When do you worry about oxygen?

[le_tex]

I apologize if this has been posted before...


I'm new to wine making, and I'm trying to make various fruit wines from pulp (wild plum, muscadine, apple). I started primary fermentation in a plastic bucket, and then racked to a glass carboy for secondary fermentation.


At what point should I be worried about oxygen affecting the wine?


Should I limit how much oxygen touches my wine in the primary fermentation bucket? If so, why do the instructions say to punch down the pulp on a daily basis?


At what point will the wine turn into vinegar? Is it a very fine line, or is the whole process pretty forgiving?

 

[Waldo]

Only after fermentation has slowed down considerably or completed does exposure to oxygen become a real issue. Especially after it has completed, you want to keep your carboy topped up to limit the exposure.

 

[NorthernWinos]

Welcome le tex....hope you enjoy your stay here and get the answers you seek and share your knowledge...stay awhile.

 

[jobe05]

Le Tex, welcome to the forum, you pose an interesting question that really isn't covered anywhere that I have seen.

In talking with other wine makers locally, we have come to the conclusion that the reasoning for racking from primary to secondary at 1.010 for a 6 gallon batch, and racking at 1.020 for a 3 gallon batch is due to the head space in the primary, vs the co2 being created by the must to protect the wine. In other words, if you let the SG drop much further, you run the risk of exposure.

In the secondary, you have decreased the head space considerably, and less of a co2 blanket is needed to maintain positive pressure and keep out the air. After this stage, you will want to make sure 100% of the time, that your carboys are topped off to whithin an inch or so of the bottom of the bung.

Again, thats not scientific, it's just reasonable deduction from some of us with limited experiences.

 

[PeterZ]

Le Tex, it depends a lot on how you set up your primary.

In the beginning a little oxygen is necessary in the must because the yeast need it to reproduce. Once fermentation is rocking in the primary the produced CO2 drives off any remaining O2 (and N2) in the wine, because an overdise of one gas tends to drive out other gasses, a process in industry called sparging.

If your primary is a bucket is just covered with a clean towel, then you need to rack to glass while fermentation is still active so you can reform the CO2 cap in the carboy under an airlock.

If, OTOH, your primary has a tight fitting lid with an airlock, you are already safe from that problem and can do all of the fermentation in the primary. In fact one kit manufacturer, RJS, now has their instructions set to do this. The advantage here is that you can fill the secondary to the neck and proceed directly to stabilizing and clarifying without worrying about continued fermentation causing a volcanic eruption through the narrow neck of the carboy.

Punching down the fruit has several reasons. Fruit floating on the top is not contrinuting flavor to the wine. It is also subject to the growth of wild molds, which can impart an off flavor. Molds are everywhere, so they are in your fruit (including grape) wines, but they like moist, not wet, environments. The top of a fruit cap is perfect, but inside the must is not.

A little oxygen in wine is not anything to worry about. Part of the aging of a bottle of wine is the result of tiny amounts of O2 diffusing through the cork over time. We decant young wines and let them breathe to accelerate that process. Too much O2 will oxidize the wine, turning a red to a tan. This is not always a bad thing - tawney port is oxidized ruby port - but usually it ruins the wine.

Vinegar does not happen by O2 alone. It also requires a bacteris from the Acetobacter sp. family. This bacteria uses alcohol and O2 to create acetic acid, the acid in vinegar. This process is also what makes sourdough bread. The yeast in the starter creates alcohol (from starch in the flour instead of sugar) and the bacteria converts it to acetic acid. That is the source of the tanginess of sourdough bread.

 

[Jack on Rainy]

Le Tex,

This forum has added more info and fun to this addictive hobby for me than I can tell you. Welcome.

The O2 question you raise has been covered but I wonder why no one has
mentioned filling the head space with argon or other inert gas after
fermentation is complete to displace O2. In my case, I have not wanted
to dilute my batches after the initial topping up in the primary so I
use inert gas to fill that space.

And thanks again Peter for context to this hobby. My wife has been
tolerant and even supportive of my wine making taking over the house.
She will surely enjoy your comments about sourdough.

 

[le_tex]

Thank you very much for your quick responses. It's nice to feel welcome to learn!


I think I have a better grasp on the oxygen issue now.I haven't started thegrape and apple wine yet, so I can apply your advice on those upcoming batches.


One more questions for now - how do you know when fermentation has ended?

 

[grapeman]

Most importantly is the use of a hydrometer. Take the inital starting reading and monitor the fermentation with it. When in the secondary, watch the bubbles and when they have slow to almost a stop, check it again. If the SG is below 0.996 check again a day or two later. If it doesn lower any more, then the fermentation is done.(This assumes you haven't started a malolactic fermentation in the grape wine).


Ask again when you start these others and we will give you more guidance.


By the way- you do have a hydrometer don't you? This is probably THE single most important piece of equipment you need and is under $10!


By the way Welcome to the forum!

 

[le_tex]

That makes sense. I do havea hydrometer - Fine Vine Wines set me up right with a starter kit!


I feel like I'm "armed and ready" to try my next wines. Thank you all for your help!

 

[Wade E]

1 more thing to add, some people start with a higher SG (Starting Gravity) to end up with some residual sugar for a slightly sweeter wine which you can only acheive with a lower abv yeast (one which will only go to 13 or 14) abv. and if you do this your finished gravity will stop higher than 0.996 so you will have to check a few days in a row like appleman said to make sure that the SG is stable.
Edited by: wade