Studies On The Discriminant Technology Of Wheat Freshness

In this paper, more than 300 wheat samples of four different provices were measured for their fatty acid value, catalase activity and electrical conductivity, and the relationship between the three indicators and the storage time was discussed.The results is that the fatty acid value showed an upward trend, the catalase calue decreased and the conductivity value changed not obvious. It have greater difference between the new wheat and the old wheat for the catalase activity, so the catalase activity as the indicator for indentifying the wheat freshness is feasible.Hydrogen peroxide oxidized with benzidine hydrochloride which catalyzed by catalase produces a blue conjugated compounds, the more catalase activity, the deeper the color of the solution.The reaction mechanism was investigated briefly by UV-spectrophotometry and ESI-MS.The optimal test conditions were obtained though the single factor test and the orthogonal experiment,that is shaking 2minutes, extracting under 40℃, benzidine dihydrochloride solution 0.04% and H2O2 solution 0.10%.Taking the absorbance values of wheat, the initial rate and the reaction rate for the discriminant index, the discriminant function was estabilished by the discriminant analysis.All the wheat samples were divided into two classes and three classes in accordance with the harvest time. And their accuracy rate is 96% by the revert analysis and the cross-validation.The result is feasile and accurate.Then all the wheat were divided into 4 classes according their actual harvest time.The accuracy rate is 85.1% for 0 classess,36.7% for 1 classes,30.1% for 2 classess and 74.2% for 3 classes respectively.It is low accuracy.Similarly, taking the same indicator, wheat freshness grade was established by the SVM.The results showed that the correct rate can reach 85.76% for the three grades and 97% -98% for the two classes.