Methyl Ketone Production in Milk-Fat-Coated Microcapsules. 2. Methyl Ketones from Controlled Concentrations of Free Fatty Acids

¹ Department of Food Science and Center for Dairy Research, University of Wisconsin-Madison, Madison 53706

The effects of controlled availability of substrate on the production of methyl ketones in milk-fat-coated microcapsules were studied to determine the suitability of the microcapsules for the accelerated ripening of cheese types that would derive flavor benefits from added methyl ketones. In a 2 x 2 factorial experiment, microcapsules were made containing Penicillium roqueforti spores, phosphate buffer, and one of two levels of a low melting fraction of milk fat in water emulsion. The emulsion had been incubated with pancreatic lipase for 4 or 8 h. Production of methyl ketones (2-pentanone, 2-heptanone, and 2-nonanone) and FFA (hexanoic, octanoic, and decanoic acids) during the 30-d incubation at 10°C were analyzed by gas-liquid chromatography. Methyl ketone concentrations increased initially but then rapidly decreased in the first 200 h of incubation and eventually declined to near zero. Free fatty acid concentrations were initially high, but they rapidly decreased in the first 50 h of incubation and stabilized near 250 µg/g capsules. 2-Nonanone was the most abundant methyl ketone, but its precursor, decanoic acid, was generally no more abundant than hexanoic acid, the precursor of 2-pentanone. Because the highest concentrations of methyl ketones produced in these capsules were much lower than the levels produced in microcapsules with lipase (18), this method seems promising for controlling levels of methyl ketones produced by this microcapsule system.

Key Words: microencapsulation • cheese flavor • methyl ketones

Submitted on October 18, 1990
Accepted on February 26, 1991