Dismissing enological myths: effect of ethanol and maceration enzymes on grape seed tannin extraction. Enological implications

During maceration, proanthocyanidins are extracted from skin and seeds. It is commonly accepted that skin proanthocyanidins are more readily extractible, whereas extraction from seeds requires longer maceration and is favored by the presence of ethanol. 

Wine proanthocyanidin composition can be manipulated by winemaking practices, with several of these practices based on the assumption that ethanol from fermentation is necessary to disorganize the outer lipidic layer that covers and isolates the seeds, meaning that seed proanthocyanidins are only extracted if ethanol is present. In this way, low temperature prefermentative macerations are designed to increase the extraction and stabilization of the polyphenolic compounds from skins and it is commonly assumed that the extraction of the more aggressive seed proanthocyanidins would be very limited since alcohol is not present.

Trying to clarify this, we used a model solution to determine how ethanol and time affect the amount and characteristics of proanthocyanidins extracted from seeds.

We have also described the effect of different pure enzyme activities and commercial preparations on the release of proanthocyanidins from grape seeds.

The paper reproduced in this video-seminar was presented at the 2013 International SIVE Awards “Research for Development” (8th edition of Enoforum; 7-9 maggio 2013, Arezzo, Italy)

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