| Polyphenol oxidase(PPO) is a kind of protease connecting Cu elements which widely exists in animal, plant and micro-organizm, and which affects quality and nutrition of products. There is some PPO in wheat grain, and it mainly affects the whiteness of flour and flour base products in processing and storage of wheat. So much more attention is paid to PPO in wheat breeding. The experiments mainly studied changes of PPO activity to provide the theories for the wheat quality improving.The rerults showed as the follows.1,PPO activity had significant variance in different stages and had different variance leve among different cultivars, and the PPO activity had different variance leve in each developing phase among different cultivars. There is no significant effect on the PPO activity among interaction of genotype and stage. The different developing phases is mostly factor on affecting the PPO activity.2,PPO activity declined at first, then increased gradually, the trend of which is different among cultivars during wheat grain development.3,There is the commonness of change of PPO isoenzymes among different cultivars during wheat grain development. There is always larger molecular weight PPO during wheat grain development, and some changes is presented by middle weight and lower molecular weight PPO during wheat grain development, which is disappeared in ripe grain. With the development of grains, the low PPO reduced gradually, and disappeared in ripe grain.4,Extracted, assayed PPO from the bran of 15 wheat genotypes, PPO mainly exists in bran, PPO activities were 10-fold and 60-fold higher than in flour and whole meal, respectively, and well correlated to PPO activities in whole meal(0.74, P<0.01). The differences among genotypes were great and could be helpful to selection in breed program.5,Methods of measuring polyphenol oxidase activity in wheat with catechol as substrate was researched. Polyphenol oxidase activity in whole meal was about four times as it in flour. The correlation coefficient between PPO activity in whole meal and in flour was 0.7198(P<0.01), while it was 0.2626(P<0.05) between PPO activity in whole meal and in seed The correlation between PPO activity in flour and in seed did not reached significant, so did correlations between PPO activity and flour color. PPO activity in flour and whole meal significantly related to L* of fresh dough sheet, at 0.05 and 0.01 level, respectively. PPO activity in seed significantly related toΔa0-24h and a* of fresh dough sheet at 0.01 level. PPO activity in flour significantly related toΔb0-24h. The correlation between PPO activity in seed and other criterions of color had a tendency to positive significant. |
