Originally Posted by The_Chemist
I have been making wine for years now but just recently started making beer and I have a general question concerning how to get the most from the malt in making a wort. I may not have a complete understanding of many of the technical terms, so bear with me. Also, I looked high and low but this question appears to be too fundamental find in a FAQ or with the search function.
Okay, so considering the malt, the main goal when making the wort is to extract the fermentable sugars and other flavor/aroma compounds from the malt into the water that becomes the wort. My question is in three parts:
1) I don't fully understand why the bag to contain the malted grains is necessary except in that it makes it easier to remove the solid bits. Is there another purpose for using this bag?
2) If you want to do a good extraction, you want to use as much 'solvent', in this case water, as possible. Why do many recipes tell you to use less water and then fill the fermenter up to desired level. This seems like it might lead to a poorer extraction than is possible.
3) This is the big one. Why is it not common to leave the malted grains in the primary fermenter for the entire primary fermentation instead of removing them before pitching the yeast. Would this not give a more complex brew and make the most of the grains?
Thanks in advance for your answers!
1. The bag is to remove the grains. Most AG brewers don't use a bag, we use a false bottom, braid, manifold, etc, to separate the sweet wort from the grains (the "lauter" step).
2. It has to do with proper ph. For best efficiency and flavor (not extracting unwanted tannins from the grain husks) you want to keep the grain/water ratio at 1-2 quarts of water per pound of grain. There are some other things, too, like a thicker mash tends to give a more dextrinous wort with more long-chained sugars, and a thinner mash tends to favor a more fermentable wort, but generally it's the ph you're concerned about. We don't fill the fermenter with water, we sparge the grain ("rinse") with up to .5 gallons of water per pound of grain and then boil the wort. I think you're confusing extract recipes with all-grain recipes. In extract recipes, you fill the fermenter after you're finished brewing. But, you don't have to worry about extracting sugars from the grains- that's already done for you with using extract to begin with.
3. Well, for one thing, you don't want to boil grains. That will cause tannin extraction. If you don't boil the grains, they aren't sanitized. Grains are notorious for being contaminiated with lacto (among other things). So, you'd be steeping lacto bacteria in your fermenter, and you'd have a definite lactic acid sour mash going on. Also, once you've mashed the grains, you've extracted all the color, sugar, and flavor you're going to. Leaving it in the fermenter just wouldnt' make sense.