Changes in Amount of Nitrogenous Compounds from Skins and Seeds of Four Grape Cultivars During Extraction Using Juice- or Fermenting Must-Like Model Solutions

Changes in the amounts of nitrogenous compounds (total and free amino acids, peptides, and proteins) were investigated during extraction under oenological winemaking conditions from seeds and skins of two Japanese cultivars (Koshu and Muscat Bailey A) and two European cultivars (Chardonnay and Cabernet Sauvignon) using juice-like model solutions and fermenting must-like model solutions. Two maceration systems, one prior to fermentation (without ethanol) and the other, during fermentation (with ethanol), were used. The amounts of nitrogenous compounds extracted increased with time. The amounts extracted varied with the cultivar. The nitrogenous compounds were gradually extracted from seeds, whereas those from skins were almost completely extracted on the first day. The presence of nitrogenous compounds, in particular free amino acids extracted from seeds and/or skins, may be relevant as nutrients for yeast growth during fermentation.