Studies On The Color Of Wheat Products And Characteristics Of Polyphenol Oxidace

In this paper, the total content of phenols and activity of polyphenol oxidase in wheatpowder during different processes were studied. It turned out that: the total content of phenolsin wheat were very low, the total content of phenols in zhoumai16and zhoumai22werehighest among the selected12wheat varieties. In the break system and reduction system, thepolyphenol oxidase of wheat showed stronger activity when it’s more closer to the end. Thewhite degree of flour was brighter than flour slice. With the extension of standing time, thewhite degree of flour slice decreased gradually, while the color darkened gradually instead.The correlation analysis between the composition of wheat and the color of wheatproducts were studied, the results showed that: The protein content and PPO activity of wheathad significant negative correlations with L*point of flour and flour slice; the total content ofphenols had insignificant negative correlations with L*point of flour and flour slice; theprotein content had positive correlations with△E*point of flour and flour slice; the totalcontent of phenols had insignificant positive correlations with△E*point of flour and flourslice; With the extension of standing time, the PPO activity had remarkable positivecorrelations with△E*point of flour and flour slice.The characteristics of polyphenol oxidase in wheat were researched, the results showedthat: the optimum temperature of wheat polyphenol oxidase was40℃, the optimum pHwas6.0. Then we selected10different kinds of phenolic compounds, which were used as substrateto determine the activity of polyphenol oxidase in wheat. The results showed that: the enzymehad stronger oxidative activity to pyrogallic acid and catechol. The phenolic substances whichwere extracted from wheat were analyzed by high performance liquid chromatography, theresults showed that: the phloroglucinol existed in the wheat. Thus we can speculate that thepossible substrate of polyphenol oxidase was phloroglucinol.13kinds of food additives, especially nutrition fortifiers on the influence of wheatpolyphenol oxidase activity were studied, the results showed that: ascorbic acid, citric acid,cysteine and nicotinic acid could inhibit the activity of wheat polyphenol oxidase well. Thecompound enzyme inhibitors with good effects were confirmed though orthogonal experiment. Two groups of good plan were ascorbic acid0.02%, cysteine0.06%, citric acid0.03%,nicotinic acid0.16%and ascorbic acid0.02%, cysteine0.048%, citric acid0.05%andnicotinic acid0.12%.The compound enzyme inhibitors on the influence of different wheat products wereresearched, the results as follows: the color of wheat products showed obvious improvementafter the addition of compound enzyme inhibitors to the flour. These inhibitors were mostlynutrition fortifiers which human body needs at the same time, so they had very importantsignificance.