Antifreeze Protection Effect of Gamma-polyglutamic Acid on Frozen Dough and Noodles

The aim of this work was to explore the antifreeze protection effect of high molecular weight γ-poly glutamic acid(γ-poly glutamic acid,γ-PGA,molecular weight about 1000000)and low molecular weight γ-PGA(molecular weight<50000)on frozen dough and noodles after different freezing time. A differential scanning calorimeter(DSC)was used to determine the freezable water contents in the dough. A rotational rheometer was used to measure the storage modulus and loss modulus of the dough. Texture profile analysis(TPA)was used to measure the hardness,gumminess and chewing properties of frozen dough. Cooking performance tests were carried out on frozen noodles and their cooking absorption was tested. The results showed that the endothermic enthalpy and freezable water contents of dough with 0.5% and 2% low molecular weight γ-PGA were significantly lower than that of 2% high molecular weight γ-PGA group and the control group during the frozen storage. The rheological properties showed that the storage modulus and loss modulus of dough of 0.5% and 2% low molecular γ-PGA group were higher than that of 2% high molecular weight γ-PGA and the control group,and the trend was more obvious over freezing time. TPA test showed that the hardness and gumminess of dough with 0.5% and 2% low molecular weight γ-PGA were lower than that with 2% high molecular weight γ-PGA. After same freezing time,there was no significant difference in the antifreeze protection effect between the addition of 0.5% and 2% low molecular weight γ-PGA groups(p=0.7199). The low molecular weight γ-PGA possesses stronger antifreeze protection effect on frozen dough and noodles,and would have great development potential in antifreeze protection of flour products.