Abstract

The effect of different fractions (lipids, solids soluble in aqueous ethanol (ES), soluble protein (SP), and the residue after the extractions) of yellow lupin (Lupinus luteus), linseed (Linum usitatissimum), and soybean (Glycine max) meals on in vitro porcine pancreatic lipase (PPL) activity was determined. PPL activity against emulsions prepared with the different SPs unprocessed or denaturated by heat, digested with pepsin and homogenized at high pressure was also evaluated. In general, the lipids, ES, and the residue fractions increased PPL activity (8.4-80.0%) whereas it was reduced by the SPs of lupin (25.3%) and linseed (30.8%) at a low concentration. Residual activity after incubating the enzyme with the SPs was found between 13 and 46% depending on the source and the incubating period. The rate at which PPL hydrolyzed emulsions in which lipid droplets were covered first by gum Arabic and then with the protein was influenced by the treatment of SP; less free fatty acids were released from emulsions containing the denaturated and digested SPs. PPL activity against emulsions that contained the homogenized SPs was higher (108-174%) than the activity against emulsions that contained the untreated SP. Practical applications: Lupin, linseed, and soybean meals contain various fractions that increase the activity of PPL; however the soluble proteins of lupin and linseed exert the opposite effect at low concentrations with the subsequent reduction of lipolysis products. Besides emulsions prepared with denaturated or protease digested seed proteins are hydrolyzed at low rates by PPL. This property of the seed proteins could find use in the developing of foods for weight control for instance plant-based milks and creams. On the other hand, high pressure homogenization could be used as a treatment for decrease the negative effect of seed proteins on the activity of PPL.