Abstract:

Starch physicochemical properties include viscosity, crystallinity, gelatinization and thermal properties, which can directly or indirectly affect dough and final products qualities. Many researches showed that the correlation of starch granule size, amylose content and ratio of amylose content to amylopectin content with viscosity properties was significant. We studied starch viscosity property, damaged starch content and crystal property in different types (waxy or non-waxy) of wheat or wheat cultivars and their reciprocal relationship in Yangzhou University. Pasting properties of starch were measured by the Rapid Viscosity Analyser Super3 (Newport Co., Australia). Four different types of viscosity profiles were got. For strong-gluten wheat, final viscosity value was higher than peak viscosity value. For medium-gluten wheat, final viscosity value was slightly higher than peak value or almost the same. For weak-gluten wheat, final viscosity value was a little lower than peak value or almost the same. The pasting parameters of waxy wheat were lower than those of the others (non-waxy). There was significant difference in RVA profile among different cultivars with the same type (strong-gluten, mediate-gluten, weak gluten or waxy wheat), which induced the changes of pasting parameters after their reaching peak viscosity. During milling, some starch granules can be mechanically damaged. Different cultivars flour milled by Branbender mill had different damaged starch content, which were tested by SDmatic (Sweden). The order of damaged starch content of wheat flour was strong-gluten wheat>medium-gluten wheat>weak-gluten wheat>waxy wheat. X-ray diffraction of flour investigated with Diffractomes Bruker Axs D8 Advance (Germany) in different wheat cultivars showed their peaks at angle 15º, 20º, 23º, 17º, and 18º, which retained the typical A-type pattern. The order of intensities of X-ray diffraction peaks was 18º>17º>23º>15º>20º, which was the main difference among them. Degree of crystallinity ranged from 28.97%–36.97%. It might be concluded that amylose content, the ratio of amylose content to amylopectin content and damaged starch content have significant effects, while crystallinity has no significant effect on starch pasting properties.

Key words: Wheat (Triticum aestivum L.), Starch, Physicochemical properties