Help with Hop addition adjustments

[Phlyborn]

Tomorrow I'm going to brew a 10 Gal. English Brown Ale @ 1.055 SG and 27 IBU. It was going use 3 additions of Styrian Goldings. 1.25oz first wort-60min, 1.25oz 30min and 0.60oz 10min (totaling 3.1oz). In BS the Acid content of the hop were listed as 5.40%. When i went to the LHBS i asked that the hop weights be adjusted to make up for the difference in Alpha % since usually what they have doesn't match. I've done this before and the difference was not usually too far off. So, Looking at it last night I was given 5.5oz because the alpha content was only 2.8%. Currently I'm looking at 3oz FW 60min, 1.5oz 30min and 1oz 10. My question is, what differences should be expected when making these increases to match Alpha %? I'm thinking the aroma and flavor would be first to change and if so, should i be concerned about upping the amounts at 30min and 10min in the boil? The IBU's would decrease if not adjusted. This is something I've never encountered before in 3 years of brewing. So it as me thinking.

 

[myndflyte]

That's an interesting question. Based on what I've read (which may be incorrect, so point out any flaws in my thinking), the alpha acids only contribute to the bittering aspect while flavor and aroma come from the hop oils. On the one hand, I think I'd keep the aroma addition the same as the original recipe, the 30 min addition, you could maybe bump up a bit, but I think the most of the adjustment should come at the FW hop to match the IBUs.

Now on the other hand, I really don't know enough about hops to say that the aroma/flavor character between a 5.4% AA hop vs a 2.8% AA is going to change drastically. Is it that the flavor and aroma of a lower acid hop is proportionally lower than a higher acid hop? But your 30 and 10 min additions aren't really that different from the original recipe, so going with the new plan would probably be good anyway.

I'm sorry I didn't give a definitive answer but it's really an interesting question.

 

[bradleypariah]

I'd keep the aroma addition the same as the original recipe, the 30 min addition, you could maybe bump up a bit, but I think the most of the adjustment should come at the FW hop to match the IBUs.

Agreed.

 

[stz]

Beer mat maths here. There are a few ways to work this out.

Use 68g at 60 and 30 and then 17g at 10. This is based on weight x AA% required / AA% possessed. This is the simplest way to adjust for variation in AA by bag on the fly and is the way I usually work. While specific essential oil levels (myrcene, humulene, caryophellene, farnesene) change from batch to batch you can't get too hung up on it unless you've equipment more sensitive than your nose. I'd highly recommend your nose. You do say you want 27 IBU though, so lets check that (assuming a 23L boil)

10 minutes
0.080 utilisation factor
2IBU
30 minutes
0.170 utilisation factor
14IBU
60 minutes
0.221 utilisation factor
18IBU

Total 34IBU. This is assuming a 23L boil. Whoever designed the recipe will have different utilisation, potentially different volumes etc. The cool thing about being given IBU's total or even percentages of a total contributed by each hop is you can scale a recipe to your system and ingredients.

Anyway you likely know all this, your question. More hop mass = more vegetative matter, thus potential vegetative flavours and losses to absorption. I wouldn't worry about this in a beer like that though. You should smell them and make a decision.

Everybody has a slightly different approach to brewing. I find it difficult to not follow rules so I usually make some. I decide what my vision for the beer is to be and quite quickly nail down a target IBU. I then decide on how much aromatic quality is desired and where these hops will be used and then break a ratio down of where in the boil these hops will have to go to do this. Half bittering half aroma? Half bittering, quarter aroma quarter whirlpool? All whirlpool?

On the day though the rules go out the window and I get pretty uncomfortable. Sometimes I open a bag and they are less than optimal or awful and need to make last minute substitutions or changes. There isn't much point in setting out to brew a beer to showcase a certain hop character and the hops are stale. This is when it becomes more like cooking, trying to make the best with what you've got.

 

[Phlyborn]

That's an interesting question. Based on what I've read (which may be incorrect, so point out any flaws in my thinking), the alpha acids only contribute to the bittering aspect while flavor and aroma come from the hop oils. On the one hand, I think I'd keep the aroma addition the same as the original recipe, the 30 min addition, you could maybe bump up a bit, but I think the most of the adjustment should come at the FW hop to match the IBUs.

Now on the other hand, I really don't know enough about hops to say that the aroma/flavor character between a 5.4% AA hop vs a 2.8% AA is going to change drastically. Is it that the flavor and aroma of a lower acid hop is proportionally lower than a higher acid hop? But your 30 and 10 min additions aren't really that different from the original recipe, so going with the new plan would probably be good anyway.

I'm sorry I didn't give a definitive answer but it's really an interesting question.

Your reply helped, thank you!