There are numerous potential causes of stuck fermentation. Acetic acid toxicity has been suggested as a cause of a stuck fermentation because it can inhibit the growth and fermentation activity of Saccharomyces cerevisiae, particularly at the end of fermentation when the concentration of acetic acid and other toxic compounds, such as ethanol, is highest. The experiment was performed in laboratory scale trying to emulate commercial fermentation conditions. The amount of sugar fermented after 20-21 days was dependent of the strain of Saccharomyces cerevisiae and was correlated with the concentration of acetic acid at the time of restarting for a concentration between 0.5 and 2.0 g/L. That is, the concentration of residual sugar increased with the concentration of acetic acid. In ferments that contained 4 g/L of acetic acid, however, the ferments remained stuck, albeit at a lower residual sugar concentration than the original ferment. At a concentration up to 4 g/L, and in presence of 13 pourcentage of ethanol, acetic acid did not prevent the restarting of the stuck ferment. Effective treatment of the incomplete fermentation was possible, therefore, in the presence of up to 2 g/L of acetic acid. The effective restarting ferment under the harsh condition examined indicates that the role of acetic acid in causing stuck fermentation requires further investigation.