The instant invention relates to processes and systems for the fermentative production of ethanol. The ethanol is produced by fermenting a fermentable carbohydrate with a yeast, whereby acetaldehyde is externally supplied to the yeast cell for reducing glycerol by-product formation by the yeast cell, for improving the performance of yeast at high ethanol levels and/or for suppression of infections during the fermentation. The acetaldehyde that is externally supplied to the fermentation medium can be produced by catalytic oxidation of ethanol. Advantageously, acetaldehyde production from ethanol is integrated in a system for ethanol production. Thus, in another aspect the invention relates to a system for producing ethanol, e.g. an ethanol plant, which system, in addition to the usual means for fermentative production of ethanol, comprises a means for producing acetaldehyde by catalytic oxidation of ethanol. The invention further relates to a process for disinfecting fermentation equipment such as fermenters and bioreactors, as well as fermentations feedstocks, wherein the equipment and/or feedstocks is disinfected with high concentrations of acetaldehyde, which are then diluted to non-toxic concentrations by addition of the fermentation medium.

An object of the present invention is to provide a technique for masking the bitterness and astringency of an unrefined distilled plum liquor.

By incorporating a specified amount of at least one selected from isobutyric acid, acetic acid, and benzaldehyde in an unrefined distilled plum liquor, there can be provided a distilled plum liquor in which the bitterness and astringency derived from the unrefined distilled plum liquor is masked.

A process for producing a distilled ethanol product comprising an antioxidant component and an ethanol component is described. In the process, plant matter containing antioxidants is washed, frozen and exposed to an input volume of ethanol. Antioxidants are ethanolically extracted from the frozen plant matter. The plant matter and the liquid ethanol fractions are then separated and the plant matter having antioxidants extracted therefrom is used to produce ethanol which is subsequently used to extract antioxidants from a second batch of plant matter. The ethanol fraction having antioxidants therein is stored or diluted for later use.