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

Gelatinized starch gels of waxy maize and high-amylopectin potato were subjected to different time–temperature conditions, aiming at producing extensive amounts of retrograded amylopectin. The purpose was to investigate the impact of amylopectin retrogradation on the resistant starch formation and on the rate of starch digestion with porcine pancreatic α-amylase. Dried non-cycled gelatinized starch gels were used for comparison. Although differential scanning calorimetry measurements indicated higher amounts of retrograded material in the dried temperature-cycled gels no enzyme resistant starch 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 chain length distribution in the α-amylolysates was studied by high performance 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 distribution was uniform in the hydrolysates at the different stages of hydrolysis and independent of storage conditions, indicating that the mode of enzyme 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 the amylopectin, a phenomena that could be exploited when developing starchy foods with improved nutritional characteristics.