| Quick frozen dumplings were prone to cracking,browning and retrogradation during freezing and transporting,noddle soup get turbidity,losing of liquid after thawing,and these reduced the quality of the dumplings.Poly-?-glutamic acid(?-PGA)is a macromolecular synthetic macromolecule polymer,with strong water absorption and water retention capacity,it can be used as a cryprotectant in food.This paper studies the effects of different concentrations of poly-?-glutamic acid(?-PGA concentration 0,0.08%,0.25%,0.5%,0.75%,1%)on the quality of wheat flour,frozen dough and frozen dumplings.Studies show that ?-PGA has a significant effect on the properties of flour.Poly-?-glutamic acid can significantly improve the water holding capacity(WHC)of flour.With the increase of ?-PGA concentration,WHC of flour increased first and then decreased,and WHC was the highest at 0.25% ?-PGA(9.25% higher than the control).Characterization of the farinographical properties show that with the increase of ?-PGA concentrations,development time was significantly prolonged(from the initial 5.5 min to 7.3 min),The stability time also increased,and the highest extended by 53%,with improving dough kneading.Weakness decreased with the increase of ?-PGA concentration,the lowest reached 22FU(25FU less than the control),and this increased the mechanical resistance of the dough.Characterization of the extenograph properties show that resistance to extension was significantly increased after adding ?-PGA and the highest is 70 BU at 1% concentration(16% higher than the control).Flour viscosity profiles indicated that a)Pasting temperature decreased from 69.4? to 64.09? at 1% ?-PGA.b)Peak viscosity,low viscosity and final viscosity were the highest at 0.08% and decreased at other concentrations.Poly-?-glutamic acid also has a significant effect on the freezing properties of dough.Compared with those without ?-PGA frozen dough water loss of frozen dough was reduced 54% by ?-PGA.NMR and DSC showed that,compared with the control,relaxation time T2 decreased,indicating that water activity is declining,free water is difficult to be frozen,free water content decreased.Frozen water content(FWC)may be reduced 64% and enthalpy reduce 22.1J / g compared to control.All indicated that moisture is not easily frozen in the frozen dough containing ?-PGA,water migration is weakened,reduced the water loss and damage to structure.?-PGA can improve the color of the frozen dough,the yellow value and the red value are significantly reduced,with the brightness increasing.Poly-?-glutamic acid is beneficial in protecting the structure of the frozen dough.X-ray diffraction analysis of starch crystallinity in the dough found that ?-PGA can reduce the crystallinity of frozen dough,delay the crystallization of starch.Wheat gluten protein is the material basis for the formation of dough network structure,it was found that the addition of ?-PGA could reduce the cleavage of disulfide bonds between frozen dough.From the free mercapto content,without adding ?-PGA free thiol group 1.201?mol/L,while the addition of ?-PGA dough free thiol content was significantly reduced(at a concentration of 0.5% to a minimum of 0.8415?mol/L).SEM observed that ?-PGA added 0.75% of the dough microstructure uniformity,starch particles as a scaffold is tightly surrounded by gluten network and less fracture,but the dough have larger gap,starch exposed without the addition of ?-PGA.Poly-?-glutamic acid can improve the quality of frozen dumplings.The addition of ?-PGA reduced the cooking loss(up to 50.63%)and cooking belly broken(the best concentration decreased by 15%),improved freeze-thaw stability(maximum increase of 1 times).TPA and sensory evaluation found that addition the ?-PGA,increased stickiness and chewiness,improved resistance to cooking,and improved color in the frozen dumplings. |
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