Bentonite before or after fermentation?

[BernardSmith]

I don't use kits but I do check out the published instructions from time to time and I see that some kits (all kits?) including Eclipse and Selection ask that the bentonite they supply be added even before any yeast has been pitched. When people in this forum discuss clearing wine it tends to be after the wine has been fully fermented. Are there advantages to adding a clearing agent before fermentation begins? Does this apply only to bentonite and not say, to Sparkolloid. Are there disadvantages to adding a clearing agent right at the beginning? Is this done to help speed up a process for which kit buyers are thought not to want to wait or does it make good sense if I intend to use a clearing agent to add it before I pitch the yeast (and so presumably, some of the agent is being stirred up as I aerate the must in the bucket each day)?

 

[BobF]

Sorry for the cut/paste, but sometimes it's easier than typing.

Q. What is bentonite? What does it do?
A. Bentonite is a fining agent, it helps to clear the sediment out of your wine, and it also works during primary fermentation as a “nucleation site” meaning it helps the juice to ferment. Bentonite is a type of clay, known as aluminosilicate, it is found with various minerals attached to it, ours is composed of sodium and calcium. When used in winemaking, it is stirred into the wine to remove proteins and other haze causing particles. Bentonite works through adsorption, it attaches itself to a particle and together they are too heavy to stay in suspension. They then fall to the bottom of the carboy, Bentonite settles out so completely that it does not leave any residue of taste or color behind.

http://valleyvintner.com/Merchant2/FAQ/Day1.htm

 

[BernardSmith]

But this is one of the companies that instructs folk to add bentonite to the must before fermentation. And they claim that bentonite aids in fermenting juice. OK, but UC Davis publishes a piece that includes the following

"In summary, bentonite fining can lead to sluggish fermentation in some juices if the bentonite lees are
removed. This reduction in fermentation rate was not rectified by adding additional bentonite back to the
juice, or by adding macro- or micronutrients. If a sluggish fermentation is detected due to bentonite
treatment, the authors suggest adding fatty acids, or compensating with aeration."

Author: Bibiana Guerra, Editor: Kay Bogart. This summary series funded by J. Lohr Vineyards & Wines.

So clearly others are suggesting that bentonite can inhibit fermentation not enhance it..

 

[BobF]

When differences like these come up, I tend to give more weight to the commercial guys that have a vested interest in having happy customers. Kits also include fining agents other than bentonite for use post-ferment.

The research folks tend to be more ... uh ... academic.

From my own experience, I believe that having more solids means more nucleation sites for getting dissolved CO2 OUT of wine.

 

[wyntheef]

i would take that to mean that the lees/bentonite should not be racked off before fermentation is complete.

 

[SBWs]

The way it was explained to me is when added in primary the bentonite attaches its self to co2 bubbles and is carried to the top where the bubble pops and the bentonite settles back to the bottom taking more solids with it. This cycle continues throughout fermentation and therefore you don't need as much bentonite. If used after fermentation then it goes in, gets stirred around, and settles to the bottom and is done.

It is always the first thing I add when making fruit wines. 1/2 to 3/4 inch of hot water in bottom of primary and sprinkle in bentonite while swirling around water until dissolved.