FACILE SPECTROPHOTOMETRIC QUANTIFICATION METHOD OF SINAPIC ACID IN HEXANE-EXTRACTED AND METHANOL AMMONIA WATER-TREATED MUSTARD AND RAPESEED MEALS

The contribution of sinapic acid to the free, esterified, and insoluble bound phenolics of a number of Brassica oilseeds, namely Triton (B. napus), Midas (B. napus), and Hu You 9 (B. napus) rapeseed and Domo mustard (B. juncea), was determined according to a simple spectrophotometric method. Sinapic acid constituted 65-86% of free and 71-97% of esterified phenolic acids of defatted meals. The contribution of sinapic acid to insoluble bound phenolic was 7-32%. Treatment of defatted meals with 10% ammonia in 95% methanol (MeOH-NH3-H2O) resulted in the removal of 41-75% of their total free phenolics and 45-79% of the content of sinapic acid in this fraction. This process also removed 82-93% of the total esterified phenolics and 86-93% of their corresponding sinapic acid. In all cases, MeOH-NH3-H2O extraction enhanced the protein content of the resultant meals.