Microencapsulation of Cell-Free Extracts to Demonstrate the Feasibility of Heterogeneous Enzyme Systems and Cofactor Recycling for Development of Flavor in Cheese

A mixture of a cell-free extract from Gluconobacter oxydans that produced acetic acid from ethanol and a cell-free extract from Streptococcus lactis var. maltigenes, which converted leucine to 3-methylbutanal and 3-methylbutanol, were coencapsulated with substrate and nicotinamide adenine dinucleotide in a milk fat coat. The capsules were incubated as 12.8, 22, and 32C to measure production of 3-methylbutanal, 3-methylbutanol, and acetic acid and recycling of nicotinamide adenine dinucleotide/reduced nicotinamide adenine dinucleotide. Maximum amounts of 3-methytbutanal and 3-methylbutanoI were produced after 48 h at 22C, demonstrating the feasibility of encapsulating a combined CFE to recycle cofactors and produce an array of products. Capsules containing the combined cell-free extract were added to skim milk and milk containing 1.1% fat to produce cheeses with reduced fat. About 16% of the capsules were lost in whey during manufacturing of cheese from skim milk with added capsules but less for cheese made with 1.1% fat plus capsules. During ripening at 7.2 and 12.8C for 1, 3, and 6 mo, cheeses containing whole capsules with a complete cell-free extract mixture contained more 3-methylbutanal and 3-methylbutanol and exhibited a stronger malty taste than cheeses made with broken capsules or an incomplete cell-free extract mixture.