Real Vs. Apparent attenuation

[MARCELO178]

I bought T58 and S33 yeasts of fermentis, both have the apparent attenuation of 70%, I would like to brew belgium style beers with these yeasts: golden strong, dubbel, trippel and dark strong. I saw the standart attenuation of the belgium beers were about 80% to 85%.
What is the difference between Real and Apparent Attenuation?
Can I use these yeast in my brew and expect the standart attenuation?

 

[aiptasia]

Attenuation listed on the websites of yeast producers is based on their in-house testing and an average of what you might expect to see given you combine yeast, water and malt sugar. Belgians boost the attenuation of the yeast through tricks like: Candy sugar additions, oxygen supplementation, yeast nutrients and even re-pitching with fresh yeast before bottling. Ever seen Belgian beer bottles with the VERY thick glass, corked and covered with wire cages? These beers often gush like warm champagne when uncorked and are almost always re-pitched with champagne yeast before bottling.

If you want the best out of your yeast, you have to pitch the yeast in the best possible environment for rapid growth and at the proper pitching rate. For example, I like to add both yeast nutrient (DAP based) and servomyces to my wort as yeast "vitamins", and then hit the wort with pure oxygen right after pitching the yeast. If i'm brewing a Belgian recipe, more than likely it will require some candy sugar which increases the ABV but tends to thin and dry out the beer.

The last aspect is re-pitching. Many Belgian brewers will re-pitch with fresh yeast before bottling. Belgian beers tend to be very high ABV which is toxic to the yeast. High ABV brewing severely stresses out the yeast and re-pitching with fresh yeast (or champagne yeast, which is high alcohol tolerant) assures the brewers ability to get the FG of the beer lower and carbonate the beer at the same time. The thick glass bottles, corks and wire cages help prevent bottle bombs common to high FG carbonation.

 

[duboman]

Attenuation listed on the websites of yeast producers is based on their in-house testing and an average of what you might expect to see given you combine yeast, water and malt sugar. Belgians boost the attenuation of the yeast through tricks like: Candy sugar additions, oxygen supplementation, yeast nutrients and even re-pitching with fresh yeast before bottling. Ever seen Belgian beer bottles with the VERY thick glass, corked and covered with wire cages? These beers often gush like warm champagne when uncorked and are almost always re-pitched with champagne yeast before bottling.

If you want the best out of your yeast, you have to pitch the yeast in the best possible environment for rapid growth and at the proper pitching rate. For example, I like to add both yeast nutrient (DAP based) and servomyces to my wort as yeast "vitamins", and then hit the wort with pure oxygen right after pitching the yeast. If i'm brewing a Belgian recipe, more than likely it will require some candy sugar which increases the ABV but tends to thin and dry out the beer.

The last aspect is re-pitching. Many Belgian brewers will re-pitch with fresh yeast before bottling. Belgian beers tend to be very high ABV which is toxic to the yeast. High ABV brewing severely stresses out the yeast and re-pitching with fresh yeast (or champagne yeast, which is high alcohol tolerant) assures the brewers ability to get the FG of the beer lower and carbonate the beer at the same time. The thick glass bottles, corks and wire cages help prevent bottle bombs common to high FG carbonation.

+1 Great info!

To add, if doing all grain you can also adjust your mash temp lower to achieve greater attenuation as well. Most Belgian styles will finish below 1.010

 

[carton132]

Regarding your question about the difference between real and apparent attenuation:

"The gravity of beer is most often measured using hydrometers. However, hydrometers are calibrated to measure the sugar content of a solution of water. Finished beer, however, contains alcohol (ethanol) which skews the hydrometer reading because alcohol is less dense than water. Therefore, a hydrometer reading taken on finished beer will show lower (less extract content) than the beer actually contains." 1

"Real Attenuation = 0.82 * Apparent Attenuation" 2

1. http://beersmith.com/blog/2010/09/07/apparent-and-real-attenuation-for-beer-brewers-part-1/

2. http://braukaiser.com/wiki/index.php?title=Understanding_Attenuation#Apparent_vs._Real_Attenuation

 

[SpeedYellow]

Homebrewers almost always use apparent attenuation, so you don't really need to worry about real attenuation. As you probably know, the calc is super easy, for example a 1.050 OG that finishes at 1.010 will have 80% attenuation.

 

[PDX_T]

T58 should do what you want it to do. those apparent attenuation stats are usually based on a standard wort at like 1.040. You get the higher attenuation in Belgians by adding sugar, which ferments out completely. Apparent attenuation depends strongly on alcohol content. the more alcohol, the less dense it is relative to the starting OG, so the more it "appears" to attenuate. This doesn't mean there aren't still residual sugars in the beer.

Real attenuation attempts to discount the alcohol content, and measure the degree to which there are sugars left over, but all these calculations are inter-related anyway.