Abstract:
Quick-frozen steamed dumplings, a new type of frozen prepared food, the finished product will be processed steamed dumplings in the initial steaming and cooked immediately after the low-temperature freezing, to maintain the best taste and texture, consumers can eat after the purchase of a simple second steaming, because of its delicious taste and easy to cook, in recent years, by the popular groups and the group meal industry welcome. Currently, quick-frozen steamed dumplings are widely acclaimed by consumers in the prepared food industry, however, few studies related to their quality control have been reported. Acetylated Starch, Curdlan and Carrageenan were compounded and applied to quick-frozen steamed dumpling wrappers in the proportions of 6.54%, 0.52% and 0.65%, respectively, and the blank was used as the control. The changes in water content, freezable water content, color and texture of quick-frozen steamed dumpling wrappers were analyzed after retempering in fixed freezing and freeze-thawing cycles, and the influences on the rheological properties, water status, protein secondary structure and microstructure were further revealed by means of rheometer, low-field nuclear magnetic resonance (NMR), Fourier infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results showed that after 28 d of freezing or five freeze-thawing treatments, the water content of quick-frozen steamed dumpling wrappers in the control group decreased significantly and the freezable water content increased significantly after re-steaming (P<0.05), while the rate of water loss after re-steaming of the wrappers with the addition of AsCC (Acetate Starch Composited with Curdlan and Carrageenan) was significantly slower and the freezable water content was significantly lower than that in the control group (P<0.05), improving the water retention capacity of quick-frozen steamed dumpling wrappers. The brightness L* after re-steaming of the quick-frozen steamed dumpling wrappers in the AsCC group was significantly higher than that in the control group (P<0.05), which ensured the external sensory color of the quick-frozen steamed dumpling wrappers. In the control group, the hardness, elasticity and shear force of the wrappers decreased significantly (P<0.05) after re-steaming; after adding AsCC, all kinds of texture indexes of the wrappers decreased slowly, which improved the texture characteristics of the quick-frozen steamed dumplings. Under the same freezing and thawing conditions, the elastic modulus G' and viscous modulus G” of the AsCC group were significantly higher than those of the control group (P<0.05), and the content of strongly bound water in the AsCC group was significantly higher than that of the control group (P<0.05), which effectively improved the viscoelasticity and water retention capacity of the quick-frozen dumpling wrappers. In addition, the proportion of protein secondary structures such as α-helices and β-folds in the AsCC group was significantly higher than that in the control group (P<0.05), and the network structure of gluten proteins in the wrappers was denser and uniform in the microscopic field of view, which greatly improved the structural stability of the quick-frozen steamed dumpling wrappers in long-term freezing storage and repeated freezing and thawing. In this study, the compounding of hydrocolloids with modified starch can provide theoretical references for the improvement of frozen storage or freeze-thawing quality of quick-frozen steamed dumplings and other quick-frozen prepared noodle foods.