[neuse]

As I understand it, in calculating the PPG of a malt, %FGDB (Fine Grind Dry Basis) is used to calculate PPG instead of %FGAI (Fine Grind As-Is). I think I’m missing something. When weighing the malts for a mash, it is weighed as-is. Using the dry basis percentage doesn’t correspond to what is actually in the mash. So I have a couple of questions:

Why isn’t the as-is percentage used to calculate PPG instead of the dry basis percentage?

Since the PPG is based on the dry basis analysis, wouldn’t the malt weight have to be multiplied by percent moisture to get comparable maxumum yield?

[chinaski]

My guess is that there is an assumption in published ppg values that malts have a specific % moisture and that any corrections for moisture content are negligible at the scale of homebrew recipes.  Too many other more important factors affect the gravity of wort collected after the mash.

[neuse]

That could be the reason - it’s not a huge factor. How to Brew, E4 shows about 4% moisture by weight. So I guess we just standardize by using dry basis - we always understate our efficiency by about 4%.

[neuse]

I was just looking through How to Brew, E4 for some explanation and found this: “I should mention that commercial brewers are more likely to use the coarse grind, as-is (CGAI) number from the malt analysis sheet, because that number takes the moisture into account, and helps them more accurately plan their malt usage and maintain better process consistency. On a homebrewing scale, we can be less rigorous and base our efficiency on the more readily available FGDB number. To take moisture into account, multiply the dry basis number by the percentage of dry weight.” This seems to confirm chinaski’s assumption.

I don’t plan to do the math to take moisture into account - staying consistent seems much more important and getting the perfectly accurate number.