Effects Of Superheated Steam Sterilization Treatment On Qualities Of Wheat Flour And Fresh Noodles

The microbial content of wheat flour in China is high,and microbial contamination will decrease the quality and safety of wheat flour during storage,and then damage the shelf life of fresh noodles.Therefore,it is necessary to control the number of microorganisms in wheat flour.Superheated steam is a new multi-purpose sterilization technology in recent years.It has various advantages such as good sterilization effect,short processing time and low raw material loss.However,the feasibility of sterilization for food materials with low moisture,powder and easy thermal denaturation remains to be confirmed.In order to provide theoretical basis for the application of superheated steam in reducing bacteria in wheat flour,the effect of superheated steam on reducing bacteria in wheat flour was studied,and the influences of superheated steam treatment on the quality of wheat flour and fresh noodles were evaluated in this paper.The main contents and results of this paper were demonstraetd as follow:(1)Firstly,treated wheat flour by using high-speed superheated steam equipment,and studied the influence of the moisture content of raw material,superheated steam treatment temperature and time on sterilization effect and quality of wheat flour,the wheat flour superheated steam sterilization curves were obtained by Weibull model.At the same time,based on response surface analysis,the equilibrium point of superheated steam sterilization process of wheat flour was obtained.The results showed that the superheated steam sterilization efficiency was significantly improved(p<0.05),and the peak viscosity of wheat flour increased first and then decreased,the SDS sedimentation value decreased with the increase of treatment temperature,time and wheat flour moisture content.Weibull model could fit the superheated steam sterilization kinetics curves of wheat flour under different temperatures and different moisture content of raw materials well(R~2>0.95),When the moisture content increased to 17.5%,the shape parameter b increased more,indicating that the sensitivity of microorganisms was improved under this moisture content and the sterilization effect was better.Among the variance analysis results of TPC,peak viscosity and SDS sedimentation value,the F value of treatment time was the highest,followed by that of the moisture content of raw materials,and that of treatment temperature was the lowest(The higher the F value was,the greater the influence on the experimental results was).The equilibrium point of superheated steam sterilization process was:the treatment temperature was 150℃,the treatment time was 6 s,and the moisture content of raw material was 13.5%.Under these conditions,the TPC was 2.10 lg CFU/g,the peak viscosity was 2860 c P,and the SDS sedimentation value was 48.00 m L.In conclusion,superheated steam treatment can effectively reduce the microbial content in wheat flour,but it will affect its quality as well.Weibull model can fit the sterilization kinetics curve well,and the tempering treatment can improve the sterilization effect of superheated steam.The effects of superheated steam treatment conditions on the germicidal effect and quality of wheat flour were all in the order of treatment time>moisture content>treatment temperature.It can effectively sterilize and maintain the quality of wheat flour under the equilibrium point.(2)Wheat flour was treated under the conditions of process equilibrium point and the maximum of treatment temperature,time and moisture content of raw materials,respectively.The effects of superheated steam conditions on the physicochemical properties of wheat flour,as well as the structure of starch and protein were studied.The results showed that compared with the untreated wheat flour,the peak viscosity was increased,gelatinization enthalpy was decreased,swelling power(95℃)was decreased and swelling power(25℃)was increased after treated,and the index of gluten protein was decreased.The physicochemical properties of wheat flour could be well maintained under the condition of process equilibrium.The peak viscosity of wheat flour decreased from 2859.50 c P to 2652.50 c P,the gelatinization enthalpy decreased from 5.67 J/g to 2.21 J/g,and the gluten index decreased from 29.49 g/g to 16.56 g/g after increasing the treatment time,and the effect of treatment time on physicochemical properties was the most obvious,followed by the moisture content of raw materials.Compared with the untreated wheat flour,protein and starch aggregated in the treated wheat flour,the surface and internal structure of particle changed,and the secondary structure of protein shifted toβ-folding.The structural characteristics of wheat flour could be well maintained under the condition of process equilibrium,and the particle morphology was complete,the birefringence intensity almost had no change.After increasing the treatment time and moisture content,the relative crystallinity decreased from 22.33%to 17.89%and21.14%,respectively,the birefringence disappeared completely,independent starch particles were almost not observed,and the variation degree of secondary structure of protein increased.In conclusion,superheated steam treatment could affect the physicochemical properties of wheat flour in different extents,the influence of treatment time was the greatest,followed by the moisture content of raw material,and the influence of treatment temperature was less.The superheated steam treatment could change the structural characteristics of wheat flour,and the variation degree increased with the increase of the treatment time and the moisture content of the raw material.It was beneficial to maintain the physicochemical and structural properties of wheat flour under the equilibrium condition.(3)The wheat flours treated with the same superheated steam conditions as in the above chapter,and then used to make fresh noodles.The effects of superheated steam treatment on cooking,edible and storage quality of fresh noodles were studied,and the conditions of superheated steam treatment of wheat flour were defined based on the quality of fresh noodles.The results showed that compared with the untreated fresh noodles,the cooking loss and water absorption of the treated fresh noodles decreased,and the cooking time was shortened from 5 min to 1 min.The cooking loss was reduced to the minimum value of 5.23%at the process equilibrium point.After increasing the treatment temperature,time and moisture content of raw materials,the cooking loss rised.Compared with the untreated,the hardness and chewiness of the treated fresh noodles decreased.There was no significant difference in hardness(P>0.05)and slightly reduced chewiness at the process equilibrium point.When the temperature,time and moisture content of raw material increased,respectively,the hardness and chewiness were decreased greatly.Compared with untreated fresh noodles,the content and growth rate of microorganisms of the treated fresh noodles decreased during storage,and the Browning and surface adhesion of the treated fresh noodles were inhibited.The shelf life of fresh noodles was extended to 2 days at the process equilibrium point.The shelf life was further prolonged after increasing the treatment temperature,treatment time and material moisture content,respectively.In conclusion,superheated steam treatment could improve the cooking quality and prolong the shelf life of fresh noodles,but would reduce the edible quality of fresh noodles.Considering the effect of superheated steam treatment on the quality of fresh noodles,it was feasible to improve the shelf life of fresh noodles by processing wheat flour at the process equilibrium point.