Composition and thermodynamic properties of starches from facultative wheat varieties

Abstract

Effects of wheat variety and time of sowing on chemical composition and thermodynamic properties of starches isolated from grains of three facultative wheat varieties, which are spring varieties that can be grown either as winter or as spring ones, were estimated. Contents of proteins, lipids, amylose and phosphorus in starch granules as well as fatty acid profiles of surface lipids were determined. For each of the three wheat varieties, percentages of starch surface proteins and lipids (free and adsorbed on the surface of starch granules, FL and SSL) and gelatinization parameters of the isolated starches were significantly affected by sowing time. The impact of FL and SSL levels on starch gelatinization parameters and forms of amylose-lipid (AML) complexes was assessed by the differential scanning calorimetry (DSC). Spring-sowing of three tested wheat varieties resulted in reduced susceptibility to gelatinization of starches isolated from their grains, compared to starches derived from the winter-sown counterparts, due to higher percentages of both FL among total surface starch lipids (TSSL) and unsaturated fatty acids contained in TSSL as well as stronger interactions between surface lipids and proteins. The higher FL percentages among TSSL in starches from the spring-sown crops resulted in 1.8–3.8-fold higher percentages of AML complexes formed during gelatinization, compared to the winter-grown counterparts. During heating, these complexes were more prone to restructurization from the amorphous to stable crystalline form than AML complexes contained in the gelatinized starches from the winter-sown facultative wheat varieties.