Ask Mr. Wizard

Curing Sparging Woes

TroubleShooting

Mark Connell — Bedford, Massachusetts asks,
Q

I have been making a pumpkin ale for the last 7–8 years. Because I put flaked oats into the grain bill, I have always used rice hulls to prevent a stuck sparge; however, 3 out of the last 4 batches, my first runnings and sparge have been very slow. During my last batch, it took an hour to get almost 2.5 gallons (9.5 L) using 7 gallons (26.5 L) of strike water. I sparged with another 5–6 gallons (19–23 L) of water and it took almost an hour to collect as much as I could. In the past, it has taken longer than other styles to collect wort but not this long. Could I possibly be using too many rice hulls on the bottom of my mash tun? I put the rice hulls on top of my false bottom and mix into the grains. I use a 10-gallon (38-L) water cooler as my mash tun. Grain bill: Pale malt, Caramunich® malt, Munich malt, caramel 40L, flaked oats, white wheat malt, and Victory® malt for a total of about 13 pounds (5.9 kg) for A 5-gallon (19-L) batch. My last batch was double. I also put about 30 ounces (850 g) of canned pumpkin in the mash.

A

The likely culprit to this problem, assuming that you have been using the same basic recipe over the last 7–8 years, is beta-glucan from the flaked oats. I am betting on this ingredient because the problem you describe is typical for how high-molecular weight beta-glucan gums associated with certain grains, most notably unmalted oats, rye, wheat, and barley, affect wort recovery. But why now?

There are so many things about brewing raw materials that can cause brewers headaches because our raw materials are inherently inconsistent. Crop variability can be classified into two big buckets; variability due to genetics and/or variability due to environment. Or, in the parlance of geneticists, G x E influences. Even when brewers select/purchase specific varieties of barley, for example, there is still considerable variability within and between crop years based on environmental variables such as growing region, temperature, rainfall, farming techniques, and harvest conditions. Add to this the different ways that cereal grains are processed and the permutations become huge.

The beta-glucans found in oats creates the gummy consistency of porridge and can lead to a frustrating brew day when the mash sticks up. Photo by Marco Verch

So why am I focusing on the unmalted oats in your recipe? For starters, oats are a great source of beta-glucan gums that slow wort collection. The other reason is that the oats are the one “generic” ingredient in your grain bill. While oat variety and processing nuances, such as flake thickness and flaking conditions, can have a real influence on how oats perform in the mash, most brewers, including most commercial brewers, know very little about the flaked oats purchased for brewing.

Using rice hulls is a good start to warding off wort collection issues associated with troublesome ingredients, like oats, but may not be enough for particularly gummy lots. The addition of beta-glucanase to the mash is an option that has increasingly become more common as the popularity of hazy IPAs continues to grow and brewers are exploring ways to minimize the bumps that come with using unmalted grains. And as a continuation of this approach, the use of malted oats, both naked and fully clothed (with hull), is also on the rise. The next time you brew this beer or another beer with oats, consider using a different flaked oat, adding beta-glucanase and a respective rest to the mash, and/or subbing malted oats for some or all of the flaked oats. Hopefully one of these suggestions works and you will not have to turn to Plan B; smashing pumpkins.

Response by Ashton Lewis.
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