Studies on alpha-amylase degradation of retrograded starch gels from waxy maize and high-amylopectin potato

Gelatinized starch gels of waxy maize and high-amylopectin potato were subj ected to different time-temperature conditions, aiming at producing extensi ve amounts of retrograded amylopectin. The purpose was to investigate the i mpact of amylopectin retrogradation on the resistant starch formation and o n the rate of starch digestion with porcine pancreatic alpha-amylase. Dried non-cycled gelatinized starch gels were used for comparison. Although diff erential scanning calorimetry measurements indicated higher amounts of retr ograded material in the dried temperature-cycled gels no enzyme resistant s tarch was detected in any of these samples. However, all cycled starch gels were less-readily degraded by the enzyme than the non-cycled gels. The cha in length distribution in the alpha-amylolysates was studied by high perfor mance anion exchange chromatography after debranching with isoamylase. The main products of hydrolysis were low molecular weight carbohydrates with a degree of polymerization of 1-9 and various branched dextrins. The chain di stribution was uniform in the hydrolysates at the different stages of hydro lysis and independent of storage conditions, indicating that the mode of en zyme action remained unaffected by retrogradation. The waxy maize and high- amylopectin potato starches responded similarly to temperature cycling. It was concluded that temperature cycling resulted in a slower hydrolysis of t he amylopectin, a phenomena that could be exploited when developing starchy foods with improved nutritional characteristics. (C) 2000 Elsevier Science Ltd. All rights reserved.