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W i n e s & V i n e s D e C e M b e r 2 0 1 4 79 maid, for example, has several options that winemakers can choose from based on their specific wine: Fermaid k, Fermaid O and Fermaid A. Although there are differences in what nutrient suppliers consider a high-, medium and low-YAN reading, the general principle is the same: use the initial YAN content and Brix of the juice/must in order to determine proper nutrient supplementation. Some consideration may also need to be given to yeast strain selection, as some yeasts have higher nitrogen requirements than others and should be treated accordingly. Most suppliers offer a chart that indicates how much nitrogen is contributed to the YAN value based on the dosage rate of the product. For example, at a 30 g/hL (grams per hectoliter) addition rate of GoFerm, the product contributes 10mg N/L (milligrams of nitrogen per liter) to the YAN concentra- tion. If the addition rate was doubled to 60 g/hL, then 20mg N/L are contributed to the YAN value. Therefore, if the must's starting YAN was 150mg N/L, a 30 g/hL addition of GoFerm will bring the YAN up to 160mg WineEast Hydrogen sulfide development in wine H ydrogen sulfide (H 2 S) is a universal winemaking problem. Most researchers agree that H 2 S is developed through the sulfate reduction pathway. When sulfate (SO 4 2- ) is brought into the cell, it undergoes a series of transforma- tions before it is made into sulfide (S 2- ) and H 2 S. Hydrogen sulfide is used to develop the two sulfur-containing amino acids, methionine and cysteine. In order for cysteine and methionine production to continue, an equal amount of nitrogen (from the nitrogen compound pool) needs to be available to match with the H 2 S concentration. If there is not enough ni- trogen available to make the amino acids, H 2 S concentrates within the yeast cell. As H 2 S is toxic to the yeast cell, it is dif- fused into the surrounding media: wine. Sulfite (SO 2 ) added to the must as potassium metabisulfite (kMBS) bypasses the regulatory sulfate-reduction pathway by diffusing through the cell membrane and immediately reorienting in hydrogen sulfide. Large additions of kMBS to the must (more than 80 ppm) have been shown to in- crease H 2 S concentrations in wine. Hydrogen sulfide can also be produced as methio- nine and cysteine degradation, which may be a reflection of yeast stress or autolysis. D.G. Natural Corks Champagne Corks Twinline Corks Bartops VISION Synthetic Corks G-Cap® Screw Caps Sales Representatives: Chris & Liz Stamp info@lakewoodcork.com lakewoodcork.com 4024 State Route 14 Watkins Glen, NY 14891 607-535-9252 607-535-6656 Fax PIONEER INNOVATOR PARTNER As H 2 S is toxic to the yeast cell, it is diffused into the surrounding media: wine.