Tailoring the Textural Attributes of Butter Fat/Canola Oil Blends via Rhizopus arrhizus Lipase-Catalyzed Interesterification. 1. Compositional Modifications

Butter fat/canola oil blends ranging from 100% butter fat (w/w) to 60:40% butter fat/canola oil were enzymatically interesterified with an sn -1,3 specific lipase from Rhizopus arrhizus in a liquid/solid two-phase system. Interesterification progress was monitored by following the changes in the relative proportions of 50-carbon triacylglycerols (TAGs) to 38-carbon TAGs (50/38 ratio) as a function of reaction duration. Most of the changes in TAGs occurred within the first 24 h of reaction. As the proportion of oil in the blend increased, greater changes in TAG composition became apparent. The interesterification reaction was optimal at 0.35% water content (w/w). The initial rate of hydrolysis was linearly dependent on initial water content within the range 0−0.55% water (w/w). Free fatty acids released ranged from 3 to 4.5% after 96 h of interesterification. The predominant free fatty acids were oleic acid (18:1) and palmitic acid (16:0). The lipase displayed little activity toward butyric acid (4:0) and caproic acid (6:0) residues. Monoacylglycerol levels ranged from 1.4 to 2.4% and diacylglycerol levels from 1.5 to 2.0% in all blends.