Issue link: http://read.dmtmag.com/i/590181
w w w. v w m m e d i a . c o m N o v - D e c 2 015 | V I N E YA R D & W I N E RY M A N A G E M E N T 7 1 UNDERSTANDING THE CAUSE What causes reduction? It's the yeasts during the fermentation pro- cess. The main culprit is hydrogen sulfide (H 2 S), which smells like rot- ten eggs and sewers. Humans are quite sensitive to it, and can detect it at levels of 50-80 mg/L. During fer- mentation, yeasts produce between zero and 300 mg/L of H 2 S. Though studies have shown that 1 in 100 yeast strains don't make any H 2 S at all. H 2 S is the main source of reduc- tion problems in wine. Once it is present, it can then go on to produce more complex volatile sulfur com- pounds, which are hard to eliminate. For this reason, wine scientists have been eager to understand what is causing the yeast to release H 2 S, and to work at producing yeast strains that maintain desirable char- acteristics while not producing H 2 S. Recently, some of these new strains have begun to reach the marketplace. "Hydrogen sulfide is a common natural contaminant that occurs during the winemaking process," explained John Husnik, CEO of Renaissance Yeast, a Vancouver, B.C.-based company that special- izes in low H 2 S-producing strains. "As it is well established that the main source of H 2 S occurs during yeast fermentation, it is advanta- geous to address this issue at this point in the winemaking process and not after this reactive chemi- cal has had a chance to affect the quality of the wine. Removing H 2 S after it has already formed is not ideal since it can further react to form other defect-causing volatile sulfur compounds, such as mer- captans and disulfides. Essential- ly, we advocate that prevention of this fault is better than remediation after the quality of your wine has been compromised." Husnik explains the impact of H 2 S on wine. "At high concentra- tions, H 2 S is easily distinguishable as a rotten egg smell or sewage- like odor, and mercaptans and disulfides are experienced as burnt rubber, rotten cabbage, garlic and onion-like odors. Importantly, at very low levels in a complex matrix cases, it is known that H 2 S acts to mask the wine and prevents the expression of the wine's full com- plexity, flavor and aroma." like wine, the presence of H 2 S and other negative volatile sulfur com- pounds may not be easily detected as the above-listed faults. In these John Husnik of Renaissance Yeast says it's better to address H2S issues during fer- mentation than to try and remove it after it's already formed. Letina tanks, sanitary valves and fittings. St. Patrick's of Texas • StPats.com 50,000 square feet of Stainless Steel