What's the purpose of the boil?

[Chuck179577]

What exactly is the purpose of the boil beyond hopping and sterilizing?

It seems there's this magic number of a 1 hour boil, but where did that one hour come from?
Any reason why the boil couldn't be less time for a beer with a lower hop profile?

These are the things that keep me awake at night... go figure!

 

[Matt3989]

You need the boil to extract the bitterness from the hops, and to sterilize everything. But heating the water and malt above 90dF causes DMS to form, so you boil it because the DMS will steam off easily (with lower phase shift temp than water), that's also why you shouldn leave the lid on for a boil. No one likes a bandaid flavored beer....

 

[Slainte-brew]

In you are doing extract then it really just is about the hops and sterilizing. When you have all grain brews there are other things going on like DMS, proteins, etc.

 

[diS]

Boil have several purposes:
- disinfection of wort
- isomerisation of hop acids
- driving off DMS
- protein coagulation/hot break
- increasing gravity
- ...

I think 60 min. boil comes from hop utilization and DMS evaporation. You"ll find information's that for pilsner malt 90 min. boil is recommended to drive off huge amount of DMS.. although I boil it 60 min. w/out undesirable effects.

 

[TNGabe]

I've read that traditional Belgian brewers believe a beer has to be 'cooked' to age well. A long boil is one way to make a darker beer without speciality malts.

 

[Captain Damage]

A 90 minute boil is often recommended for beers that are made from less-well modified malts, such as pilsners. It's to cook off DMS precursors. But for most modern, well-modified malts 60 minutes is sufficient. The hop utilization curve starts to level off at just about 60 minutes, so boiling longer than an hour is sort of a diminishing returns land as far as alpha acid extraction goes.

If you're brewing with extract, you really don't need to boil for an hour since DMS isn't an issue. Your recipes must be adjusted for the fact that you're boiling the hops for less time, but this is easy to do with brewing software. There is actually an advantage to boiling extract worts for, say, 15 minutes instead of 60. You'll get less caramelization, meaning lighter color and less caramel flavor - i.e., probably closer to what the recipe designer intended.

Keep in mind though that with a 15 minute boil you will not be boiling off very much of the hop flavor and aroma compounds, and you will need more hops to achieve the same bittering effect. So you may want to switch from a bittering hop, who's flavor and aroma you don't care for, to an aroma variety. But of course, aroma varieties generally have lower AA ratings, so you will need more of it - again, brewing software will help to calculate this.

 

[DonMagee]

I've read that traditional Belgian brewers believe a beer has to be 'cooked' to age well. A long boil is one way to make a darker beer without speciality malts.

Yep, the Maillard reaction is useful for darkening beer and creating carmel flavors.

 

[Matt3989]

Yep, the Maillard reaction is useful for darkening beer and creating carmel flavors.

I didn't study much chemistry or the culinary arts in school, but it was my understanding that the mallard reaction requires heat >300°F to even start (then you get more reactions/different flavors up to 500). So you won't get any mallard reaction during a boil without a pressure cooker.

 

[freisste]

I didn't study much chemistry or the culinary arts in school, but it was my understanding that the mallard reaction requires heat >300°F to even start (then you get more reactions/different flavors up to 500). So you won't get any mallard reaction during a boil without a pressure cooker.

There are different types of Maillard reactions. They are much more pronounced at high temperatures (300F+, as you stated). This is why bread turns brown. However, they are also present at lower temperatures. In fact, Maillard reactions take place in your body.

 

[the_bird]

I didn't study much chemistry or the culinary arts in school, but it was my understanding that the mallard reaction requires heat >300°F to even start (then you get more reactions/different flavors up to 500). So you won't get any mallard reaction during a boil without a pressure cooker.

Do a small decoction mash. Boil a small portion of your mash for 5-10 minutes and add it back to the rest of the mash - you'll notice a dramatic color change, just for a relatively short period at 212° (and at atmospheric pressure).

 

[Matt3989]

Ahhh, good to know. I looked into it a little further and found some pretty cool info. This article goes pretty indepth about the purpose of heating foods and the maillard reactions that take place.

http://kitchenscience.sci-toys.com/heating

not about beer, but still informative.

 

[unionrdr]

I only use shorter boils if my LME is pre-bittered (I like bittering only types,like Cooper's OS cans). Plain DME's in the boil for whatever hop additions to keep colors light & no "twang". Otherwise,the 1 hour boil gets it when doing my own bittering.

 

[chungking]

Why doesn't lme have dms? Does dme have dms? I understand now that lme does not require a hour long boil, or even a 15 minute boil, but what about dme?

 

[the_bird]

My understanding is that the DMS precursors are removed in the manufacturing process. Keep in mind, the extract manufacturers are essentially just doing a massive mash and concentrating the resultant wort. There was an interview a few years back - must have been on Basic Brewing Radio - with a guy from one of the malt extract companies where they talked about that.