Different dairy-like fat fractions were added to raw skim milk in order to determine their effect on lipase production by Pseudomonas fluorescens growing on raw milk at 7 degrees C. Supplementation with preparations of fat globule membranes, mixtures of capric acid, glycerol monocaprinate, and glycerol dicaprinate, cholesterol, or lecithin at concentrations similar to those occurring in whole milk had only slight effects on lipase production, whereas supplementation with 0.9% glycerol trioleate decreased lipase activity in milk by 90%.