Wort Stability Test

I stumbled across an old post over at the Fledgling Brewer blog a couple weeks ago that piqued my interest. Titled, Homebrewer, Heal Thyself: The Wort Stability Test, it introduced a simple sanitation test that I’d actually done in the past, but hadn’t considered as being a thing with a name to itself.

A couple years ago, I fought with some off-flavors after bottling. In trying to find the source of the off-flavors, I bottled some wort from various stages of the cool side and tested how they tasted 4 or 5 days later. All of them were fine, until I got to the bottling end of things, and through process of elimination, I eventually narrowed things down to the bottling bucket or spigot (I replaced both).

As it happens, a simpler version of this test is discussed on the commercial side of the Wyeast Labs site:

It is important that a brewer regularly check the stability of the wort produced. A very simple and effective method is a wort stability test. This test can be performed by any brewery with or without a lab. The wort stability test consists of aseptically pulling a wort sample (post heat-exchanger) into a sterile sample container and holding that sample for 3 days in a warm area. If the sample remains clear and no CO2 is formed, the wort is stable. If the wort clouds up, CO2 is formed, a film develops on the surface, or off aromas are detected, then you know that you have a problem.

Wort Stability Sample This is such a simple sanity check, it seems worthwhile to do at least once or twice a year, so I pulled about 8 ounces of wort on it’s way to the fermenter into a sanitized beer bottle this Sunday when I was brewing what I’m calling the Freezer Burner APA.

This was especially timely because I’m planning on harvesting and rinsing the yeast from this batch of beer to repitch into an IPA I’m making in a few weeks, so I’d like to make sure it’s reasonably free from bacteria and other spoilers.

You can see the sample isn’t brilliantly clear, but it tasted and smelled exactly like the fresh wort going to the fermenter 3 days prior, and I believe some of the cloudiness was due to my less-than-careful pouring from the bottle into the sample jar.

I’ve never repitched yeast before, but knowing the initial batch had a nice healthy starter, controller fermentation temperatures, and the wort was essentially as sanitary as we can hope for going into the fermenter gives me a little extra piece of mind that I won’t be ruining 10 gallons of wort in a couple weeks by pitching less than clean yeast slurry.