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AACC International Approved Methods - AACC Method 22-85.01. Measurement of Polyphenol Oxidase in Wheat Kernels (L-DOPA Substrate)

AACC International Approved Methods


AACCI Method 22-85.01
Measurement of Polyphenol Oxidase in Wheat Kernels
(L-DOPA Substrate)


Discoloration in dough is an end-use quality defect. A bright, clear color that remains stable over time is desired. Discoloration, in the form of grey, brown, or green shades, or general “dullness,” has long been attributed to polyphenol oxidase (PPO). PPO is located predominately in the bran coat of wheat kernels. Problems with enzymatic discoloration occur in Asian noodles (especially alkaline noodles) and in any doughs, including refrigerated doughs, that are held for periods of time before baking or boiling. This method is a relatively rapid, small-scale, nondestructive test for PPO; applicable to both breeding and commercial applications. It utilizes L-dihydroxyphenylalanine (L-DOPA) as a substrate, and meets the criteria for a practical test for breeding programs. The L-DOPA method here is specific for whole wheat kernels, but it can be adapted for use on flour or ground wheat samples.