Effect of mechanical damage and incipient sprouting on polyphenol oxidase activity of wheat seeds.

NOVEMBER 5-9, 2000 KANSAS CITY, MISSOURI

A A C C 2 0 0 0 A n n u a l M e e t i n g

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Effect of mechanical damage and incipient sprouting on polyphenol oxidase activity of wheat seeds. H. G. Chang (1,2), T. Demeke (1), and C. F. Morris (1). (1) USDA/ARS, Western Wheat Quality Lab., Pullman, WA 99164 USA; (2) Dept. of Food and Bioengineering, Kyungwon University, Sungnam 461-701, South Korea.

Polyphenol oxidase (PPO) is the major enzyme responsible for browning of wheat products. PPO activity has been measured in whole kernels and flours using substrates such as catechol, tyrosine and L-DOPA. An L-DOPA assay on whole seeds has given satisfactory measurement of PPO activity in our lab. Mechanical damage occurs during harvesting and grain handling. The effect of this mechanical damage on PPO activity as assayed by our L-DOPA test is not known. Seeds were mechanically abraded to remove part of pericarp and embryo to determine the impact on PPO activity. The contribution of embryo vs. endosperm/pericarp towards PPO activity was also assessed. Seeds were allowed to imbibe water for different lengths of time to determine the effect of incipient sprouting on PPO activity. Results obtained will be discussed.