The first few days

[Billy-T]

Hi all,
I am new to making wine and I am curious. Why is the primary fermenter left open for a few days days without a water lock? Then the wine is racked into a secondary with a lock for some time.
Doesn't the yeast eat up the sugars without making any wine of it when it's exposed to air?
Billy

 

[cpfan]

Doesn't the yeast eat up the sugars without making any wine of it when it's exposed to air?
Billy

Well Billy, that's one I haven't heard of before. Where did you hear that one?

As I understand it, yeast needs oxygen in the initial stages. This is usually accomplished by brisk stirring of the must prior pitching the yeast. The stirring incorporates O2 into the must.

There is a large split between people who do their primary in sealed pail with an airlock, and those who use a lightly covered open fermenter.

I use primary fermenters that have a loose fitting lid and a large amount of head space. Using a primary with a small amount of head space creates a strong possibility of a vigourous ferment causing a mess (either out the air lock or pushing up the lid).

Either way the yeast + sugar reaction is going to produce alcohol, CO2, and SO2.

Steve

 

[Billy-T]

Thanks for the reply,

I meant the open fermentor, often described as a pail with a damp towel over it.

I was thinking that the open fermenter would let oxygen in, but of course since CO2 is heavier than air it will sit on top with or without an airlock. I put the lock on anyways just to keep out any little flies that might like the smell of the berries.
Billy

 

[Luc]

Billy,

By using an 'open fermenter' that means a fermentor with a cloth
over it to protect the wine makes it easier to press the cap down several times a day.

The cloth is used to keep the flies out.
The fermentation will indeed put a layer of CO2 on top of the wine.
But stirring (while pressing the cap down) will introduce some oxygen in the must anyhow.

The jury is still out on this one.

First most yeast live at the bottom of the primary (or secondary for that matter). Not much of oxygen at the bottom of the fermenter with all that must on top of the yeast.....

Then when the yeast is fermenting at the bottom of the primary it will produce CO2 which will replace the oxygen in the must.
So again not a lot of oxygen available.

Third at a certain point the yeast will go anaerobic itself (as modern science now believes) so.

On the other side:
Must (as home winemakers make it) will have oxygen dissolved in it (unless the must is cooked). The oxygen gets in there by splashing and general manipulation of the must.
Then some oxygen will be dissolved when one stirres the wine as in pressing down the cap.
And initially there will be enough oxygen in the headspace of the primary for the yeast to use.

So the jury is still out for the verdict.
I have done both: fermentation with a cloth on the primary and fermentation with the lid on and an air-lock attached. Both worked fine.

If you pitch the yeast on the must I would leave the primary open (covered with a cloth) for the first days.
When using a yeast starter (like I always do) you can ferment with the lid on and an airlock.

Making a yeast starter is easy, look at my weblog entry:

http://wijnmaker.blogspot.com/2007/08/gist-starter-yeast-starter.html

it never fails me and I almost always have a firm fermntation within a few hours.

Hope this helps confusing you some more

Luc