Effects of particle size and water content during cooking on the physicochemical properties and in vitro starch digestibility of milled durum wheat grains
2018
Guo, Peng | Yu, Jinglin | Wang, Shujun | Wang, Shuo | Copeland, Les
The effect of water content and particle size on physicochemical properties and in vitro starch digestibility of three milled wheat fractions was investigated. The crystallinity of three milled fractions of particle sizes <0.15 mm, 0.15–0.25 mm and 0.25–0.5 mm decreased from 36% to 25% after heating at 27.2% moisture, and was almost undetectable after heating with higher water contents. The short-range molecular order, as determined by Fourier transform infra-red and laser confocal micro-Raman spectroscopy, was reduced gradually with increasing water content during cooking. The enthalpy changes of the three milled fractions after heating with 27.2% water was decreased by about 45%, and no endothermic transition was observed after heating with higher water contents. The pasting viscosities first decreased and then increased as water content was increased during cooking. Heating at low water content increased greatly the in vitro enzymatic digestibility of starch in three milled fractions, and there were no further increase as the water content increased up to 72.7%. From this study, we conclude that water content plays a more important role in the disruption of ordered structure of starch, whereas particle size influences more greatly the in vitro starch digestibility of milled fractions.
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