Study On Shelf-life Extension Of Semi-dried Whole Wheat Noodles At Ambient Temperature

Semi-dried whole wheat noodles(SWWN)are rich in dietary fiber and physiologically active substances,which are convenient to eat and meet consumers’ requirements for noodle taste and nutrition,and exhibit great market potential.However,whole wheat flour has high bacterial content and rich enzyme activities,which will affect the quality and shelf life of SWWN.Therefore,this article mainly studies the effect of superheated steam(SS)treatment on the quality of whole wheat flour and the storage stability of SWWN,and improving the quality and shelf life of SWWN by using acidity regulators,moisture regulators and deoxidizer.The corresponding improvement methods can provide a theoretical basis for extending the shelf life of SWWN.Firstly,the effect of superheated steam treatment on the quality of whole wheat flour was studied.SS treatment significantly reduced the microbial content of whole wheat flour and the activities of lipase,lipoxygenase and polyphenol oxidase(p<0.05).At 155~170℃,the development time,stability and C2 torque of whole wheat dough were significantly improved,and the dough strength enhanced.SS treatment could improve the rheological properties of whole wheat dough.SS treatment increased the peak viscosity,through viscosity and final viscosity of whole wheat flour,and reduced the gelatinization temperature and enthalpy of whole wheat flour.Scanning electron microscope and SDS-polyacrylamide gel electrophoresis showed that SS treatment promoted the interaction between protein and starch in whole wheat flour.Secondly,the effect of SS treatment on the storage stability of SWWN was studied.The hardness of SWWN increased with the increase of processing temperature,the cooking loss was slightly reduced,and the water absorption was significantly reduced.SS treatment significantly reduced the total plate count(TPC)of SWWN(4 lgCFU/g to 1~2 lgCFU/g),and delayed the growth of the TPC during storage.Treated at 170℃/10 s,the TPC reached the level of incipient spoilage(6 lgCFU/g)after 5 days.SS treatment significantly reduced the acidity and enzyme activities(lipase,lipoxygenase and polyphenol oxidase)of SWWN,reduced the growth rate of free fatty acid during storage,inhibited the lipolytic rancidity during storage of SWWN,and delayed the deterioration during storage.SS treatment could improve the storage stability of SWWN.Thirdly,the effect of acidity regulator on the microorganism and quality of SWWN was studied.Potassium carbonate,sodium carbonate and monosodium fumarate reduced the water activity and polyphenol oxidase activity of SWWN.0.6% potassium carbonate and 0.5% sodium carbonate(pH 9.0)could inhibit the growth of the TPC and mold and yeast count(MYC)during storage of SWWN,TPC was lower than 6 lgCFU/g,mold and yeast count of SWWN with 0.5% sodium carbonate exceeded the level of incipient spoilage of MYC(2.18 lgCFU/g)after 6 d.The total plate count of SWWN with 3% monosodium fumarate(pH 4.2)could be kept at around 2.2 lgCFU/g during storage,and MYC reached the level of incipient spoilage(2.18 lgCFU/g)after 5 d.After the addition of 3% monosodium fumarate and 0.5% sodium carbonate,the hardness of SWWN decreased by 19% and 10% respectively,and the cooking loss and color difference increased significantly(p<0.05).In addition,the effect of moisture regulators on storage quality of SWWN was studied.The addition of phosphate reduced the polyphenol oxidase activity and water activity of SWWN.Phosphates reduced the initial MYC in SWWN,and delayed the growth of MYC during storage.Disodium phosphate,sodium pyrophosphate,sodium tripolyphosphate and sodium hexametaphosphate were compounded at 3:2:4:2,the compound phosphate addition ratio was 0.4%.Compound phosphates reduced the hardness of SWWN,and water activity decreased to 0.897.Compound phosphates delayed the growth of MYC and retarded the increase of acidity during storage.Sorbitol significantly reduced the water activity of SWWN(p<0.05).Ethanol(2%~3%)inhibited the growth of TPC in SWWN during storage,and TPC maintained a platform period.Sorbitol and ethanol could reduce the degree of hardness reduction during storage of SWWN,delayed the deterioration of noodle quality.Finally,the effects of integrated fresh-keeping on storage stability of SWWN were studied.Superheated steam treatment significantly reduced the microbial content and decreased the enzyme activities of SWWN.Moisture regulators and deoxidizer delayed the deterioration of noodle quality,the growth of microorganisms and the increase of acidity and fatty acidity during the storage.Comprehensive fresh-keeping significantly prolonged the shelf life of SWWN,and the shelf life was extended to more than 2 months.