Brewing in a Bag

After reading about it in the January/February issue of Zymurgy, I've been wanting to try the whole brew in a bag process. It seems like a remarkably easy way to handle grain mashing, and the Zymurgy article claims it's as efficient as the more traditional mash-and-sparge approach. I wanted to try it with my last beer, a Poi Wheat ale, but I didn't have a grain bag, and I wasn't sure how much additional gravity would be added by the poi. In the end I used a modified approach in which I mashed the grains in six and a half gallons of water, instead of my usual one-or-two-quarts-per-pound mash with a two-quart-per-pound sparge, and then drained it into the kettle. Grain absorption meant I had to add more water, which I ran through the grains straight from the tap. I was satisfied with the original gravity I wound up with, but my questions about brewing in a bag weren't really answered.

Since then I've acquired a grain bag big enough for an all-grain brew, and yesterday I used it for the first time. What's more, since I brewed a recipe I've brewed before, I was able to compare the conversion achieved with the brew-in-the-bag method to the conversion I achieved previously, with a separate mash and sparge. (If you want the end result, you can skip to the bottom of this post--what follows is a bit of detail about the process I used.)

In order to compensate for grain absorption, this time I started with about eight gallons of water in the kettle. I brought it to 165 degrees Fahrenheit, put my bag in the kettle, and dumped my grains straight into the bag. I mixed them around a bit, and then twisted the top of the bag in hopes of keeping the grains from sneaking over a dropped edge. And then I put the lid on the kettle and let it sit for an hour.



I should mention that I added 10.5 pounds of room-temperature grains to eight gallons of heated water, and the relatively small amount of grains meant that the mash temperature only dropped to about 160. I didn't add heat at any point in the 60 minute mash, and after an hour the temperature had dropped to 144. Those are sort of unusual mash temperatures, which probably affected the original gravity I ended up with. And it's likely that the high starting temperature resulted in a more dextrinous wort, with less fermentable sugars, which will result in a heavier-bodied beer. (I love heavy-bodied beers, but since I've moved to Hawaii I've been trying to lighten them up a bit, so my hot mash was probably a mistake.)

Anyway, after an hour I started the flame again, and immediately after that I lifted the grain bag out of the wort. I held the bag above the wort for a few minutes, wanting to let it drain more wort into the kettle. But before long I decided I'd just throw the grain bag into my old bucket fermenter, let the wort separate out there, and then open the tap to pour that wort into the kettle. (In the picture below you can see the shadow of the wort that's starting to gather at the bottom of the bucket.)



After that, it was brewing like normal.

The end result? My previous brew of the same recipe had an original gravity of 1.058. This brew, using the brew-in-the-bag approach, resulted in an original gravity of 1.055. So I lost .003 points, or around one-tenth of a percent of potential alcohol. But I also cut my total brewing time by nearly an hour and a half.

For me the time reduction and the greater simplicity make the brew-in-the-bag mash a winner. I'm planning on using the big grain bag for my next batch.