Required temperature for alpha-acid isomerization

[iancraig]

Hello All,

I am currently doing extract+steeped-grain brews, working my way through some of the recipes in John Palmer's book.

One issue I have is that my feeble electric hob can struggle to maintain a boil during the hops additions unless I leave the lid on. As yet I haven't noticed the DMS off-flavours that have been reported due to keeping the lid on. So in that sense, so far so good.

However, I was wondering if I really need to *boil* the hops. I am thinking about keeping the lid to get to the boil (I never really see any significant hot break) and then doing the hops additions with the lid off. The temperature during the hops additions would fall over the hour, but not significantly. I guess not below 90C.

So finally to my question: Does anyone know what temperature(s) are actually required for the hops alpha-acid isomerization? Obviously higher temperatures would push the reaction through at a faster rate, but would 90C be OK?

Any pointers to such information would be great!

All the best,

Ian

 

[Clint Eastwood]

If I remember exactly I once read somewhere it's 75c but you wont get them all out and will take longer. Maybe if you are not getting the bitterness you could try increasing the hops.
You will also struggle with the protein conversion too at normal boil times too. Do you normally make cloudy beer?
Ill see if I can find the source of my info and reconfirm.
Another thought you could try to boil the hops in a smaller separate pan that can achieve the boil. You could then add this hops and all to the brew kettle after an hour.

 

[graysalchemy]

You need quite a vigarous rolling boil for at least 60 minutes to secure the hot break otherwise as said above you will get cloudy beer. :thumb:

I boil with my lid partial on for all the boil means i can use one kettle element instead of 2 in a 60L boiler. Also try adding your hops at the beginning of the boil I do that as well then you don't kill the rolling boil when the hops go in.

With regards to DMS any dms is driven off before the boil or at least early on and Uk malts have less DMS precursors than US malts where this myth came from.

:thumb: :thumb:

 

[JKaranka]

You can boil with the lid just slightly open to keep the boil

 

[Duxuk]

I was unaware of the DMS issue 'til recently reading about it on the forum. I've done extract/ steeped and partials before starting AG all with the lid on. The beer tastes great :thumb: maybe I like the taste of DMS!
Try it with the lid on, I don't think you're likely to find any problem.

 

[iancraig]

Many thanks for the replies (I was away over the weekend so am only getting around to reading them now).

Based on your comments, I will continue to just leave the (partially) lid on.

I'll worry about DMS off-flavours as and when they turn up!

Ian