EFFECTS OF SKIN CONTACT AND SETTLING ON THE LEVEL OF THE C18 2, C18/3FATTY-ACIDS AND C6 COMPOUNDS IN BURGUNDY CHARDONNAY MUSTS AND WINES/

In the present study, a skin contact process (maceration) was applied on Chardonnay grapes and the results compared with those from a contro l sample obtained directly after pressing and without maceration. Afte r the skin contact trial four different sets of conditions of settling were realized. Routine analyses were carried out on musts and wines a t the end of the alcoholic fermentation. It appears that skin contact greatly affects the acidity of musts and wines. From our experiments, two comparisons can be made. The trial of skin contact (16 h at 20 deg rees C) is compared with the control sample within the same conditions of settling (24 h storage at 20 degrees C). Secondly, from the shin c ontact trial, four different conditions of settling are compared: 24 h at a low temperature (15 degrees C); addition of pectinase and 24 h s torage at 20 degrees C; with no settling; 24 h storage at 20 degrees C , The effects of these different methods of white wine elaboration are demonstrated by the determination of the concentrations of certain C6 compounds and their lipid precursors (C18:2 and C18:3 fatty acids). C 6 aldehyde and alcohol compounds (hexan-1-ol, (E) hex-2-en-1-al, (Z) h ex-3-en-1-ol and (E) hex-2-en-1-ol) were analyzed by gas chromatograph y during wine elaboration. Lipid precursors (linoleic (C18:2) and lino lenic (C18:3) acids) were also determined by GC. During skin contact ( between 0 and 16 h), the evolution of C6 compounds and fatty acids con tents is studied, Analyses show that shin contact begins with an impor tant production of CG compounds, especially hexan-1-ol and (E) hex-2-e n-1-ol. After 2 h of skin contact, a loss of C6 compounds occurs by ad sorption on macromolecules and skin components. Without pressing, skin contact induces a loss of C6 compounds. On the other hand, the combin ed skin contact/pressing increases the release of precursors into the medium and the production of C6 compounds in the must. One of the prin cipal effects of settling is also a loss of hexan-1-ol and is linked t o the loss of lipid precursors. In the musts as well as in the wines, settling conditions can change the direct consequences of skin contact .