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When aeration is good but oxygenation is bad

carboy areation wort shake

How to properly aerate wort for brewing


While in some ways beer brewing is simply following a recipe but it sure is not like making a cake. There are some many variables at play.

Is the yeast viable?

How much hops do I need?

Is my equipment germ-free?

Is the temperature correct?

And on and on.

There's also one more variable that sometimes gets overlooked in the brewing and bottling processes and that's the role that oxygen plays in fermentation.

Oxygen supports yeast growth and effectively then has an influence on the ABV of one's beer so understanding the best way to manage this element will help improve your beer drinking experience.

First up, let's discuss the:

The relationship between yeast and oxygen


The yeast in your beer requires the presence of oxygen so that is can develop new yeast cell walls. The oxygen is used to develop unsaturated fatty acids and sterols, of which the yeast membrane is built.

Good oxygen levels promote strong yeast which in turn means it can handle high alcohol concentrations which means it was last longer and do a better job on your beer.

An efficient yeast means one gets quicker fermentation times and a reduce chance of a stuck fermentation. This also will mean that you will get fewer off flavors in your beer.

The higher the desired ABV, the more oxygen required


We made reference to it above but if you intend to make a high alcohol beer, you need to create an environment where the yeast can handle that - and a strong yeast is key.

At the same time, you are probably intending to pitch your yeast at a higher rate than you would for a 'session beer' so, all things being equal, you'll want to increase the oxygen ready to be used by that yeast.

How to aerate your wort with oxygen 

Before you aerate your wort the first thing to consider is WHEN.

If you aerate when the wort is too hot (this includes being warm) there is a vastly increased change the oxygen will bind to wort particles. 

If this happens, the risk is that over time these compounds will begin to break down, adding the oxygen back into the beer. The harm occurs as the oxygen can tend to oxidize the hop and alcohols.

This can produce 'off flavors' which are often described as being like 'wet or damp cardboard' or sherry like.

How to prevent oxygen from getting into your beer


We discussed above that aeration at hot temperatures is undesirable - so cooling your wort quickly is the best thing you can do.

Using a wort chiller will quickly bring your beer down to the right temperature so you can pitch your yeast but before you pitch, it's the time to oxygenate.

Carboys

If your wort is in a glass carboy, cover the mouth of the carboy with a cap and gently rock the carboy back and forth to encourage oxygenation of the wort. You can do this with a plastic fermenter too. 

Just make sure you have a firm grip!

If you're making a beer with a kit, once you have the kit in (along with hops and brew enhancer) then I fill it up with water from the garden hose. This will easily add plenty of oxygen to the wort. 

Once your beer is in the fermenter and fermentation is to begin, it's pretty simple to keep the oxygen out - you need to ensure the drum or carboy is tightly sealed and that your bubble airlock / air vent has water in it.

Then try not to move it again!

When bottling your beer, a bottling wand and a steady hand will help to prevent aeration. Do not leave your filled bottles uncapped for too long either!

stirring wort with a whisk

Other tricks for stirring in oxygen:
  • Use whisk. Get in there and use some elbow grease
  • Use a beer spoon. Not as efficient as a whisk but a strong arm will make some foam
  • Add an implement into a drill and use that
  • Use a siphon tube to spray the wort into the fermenter
Whichever agitation method s used, make sure that your implement is clean and sanitized to prevent risk of infection

Another great method is to use an aquarium pump for aeration. Check out this instructional video on how to configure the pump.


If using an aquarium fish style pump, you need to make sure the diffusion stone is clean and sanitized and is small enough to fit into the neck of the carboy. The stone also needs to have a small micron level of  between .5 to 2 to ensure lots of gas bubbles are produced.

diffusion stone for wort oxygenation

For best results, aerate your chilled or cool wort for 20-30 minutes.

When racking beer, try not to disturb the beer too much


When you're racking to a secondary fermenter or to your fermenting bucket it's imperative to prevent the liquid from splashing or getting agitated. When using a siphon it's best to keep it smoothly flowing.

Do I have to oxygenate my beer?


No.

You do not need to proactively aerate your beer, fermentation will still occur.

The point of aeration is that you are trying to give the yeast a leg up.

That said, some brewers are known to starve the yeast of oxygen as this assists with the beer profile they desire. This process is called anaerobic fermentation.

