Interactions between canola proteins and phenolic compounds in aqueous media

Proteins and phenolic compounds are readily extractable from canola meal at alkaline pH. In aqueous media they interact to form complexes, thus contributing to the dark colour and undesirable taste of canola protein products recovered from alkaline extracts. The interactions between phenolic compounds and canola proteins were, therefore, studied at pH 12.0 and 3.5 using a novel system that combined a series of chemical treatments with membrane processing to break phenolic–protein complexes and then separate the released phenolic compounds from the proteins. This method was able to classify the extracted phenolic compounds into different fractions according to their bonding mechanisms to canola proteins. In total some 50% of the extracted phenolic compounds in these extracts formed complexes with canola proteins by different mechanisms, among which ionic bonding was predominant. The phenolic fractions bound by hydrophobic interactions, hydrogen bonding, or covalent bonding were relatively small, each constituting less than 10% of the total extractable amount.