Kinetics of Flavor Formation During Grape Juice Fermentations
Using solid phase microextraction coupled with gas chromatotgraphic analysis, we are able to ?continuously? monitor ester production throughout grape juice fermentations. In previous studies we used this technique to monitor differences in production of acetate and fatty acid ethyl esters that could be related to the progression of the fermentation. In addition a multi-peak pattern of ester production was observed which had not previously been reported. During the past year (2002-2003) our studies showed that:(a) Yeast inoculation level can significantly impact the concentrations and production profiles of the ethyl esters and acetate esters studied. However, other fermentation parameters (e.g., initial sugar levels, yeast nutrients, etc.) appear to influence ester formation as much as yeast inoculation level. The effects of inoculation level are also dependent on the specific ester studied. (b) Initial sugar concentrations impact ester formation profiles and there is an interaction between initial Brix levels and yeast inoculation level. These differences do not appear to be fully explained by differences in total cell counts and cell viability, but may be influenced by other juice components or fermentation variables.