high molecular weight (HMW) amylopectin, the duwx and aeduwx starches contained 40 and 80%, respectively, intermediate branched material of low molecular weight (LMW). As gelatinized, the amylopectin of the wx starch was easily hydrolyzed into small dextrins by the alpha-amylase of B. amyloliquefaciens, but components of duwx and aeduwx possessed partial resistance to amylolytic attack. Residual material of intermediate size obtained by a 4-hr alpha-amylolysis could not be separated from LMW dextrins by fractional precipitation in methanol. It is suggested that this material possessed a more regularly branched structure, in which the D-glucosyl chain segments were too short to allow alpha-amylase action. The granular starches of duwx and aeduwx genotypes were initially considerably more resistant than the wx sample to alpha-amylase attack. This was possibly due to an altered structure in the amylopectin component or the high content of intermediate material in the former granules.
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