Over attenuation with pectic enzyme?

[Foster82]

So I made a 1 gallon test batch of a strawberry ale and it ended up extremely dry. I added pureed (also heated to a boil) strawberries at flame-out. The beer was not clearing after primary fermentation had finished so I added some pectic enzyme, which did cause the beer to clear. However when I added it a slow secondary fermentation kicked off. Attenuation ended up at 89% (FG 1.005), making the beer extremely dry and almost wine like. The FFT ended at 83% (FG 1.008) which was prior to addition of the enzyme. Now I do know my mash temp was on the low end and I expected a fairly high attenuation but not 89%.

Does anyone know if pectic enzyme also breaks down unfermentable sugars, leading to extremely high attenuation? Or should I blame this one on low mash temp. Yeast was US-05 fermented at 69 degrees.

 

[LarryBrewer]

Based on the FFT it looks like the enzyme did make a significant difference.

According to this, under the Chemistry section, the pectins may contain sugars in their chemical makeup:
Rhamnogalacturonan I pectins (RG-I) contain a backbone of the repeating disaccharide: 4)-α-D-galacturonic acid-(1,2)-α-L-rhamnose-(1. From many of the rhamnose residues, sidechains of various neutral sugars branch off. The neutral sugars are mainly D-galactose, L-arabinose and D-xylose, with the types and proportions of neutral sugars varying with the origin of pectin.
http://en.wikipedia.org/wiki/Pectin

So, the enzyme probably did release these sugars into solution that were previously trapped as part of the pectin molecules. The yeast then gobbled them up.

Next time, potassium sorbate could be used to halt fermentation and retain some sweetness, and/or go with a higher mash and less attenuating yeast.

At this point you could also add potassium sorbate, then back sweeten with sugar to taste. That's a popular technique with white wines.

 

[Foster82]

Doing some research myself I believe your are correct Larry, in that the secondary fermentation was the pectin being broken down, however I don't believe it caused the over attenuation. In the end i believe a low mash temp may have been the downfall, because the enzyme should not have affect any unfermentable sugars created during the mash process (althought the secondary fermentation had me believing this). I might give this another go playing closer attention to my parameters.

 

[LarryBrewer]

83% does seem high for US-05. In another thread, someone else got 80%+ attenuation out of US-05. My records were something like 73% and 76% the last two times I brewed with it.

 

[JAMC]

This is purely anecdotal, but I made a similar kind of thing last year and got the same outcome - a pink-tinged beer which was positively wine-like in it's dryness and tartness. I didn't add any enzymes to my batch.

Maybe we should ask what the extract potential of strawberry juice/puree is? If it's significantly higher than pale malt, then we're naturally going to end up with a dry batch and higher attenuation.

 

[Nosybear]

Some kind of wild yeast, maybe? The berries carry them and if you don't pasteurize then well, they can do very bad things, wine-like flavors being just one. If the fg is still rising, look to sanitation. Best distance-diagnosis I can offer...

 

[Foster82]

My main concern was the pectic enzymen breaking down the unfermentable sugar, but that does not seem to be case.

Maybe we should ask what the extract potential of strawberry juice/puree is? If it's significantly higher than pale malt, then we're naturally going to end up with a dry batch and higher attenuation.

Doing the math based on the nutritional information of raw strawberries (7g of sugar / 152g of berries) I worked out the PPG to be around 2.13 PPG which is in line with information found on morebeer's site.