Causes of Ribes Flavor in Cheese

A study has been made of Ribes flavor (or catty flavor) which occurs occasionally in cheese. The flavor defect was found to be caused by 2-mercapto-2-methyl-pentan-4-one. This component is unstable and decomposes during the analysis. Its precursor, mesityl oxide, was isolated from Ribes cheese and identified by GLC, IR-spectrometry, and coupled GLC/mass-spectrometry. This component is absent in normal cheese. Addition of hydrogen sulfide to mesityl oxide takes place easily and leads to the formation of the Ribes flavor component. Its threshold value was determined to be approximately 1:10 10 in refined liquid paraffin. It is not clear how this flavor develops in cheese, but one or more of the following factors may play a part: the cheese coating, the microflora of the cheese rind, the surface of the cheese tray, and conditions in the cheese store.