Correlation Analysis About Microbial Activity Values And Wheat Quality During Different Storage Period

This paper used the common wheat as raw material, after impurity removal,insecticidal action and then mixed it uniformly, adjusted the moisture content from theoriginal value12.86±0.08(%) to14.00±0.10, that is sample Ⅰ(thematched group group);added to sampleⅠthe compound fungicide powder (0.5%wt) that consists of four parts6-Sodium Diacetate (SDA) and one part Potassium Sorbate, blended it uniformly, that issampleⅡ （the experimental group）. Put these two samples at a condition ofconstant-temperature and closed human-made storage environment for0,30,60,90,120,150,180days in succession.During this process, many indexes such as the microbial activit y and number inevery phase, the physical and chemical quality, microstructure, biological activity,rheological properties of dough, textural properties, cooking and eating quality of wheatwere measured and correlatively analyzed. The test results show as follows:(1) The quantity and activity of microorganism of two groups of wheat in differentperiod of storage:With the storage time prolonging, the total number of colonies of sampleⅠandⅡfirst increased and then decreased, the number of samples storage for90days are at most,but the total number of colonies of sampleⅠare far more than the number of sample II;the fungal number of sample I and II had continued to increase, the number of samplesⅠincreased rapidly after storage for90days, and reached the most at180thday, the numberof sample II had been increasing slowly but steadily, finally reached the most at180thday.The experimental results of sampleⅠshowed that at90thday the total colony numberreached the peak, then began to decline rapidly, the average diameter of plaque reachedto the max, that is8.6mm, at the time of60thday, then began to become smaller; and thenumber of fungi increased slowly until90days, then increased rapidly, the averagediameter of plaque also increased all the time. The experimental results of the sampleⅡshowed that the total number of colonies began to slowly increase, reach a maximumvalue of2.1mm at the time of90thday, then began a slow decline, reached the minimumvalue at150thday, then increased slightly; the total number of fungi had been slowlyincreasing, the average diameter of plaque reached a maximum of5.8mm at180thday ofstorage.(2) The correlation analysis between microorganisms and the physical and chemicalquality of Wheat: Indexes(Y) such as whiteness, bulk density, hardness of wheat flour of wheat have anegative significant correlation with storage time (X1), microbial quantity (X2)(Y=a+bX1+cX2, C <0); Fatty acid value, acidity, conductivity, MDA content is positiveobviously correlation with microbial quantity, especially has significant positivecorrelation with the fungal activity (P0.01); sedimentation value and the content ofreducing sugar also has a good linear relationship with storage time. Microstructureshowed that the quality and quantity of inner starch and protein of wheat are most affectedby the microorganism; the change of skin powder layer is larger than the heart powderlayer.(3) The correlation analysis between microorganism and the biological activit y ofwheat:The activity of-amylase has a significant negative correlation with sedimentationvalue, in the initial storage period, the activity of-amylase tended to increase, but with abig increase in the number of microorganisms it decreased; the germination rate of wheat,germinal length and weight and the activit y of peroxidase decreased with the extension o fstorage time, has a very significant negative correlation with microbes (P0.01); thecompound fungicide has certain influence on the germination rate of wheat.(4) The correlation analysis between microorganism and rheological properties ofdough.With the prolong of storage time, the water absorption rate, peak viscosity andductilit y of dough are increasing; the shear stress, wet gluten content, elasticity, setback,pasting characteristics all have a decreasing tendency, and the falling number decreasesfirst and then increases. Hybrid experimental instrument showed little change in theformation time of the dough, and the stability time of dough is greatly shortened and softdegree decreases. The viscoelasticity, gelatinization, retrogradation value of dough arevery obviously influenced by microorganism.(5) The correlation analysis between microorganism and the cooking and eatingquality of wheat powder.The test results of sample I and II show that the general sensory score of the noodlesand steamed buns both decrease with the storage time prolonging, and the drop speed ofsample Ⅰhas a extreme significant binary linear correlation with the microorganism.However, the drop speed of the general sensory score of sample Ⅱis slow and uniform;texture analysis results are consistent with the general sensory scores.