Study On Preservation And Quality Improvement Of Cooked Wet Noodles

The shelf life of cooked wet noodles(CWNs)is usually extended by acid soaking and pasteurization process(ASPP)However,the ASPP will cause unpleasant sour taste in the CWNs.Meanwhile,the aging of starch also leads to a poor edible quality and the deteriorate of storage quality in CWNs.Aiming at the above problems in CWNs,this paper would replace the ASPP with the interval multiple pasteurization process(IMPP),to remove the sour taste.Based on the IMPP,the edible quality of CWNs was improved by using soybean milk instead of water and epigallocatechin gallate(EGCG)would be added to CWNs to suppress the starch aging.Finally,the EGCG and soybean milk were added to the CWNs with the IMPP to improve the quality of CWNs further.Firstly,the parameters of IMPP were explored.The activation effect of different insulation treatment conditions on the thermophilic spores in CWNs was studied.At the same temperature,with the increase of temperature holding time,the number of the thermophilic spores in CWNs first decreased and then increased,and the optimum holding condition was 36℃for 3 hours.On this basis,the sterilization temperature(98℃)and the total time(30 min)were controlled,and the sterilization times(1～5)of the IMPP were optimized.The results showed that using98℃-10 min for sterilization three times,with an interval of 3 hours between each sterilization,and using 36℃of temperature to activate the thermophilic spores,the total plate count(TPC)of CWNs could be less than 10~6 CFU/g after 90 days of accelerated storage(40℃).The sensory evaluation scores of CWNs prepared by the IMPP were 83.03～84.60 during the storage at room temperature(25℃),significantly(p<0.05)higher than that in the CWNs prepared by ASPP(69.28～77.71),and improved by 8.87%～19.85%.Secondly,the effect of adding soybean milk on the quality of CWNs during storage at room temperature(25℃)was studied.The initial hardness during storage increased significantly(p<0.05)from 5.06×103 g to 5.51×103 g(increased by 9.01%)with the increase of soybean milk concentration(0～7.75%,w/w).When the concentration of soybean milk was7.00%,the final hardness(7.85×103 g)was significantly(p<0.05)lower than that of control group(8.47×103 g).With the increase of soybean milk concentration(w/w),the sensory evaluation scores first increased and then decreased.When the concentration of soybean milk was 7.00%,the sensory evaluation scores were 88.30～90.90 during storage,which was6.35%～7.44%higher than that of the control group.Magnetic resonance imaging(MRI)showed that the addition of soybean milk enhanced the hydrogen proton density of CWNs during storage,and improved its ability to bind water.The sodium dodecyl sulfate extractable protein(SDS-EP)of CWNs was significantly(p<0.05)decreased from 19.31%to 14.69%after being added with 7.00%soybean milk.The content of disulfide bond was significantly(p<0.05)increased from 29.53 to 36.20μmol/g,indicating that the addition of soybean milk promoted the cross-linking of protein disulfide bond.Next,the effect of EGCG addition on the aging of CWNs under accelerated aging(4℃)storage condition was studied.With the increase of EGCG addition(0～0.30%,w/w),the initial hardness and final hardness were significantly(p<0.05)decreased during storage(decreased by5.63%and 8.61%,respectively).After adding 0.20%EGCG,the final increase rate of starch aging degree(26.62%)was significantly(p<0.05)lower than that in blank group(58.66%).In Avrami equation,k value decreased from 0.85 to 0.32,indicating that the addition of EGCG inhibited the aging of starch.Adding EGCG decreased the starch iodine combining ability significantly(p<0.05).Fourier infrared spectroscopy(FTIR)results showed that EGCG interacted with starch in the CWNs mainly by non-covalent bonds(mainly hydrogen bonds).Finally,the amount(w/w,based on the dry weight of flour)of 0.20%EGCG and the concentration(w/w)of 7.00%soybean milk were added into the CWNs.Based on the IMPP,the changes of texture quality under accelerated aging(4℃)storage and sensory quality under25℃storage in CWNs were studied.During storage,the texture results showed that the combined addition could further inhibit the aging of CWNs than adding soybean milk only.The results of sensory evaluation showed that the combined addition could improve the sensory evaluation score significantly(p<0.05)compared with adding EGCG alone.Therefore,soybean milk and EGCG could complement each other,and played a better role in improving the quality of CWNs.