Forced Wort Test

[Ipscman]

I frequently take a wort sample, just before pitching, put it in a test tube and put it in a warm, dark place for 2-4 days to check for obvious haze development. If any appears it is usually a sign of bacterial growth.

Problem. Two days ago I did this and when I popped the lid off the tube it gushed out a bit and at the bottom of the tube appeared to be nucleation bubbles arising just as if there was CO2. But this was before pitching. There is a little sediment on the bottom of the tube. Smells and tastes like wort recipe. Nothing unusual.

Question 1: When force testing wort, do you usually leave access to air (maybe a somewhat loose tin foil cover, or was my method with a screw on cap prefereable and why? [ I noticed today that DeClerck suggests putting a cotton ball in the top - so maybe it needs air to test properly?]

Question 2: Why gushing? Just enough to overflow the tube for a few seconds, not like fusarium in a beer where the bottle never stops gushing. More like beer foam for about 20 seconds. What could be the cause? Bacteria? Mold (post boil?) Gremlins?

Any ideas are welcome.

Mark
Hidden Well Brewery

[GimmeAles]

As a homebrewer, I find this an interesting new test to try. I recently started doing forced fermentability tests (especially for my bigger beers), but those require yeast and a large 02\Oxygen exchange over a couple days, and for a different purpose, so definitely not the process you used. Still, from my amateur analysis, this sounds like some yeast got in there somehow, especially since it doesn't smell or taste off.

If nothing else, thanks for the tip on a new test to try! Out of curiosity, is this something you do occasionally or for every batch?

Cheers!
- Ryan

[Ted Briggs]

Obviously something caused this to ferment. If your smell/taste test detects no funkyness I would guess yeast, without plating it there is no way to be sure though. The teqnique of a cotton ball, dipped in Alcohol and rung out, is a steril way oh capping while alowing gas to escape.Im inclined to blame the sampling method vs overall contamination though. Perhaps you might want to send a sample from that batch in for plating if you cant do it yourself just to be safe.

It may taste ok, but you may be building your contaminate load and get poor results from subsecuent pitches. Which is the purpose of this test, to quickly determine the sanitaryness(?) ,before the batch is done, for repitching.

Forced fermentation is a different technique used to determine maximum attenuation so you can gudge the progress of the batch.

PS. GimmeAles "As a homebrewer..." Please scroll up and read the logo in the left corner of the page.

[Ipscman]

As a homebrewer, I find this an interesting new test to try. I recently started doing forced fermentability tests (especially for my bigger beers), but those require yeast and a large 02\Oxygen exchange over a couple days, and for a different purpose, so definitely not the process you used. Still, from my amateur analysis, this sounds like some yeast got in there somehow, especially since it doesn't smell or taste off.

If nothing else, thanks for the tip on a new test to try! Out of curiosity, is this something you do occasionally or for every batch?

Cheers!
- Ryan

Hey Ryan, I respect your desire to learn more. Many craft brewers started out at home just like you. The fact that you're using pure oxygen in fermenting high gravity beers indicates you take brewing seriously. If you want to go further get some more books on the subject. Homebrewers gain a lot from Palmer's, How to Brew. I have over 60 books on brewing with most of the major professional texts available. If I could recommend one to start with it would probably be Goldammer's, The Brewer's Handbook. In fact you can read the entire volume online free. Just google it. Others I rely on include Briggs, Brewing: Science and Practice, Kunze's, Technology, Brewing and Malting, and Priest's, Handbook of Brewing.

I first learned about the forced wort test from Jen DeClerck in his 2 volume set, A Textbook of Brewing. The subject was also covered a few years back in Brewing Techniques magazine. It is a quick and inexpensive way to test your pre-fermentation sanitation. You simply sanitize your dispense (spigot, cock) using flame and alcohol or StarSan, pour 50 ml or so post whirlpool into a sterile test tube, put it in a warm (usually 30*C/77*F recommended), dark place and wait 4 days. If no haze, bubbles or obvious signs of bacterial growth appear, and if the wort smell fine (none of the classic smells of acetaldehyde, DMS, diacetyl, hydrogen sulfide, etc.) then you're doing pretty good. If there is evidence of a problem you may need to go back and find where that is occuring. Plating and microscopy will probably be required to nail it down with certainty.

Most brewing textbooks discuss gram negative and positive bacteria. While most homebrewers don't go to this level of investigation, professionals have to with some sort of lab set-up plating for various bacteria, molds or wild yeasts. Brewing Techniques did a study with semi-pro award winning homebrewers and as I recall close to 95% of the 30 brews tested had bacterial contamination. Most people are just oblivious. A professional has a brand reputation to protect. It is not a hobby but a profession they take pride in. The focus of this board is to provide craft brewer's a venue to share, learn and solve problems in their business. Probably a great place to lurk and learn. But if too many homebrewers muddy the water, it may lose its original focus and purpose.

Happy brewing.

[KWLSD]

Hi, you can do a quick 'sense-check' on this in the future by using two test tubes:

- If neither has any problems, you're ok
- If one is good, the other suspect, then look at physical hygiene
- If both are suspect, a good possibility of wort infection

Without doing specific media tests it would be difficult to identify what caused your unexpected result, however.

[liammckenna]

Was this oxygenated cold wort you put in the test tube with the screw on cap?

It may just be that O2 came out of solution as the tube warmed up?

Pax.

Liam

[Ipscman]

Great suggestions across the "board." Now I don't trust my memory and notes aren't specific enough. Too many new batches already. I believe I took the sample directly from the whirlpool. However, it acted like it was just releasing oxygen. When I checked again next day and two, releasing the cap no longer produced that reaction. It may have been the temperature of the wort into the bottle which was immediately sealed (@ 90*C) and the cooling effect without access to equalized oxygen that produced the effect?

Now I'm suspecting that the tight screw-on cap may have been the culprit, trapping the oxygen as it interacted with hop and polyphenol residue. This may be why DeClerck recommended cotton balls instead of caps?

Then again, I've never used caps often and haven't see this reaction previously. I may go ahead and plate it later to be certain. Everything else seems as normal.

I'll try and post back on the results.

Mark
Hidden Well Brewery