Late extract addition in full boil

[Rob2010SS]

Hey guys. I just got a new kettle today so I'm going to do a full boil for a 5 gallon extract batch. The guy i got the kettle from said that the kettle has a boil off rate of 1.25-1.5 gal/hr. So I'm going to start with 6.25 gallons of water and boil for the full 60 minutes. My question is should i do a late extract addition - half of the extract up front and do the other half at the last 15 min, or does that only apply to a partial boil?

Thanks

 

[Sailingeric]

When I did extract I would do about 1/3 at the start and rest at flame out to avoid darkening of the wort.

 

[Rob2010SS]

When I did extract I would do about 1/3 at the start and rest at flame out to avoid darkening of the wort.

Sailingeric you did this on full boils and not just partial boils?

 

[ncbrewer]

The norm seems to be 1//4 to 1/2 of the extract added early for a partial boil. So it looks like 1/2 to all the extract could be added early for a full boil. Some target a particular boil gravity - maybe around 1.040. That's another option.

 

[RM-MN]

Sailingeric you did this on full boils and not just partial boils?

You will get less darkening with a full boil than you would with a partial boil but it will still darken.

The boil off rate will depend on you, not on the pot. You control how much BTU's are added by the flames you use and that determines the boil off. When you reach the boil, turn the heat down until the wort is just barely rolling and your boil off will be less. You also can adjust the boil off with the amount of time. If you aren't boiling off enough, boil longer. If too much is being boiled off, stop the boil early. There isn't anything magical about 60 minutes. Hop add most of their bitterness in the first 30 minutes.

 

[Sailingeric]

Sailingeric you did this on full boils and not just partial boils?

Full boils.

 

[Gillkid]

Does any of this affect the hop isomerization? If so, how much of a trade-off?

 

[Yooper]

Does any of this affect the hop isomerization? If so, how much of a trade-off?

No, not exactly. What does affect hops utilization is the partial boil. That is, the hops are isomerized in the partial boil, and so the IBUs are diluted when topped up. What I mean is this- there is a maximum of about 100 IBUs that can be isomerized in wort before the wort is saturated with those oils.

So, say you have 80 IBUs in the boil, and you're boiling 2.5 gallons. At the end, when you add another 2.5 gallons of water (with 0 IBUs), you'll have 40 IBUs in the end. This isn't a problem for most beers, but making a big IPA where you want 80 IBUs isn't possible. That's one of the beauties of a full boil- you can maximize the hops utilization.

Adding the extract late in the boil does change the calculations on brewing software, because the calculators take the boil gravity into account when doing the IBU estimate. In my experience, that doesn't happen. It's when you go from partial boils to full boils (and not when the extract is added) that changes it.

So I would add the hops just as if it was a full boil, and calculate the recipe that way (or follow the hopping of the AG version of the batch, which assumes a full boil) and not take the late edition of the extract into the calculation.

 

[ncbrewer]

For the last few years there's been a lot of controversy about the effect of boil gravity on hop utilization. According to J Palmer in an interview with J Blichman, it has been settled, and the traditional formulas are considered to be pretty much correct, if not super accurate (depends on your equipment and other variables). Here is the link: https://www.homebrewtalk.com/showthread.php?t=628842

PUBLISHED 8-22-16
JOHN PALMER stated that there are many vairables not accounted for in the current models, but he does not have any information that would allow an improved formula. The current models aren't terribly accurate, but if you use the same one all the time, your beer will be consistent.

He also stated that utilization will improve at a higher pH. But it will produce a harsher, coarser bitterness. He doesn't recommend raising the pH to improve utilization.

At roughly 11:15 minutes John Blichman asked “John, does wort specific gravity change hop utilization? John Palmer answered “It really does not. Wort gravity, and maybe this is one of the little details that is changing in How to Brew, is that while overall utilization does change with boil gravity, the isomerization of the hops does not. That rate is strictly dependent on gravity and pH. The way that gravity, boil gravity or wort gravity, effects utilization is that it's the amount of trub that that higher gravity generates. The cold break, the hot break, that amount of protein is more surfaces for these alpha acids to cling on to and be carried out of solution. I've talked with a number of experts over the past year about this, and while we don't have solid studies and data to say this definitively, all of us feel that this is a reasonable hypothesis for how wort gravity affects utilization, and it's due to higher protein content pulling more alpha out of solution.”