Stuck Fermentation

stuck fermentation, winemaker’s nightmare involving an alcoholic fermentation which ceases before completion. Such fermentations are notoriously difficult to restart and the wine is at risk of spoilage from oxidation and bacterial disease. Before cooling equipment was commonplace, fermentation temperatures could reach a dangerously high level, often in excess of 35 °C/95 °F. In extreme cases, with temperatures nearing the range at which yeasts are killed, over 40 °C, the yeast cells release compounds which inhibit future yeast growth, thereby making it difficult or impossible to restart such fermentations, even after cooling.