Methyl Ketone Production in Milk-Fat-Coated Microcapsules. 1. Variation of Lipase and Spore Concentrations

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

Milk-fat-coated microcapsules containing pancreatic lipase, Penicillium roqueforti spores, a low melting fraction of butter, and phosphate buffer were evaluated for their ability to produce methyl ketones to enhance blue cheese flavor and to accelerate cheese ripening. Lipase and spore powder levels were tested in a 2 x 2 factorial design experiment with a center point. Production of 2-pentanone, 2-heptanone, and 2-nonanone, plus hexanoic, octanoic, and decanoic acids during 26 d at 10°C was determined using gas chromatography. The three methyl ketones increased steadily for approximately 400h before leveling off near 12 mg/g capsules. Free fatty acid concentrations increased initially but rapidly decreased to near zero as they were utilized by the spores. Capsules containing the high lipase level produced significantly more FFA and methyl ketones than capsules with the low level of lipase. Spore amounts had much less effect on methyl ketone production. Preference of the spore enzymes for hexanoic and octanoic acids initially led to higher levels of 2-pentanone and 2-heptanone than 2-nonanone. As octanoic and hexanoic acids were depleted, however, the decanoic acid that the lipase produced in abundance was utilized to yield high levels of 2-nonanone. These results indicate that not only can these milk-fat-coated microcapsules be used to produce methyl ketones, a major component of blue cheese flavor (2, 3, 16), but also that environmental factors may be manipulated to control the reactions.

Key Words: microencapsulation • cheese flavor • methyl ketones

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