How to correct over-attenuation in beer after fermentation

Yeast laboratories perform numerous tests so they can give us brewers details as to how we can expect yeast to behave. Along with the various flavours a yeast can provide, the lab also provides a range for which a product can attenuate. Punch this into our brewing software and we have a general idea of what our final gravity should be. But what do we do in the case that our beer over-attenuated and is now too dry?

Root Cause?

If you have brewday and fermentation notes, take a look over them to see if there is anything that stands out. Was your mash temperature too low? Maybe your mashout didn’t work out? Or maybe you’re using a new yeast.

Looking over this information should provide insight into what caused the problem. With these details, you make the appropriate adjustments and should avoid over-attenuation in the future.

What yeast?

This is an important question to ask because the back-bodying technique will only work with certain yeast strains. In particular, you need to be confident that any non-fermentable sugars which get added to the product won’t be refermented. There’s really two main kinds of yeast to be mindful of: diastatic yeast and brettanomyces.

Diastatic Yeast

This is a property that some yeast strains (Belle Saison, Wyeast 3711, etc) will exhibit when placed within certain environmental stressors: such as a low-nutrient environment within a bottle. These yeast will produce an enzyme that will further break down dextrins and other complex sugars into something the yeast can consume.

The strains of yeast that most often behave this way are saison strains. So if your beer fermented with saison yeast is too dry, you’re kinda stuck. If you do choose to back-body, be sure that the product is consumed fairly quickly if you’re packaging into bottles and that it is kept very cold.

If you are interested in learning more about this property of yeast, there’s numerous research papers that cover this exact topic.

Brettanomyces (aka Brett)

Another species of yeast that are often associated with funk and other characteristics that weren’t usually considered nice in “regular” beer. These yeasts have become quite popular for their unique flavours they can give to beer. Brett is somewhat like a scavenger and given enough time basically consumes everything it can.

Again, if you’ve used this kind of yeast you’ll need to live with the beer you’ve ended up with. However, if your beer has brett in it consider bottling it as is and aging it! Over time brett beers evolve and can be something amazing.

Back Bodying

If you are using a “normal” yeast then you are most likely safe. The yeast shouldn’t be able to break down and ferment any sugars you’re going to be adding. The newly added sugars will remain in solution and help give your beer more body. These sugars aren’t going to have the same character as what you’d get from grain, but it can help round out the beer a bit more.

The types of sugar to use for adding body are those which don’t add any kind of sweetness. The larger a sugar molecule gets, it is usually perceived as less sweet. Two of the most commonly used sugars for body and mouthfeel are Lactose and Maltodextrin. In most cases these are added during the boil as a way to add body before the beer is fermented. However, it is possible to add these sugars to beer after fermentation has occurred.

Calculating sugar additions

Literature such as How to Brew includes some quick lookups on how much extract various sugars will add to your batch of beer. For performing quick calculations these work great, though it is possible to get exact values from suppliers.

  • Lactose – Extract: 99%, Moisture: 5.2%, PPG: 44 (Palmer: 46), PKL: 387 (Palmer: 384)
  • Maltodextrin – Extract: 95%, Moisture: 4.5%, PPG: 44 (Palmer: 42), PKL: 374 (Palmer:  351)

Something that needs to be taken into consideration is how much liquid you are going to be using in order to dissolve and sanitize the sugars you’ll be adding. This is highly dependent on how much sugar you’ll be using, and in some cases using too little water will result in a extremely viscous solution. In most cases you’ll be using less than 500g of sugar, so working with a 1L of priming solution should be more than adequate. Keep in mind this water addition is going to have an impact on the gravity of the beer, and the new final gravity should be calculated.

Example: 20L of beer at 1.005 is going to have 1L of priming solution added. Calculate the new FG.

20 x 5 = (20 + 1) x G G = (20 x 5) ÷ 21 G = ~4.76

So at the end we will have 21L of beer with a gravity of ~1.0048. All we need to do now is figure out how much sugar we need to use in order to adjust our gravity to what our target is.

Example: How much maltodextrin is need to increase the gravity of 21L of beer at 1.0048 to an FG 1.010?

FGIncrease = 1.010 - 1.0048 => 0.0052 => 5.2 "points" totalGravityPointsNeeded = 5.2 x 21 = 109.2 kgMaltodextrinFLW = 109.2 / 374 = 0.291 kg => 291g kgMaltodextrinPalmer = 109.2 / 351 = 0.311 kg => 311g

Both the calculated PKL and that provided from Palmers How to Brew were used to see how much of a difference there would be. The discrepancy is only 20g, which is pretty good. To play it safe, using 300g of Maltodextrin should provide a decent increase in body within 1 point of the target.

Alternatively: Using your brewing software you can play around with your batch and figure out how much sugar would need to be added to increase your OG & FG by approximately 5 gravity points.

Adding the Sugar

The sugar and water are combined in a saucepan and brought to a boil. Bringing to a boil can be enough, however boiling for 10 minutes should be more than enough to ensure the liquid is sanitary.

After the boil the liquid can be added to your bottling bucket or keg and the finished product is racked on top of it. I often allow the thermal mass of the beer to cool the heated sugar down, though cooling the solution to room temperature in an ice bath is also viable.

Considerations

Consider packaging a few bottles of where it wasn’t back-bodied to see what the difference is. It’s a fun way to see how much of an impact it makes and to see what other flavours you might tease out by adding more body to your beer.

I often keep Coopers Carb Drops on hand since it makes it a lot easier to perform little trials such as this.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

About Chris

If there is a place that serves or sells beer I've never heard of, I'll find a way to get there. A fan of the humble Pale Ale, though always willing to try a pint of something new. I also enjoy brewing my own beers and love sharing the science of the beer making process.