| Fresh noodles（FNs）are a staple food for many consumers due to their robust wheat flavour and silky texture.However,FNs have a short shelf life due to rapid microbial growth and quality degradation.Surfactin is a lipopeptide produced by Bacillus subtilis（ATCC21332）fermentation with antimicrobial and emulsifying properties.This paper combined the use of calcium propionate and sodium stearoyl lactate（SSL）to study the changes of microbial content,appearance quality,and edible quality of FNs during storage with different formulations of surfactin and investigated preliminary the mechanism of surfactin’s effect on starch granules and the gluten network during storage of FNs in order to provide a potential possibility of surfactin’s use for FNs preservation.The following are the main findings:Surfactin could inhibit the growth of microorganisms in FNs and increase their shelf life at 37°C and 25°C.The effect of various additions of surfactin（0.0%S,0.2%S,0.3%S,and0.4%S,based on flour weight,w/w）and compounded calcium propionate（0.3%S+0.025%B,w/w）on the microbial content of FNs was examined.The 0.4%S and 0.3%S+0.025%B had the best preservative preservation effect,compared with the 0.0%S,the storage time of FNs was extended from 8 h to 32 h and 28 h at 37°C,respectively,and from 24 h to 72 h at 25°C,whereas there was no difference between the 0.4%SSL and the 0.0%S.Moreover,the addition of surfactin slowed the p H and acidity decline of FNs during storage.Surfactin enhanced the cooking quality and textural properties of FNs and inhibited their turning yellow,but decreased brightness.Color change,enzymatic browning,water absorption,cooking loss,hardness,and elasticity of cooked noodles were examined during storage of FNs at 25°C using a colorimeter and a mass spectrometer with 0.0%S and 0.4%SSL as control groups,and the results demonstrated that FNs containing surfactin had higher PPO activity but lower b*during storage.The b*of the 0.0%S,0.2%S,0.3%S,0.4%S,0.3%S+0.025%B,and0.4%SSL groups ranged from 13.07,12.02,11.95,12.22,11.93,and 12.79 to 14.55,10.74,9.44,8.21,9.44,and 14.28,respectively,from 0 h to 72 h.Surfactin increased the hardness and tensile strength of FNs and slowed their deterioration during storage.The hardness of the 0.0%S and0.4%SSL groups decreased from 19.23 N and 18.82 N to 14.94 N and 13.94 N from storage at0 h to 72 h,and the tensile strength decreased from 11.58×10-2 N and 13.18×10-2 N to 8.93×10-2 N and 9.25×10-2 N,while the hardness and tensile force of the 0.4%S group changed from 24.83 N and 15.80×10-2 N to 22.45 N and 12.69×10-2 N,respectively.Surfactin decreased the water absorption and cooking loss of FNs and inhibited the deterioration of cooking quality during storage,with cooking loss increasing from 8.90%and 6.83%to 10.75%and 10.02%from 0 h to 72 h for the 0.0%S and 0.4%SSL,respectively,and from 5.58%to 6.32%for the0.4%S.The addition of surfactin induced protein aggregation in FNs,thereby increasing the compactness of the gluten network and decreasing the degree of gluten network and starch granule damage during storage.Sodium dodecyl sulphate gel electrophoresis（SDS-PAGE）,high performance liquid phase size exclusion chromatography（SE-HPLC）,and free sulfhydryl group content revealed that the addition of surfactin slowed the decrease of high molecular weight gluten subunits（HMW-GS）during storage,and the gluten protein aggregate content of0.0%S,0.2%S,0.3%S,and 0.4%S groups decreased from 38.47%,42.25%,43.33%,and 41.57%at 0 h to 24.66%,30.82%,29.39%,and 33.32%at 72 h,respectively.The stability of protein secondary structure in FNs was determined by Fourier transform infrared spectroscopy（FTIR）.The results showed that the addition of surfactin had no effect on the secondary structure of gluten proteins at 0 h,but inhibited the decrease of theα-helix and the increase of random curl during storage.Theα-helix and random curl contents at 72 h were 12.54%,11.43%,12.23%,and 11.21%,10.24%,11.61%in the 0.2%S,0.3%S,and 0.4%S,respectively,compared to 8.89%and 17.79%in the 0.0%S.Laser confocal（CLSM）images demonstrated that surfactin improved the integrity of the gluten network and its storage stability.Rapid viscosity analyzer（RVA）,X-ray diffractometry（XRD）,and differential scanning calorimetry（DSC）were used to examine the changes of starch granules during storage.The results indicated that surfactin increased the pasting viscosity of starch in FNs and that the relative crystallinity and enthalpy of pasting（（35）H）of starch granules increased with the increase in storage time. |
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