Study On Restraining Retrogradation Of Instant Wet Rice Noodles

Our country is a major grain-producing country, which is mainly in early indica rice.Because of its poor quality and poor taste, people are little direct consumption of indica rice,so rice grain especially early indica rice grain press a library to severe. In addition, it is notgood use of a large number of broken rice after rice processing each year. Therefore, thedevelopment of rice noodles is an effective way to solve the problems of pressing a library ofindica rice grain and promote new pattern of the grain producing industrialization, and it hasa very important economy and social significance.Now instant wet rice noodles can be eaten just by boiling water soaking, and the majorityof consumer like it because of its smooth taste. But it is easy to aging during storage, so thatthe rice noodles’s luster are lost, viscoelastic weakened, taste hardened and flavordeterioration, and the aging phenomenon affects the instant wet rice noodle products in themarket share. Therefore, it has become one of the key issues to the industrialization of instantwet rice noodles that it is extend the shelf life of instant wet rice noodles by improving theinstant wet rice noodles retrogradation.Initially, it was used controlled enzymatic technology to improve the aging of the instantwet rice noodles. With the hardness indexes, three types of amylase were selected betweenmaltase,α-amylase andβ-amylase, and we find that the best restrain retrogradation effect ofthe enzyme is maltose. The optimum enzymatic hydrolysis parameters was determined bysingle-factor tests and orthogonal analysis. It was shown that the optimum hydrolyticcondition was enzyme dosage 0.06%, temperature 60℃, time 30min, and pH5.5. Theinstantwet rice noodles’s hardness was 1.02kg under the optimum enzymatic hydrolysis condition.Compared with instant rice noodles maded from pure indica rice, its hardness has beendecreased by 85.6%. Through comparisoned of rice noodles’s properties of textural properties,sensory score, broken rate and DSC between enzymatic hydrolysis before and after, it wasshown that the instant wet rice noodles restrained retrogradation, and improved the texturalproperties and taste quality, but increased the broken rate of finished product.Although enzymatic hydrolysis improved the retrogradation of instant wet rice noodles,but the hydrolysis process was complex, and the enzymes price was high, so we considerthough the modification of physical properties to improve the retrogradation of the instant wet rice noodles. The results showed that: the best raw materials mixed condition was early indicarice 88.9%, guar gum 0.4%, glutinous rice 15%, and soluble soybean polysaccharide 3.5%.The instant wet rice noodles’s hardness was 2.89kg under the best raw materials mixedcondition. Compared with instant rice noodles maded from pure indica rice, its hardness hasbeen decreased by 57.7%, lower than the enzymatic hydrolysis of 27.9%, so the restrainedretrogradation effect of instant wet rice noodles under the raw materials mixed condition wassmaller than instant wet rice noodles under the optimum enzymatic hydrolysis condition.Through comparisoned of rice noodles’s properties of textural properties, sensory score,broken rate and pasting properties between raw materials mixed before and after, it was shownthat the instant wet rice noodles restrained retrogradation by the modification of physicalproperties, and significantly reduced the broken rate , improved the textural properties and thequality of morphology, cooking and taste.To understand the retrogradation mechanism of starch fully, and explore more innovativerestrained retrogradation method, we researched the retrogradation mechanism by studyingthe storage time, storage temperature, and the external branch of the chain length on theinstant wet rice noodles. The results showed that: the retrogradation of the instant wet ricenoodles gradually increased with the extension of storage time. The fastest retrogradation ratewas in the first week of storage in 4℃, and it completed short-term retrogradation in one day,and basically completed long-term retrogradation in three weeks. The instant wet rice noodleswas easier to aging at 0-4℃, and the retrogradation of the instant wet rice noodles graduallydecreased with the rise of storage temperature when the temperature more than 4℃, so it wasmore appropriate for storage at room temperature. In addition, distributions of the chainlengths greatly effected retrogradation of the instant wet rice noodles, and the retrogradationof the instant wet rice noodles gradually increased with ten oligosaccharide’s content of theexternal branch chain, so it restrained retrogradation of the instant wet rice noodles in someextent by reducing DP≥10 of the chain lengths of external branch starch.