Oxidation in Beers

I'll admit I had a flavor problem that I had a difficult time tracing, and it ended up being oxidation. This article will describe how I arrived at the conclusion that oxygen was to blame, and also how I addressed the issue.

The curious thing about the off-flavor was that my beer tasted perfect when primary fermentation was done, when I transferred to secondary, when I transferred to the keg, and probably 2-3 weeks after that. However, as the beer aged, it took on tastes similar to sherry or cough syrup...regardless of the style of beer.

John Palmer writes about off-flavors in his How To Brew publication (see section 21.2), and this helped confirm the flavor. Additionally, a couple friends offered advice on how to diagnose and address it. I'll admit I was somewhat lax when it came to preventing oxidation, so I took the following steps:

• When I transfer beer to the secondary, I purge the secondary vessel with CO2, and siphon slowly, all while flowing CO2 gently.
• When transferring to the keg, I follow the same procedure: flowing CO2 into the keg during transfer.

It doesn't hurt to make a few other changes that were probably overdue, or just good practice, so I also did these:

• Replaced all beverage and siphon tubing.
• Ran PBW through by counterflow chiller multiple times, and let it sit for a while, too.
• Ferment in glass (I will be avoiding white food grade plastic, as it is not impermeable to oxygen, and also can take on flavors).
• Use only the refractometer Santa gave me from now on.
• Watch my sparge temperatures more carefully.

So far, the chocolate coffee oatmeal stout I made has passed the 4 week mark, so I'm pretty confident the problem was either solely oxidation, or oxidation plus old serving/siphon lines. If you notice a sherry-like or cough syrup taste (I never got the cardboard taste many describe), you may have the same issue that plagued a few of my beers. It is a terrible waste to spend all the time, effort, and money on great beer, and have it spoil!

Brew Session Illustrated

This weekend, I made a batch of Imperial IPA from this recipe. Had my friends Eric and Tina over to help make the beer, and we also got to sample some homebrew. Tina made a phenomenal Irish Red that has a big hit with everyone!

So here is a pictorial of the session.

1. Add water to the HLT (Hot Liquor Tank). The amount that will be added to the mash tun will be about 1 quart per pound of grain. In this case, that works out to 17 quarts, but I round up to 5 gallons to heat (I'll only use 17 or so quarts of that for the mash).

2. Here is a picture of the water in the HLT. I put a floating thermometer in here to monitor the temperature.

3. Whenever I have a burner running, I run these fans on high. They are attached to a piece of plywood that fits into my walkout basement door frame, and push basement air out. On the other side of my basement, I have 3 windows open to supply fresh air. If you brew indoors, always keep a CO detector nearby!

 4. Here is the burner lit under the HLT, getting the water up to around 165 Fahrenheit degrees. They are simple turkey fryer burners that I modified for natural gas. Propane is delivered at high pressure, so the orifice (brass part) has a very small opening. Since natural gas is delivered at much lower pressure, I simply drilled out the orifice to allow more gas through.

5. While we wait for the water in the HLT to get up to temperature, we can crush the grain. Since 17 pounds is a lot of grain, I opt for a cordless drill running in low gear and a medium speed.

6. When the water in the HLT got to 165, we combined the crushed grain and hot water in my newly designed mash tun. Stir well to break up dough balls! I fine-tune the mash with some cold water until the mash reads about 154 on my floating thermometer. Then it sits for about 1 hour to allow the enzymes to convert starch into sugar.

7. While the mash is sitting for an hour, I add more water to the HLT and heat it to around 180. This will be used to sparge (rinse) the grain in the mash tun. The grain bed needs to be "set" in order to clear the manifold of grain husks and particles. I use my March pump to slowly reintroduce the wort back into the mash tun. It only takes a pint or so until the wort is clear (it will be foggy, but no chunks).

8. Here is a picture of the fly sparge operation. You can see the HLT on the left introducing 180 degree sparge water into the mash tun, and the March pump pushing hot wort from the mash tun to the boil pot. It is important to have the HLT water diffused so it doesn't drill a hole through the grain (see blue coffee can lid above), and drain slowly by throttling the pump output.

9. Here is what the pump discharge looks like going into the boil pot.

10. One of many hop additions. It is, after all, an IPA we're making!

11. During the boil, I like to multi-task a little. This means cleaning out the mash tun, the pump, the hoses, etc. Also, sanitize anything that will contact cooled wort. See my post on Saving Time Brewing for more ideas.

12. Then after the boil is done, I give the wort in the boil pot a good stir in one direction to "whirlpool" it. All the hop particles and the hot break forms a cone in the center, away from the output port. This means less of this will end up in the fermenter and, ultimately, the beer. Here, the counterflow chiller is attached and ready for action.

13. Run the chiller and drain the first few ounces to clear the valve. This junk gets dumped.

14. Take a gravity reading. I was little low.

15. Here is the chiller running. With nice cold NY water, it brings the wort from over 200 degrees to around 62 degrees. I can control the wort flow and the water flow to get the right temperature going into the fermenter.

16. I made a yeast starter, so it is going in now. I always add the yeast about halfway through so that I can be guaranteed that the wort is at the right temperature. For example, if it is too hot, I will crank the water flow and throttle back the wort valve. If the wort is too hot, it can kill the yeast.

17. Here is a good view of the cone I mentioned in step 12. It is pretty apparent once most of the wort has drained from the boil pot. You can see the output pipe at around the 11 o'clock position.

18. To get the most out of the boil pot, I wedge a piece of wood on the back side to tilt it forward a little.

19. Once all of the wort is out of the boil pot, it helps to aerate the beer (wort+yeast) that is in the fermenter. Some people use an oxygen stone, some use air, other like to stir a lot...I use a paint stirrer on the end of my cordless drill to whip it up.

20. Here is the fermenter, all sealed up. It started bubbling within 12 hours, thanks to a healthy starter, plenty of sugar, and a good whipping!