Effects of Xanthan Gum and Guar Gum on the Freeze-thaw Stability of Wheat Starch
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Abstract:
Wheat starch was mixed with xanthan gum and guar gum at different mixing ratios, and detection of water syneresis rate, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were performed to study the effects of hydrocolloids (xanthan gum and guar gum) on the freeze-thaw stability of wheat starch after five freeze-thaw cycles. The results showed that the water syneresis rate of the wheat starch was enhanced with increasing freeze-thaw cycle number; xanthan gum and guar gum significantly decreased the water syneresis rate, thus inhibiting wheat starch aging during the freeze-thaw process. Additionally, the improvements in freeze-thaw stability were more significant with increasing hydrocolloid concentrations. After five wheat starch freeze-thaw cycles, a large number of holes were formed in the starch gum matrix, and some discontinuous silk- and fiber-like structures were formed, with a thin substrate. With the addition of hydrocolloids, the apparent structure of wheat starch changed: the number of holes decreased, the starch substrate was thickened, and a sheet-like network structure was formed. Therefore, both xanthan gum and guar gum can improve the freeze-thaw stability of wheat starch and the improvements from via hydrocolloids addition are concentration-dependent.
