Jeremiah Loyd,* Garrett Morales, Sonet Van Zyl, and Stephan Sommer
*Fresno State Viticulture and Enology, 2360 E. Barstow Avenue, M/S VR89, Fresno, CA 93740 (jeremiahloyd@mail.fresnostate.edu)

Commercial grape quality is assessed visually. Contamination can potentially lead to loss of quality, yield, and profit. Fungal infections, such as Botrytis, Penicillium, and Aspergillus, can negatively affect the progression of fermentation and the overall flavor profile of the finished wine. The study objective was to use analytical testing of FT-MIR spectroscopy on incoming different levels of sour rot to assess quality, evaluate fermentation kinetics, and perform sensory analysis. Over the past three years, 13 tons of grapes have been collected to facilitate winemaking with grapes from 10 different vineyards, producing a total of 72 wines. Grapes were harvested separately from each vineyard and divided into clean and microbially impacted clusters. The visually clean grapes were dosed by percentages of infected grapes at 0, 5, 10, 15, and 20%, by weight in reds and by volume in whites. Infected grapes initially showing higher levels of volatile acidity did not directly correlate with higher volatile acidity in a finished wine, sometimes even having less. On the other hand, greater sugar levels in impacted juice did lead to more ethanol in the finished wine. 3-AFC difference testing and ranked preference testing were performed with 16 panelists who were tracked over eight groups of wines. Higher levels of impacted juice/must could not be discerned while lower levels could be differentiated.

Funding Support: California Winegrape Inspection Advisory Board Agricultural Research Institute