Research On Preservation And Texture Quality Of Wet Raw Noodles

Wet raw noodles are popular with consumers owing to its properties of fresh, tasty, chewy and sweet-scented. Wet raw noodles have a good edible quality and taste for its high water content. However, since the water content of wet raw noodles is high, the noodles in storage are apt to be contaminated by microorganism and spoilage. Short shelf life is always the bottleneck in the industrial production of wet raw noodles. Therefore, different antisepsis and preservation technologies were used to prolong the noodles’ shelf life, and the influence of water addition on the texture characteristics, cooking characteristics and microstructure of wet raw noodles was researched in the study. It could provide a theoretical basis for industrial production of wet raw noodles. Main contents and results were as follows:1、The influence of sugar, sugar alcohol and heat treatment on the water activity and microorganism of wet raw noodles were studied. The results showed that the composite of sorbitol and trehalose could reduce the water activity of wet raw noodles, when the composite ratio was 3:2, and their addition was 6%. With the noodles being heated for 8min at 105℃, the composite could significantly reduce the water activity and the original microbial content of wet raw noodles and extend its shelf life.2、Using the inhibitory rate about bacteria and mould as evaluation index, effect of microwave power, germicidal time and sample weight on the germicidal efficacy of wet raw noodles and the optimum processing conditions of microwave sterilization which was chosen by orthogonal experiment were studied. The original amount of microorganism in wet raw noodles was significantly decreased and the noodles’ shelf life lasted 2d under the condition of microwave power 800W, germicidal time 30s and sample weight 150g.3、The fumigation inhibitory effect of some essential oils and isolate spices on the common spoilage organisms in wet raw noodles was compared in the study, which including linalyl oil, bergamot oil, tea tree oil, rosemary oil, orange oil, ginger oil, thymol, eugenol, anethole and citral. Results indicated that thymol and anethole had a better antibacterial effect, and then they were recombined in the experiment. The composite spices showed a notably synergistic interaction when the optimum proportion of thymol and anethole was 2:1. All tested spoilage organisms were completely inhibited by the composite spices of 0.0625μL/mL. The composite spices also had a significant inhibition effect on the bacteria and mould in wet raw noodles. When the spatial concentration was 0.05μL/mL, the colony count and fungi count in the noodles which had been heated were less than 10CFU/g after 8d, which met the microbiological standard.4、Effect of heat treatment and the combination of microwave and heat treatment on the microorganism in noodles with alcohol was studied. Results showed that both these two measures could prolong the noodles’shelf life and reduce the impact of alcohol on the flavor of noodles, and the former was better than the latter. The shelf life of noodles with 4% alcohol addition and 7min heat-treatment was more than 27d, while the shelf life of noodles, which was with the same alcohol addition,5min heat-treatment and microwave sterilization at 800W for 20s, couldn’t reach 9d.5、Effect of water addition on the texture characteristics, cooking characteristics and microstructure of wet raw noodles was discussed, and the quality of wet raw noodles and dried noodles was compared. It was found that the water addition had a significant influence on the texture characteristics of wet raw noodles and cooked noodles. The hardness, cheesiness, springiness, resilience, maximum shear force and maximum shear stress of wet raw noodles all decreased with increasing water addition, while the adhesiveness increased with increasing water addition slightly. The texture parameters of cooked noodles all increased with increasing water addition except for the adhesiveness. When the water addition was more than 32%, the change of the hardness, springiness and maximum shear stress of cooked noodles was small. The water absorption of noodles increased with water addition at first and then reduced, but the optimum cooking time, loss ratio and turbidity reduced with water addition. When the water addition was between 34% and 38%, the noodles had a good texture quality and eating quality.By comparing the texture and cooking quality between wet raw noodles and dried noodles, it was found that the hardness, cheesiness, maximum shear force, maximum shear stress, adhesiveness, water absorption, loss ratio and turbidity of dried noodles significantly increased, and the quality and palatability of noodles became worse as a result of its dewatering by drying process.The microstructure of wet raw noodles and cooked noodles with water addition of 28%, 36% and 44% was observed by scanning electron microscope. The wet raw noodles with lower water addition had a loose gluten network where the void is large. Many free starch granules stayed outside the network instead of being wrapped in it. Proteins and starch fully swelled with increasing water addition and formed a compact network in which starch granules were tightly bound by proteins. In the cooked noodles with lower water addition, the starch granules were stacked closely and the protein matrix could not form fine meshes to twine the starch granules. However, starch granules could be hung up on the surface of protein network or in the void of network by the fine protein meshes in the cooked noodles with high water addition, and the network structure became loose.