Notes from the Eastern Viticulture Workshop---Part 3

Following a nice break for lunch, Charlie Koines spoke about "Risk Management and Crop Insurance Programs". He gave us a handout that summarized all of his presentation so that it was quite easy to follow. He asked if any in the audience had crop insurance. This was a trick question because he knew that no one in Connecticut currently has crop insurance for their grapes. Connecticut growers do have the ability to insure their crop if the grapes are grown for wine or juice. At this time, table grapes are not insurable. The insurance period begins on November 21. The information sheet provided by Charlie Koines can be accessed at: Grapes New York Risk Management Agency. This pdf is a concise summary of the information regarding grape crop insurance.
Dr. Sara Spayd gave the only enology talk of the session. Her presentation was entitled "Nitrogen Nutrition in Fermentation." Nitrogen is important for the following processes:

• Yeast require nitrogen for growth
• Vitamins including thiamine and biotin necessary for yeast growth contain nitrogen
• Fusel alcohols that contribute to wine flavor contain nitrogen
• Pyrazine compounds contain nitrogen
• Amines contain nitrogen

The must should be tested for nitrogen content. Yeast assimilable/available nitrogen (YAN) is a measure of ammonium and α-amino acids. The appropriate amino acid measurement is important because proline can be one of the more abundant amino acids in the must, however, proline is not a primary amino acid and the nitrogen is not available to yeasts. It is also important to know the arginine concentration of the must because arginine metabolism leads to the formation of citrulline and ornithine, which can form urea. Urea in combination with ethanol forms ethyl carbamate or urethane, which is a minor carcinogen.
YAN necessary for fermentation:

• Minimum 150 mg YAN/L for white wine fermentation at 55 ^oF
• Healthy 400 mg YAN/L
• Australian standard 600 mg YAN/L

Nitrogen can be added to fermentation in the form of diammonium phosphate (DAP). Most enologists that Dr. Spayd spoke with preferred to add DAP rather than correct nitrogen deficiency in the vineyard. She mentioned that in addition to having a pH meter in the laboratory, a spectrophotometer can be very helpful in measuring amino acid concentration as well as phenolic content of the must.