In order to study the effects of γ-polyglutamic acid (γ-PGA) on the freeze-thaw stability of wheat starch gel, properties of wheat starch gel with different ratios of γ-PGA were measured, including aging enthalpy, moisture migration, crystallinity, and microstructure. The results showed that the aging enthalpy and aging rate of wheat starch gel decreased with increasing γ-PGA, and the aging rate decreased by 10.94% after seven freeze-thaw cycles, which enhanced the thermal stability of the starch gel. Moreover, after five freeze-thaw cycles, the proportion of deep-bound water in the starch gel increased by 3.19%, and the proportion of weakly bound water decreased by 1.63%. γ-PGA reduced ice crystals formation and water molecules migration. Furthermore, the crystal form of the starch gel did not change, but its crystallinity decreased by 3.55%. Besides, γ-PGA made the starch gel have uniformly distributed small pores and a more compact microstructure. In conclusion, γ-PGA inhibited the recrystallization of starch molecules, delayed starch aging and improved the freeze-thaw stability of wheat starch gel, and these effects were the most evident with 0.7% (w/w) γ-PGA. This paper provides a theoretical basis for protecting starch products from being frozen.
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