Pre-ferment clarification risks of white must.

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Backwoods, but not backwards...
Sep 18, 2016
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North Central Arkansas Ozarks
Admittedly in my 15 years of making wine from my vineyard grapes I have had virtually no incidence of the stuck fermentation phenomena. I will chalk it up more to luck than any superior command of viniculture.

Some winemaking textbook authors have offered many reasons for the incidence of stuck fermentation. One explanation being the pre-fermentation clarification of white grape juice. This practice possibly lowers the quantity of resident nutrients/minerals used by the yeast in making a healthy ferment.

In my case I have only one practical option when readying my white must. I cold ferment all the juice (usually between 15-20 gal) in a single refrigerated vessel. Free run and moderately pressed is all combined. I would love to isolate and ferment just the free run but my setup and harvest poundage makes that impractical.

I am unaware of any study or investigation into the difference between nutrient levels, unsaturated fatty acid levels, ergosterol, etc. between pre-ferment clarified and unclarified must. And there is also the concern about oxidation if one waits during a clarification period.

Another valid response to these concerns is that to offest potential deficiencies nutrients can always be supplemented during the midway or end of the exponential phase of yeast growth. This is a practice I follow religiously anyway.

I may decide to increase the varietal vine number (chardonel, vidal) to allow more available juice to be split up and fermented separately. Looking at that clear free run coming off the press makes one wonder how much better it might be fermented alone.

A related issue is choosing whether to let the must sit for X hours pre-ferment with a pectic enzyme addition and ice jugs. Is the potential benefit of a greater yield outweighed by oxidation and wild yeast concerns? Some might say the fermentation process eliminates any initial discoloring/oxidation issues.

Tweaking these "steps" is always with the intention of improving the final product (bouquet, aromatics, mouthfeel, what have you).

I am certainly interested to know other approaches and philosophies about maximizing quality. It is an eternal and enjoyable endeavor.