Beer Oxidation

If you’ve ever cut an apple and left it sitting, you’ll notice it goes from an off-white to a brownish color in just a couple of minutes…

That’s oxidation in a nutshell…

… and it happens with beer just like it does with fruits, metals, and other things…

I’ve understood this topic for a while, but have yet to come up with a simple explanation for it, though I think I finally got one…

Picture a bead necklace… the bead necklace is balanced by having an equal negative and positive charge…

Now our good friend oxygen here comes along and steals one electron (negative charge) from one of the beads… this bead becomes a free radical…

Everything seems fine at first, but what happens at this point is that the bead that just lost its electron tries to take one from the bead next to him…

The problem however is that the electron just stolen is not compatible and it doesn’t balance the free radical bead… and now two beads are missing electrons… two free radicals are formed…

The next bead will try to balance itself as well and this starts that process of oxidation…

One bead starts to steal the negative charge from the next one until all beads are missing a negative charge…

That’s when you see the apple turn darker and darker…

When you expose your beer to oxygen, this is the risk… after primary fermentation, any beer transfer you make needs to be done in a way that reduces contact with oxygen…

It’s the reason why you must purge your kegs when you keg… you push CO2 and release the pressure relief valve for about 20 seconds to push all the oxygen out…

Oxygen is the most common substance known to cause oxidation, but if you notice the way I explained it, oxidation is more about a substance losing electrons…

This is important because the opposite reaction is called Reducing… when a substance adds electrons to another substance…

Good examples of reducing substances found in beer are sodium, magnesium, iron, zinc and aluminium…

Many times when I transfer beer a few bubbles will develop during the first minute or so of my siphoning while I squeeze out the bubbles from the hose…

I may get a bit of splashing or bubbling at the end when I stop the siphon and this is indeed putting the beer in contact with oxygen, but the beer doesn’t oxidize because of the reducers…

I haven’t tested this yet, but I’m willing to bet that brewers that use soft water or RO water like myself are more prone to beer oxidizing than those with hard water which may contain higher levels of minerals that could serve as reducers…

The one thing I do know for sure is that dark malts carry antioxidants… antioxidants are reducing agents and one of the most common ones in beer are polyphenols…

These antioxidants stop that chain reaction…

That’s the reason why dark beers tend to age better than light beers… the antioxidants help keep the beer from oxidizing…

… and it’s only one factor that determines how long you should age a beer for before drinking it…

A beer that oxidizes tends to pick up a caramel like flavor, but it’s not a smooth flavor… it throws off the balance of the beer…

If you use hard water I’d love to hear any experiences with oxidation that may help me determine if hard water is indeed a good way to battle oxidation… let me know…

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