Study On Mechanism And Application Of Inhibition Of Rice Starch Retrogradation By A-maltotriohydrolase

The characteristics of high starch and high moisture of instant rice products make it prone to retrogradation and other quality deterioration in the process of circulation and sales,resulting in a great waste of grain resources and hampering the further development of rice products industry.Previous studies have found that ?-maltotriohydrolase could act on amylopectin through internal and external cutting,effectively controlling the retrogradation process of amylopectin,which has the potential for development and utilization.This study used ?-maltotriohydrolase from Microbacterium imperial to catalyze the hydrolysis of rice starch,explored the dose-response relationship of ?-maltotriohydrolase on the molecular structure and retrogradation properties of starch,and analyzed the mechanism of its highefficiency inhibition of starch retrogradation.The ?-maltotriohydrolase-treated rice starch(EMS)was also added to rice cake so as to provide theoretical basis and technical reference for the popularization and use of this enzyme.Firstly,the dose effect relationship of ?-maltotriohydrolase on the molecular structure and retrogradation properties of rice starch was studied.It was found that ?maltotriohydrolase acted on rice starch through internal and external cleavage and significantly affected its anti-retrogradation effect.On the whole,?-maltotriohydrolase acted on the outer chain of amylopectin with external cutting in the initial stage of hydrolysis,and on the inner chain of amylose and amylopectin with internal cutting to reduce their molecular size in the later stage.?-maltotriohydrolase could effectively inhibite the retrogradation of rice starch.When the addition of ?-maltotriohydrolase was?500U and the hydrolysis rate of starch was?25.96%,the length of starch chain significantly reduced and a large number of small molecules of dextrins and maltotritose were generated.When stored at 4? for 14 days,the structural modification delayed the combination of the ordered structure of water and starch chain,hindered the recrystallization of starch and completely inhibited its retrogradation process.Secondly,the mechanism of ?-maltotriohydrolase inhibiting starch retrogradation was analyzed by means of alcohol precipitation classification and recombination technology.The conclusions were as follows:the average Rh of components GC1,GC2,GC3 and GC4 obtained by alcohol precipitation EMS decreased continuously.After starch debranched,the proportion of DP<9 increased,while the proportion of DP 25-130 and DP>130 decreased continuously.When gelatinized and stored at 4? for 14 days,the addition of alcohol precipitation components significantly reduced the retrogradation enthalpy and hardness changes of rice starch during storage and delayed the production of ordered structure and recrystallization.The order of effect was GC4>GC3>GC2>GC1.GC3 and GC4 can effectively reduce the loss of water and the migration and rearrangement of starch chain during storage,and thus prevent the retrogradation of rice starch.The results showed that the high anti-retrogradation effect of ?-maltotriohydrolase came from the production of small molecule branched chain dextrin and maltotriose.Finally,this study mixed EMS and rice flour in different proportions to prepare rice cakes and thus explored the anti-aging effect of EMS on these cakes.The results indicated that when the ratio of rice flour/EMS was 92:8 and 88:12,the comprehensive score of rice cakes remained above 60 points during 14 days of storage,which could effectively prolong the storage period without destroying the original sensory quality of rice cakes.The results indicated that when the ratio of rice flour/EMS was 92:8 and 88:12,the comprehensive score of rice cakes remained above 60 points during 14 days of storage,which could effectively prolong the storage period without destroying the original sensory quality of rice cakes.The addition of EMS effectively delayed the downward trend of water activity,reduced the retrogradation enthalpy and the change of ordered structure and recrystallization of rice cakes during storage,and thus inhibited the aging of rice cakes.