Cocoa butter biosynthesis: Effect of temperature onTheobroma cacao acyltransferases

Abstract

Enzymes catalyzing the first and last steps in cocoa butter biosynthesis were studied in microsomal preparations from developing cocoa seeds. Both the acyl-CoA:sn-glycerol-3-phosphate 0-acyltransferase (EC 2.3.1.15) and the acyl-CoA:1,2-diacylglycerol 0-acyltransferase (EC 2.3.1.20) showed broad specificity for three fatty acid donors (palmitoyl-CoA, stearoyl-CoA and oleoyl-CoA), but the relative amounts of incorporation of these fatty acids into lysophosphatidic acid and triacylglycerol were influenced by temperature of incubation. The selectivities of the two acyltransferases for saturated vs unsaturated acyl-CoA’s also were investigated over a range of temperatures. The data indicate that, in general, the ratio of saturated to unsaturated fatty acids incorporated into glycerol esters increases with increasing temperature of incubation, consistent with the hypothesis that temperature effects on these enzymes contribute to the phenomenon of “soft” cocoa butter, i.e., that cocoa butter obtained from seeds grown in cooler climates has a lower melting point than that prepared from seeds grown in warmer climates.