Over-attenuation, honey, and sour flavors

[Horseflesh]

A couple of weeks ago we made a honey nut brown ale. The AG brew day went fine. The mash temperature was in the 151F - 153F range, which in retrospect I realized was a mistake... I wanted to mash warmer than that, to leave more unfermentable sugar.

2 lbs of pasteurized honey was added to the fermenter, and WLP 002 English Ale yeast went to work on the 1.051 wort, held at 65F for 1 week and then 70F for the second week. I did not make a starter.

The beer is now at 1.007, apparent attenuation 85.7%, which is much more attenuated than I expected. The yeast data sheet says it should not be higher than 70%.

The beer is very dry and to me seems to have a very slight sour note. It isn't bad, but it isn't what I expected, even allowing for the mash temp of ~152F.

I guess these are my questions...

Can the use of honey cause what looks like over-attenuation? That doesn't really make sense to me, because sugar is sugar, but...

Can you experience a slight sour note in a very dry beer, or is sourness always an indication of infection?

Is it possible to have a minor infection? This beer is not a bucket of vinegar, but in all the reading I have done infections always seem to be total disasters if they are present.

In about 14 batches this is the first real head-scratcher I have had, and the first time I have worried about infection.

Additional info--

The beer is 14 days old, and sampled from the bucket.

All my hydrometers, refractometers, and thermometers are spot on.

The honey was pasteurized at 176F for 2.5 hours. BTW, the honey smell and flavor in this beer is much improved over the last time I made a honey nut brown as an extract beer, with honey in the boil.

Thank you in advance for any commentary!

 

[NTexBrewer]

The short answer about honey and other sugars (dextrose, cane sugar, beet sugar, agave nectar etc.) is that they do affect the attenuation of your beer. These sugars are simple sugars and will ferment completely.

Sugars from malt is made up of complex sugars and some of these sugars will not ferment completely.

As a simple example lets say you have two beers with a gravity of 1.050 or 50 points

Beer A is all malt, Beer B is half malt half honey. With beer A you would take 50-(50 x 70%)= 15 so you would expect a final gravity with 70% attenuation to end at 1.015

Beer B you eliminate the sugar from your starting gravity. In the simple example above that would mean your gravity from malt is 1.025. To calculate your estimated final gravity you would have 25-(25 x 70%) = 1.0075

For both beers the starting gravity was 1.05 but you see that the apparent attenuation for Beer B is greater.

I ran the numbers with your beer. I'm assuming that when you said the wort was 1.051 that included the honey. 2 lbs of honey in 5 gallons contributes 16.8 points. So the gravity from grain is 51 - 16.8 which is 1.034.

Using 1.034 and the final gravity of 1.007 your attenuation from your malt came out to (1-(7/34))x100 = 79.4%

This is still high if the yeast is supposed to have a 70% attenuation.

 

[Horseflesh]

Thanks a bunch, that is super helpful!

 

[Beezer94]

Also the attenuation numbers provided by the yeast companies do not mean you cannot get beers that fall well outside that range. They use specific in house tests, that are mostly for comparing attenuation between that one, specific company's yeast products and not necessarily real world numbers.

For instance WLP002 says 63-70% attenuation and WLP001 says 73-80% attenuation so I know WLP001 is going to give me better attenuation in the same recipe with the same mash temperatures, not specifically that it will fall within that range.

In the real world I've gotten 75-86% attenuation with WLP001 without using highly-fermentables like honey or corn sugar, and 70-80% attenuation with WLP002 again without honey/sugar.

 

[Horseflesh]

Also the attenuation numbers provided by the yeast companies do not mean you cannot get beers that fall well outside that range...

Good to hear, as this often happens to me! I was never sure how reliable those numbers were outside the lab.