Hydrolytic action of alpha-amylase on high-amylose starch of low molecular mass
2000
Rendleman, J.A. Jr
High-amylose starches of low average degree of polymerization (dp 61-71), formed as fine granules by interaction of Bacillus macerans cyclodextrin glucanotransferase with alpha-cyclodextrin (CD) at 2-70 degreeC, are highly insoluble in water and not gelatinizable under normal cooking conditions (100 degreeC). Samples of CD-derived starches, both cooked and uncooked, were subjected to hydrolysis in vitro by human salivary alpha-amylase at 37 degreeC under conditions chosen to resemble those in the human intestinal lumen. Released low-molecular-mass saccharides were determined quantitatively by HPLC and the results compared with those from similar studies with natural starches. Among uncooked starches, CD-derived starch showed very low reactivity towards alpha-amylase, along with potato starch and a high-amylose hybrid corn starch (64% amylose). Cooking greatly enhanced reactivity of natural starches, but only moderately increased reactivity of CD-derived starches. Susceptibility to hydrolysis of cooked starches increased in the following general order: CD-derived starch (apprxeq 100% amylose) < 100% corn amylose (isolated by the butan-1-ol method) < hybrid high-amylose corn starch (64-66% amylose) < waxy maize starch (99-100% amylopectin) apprx ordinary corn starch (apprxeq 25% amylose) < potato starch (apprxeq 25% amylose).
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