Characterization of Amylose-lipid Complexes Derived from Different Wheat Varieties and their Susceptibility to Enzymatic Hydrolysis

Starches from eight wheat varieties were analyzed for contents of dry matter, protein, pentosans, apparent and total amylose, total lipids, starch lipids, phosphorus, lysophospholipids and amylose-lipid complex (AML). Processes of starch gelatinization, reversible dissociation of AMLs and its susceptibility to degradation by α-amylase were monitored by differential scanning calorimetry (DSC). Degree of crystallinity of starches were evaluated based on X-ray diffraction pattern. Starches from different wheat varieties show some slight differences in terms of chemical composition, thermal properties and susceptibility to enzymatic hydrolysis. Endotherms and exotherms of most starch samples obtained by DSC contained single peaks, which indicated that AML complexes existed in one polymorphic form. Only AMLs formed by amylose from Symfonia cultivar was reflected by the double-peak exotherm on cooling of starch gel. Our studies showed that there was no correlation between AML content and enthalpy of its degradation in native starch. During enzymatic hydrolysis of starch AML complex in all examined starches underwent considerable degradation. Enthalpies of dissociation of AMLs, which remained after amylolysis were significantly lowered (80--90%) as compared to that of undigested starch. The susceptibility of AMLs to degradation by α-amylase did not depend on its amount (based on calculation from LPLs), but probably on its structure.