Cereal Chem. 70:51-55   |  VIEW ARTICLE

Distribution of Polyphenol Oxidase in Flour Millstreams of Canadian Common Wheat Classes Milled to Three Extraction Rates.

D. W. Hatcher and J. E. Kruger. Copyright 1993 by the American Association of Cereal Chemists, Inc. 

Polyphenol oxidase (PPO) levels were determined on individual and pooled millstreams of five cultivars representative of five different classes of Canadian wheat. The wheats were milled on a pilot mill to extraction rates of approximately 75 (conventional), 80, and 85%. Enzyme activity in individual streams ranged widely but increased with increasing bran contamination in the millstreams. With the exception of the soft spring wheat cultivar, PPO levels, as a percentage of total activity, were similar for the different wheats at similar cumulative flour yields. Less than 10% of the total PPO activity was present in cumulative flour streams corresponding to 70% extraction, after which the amount of the enzyme rapidly increased. Slightly more PPO activity appeared in the lower ash streams if the wheats were milled to a higher extraction using this mill flow. PPO activity was linearly correlated with ash content (up to 2.0% ash) and flour grade color figure (up to 5 units).