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Partial Analysis of Milk Triglycerides with Lipase Iodine¹³¹ Retention in Calves¹

Department of Animal Industries University of Connecticut, Storrs

J. A. Alford

USDA, Beltsville, Maryland

ABSTRACT

The microorganism Geotrichum candidum (GC) produces an extracellular lipase highly specific for oleic acid in both natural and synthetic triglycerides (TG) (1, 2). Oleate was removed from the latter, regardless of position. The enzyme also differentiated between geometric isomers releasing about 95M% oleate (in the free fatty acids) from glyceryl 1-elaidate 2, 3-dioleate and from margarine (7). The utility of the pancreatic lipase method for studying TG structure encouraged us to determine whether GC lipase could be used for the same purpose with milk fat. The results are reported herein.

Butteroil was obtained by churning cream, melting the butter, and Altering the clear oily layer. To provide a standard substrate for comparisons in several of our investigations, quantities of 15–20 g were dispensed in screw-top tubes and stored at –20 C. As needed, samples were melted and purified on an alumina column, the process monitored by thin-layer chromatography (TLC). The butteroil (0.5 g per 8 ml) was dispersed with a Waring Blendor, in phosphate buffer (pH 6.7), containing 1% gum arabic to which were added 0.5 ml of 1% CaCl₂ and 25 mg of enzyme preparation in two milliliters of plain phosphate buffer.

¹ Scientific contribution, Agricultural Experiment Station, University of Connecticut, Storrs. Supported in part by Public Health Service Research grant AM-02605-07 from the Institute of Arthritis and Metabolic Diseases.