Exchange Rates VI: An Example

In the Exchange Rates series, we’ve discussed how to convert recipes from all-grain to extract formulations. Our topics have included how to

1. Convert base malts to extracts
2. Convert specialty grains
3. Account for extract composition
4. Deal with adjuncts
5. Account for hops utilization

Now it’s time to put these ideas to work with a complete example. Consider the O’Davey Irish stout from our Easy Irish Stout article:

O’Davey Stout

Batch size: 5 gallons/19 liters (5.25 gal/19.9 l before packaging)
OG: 1.045
FG: 1.011
ABV: 4.4%
IBUs: 43

GRAIN/MALT BILL

6 lb (2.7 kg) pale malt
2 lb (0.9 kg) flaked barley
1 lb (0.5 kg) roasted barley

HOPS SCHEDULE

2 oz (57 g) Willamette [6% AA] at 60 minutes

YEAST

Danstar Nottingham dry yeast

DIRECTIONS

Mash for 60 minutes at 152°F (66°C). Boil for 60 minutes following the hops schedule. Ferment 10 days at 64°F (18°C), keg or bottle, and enjoy!

Let’s break it down according to the topics we’ve discussed. The grain bill includes pale malt (a base grain), roasted barley (a specialty grain), and flaked barley (an adjunct). The pale malt can be converted to a simple malt extract syrup, and the roasted barley can be steeped, but what to do with the flaked barley adjunct? Well, we have two ways to deal with it:

1. We can substitute an equivalent amount of extract for it.
2. We can conduct a mini-mash with some of the base malt and make up the rest with extract.

Because flaked barley lends such a creamy mouthfeel to this stout, I suggest doing the mini-mash. Now, I know that when I do a mini-mash in my kitchen, I don’t get great efficiency, only about 50 percent. I could probably experiment and increase that number, but I do small mashes so infrequently that I just accept it and move on. So, let’s say we’ll mash the flaked barley with two pounds (907 g) of pale malt and that we’ll steep the roasted barley.

Flaked barley has a potential extract yield of 32 ppg (points per pound per gallon)

Pale malt has a potential extract yield of 36 ppg (points per pound per gallon)

So, at 50 percent efficiency, mashing 1 pound (504 g) of flaked barley with 2 pounds (907 g) of pale malt for a 5.25 gallon (19.9 l) batch will give

((1lb × 32ppg + 2lb × 36ppg) ÷ 5.25 gallons) × 50% = 10 gravity points

This means my mini-mash on its own would give my beer an original gravity (OG) of only 1.010. But the expected OG is 1.045, which I need to make up with malt extract.

I need to get 45 - 10 = 35 gravity points from malt extract. Liquid malt extract (LME) has a gravity contribution of 36 points per pound per gallon, which means I need

(35 points ÷ 36ppg) × 5.25 gallons = 5.1 lb (2.3 kg) of LME

So, my mash schedule will look like this:

Mash 2 pounds (907 g) of pale malt with 1 pound (454 g) of flaked barley for an hour. At the same time, I can steep 1 pound (454 g) of crushed roasted barley in my boil kettle for half an hour, just as I would with any other specialty grains.

Drain the sweet wort from the mash into my boil kettle and sparge with a small amount of hot water to liberate as much of the available sugar as I can.

Top up with 5.1 pounds (2.4 kg) of pale liquid malt extract and proceed as usual.

Note that I could have avoided the mini-mash altogether by simply using more malt extract in place of the flaked barley. In that case, I would have needed

(45 points ÷ 36ppg) × 5.25 gallons = 6.7 lb (3 kg) of LME

Let’s also assume that my boil kettle is only three gallons (11.3 l), so I can only boil about 2.5 gallons (9.5 l) instead of the full 5 gallons (19 l). To keep the bitterness consistent, I would add only a portion of the extract up front so that my boil gravity is about the same as if I had boiled a full volume. The contribution of the mini-mash is small, so I would just add half the extract up front and the rest during the final ten or fifteen minutes of the boil.

After the boil, the chilled concentrated wort goes into the fermentor, topped up with cold water and fermented as usual.

That’s really all there is. Once you understand how the individual pieces of a recipe contribute to the final beer, you can easily convert between all-grain and extract formulations.

Whether you’ve recently purchased a starter kit for yourself or received one as a gift, trust the knowledgeable craft-beer enthusiasts at Craft Beer & Brewing to give you the information you need to brew great beer the first time and every time. Sign up today for CB&B’s _Make the Most of Your Extract Kit _online class.