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Polyphenol oxidase activity in extracts of bran and flour from a variety of wheat cultivars. Allan
Liavoga, Kwon-Joong Yong, Kate Bagorogoza, and Moses Okot-Kotber. Kansas State University,
Department of Grain Science and Industry, Manhattan, Kansas 66506, USA.
Polyphenol oxidase (EC 1.14.18.1) is a copper containing enzyme that
is widely distributed in plants and it catalyzes two reactions in the presence of molecular oxygen:
Hydroxylation of monophenols to o-diphenols (monophenolase activity) and oxidation of o-diphenols to
o-quinones (diphenolase activity). It is this latter property that makes polyphenol oxidase (PPO) an important
enzyme in food industry, for example, causing browning in some of wheat-based food products. Little is
known about spatial molecular distribution and characteristics of PPO in wheat varieties. Our studies focus
on determinations of the enzyme activities based on protein content in the extracts of bran and milling
fractions of various cultivars grown in central states of the USA. We have found varietal differences in the
levels of activity irrespective of whether hard white or hard red winter wheats are used. There is some
relationship between the growing locality and PPO activity in several cultivars grown in two localities
within the same region or in two localities in different states. The primary activity in the milling fractions,
including flour, is believed to have been derived from the bran during milling processes. These relationships
are discussed in the poster.
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