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BIAB - why worry about efficiency?

I’m only just getting back into brewing and I’m really interested in BIAB brewing.

I’ve seen a lot of online folks talk about squeezing the bag or doing other things to push out more wort. I’ve got to think you risk some tannin extraction with this. I understand you are trying to maximize efficiency but it seems like a weird trade off to risk tannin issues especially when that’s one thing BIAB helps minimize.

Also, I see people doing mashouts by raising the temp prior to removing the bag. Isn’t there a risking scorching the bag (yes I know about FBs) or over/uneven heating the mash especially given the high water to/grain ration. It will take a lot more heat (PROPANE) & TIME to bring it up to 170ish for just a little efficiency bump.

I thought one of the biggest benefits was the simplicity with fewer places to mess things up and the time savings.

It seems you will at best see a 10% bump in efficiency with both of these. That’s maybe $2 on a 5G batch but it took more propane and more time.

So for those that squeeze the BIAB and mashout, why do you do it? Outside of efficiency, are there other benefits? Why not just keep it simple?

Why would squeezing a bag extract tannins? Tannin extraction is a result of high mash pH, something not affected by squeezing. This is an old myth that doesn’t have any basis in reality. The ROT is .5 qt/lb held back in the grain. If you could just recover half of that, on a batch with 15 lbs of grain that’s nearly a gallon of extra wort @ ~1.060, and that’s about 2.5 lbs of grain saved.

You have to heat the wort up anyway, so a mashout isn’t costing you that much in extra propane or time, though you do waste a little bit in heating the grain. Still, the grain is maybe 1/4 the mass of the water, and has about 1/3 the specific heat capacity, so it’s a small amount of waste.

There’s nothing wrong with wanting to get the best efficiency possible with BIAB, and it can still offer the time savings and simplification of not doing a sparge. You could probably save another 20 minutes if you don’t crush the grain, but most people wouldn’t be happy with the accompanying 30% efficiency, so we crush the grain.

Just the act of lifting the bag out of the liquid “squeezes” the bag enough to get you good efficiency around 70%. Squeezing the bag should get you closer to 75 or 80% efficiency.

I think the risk involved is less about tannins and more about squeezing unconverted starches out. This applies primarily if you’ve done a poor crush job, because I think if you crush finely, as is appropriate for BIAB, then there’s hardly any starch left in there after the mash. If you’re not sure if you are crushing finely enough, you probably aren’t. Run your grains through the mill twice or whatever it takes to get the starches to turn into a pretty darn fine powder. Then the starch is more accessible for conversion during the mash.

Yet even if you crush finely, there is apt to be more haze in a BIAB beer than if you had gone with the conventional fly sparge or batch sparge. It is most likely for this reason that my buddy who only does BIAB is always complaining about the haze in his brews. Try though he might, he can never get it to crystal clarity. I think this is due in part to both starch and possibly due to very low levels of tannins. I don’t think you can taste any tannin in there, but you can see the haze.

I’m a BIAB’er and for the first time in a few months I did NOT squeeze the bag with this last beer. Just to see where I’d be. My efficiency DID suffer. I went from usually hitting somewhere around 75% to 66% on this last beer. I never noticed any off flavors from squeezing in the past and from what I’ve read, it’s kind of a myth that squeezing will cause tannin extraction issues. Tannin extraction is from high Ph and either mashing or sparging with water that’s too hot. The only beers that I’ve noticed any astringent taste in are a few IPA’s that had heavy late hop additions. I started hopbursting (small bittering additions and BIG late additions) and I think that those beers really need a long time to mellow out. They had a strong astringent bite to them. I don’t contribute this to squeezing the grain sack, because I’ve done it with other non-hoppy beers and did NOT have the same problems. I’m now getting away from hopbursting because I just don’t like the results, but I WILL be going back to squeezing the sack (that’s what she said :smiley: ) to get my efficiency back up into the 70%'s.

I think squeezing the bag can also cause some of the small husk particles to come out and this can hypothetically lead to astringency. In practice I’m sure its minimal.

I’d rather do a small sparge with maybe a gallon of water, rather than squeeze the bag. I would also suggest that if you let the bag drain for an extended period, you’ll get most of the unbound water out of it without squeezing. When I mash in a cooler, I’ll let it continue to drain for 30min or more and typically get another quart or more of preboil volume.

[quote=“tom sawyer”]I would also suggest that if you let the bag drain for an extended period, you’ll get most of the unbound water out of it without squeezing. When I mash in a cooler, I’ll let it continue to drain for 30min or more and typically get another quart or more of preboil volume.[/quote] +1 Squeezing will force particles through the bag, gravity-draining won’t.

For those who do squeeze the bag, do you just use your hands? Or do you have a special technique?

[quote=“Takehiko”]For those who do squeeze the bag, do you just use your hands? Or do you have a special technique?[/quote]I use my hands…but, I first place my hands inside high temp rubber gloves. :cheers:

I place a strainer over the pot and lightly push on the sack with the lid to the pot.

Did a brew in a bag thing with a friend last year. We squeezed the bag as that was what he read to do. I questioned whether that was a good idea but he said it was common practice for this method of brewing. The beer turned out pretty good, earning him a silver medal in a local competition. A couple of judges noted a slight astringency though, and I agreed with them. I made the same recipe on my setup later (fly sparge) and didn’t notice any astringency.

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