How to use foam inhibitor to avoid 'boil over' or a 'krausen explosion'

pot boil over prevention

Beware the krausen! A watched pot never boils right? 


This rule doesn't apply on brewing day.

Even though you are paying keen attention to your boil, it takes but a second for a boil over to happen, making a mess and causing you to lose wort.

But what if there was a way to stop boil over?


Some pundits recommend that you add marbles or ball bearings to the brew to help boil over.

Or use a spray bottle of cold water whenever the foamy beast raises its head.

But if you want to make sure you don't suffer a boil-over, try using a foam inhibitor!

Foam inhibitor or 'defoamer' is a handy trick to keep your beer from boiling over.

A popular product is 'Fermcap-S'. A fancy way to describe it is that it is a "silicone based food-grade emulsion".

There are two main ways to use it - during the boil and during fermentation.

If you choose to use 'Fermcap-S' to prevent boil overs on the hot side, add 2 drops per gallon for a nice rolling boil.

If you wish to use it in your carboy or fermenter to prevent the krausen from escaping the fermenter, then the dosage is only 2 drops at the start of fermentation. If you didn't know, the krausen describes the foamy head that develops on top of fermenting beer.

If you have added your inhibitor during the boil, there is no need to add any to the fermenter as it will carry over.

When used in the fermenter, 'Fermcap-S' increases the bitterness of your beer (retained IBUs) by about 10 per cent.

This sounds dandy but why should I use an inhibitor?


Boil-overs are more likely to be a problem if you are using a smaller pot. Users of fermcap have reported being able to make a 5.5 gallon batch in a 7 gallon pot.

While mess is annoying, the real reason you want to prevent this is that the foaming can cause any top-fermenting yeast to be expelled from the fermenter before it can do its job in the wort. 

This then requires the rest of the yeast to work harder to achieve the final terminal gravity which will not necessarily occur if yeast lost has been significant.

There is also another sweet effect of using an inhibitor like Fermcap it actually can help retain the IBUS from the hops - that is to say, it can help your beer become even more bitter when the product is added to the primary fermenter.

Beer is supposed to be foamy! This seems an odd product to use?


At first thought, using anti foam may seem to be a counter-intuitive idea. It would seem fair to consider that putting something in wort or fermenting beer to control foam will also kill the head on the finished product.

However, when anti-foams are used properly, quite the opposite is true!

Using vegetable based defoamer


Instead of silcone based products, you can also try vegetable oil versions.

Vegetable oil is a known yeast nutrient and will be consumed by the yeast during fermentation of beer before bottling or kegging.

Commercial breweries use it


Big commercial breweries often use defoamers and anti-foamers as part of their beer processing but given that it's not really within the spirit of purity brewing, it appears not many commercial operations will freely admit to adding silicone based products to their beer!

So what are you waiting for? Here's the cheapest Fermcap I have found on Amazon!

Begun, the beer wars have


Begun, the beer wars have.

Actually, this has been happening for a while now.

Big commercial brewers versus the little guy.

Big commercial brewers buying up the little guy.

Big commercial brewers trying to trademark beer lingo like radler.

And everyone hates them for it.

So when Tui attempted to bully Moa brewery a few years back, Moa stood up for themselves in a deliciously brilliant way.

While they are not the littlest guy, let's call them a mid-strength brand. They are on the NZ share market, and at the time of Tui's dig, there was nothing spectacular about their share price but they were slowly picking up sales around the world.

Either way, the diss Tui made as part of their famous yeah right campaign was worty of a retort.

If you haven't read the above very word image, do it now. You'll see the story play out really well. Moa is making the point that Tui is part of a world conglomerate where there a layers of corporations and SHAREHOLDERS.

So attempting to pick on a small fish for their share performance is somewhat ironic and amounts to a form of corporate bullying.

It's also amusing as if we are comparing the flavour of Tui to Moa's product, it's this humble drinker's opinion that Moa has the superior product range.

Sure, Tui was a beer I swilled back in my University days (where my Speights drinking mate used to say of Tui beer, "Tui is a bird and let's leave it at that". And that's about what it's still great for, binge drinking at a Uni Bar or a party or summer BBQ somewhere.

Hey don't get me wrong, Lion Nathan who is owned by mega-sized Japanese company Kirin still make Steinalager, which despite its massive commercialization, it's one of the best beers around. Other drinkers will disagree but for this drinker, there's something really special about that first taste of a cold bottle at the end of the day.