Brevibacteria increase cheddar cheese flavor.

For more than three decades, scientists have suspected that methanethiol production was involved in the development of cheddar cheese flavor. However, whole cells and cell-free extracts of lactococci do not produce the compound under simulated cheese conditions in the laboratory. Previously, Pseudomonas had been found in cheese and investigated for methanethiol production.

Scientists found an enzyme, demethiolase, which converts methionine (Met) to methanethiol. Subsequently, this enzyme or organisms containing this enzyme have been encapsulated and added to cheddar cheese with varied results.

Brevibacteria have a whole different biochemistry compared with lactic acid bacteria. They are more proteolytic, produce a softer cheese, increase production of sulfur compounds, and produce dicarbonyls and fatty acids, all of which increase cheese flavor. Brevibacteria produce methanethiol from 25 times to 100 times more efficiently than lactic acid bacteria do in optimum laboratory conditions, as measured by the methanethiol-producing capacity (MTPC). MTPC is not observed in cell-free extracts under cheese conditions (4% salt and pH 5.2), but is found with whole cells.

The substrate for the enzyme consists of Met and Met-containing peptides. If Met-containing peptides are utilized, aminopeptidases could be involved in providing Met to the intracellular enzyme. Met and Met-containing peptides were found to induce MTPC in Brevibacterium linens BL2. Met-containing peptides present in cheese from casein degradation also induced activity.

Researchers found that using brevibacteria in cheese increases cheddar flavor. This is presumed to be the result of increased methanethiol production during the product's aging.

Further information. Bart Weimer, UMC 8700, Utah State University, Logan, UT 84322; phone: [phone]; fax: [phone].