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30 WINES&VINES March 2016 WINEMAKING rate until it got to -0.3° Brix. It was at that point that I noticed the first hint of acetalde- hyde, and I immediately stopped the flow of oxygen. In the next three days the Brix fell to -1.8° Brix. An appropriate amount of SO 2 was added, and now the wine smells and looks just like a freshly fermented Pinot Noir. There are no oxidative notes and no off-aromas or flavors. The other wines had similar results. My thoughts about what was happening now return to the discussion above. I had not contemplated the glucose-repression phenomenon until well after this process finished and I began evaluat- ing how this all came to pass. The rather unique environment that this trial presented had me initially worried about Acetobacter taking off in the presence of the excess of oxygen going into the wine. While I did not plate the wines, or- ganoleptic evaluation showed no noticeable increase in volatile acidity. It makes sense that the oxygen provided an extra kick to metabolism that could reactivate the aerobic pathways; it then took a longer than average time for the yeast population to re-ac- commodate to the new environment and start the final push to the end. The final sugar level at the end of fermentation for the Pinot Noir discussed above was 0.181 g/L glucose. This exercise suggests that winemakers should follow their fermentation curves criti- cally and look at changes in the curve's slope during the later parts of the cycle. Once a winemaker has good data about the average curves for his or her wines, when a fermenta- tion begins to show a different curve, early introduction of oxygen should keep it as robust as possible. The bottom line is, don't give up if a fer- mentation doesn't go to completion. Persever- ance and the delicate use of "macro" micro oxygenation can coax the pesky yeast to finish their job. Richard Carey, Ph.D., is owner and wine consultant at Tamanend Wine Consulting in Lancaster, Pa. He has written numerous articles about new technologies for the grape and wine industry for Wine East and Wines & Vines. Made In California sales @ giftboxcompany.com www.giftboxcompanyusa.com (562) 926 - 6888 HARD COVER WINE GIFT BOX The Gift Box Company Attention Detail Your success is our prioritY [gar - ] Environment that favors glucose repression [gar - ] [GAR + ] Environment that disfavors glucose repression Environment that favors glucose repression Mutation that reverses glucose repression Heritable protein-based reversal of glucose repression S. cerevisiae and other fungi with strong glucose repression BET-HEDGING PROPERTIES OF THE [GAR + ] PRION DANIEL F. JAROSZ7 ET AL., UCSF / CELL JOURNAL