Force Test on Wort

[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 (site below)
http://www.makewebs.com

 

[Walker]

I've never even heard of the term "force testing".

What exactly are you trying to accomplish by stashing a small sample of unfermented wort for a couple of days?

 

[DavidP]

IMO these samples will always become infected with ambient bugs unless you're totally sterile in your handling of the tube and wort. The tube being infected will have no correlation to your carboy being infected.

 

[llazy_llama]

I totally came into this thread expecting something about midichlorians, which I am still trying to use to replace yeast in my brews.

 

[Edcculus]

The force is strong with this one.

 

[BackAlleyBrewingCo]

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?]

You probably want a way for CO2 to dissipate, either with an airlock, foil, or just loosely screwing the cap on. Otherwise you may end up with a mess, or a dangerous pressure build up.

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?

Something's growing in there, hard to guess based on what you know so far. Let it go for a while and see if you can identify it by smell/taste.

 

[gxm]

I read about force testing in "History of Beer & Brewing". Apparently this was a big innovation in ~1860, and if they could do it then, us homebrewers should be able to.

Unfortunately, ipscman, I don't have any info to help with your actual issue. I am curious to hear more about force testing.

 

[ipscman]

I first learned about the forced wort test from Jean 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 smells 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.

 

[Walker]

Plating and microscopy will probably be required to nail it down with certainty.

Great.....

Now I have to spend another couple hundred $ on equipment.