Cereal Chem 67:217-221   |  VIEW ARTICLE

Enzyme-Resistant Starch. II. Differential Scanning Calorimetry Studies on Heat-Treated Starches and Enzyme-Resistant Starch Residues.

D. Sievert and Y. Pomeranz. Copyright 1990 by the American Association of Cereal Chemists, Inc. 

Enzymatic assay of heat-treated starches from amylomaize VII, regular maize, wheat, peas, and potatoes indicated that enzyme-resistant starch (RS) was present in all treated starches. The RS residues exhibited an endothermic transition at approximately 155 C in the differential scanning calorimetry (DSC) thermogram, which apparently was due to melting of recrystallized amylose. However, with the exception of amylomaize starch, amylose crystallites could not be detected directly in treated starches by the DSC technique. Only after degradable starch structures were removed and enzyme-resistant amylose crystallites were isolated and concentrated, could their dissociation be recorded. RS residue from amylomaize VII, regular maize, and wheat starch showed an additional small endothermic thransition between 41 and 67 C. Thermoanalytical characteristics of this transition were investigated using RS residues from amylomaize VII starch preparations. A DSC run of vacuum-dried RS residues with and without added water led to formation of the peak at 54 C. After cooling the residues, an exothermic transition occurred, i.e., the transformation was thermoreversible. Reheating and cooling of vacuum-dried RS in the calorimeter revealed that even temperatures up to 180 C did not completely destroy the structures responsible for peak formation. The role of starch, proteins, and lipids in generating the 54 C transition was investigated. The findings suggested that uncomplexed lipid components induced formation of this endotherm in some RS residues. Protein derived from amylolytic anzymes used in the enzymatic assay also seemed to play a role in generation of the endotherm.