Enzyme-fermented wine

Leo Bueno asks,

I would have to say that enzyme-fermented wines don't exist.

I don't have the chemistry to lay before you, but enzymes in general act as organic CATALYSTS to major biochemical reactions.

That is to say, they make things happen, but they are not the Prime Movers.

It is YEAST which converts grape sugars (or any fruit sugar, for that matter) into alcohol.

Enzymes can aid in the process, but whenever commercial enzymes, to my knowledge, are employed in winemaking, it's to break down proteins.

All fruit contains a kind of protein called pectin. Fruits with a lot of natural pectin, like blackberries, or pears or pineapple, produce cloudiness in juice. If in sufficient amounts, you can make jelly from that fruit, because pectin is a gelatinous, jelly-like protein substance.

Pectic enzymes break down the proteins which create "jelliness".

They are NOT employed in winemaking for fermentation, which is a totally different process. Pectic enzymes do not produce alcohol as a by-product.

In fact, aggresive yeast strains also break down pectins, but some grapes (particularly the Labrusca from NE America) are so full of pectin, that sometimes a pectic enzyme is added to the fermenter, to help with future clarification of the wine.

Pectic enzymes are occasionally employed (but very rarely) to help clarify a wine, because even most Eastern US wines are completely clarified by the action of yeast.

Some types of grapes (but a very few commercial types, such as Semillon), may require pectic enzymes, but their use in the grand scheme of winemaking worldwide is minimal.

---Bob

Eduard Buchner (1860-1917) established the concept of cell-free fermentation, for which he received a Nobel Prize. He showed that alcoholic fermentation takes place even after the yeast are killed. Thus, we know that yeast are not really *needed* to ferment sugar into alcohol; the reaction can be catalyzed by their extract, as Buchner elegantly established. I think an enzyme called zymase was the agent ultimately identified. Thus my original question.

I thought that along the way zymase or another analogous enzyme (do any exist?) had been purified and used to do, perhaps quickly and efficiently, the tricky work of fermenting grape juice into wine.

I suspect that the reason folk don't make wine this way is because of either cost, technical difficulty, or that the end-product does not taste as good as when produced by the little beasts themselves.

So, I'll appreciate hearing a bit more about why enzymes are not used to produce wine.

-- ================================================Do you like wine? Do you live in South Florida? Visit the MIAMI WINE TASTERS group at

FWIW I think I read somewhere that one of the early fermentation researchers (Pasteur?) discovered that once the yeast began the fermentation the actual yeast cells could be removed and the must would continue to ferment. It was the enzyme that the yeast created that catalyzed the sugar to alcohol rather than the yeast itself.

My mental card catalog does not have a reference for this but I might be able to dig it out if you are interested.

Art Schubert Traverse City, Michigan

I recall reading that Pasteur established that fermentation was due to the yeast (as opposed to their being a catalyst or just some johnny come latelies to the process).

-- ================================================Do you like wine? Do you live in South Florida? Visit the MIAMI WINE TASTERS group at