Ethanol biosynthesis and hydrocyanic acid liberation during fruit mashes fermentation

The biosynthesis of ethanol and release of hydrocyanic acid are important factors characterising the fermentation process of fruit mashes. The effects were determined of the fruit pretreatment and method of fermentation (with or without the addition of wine yeast) on the dynamics of ethanol biosynthesis and hydrocyanic acid liberation during fruit mashes fermentation and its concentrations in the spirits obtained. Depending on the fermentation variants, the highest rate of ethanol biosynthesis was observed between the first and third days of plum mashes fermentation, and between the first and fourth days of chokeberry mashes fermentation. In the majority of fermented mashes, the maximum dynamics of HCN liberation was recorded on the first day of the process. Spontaneous fermentation of fruit pulp resulted in much higher amounts of HCN in the spirits obtained (10.5 mg/l of plum spirit 40%, v/v, and 28.90 mg/l of chokeberry spirit 40%, v/v) in relation to the contents observed in the distillates from the mashes fermented with the addition of S. bayanus wine yeast (2.80 mg/l of plum spirit 40%, v/v, and 12.46 mg/l of chokeberry spirit 40%,v/v). The treatment with the pectolytic preparation (PEKTOZYMETM POWERMash) had no significant effect on the concentration of HCN in fruit spirits, whereas the pressure/thermal treatment reduced HCN content, especially in chokeberry distillate, by ca. 71% as compared to the reference spirit (obtained from raw pulp).