Impact of available nitrogen and sugar concentration in musts on alcoholic fermentation and subsequent wine spoilage by Brettanomyces bruxellensis

- Addition of YAN to high sugar musts did not ensure completion of fermentation.
- Grape musts containing higher YAN resulted in higher concentrations of residual nitrogen in resultant wines.
- Brettanomyces bruxellensis has low requirements for YAN present in wine.
- Ethanol content affected growth of B. bruxellensis more than available YAN.

The level of yeast assimilable nitrogen (YAN) supplementation required for Saccharomyces cerevisiae to complete fermentation of high sugar musts in addition to the impact of non-metabolized nitrogen on post-alcoholic spoilage by Brettanomyces bruxellensis was studied. A 2 × 3 factorial design was employed using a synthetic grape juice medium with YAN (150 or 250 mg N/L) and equal proportions of glucose/fructose (230, 250, or 270 g/L) as variables. S. cerevisiae ECA5 (low nitrogen requirement) or Uvaferm 228 (high nitrogen requirement) were inoculated at 105 cfu/mL while B. bruxellensis E1 or B2 were added once alcoholic fermentation ceased. Regardless of YAN concentration, musts that contained 230 or 250 g/L glucose/fructose at either nitrogen level attained dryness (mean = 0.32 g/L fructose) while those containing 270 g/L generally did not (mean = 2.5 g/L fructose). Higher concentrations of YAN present in musts yielded wines with higher amounts of α-amino acids and ammonium but very little (≤6 mg N/L) was needed by B. bruxellensis to attain populations ≥107 cfu/mL. While adding nitrogen to high sugar musts does not necessarily ensure completion of alcoholic fermentation, residual YAN did not affect B. bruxellensis growth as much as ethanol concentration.