grams per litre

[UpTheToon]

This feels like a daft question.. but I'm really not sure what the answer is.

When a recipe gives the hops in g/litre would you expect that to be for the volume of liquid you are currently working with (eg boil volume for hops in the boil and fermentation volume for dry hop) or batch volume?

Batch volume is obviously easier and static... surely it's that?

[Matt12398]

You are correct

[UpTheToon]

You are correct

Cheers. Thought it must be. Was thinking too hard...

[duncans]

I would not be so sure. I would expect all ingredients to be relative to a single volume. I would suggest this is fermentation volume or volume of finished beer, which should be pretty much the same. Could be wrong obviously but giving a hop schedule relative to the different volumes at each stage would give me a headache.

[simon12]

I to would expect it would be based on volume into fermenter as different equipment will boil off different amounts.

[Kev888]

In an ideal world the recipe will give the bitterness it achieved, along with the timings of hop additions. That will allow you to work out approximately what quantity of your own hops you need for your own boil volume at the various stages to get a similar bitterness. This approach accounts both for differing boil volumes and alpha-acid content of the hops, which can change with each year's harvest (and over time as growing/production methods improve). Some use software to help, but keep in mind that this too may make generic %AA assumptions unless you update the database's records to your particular hop characteristics.

Failing that, hopefully the recipe will provide at least the %AA of the hops used by the author, so you can at least roughly adapt to your current hops in proportion. Though (as you say) this doesn't take account of differences in boil volume between the author's assumptions and your own system. So if yours were to have unusually large losses (say to kettle dead space) and therefore have a larger boil volume for the same brew length, you may want to add a few more hops to compensate - just as you would with grain quantities.

If the recipe doesn't share its bitterness or the bitterness of the hops used then you're down to guesswork, with the recipe as a guide only. Its not worth worrying too much about IMO, because its hard to be precise even with all the figures - hop utilisation varies, the boil volume reduces over its duration, and even the %AA values are general figures for the harvest not your specific pack. The key IMO is to be consistent and keep records; once you have brewed the recipe once then you know all the details, and can adjust if you wish it to be more or less bitter next time.

Non-bittering additions are even more of a dark art, but again you can adjust these to your taste in subsequent brews. Personally I tend to just change aroma-hop quantities by the same proportion as for their bittering properties, for simplicity, but it doesn't necessarily follow that their aroma or flavour perception will directly map to their %AA content.

Cheers
Kev

[Matt12398]

I would not be so sure. I would expect all ingredients to be relative to a single volume. I would suggest this is fermentation volume or volume of finished beer, which should be pretty much the same. Could be wrong obviously but giving a hop schedule relative to the different volumes at each stage would give me a headache.

In theory, whether you are talking g/litre of the volume that goes into the fermenter vs finished volume of beer they should be essentially the same. Whatever contribution the hops make to the pre-fermentation volume and the final volume should be same unless you are doing something to remove it from the beer in between. Losses to trub/fermenter/spillages etc. do not change the concentrations of hop oils, isomerised alpha acids, etc. in a given volume as it is proportional.