Effect Of Physical Property Modification On Quality And Anti-retrogradation Of Instant Fresh Rice Noodles

As a new type of expanded food in recent years,instant fresh rice noodles are popular among consumers because of their unique taste and convenience.However,because the main raw material of instant fresh rice noodles is rice,which is rich in starch and has a high water content(55/70%),it is easy to stale during storage,transportation and retail.It will leads to the deterioration of quality and even loss of edible value.Therefore,taking effective measures to control the staling of instant fresh rice noodles is an urgent issue to be solved.In this paper,the effects of different varieties of indica rice on the quality of instant fresh rice noodles were systematically studied.The properties of indica rice gel,the anti-retrogradation mechanism of added starch and additives were discussed.A simple of instant fresh rice noodles with good taste and not easy retrogradation was produced.The main research contents were included the following:(1)Study on the influence of indica rice variety on the quality characteristics of indica rice gel and instant fresh rice noodles.By analyzing the basic physiochemical properties and gel characteristics of the indica rice,combining with the results of texture analysis and sensory evaluation of instant fresh rice noodles,the suitable early indica rice was selected from five different regions.The results showed that there were significant differences in the basic physiochemical properties of different varieties of indica rice.The differences of gelatinization properties of indica rice were mainly reflected in the breakdown and the setback viscosity,which affected the processing stability of indica rice and the short-term retrogradation of rice noodles.In the comparison of rice gel characteristics,it finds that when rice gel has higher strength and longer rupture distance,it will have better water holding capacity,and better gel stability and shear resistance.In this case,the instant fresh rice noodles has higher chewing power,firmness,elasticity and total sensory score.The results of principal component analysis showed that the sensory score of instant fresh rice noodles could be predicted by the rupture distance of indica rice gel and the moisture content,toughness and elasticity of instant fresh rice noodles.In combination of texture characteristics and sensory evaluation,the quality of instant fresh rice noodles made from See-Mew rice was the best in all 5 rice varieties.(2)Study on the effects of natural/modified starch modification on quality and anti-retrogradation of instant fresh rice noodles.In order to improve the quality of instant fresh rice noodles,the basic properties of different natural starches and modified starches were analyzed,and their effects on gelatinization,hydration and gel characteristics of rice flour were discussed.The optimum formula was determined by the elastic toughness and short-term retrogradation properties of instant fresh rice noodles.The results showed that the amylose content and average polymerization degree of mung bean starch are higher,but the relative crystallinity is lower.The addition of three kinds of natural starches reduced the solubility,swelling strength,breakdown and the setback viscosity of the mixed flour,improved the water holding capacity,and reduced the weight loss rate.Pea starch and mung bean starch could significantly increase the rupture distance of indica rice gel,thus increasing the elasticity and toughness of instant fresh rice noodles.The three kinds of modified starches could also improve the gel rupture distance of indica rice and the elasticity and toughness of instant fresh rice noodles,among which hydroxypropyl dimethyl phosphate has the highest effect.The mixture of natural starch and modified starch showed that the instant fresh rice noodles prepared by adding 10% mung bean starch and 6% hydroxypropyl dimethyl phosphate had higher elastic toughness,better quality and slower short term retrogradation rate.(3)Study on the effects of additives modification on anti-retrogradation of instant fresh rice noodles.On the basis of adding 10% mung bean starch and 6% hydroxypropyl dimethyl phosphate and adding different additives,instant fresh rice noodles was prepared.The influence of additives on the short-term retrogradation characteristics of instant fresh rice noodles was analyzed,and the best additive formula was obtained through orthogonal design.The results showed that guar gum and carboxymethyl cellulose in thickener,sucrose ester in emulsifier,and sodium pyrophosphate in water holding agent had the best synergistic effect on delaying the short-term retrogradation rate of instant fresh rice noodles.Through orthogonal experiment design,the optimal additive compound formula was 0.035% guar gum,0.15% sucrose ester,0.045% carboxymethyl cellulose and 0.10% sodium pyrophosphate.The hardness of instant fresh rice noodles increased by 3.06% in 7 days.The setback viscosity was 80 m Pa·s,the short-range order was 0.6532,and the aging degree was5.11.The short-term retrogradation characteristics of instant fresh rice noodles were obviously inhibited.(4)Study on the retrogradation behavior and digestibility of instant fresh rice noodles during storage.Using the instant fresh rice noodles without supplementary material as control group,the effects of starch and compound additives on the retrogradation behavior,in vitro digestion and microstructure of instant fresh rice noodles during storage were studied.The results showed that the addition of starch and compound additives could inhibit the increase of hardness of instant fresh rice noodles during storage,and the effect of adding starch and compound additives was better.The hardness only increased by 8.86% after 9weeks storage,and the elasticity was almost unchanged.In addition,by analyzing the results of water distribution,short-range order,relative crystallinity and retrogradation degree of instant fresh rice noodles,it was found that adding compound additive could made instant fresh rice noodles have higher binding water content,increase water binding capacity,reduce the enthalpy and relative crystallinity of staling,and inhibit the recrystallization of pullulan polysaccharide,thereby reducing the quality deterioration of instant fresh rice noodles caused by water migration and starch recrystallization during storage,and further delaying the long-term staling speed of the instant fresh rice noodles.Avrami equation was used to fit the hardness,short-range ordering,retrogradation degree and relative crystallinity of instant fresh rice noodles during storage,and a starch retrogradation kinetic model was established.It was found that the results of each staling characteristic index fitted well with the equation.From the crystallization rate constant k,the compound additives did inhibit the long-term retrogradation of instant fresh rice noodles.During the storage of instant fresh rice noodles,starch molecules recrystallize to form new crystals,which have certain resistance to enzymatic hydrolysis,and leads to the decrease of RDS content and the increase of SDS and RS content in instant fresh rice noodles.Compound additives can inhibit the recrystallization of starch,thus reducing the change of digestibility of instant fresh rice noodles.