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Observations on the α-Amylolysis Pattern of Some Waxy Maize Starches from Inbred Line Ia453

¹Department of Biochemistry and Pharmacy, Åbo Akademi University, BioCity, P.O. Box 66, FIN-20521 Turku, Finland. ²Corresponding author: Fax: +358-2-2154745. E-mail: eric.bertoft@abo.fi ³Oregon State University, Department of Horticulture, Agriculture and Life Science 4017, Corvallis, OR 97331-7304.

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 α-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 α-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 α-amylase action. The granular starches of duwx and aeduwx genotypes were initially considerably more resistant than the wx sample to α-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.