Confused about a couple things

[ultraplop]

I was reading Dave Miller's brewing book as well as John Palmer's online brewing guide, and there were a couple of things that confused me.

Both reccomend cooling the wort after its done as soon as possible for several reasons. To provide a cold break, prevent oxidation, and to prevent contamination. Not to mention the mixture has to be cool enough for the yeast to survive.

What doesn't make sense to me is how they top off the wort. Before creating the wort, Dave says to boil a large pot of water and let it sit overnight as it goes to room tempature. To me it seems like he is giving it a lot of time to get contaminated. John, on the other hand boils his top off water on brewing day. He doesn't say how long it sits, but it would probably sit there for possibly an hour or 2.

If the wort needs to be chilled right away, shouldn't the top off liquid also be cooled as soon as possible? Or better yet, wouldn't make more sense to boil the wort and top off liquid at the same time and combine them after the wort is done? At that point you could chill the entire 5-6 gallon batch as soon as possible to avoid contamination.

If you didn't do it that way it seems to be you could be working with possibly contaminated water or water that is too hot to add to an already chilled wort.

My second question is what is the difference between aeration and oxidation. Both terms kind of indicate that oxygen is getting added to the mixture. John says that you don't want the wort to take oxidation damage, but at the same time you want it to be aerated so that the yeast has oxygen to munch on. So why is aeration good and oxidation bad?

 

[loopmd]

I do not boil my "top off" water, but then again, I use bottled water. I do 2.5 gallon boils, then top off with well chilled(almost to the point of freezing) bottled water. Most people live by the rule if the water does not taste bad to drink, then it's ok to brew with. I live where the water is pretty hard and has a chorine taste. I have made batches with the water right out of the tap and never had any off tastes, it is just the clarity was not where I have been when I use bottled water.

Aeration vs oxydation. My take (for what it's worth) is that you want to aerate your wort prior to pitching your yeast as yeast need 2 things to survive....food and oxygen. After you pitch your yeast, you do not want to introduce oxygen to your wort as oxydation will occurr. I am sure someone with greater experience and knowledge will help you out more with question 2. However...aerate before pitching, never aerate after fermentation activity starts.

 

[cweston]

Most people who do partial boils just add tap water to make 5 gallons (or bottled water if your tasp water tastes bad.) If the bucket or carboy is well sanitized it's not going to be a problem. It also helps to p[itch a good healthy yeast starter: the faster the yeast start multiplying in the wort, the less chance there is for wild yeasa or any other nasties to take over.

Oxidation and aeration are pretty-much the same thing. When it's wort, and the yeast hasn't gotten to work yet, you want air in there to feed the yeast.

Once it's beer and the yeast has done its work, you don't want any more air than necessary in there.

 

[Kaiser]

If you boil water in a pot with the lid on for about 10 min and you don't take the lid off after it stoppes boiling, the water will not contaminate during the long time it takes to cool. Contaminating germs do not crawl inside your pot. They need to fall or be drafted in.

This is what I do for my starters. Boil for 10min with the lid on and let it cool overnight. Then I fill it in the starter vessel.

But for topping off your brew: you should be fine with store bought drinking water. I consider this water sterile enough for brewing purposes.

Kai

 

[Walker]

From a technical stance, aeration is dissolving air in the wort, where oxidation implies a chemical reaction that causes something(s) to literally COMBINE with the oxygen.

The reason it is important to cool wort rapidly is because the sugary solution is a fantastic breeding ground for bacteria and fungii. Plain water that is sanitary doesn't provide an attractive medium for organisms to thrive in, so the risk of your plain water becoming infected with some critter is infinitely smaller than the risk of your sugary wort getting infected. There's simply no food in plain water for nasties.

-walker

 

[Denny's Evil Concoctions]

When the wort is hot, oxygen will react with certain particles and oxidize. When the wort is cool it is safe to aerate. For the first 24hrs yeatst are in there aerobic (o2 guzzeling) stage. They eat up the o2 and any left will get scrubbed out by the co2 they produce during their anaerobic stage.

Well, that's the Coles notes verison.

edit: seems it's best to hit refresh BEFORE posting, haha. Got side tracked watching curling..

Check out: http://consumer.lallemand.com/danstar-lalvin/fortnightyeast.html

 

[Darth Konvel]

As Kai says, if you leave your boiled water covered, you're fine to leave it be. Boiled water isn't as condusive to organism growth as wort, which is basically as "bug friendly" as it can get. ie> Wort: nasties have all kinds of food to feed on and multiply, just boiled water: not so much.

Oxidation vs aeration. Oxidation is where you have oxygen chemically binding to elements in your brew. Aeration is the disolving of air into the liquid without it necessarily binding with whatever chemical agents are present. I'm honestly not entirely familiar with the chemistry of oxidation, so I can't say what would trigger it post-fermentation vs pre-fermentation - although the presence of alcohol certainly could be a factor.

edit: damn my slow posting!

 

[Walker]

I'm honestly not entirely familiar with the chemistry of oxidation, so I can't say what would trigger it post-fermentation vs pre-fermentation - although the presence of alcohol certainly could be a factor.

I'm not sure on this either, but my take on it has always been that oxidation happens due to energy in the system.

If you aerate when the wort is too hot, the heat can lead to oxidation.

If you aerate after the yeast have finished the growth phase, the energy created by fermentation can lead to oxidation.

Aerating after fermentation (ie; during the bottling process) would see a system free of extra energy, but there is nothing present to consume the oxygen so I don't know how oxidation would happen then. *shrug*

-walker

 

[BlightyBrewer]

Aerating after fermentation (ie; during the bottling process) would see a system free of extra energy, but there is nothing present to consume the oxygen so I don't know how oxidation would happen then. *shrug*

-walker

Wild yeast perhaps?

 

[ultraplop]

Thanks a lot for the clarification. My second batch turned out kind of sour; it must have gotten infected. I wanted to make sure everything including the water is perfectly clear of contamination for my next batch.

 

[Denny's Evil Concoctions]

I don't beleive its the energy casued by fermentation that causes oxidation. Hot side can oxidize failry quickly. Cold sie takes much much longer. Sicne the o2 in the first 24 hrs is eaten by the yeasties and the co2 scrubs out the rest no problem with oxidation. But the Co2 can only scrub out so much O2 so adding More leads to residual O2 levels. As well, after primary fermentation there is very little co2 being produced so any added o2 at that point is unlikly to be scrubbed out.

Good, Slovaks just scored 2 goals on the dang Ruskies in the last 2 minutes, beating the tie!

Sorry for the bad typing, but watching hockey at the same time.