Why boil the entire brew length for an hour?

[anopenmind]

Hi all,

I have a question for you, probably seems quite fundamental but I've got a scientific mind and don't know the answer, so...

When brewing with grains, why do we boil the entire brew length for an hour or longer?

I believe the answer is to infuse the wort with hops - hops are added and boiled for various lengths of time. But when I used to brew with malt extract, which I did successfully for many years, I used to boil the hops separately in a very large saucepan. I did this in a volume of water approximately 1/5 of the total brew length, which meant I needed less power to keep the boil rolling. Then I'd add this hop 'tea' to the fermenter, achieve the required pitching temperature, pitch my yeast and fermented some really rather good beer.

If I did something similar now that I'm brewing with grains, I could have my hops boiling away during the mash, I could use the hop 'tea' for sparging, I could then raise the wort to boiling temperature for a few minutes just to ensure perfect sterility and then go straight to cooling and pitch my yeast. I could save myself almost an hour doing things this way, which as a father of two 19 month old girls would really help (I only ever start brewing after they've gone to bed so brew days invariably mean a late night)

Or are there other reasons to have the whole brew length boiling for a whole hour? From a chemistry point of view, I can't see that boiling for this long does anything important for the sugars. Or does it?

 

[strange-steve]

According to Michael Mosher (chemist) and Kenneth Tranthum (physicist) in their book on brewing science there are several reasons for the boil:
Sterilisation of the wort
Increased maillard reactions
Denaturation of proteins
Reduction in volume
Elimination of DMS
Formation of trub
Reduction of pH
Improvement of clarifying agents
Hop acid conversion

Does that mean then that you absolutely must boil for an hour to achieve all of these? No, but they also point out this:
"While it is often thought that the main reason for boiling the wort is to sterilize it (reduce the number of living microorganisms) or just to allow the hop acids to form the desired bitterness for the product beer, there are a multitude of reasons for heating the wort to these high temperatures. The brewer would not spend the energy, time, and money to perform these tasks if an alternative was available or if a good saleable beer could be made in a different way."

 

[PhilBrew]

+ back when you were extract brewing, you were only able to "get away" with not boiling all your extract for all that time because the extract manufacturer had boiled it for a while before spray drying it (DME) or reducing it down to a syrup (LME)

Cheers, PhilB

 

[ppsmith]

If you’ve not seen it already, brulosophy.com is a blog/podcast where people are asking these kind of questions and experimenting to see which of them have valid reasons (i.e. not doing it would result in discernibly worse beer) and which have less impact than we might expect.

It’s not overly scientific, but it’s always good to question the things that are done that way because they’ve always been done that way.

 

[foxy]

Tim O'Rourke explains the function of the boil aptly here.
http://www.ibdlearningzone.org.uk/article/search/?searchstring=&category=22&author=140&keyword=

 

[The-Engineer-That-Brews]

Tim O'Rourke explains the function of the boil aptly here.
http://www.ibdlearningzone.org.uk/article/search/?searchstring=&category=22&author=140&keyword=

Looks like some good quality documents at that site - thanks

 

[Sandimas]

I'm one of these people who like to question things and have tried 45 and 30min boils, and haven't noticed any difference in the resultant beers. Of course you need to use more hops to hit the same IBU.

 

[Sadfield]

I'm one of these people who like to question things and have tried 45 and 30min boils, and haven't noticed any difference in the resultant beers. Of course you need to use more hops to hit the same IBU.

So, not noticed a difference other than reduced hop utilisation.

 

[GerritT]

I'm one of these people who like to question things and have tried 45 and 30min boils, and haven't noticed any difference in the resultant beers. Of course you need to use more hops to hit the same IBU.

Ditto. If I need 80 grams for a recipe, have a packet of 100 grams and don't want to have 20 grams of that hop stay in my fridge for gods know how long, I lower the boil time to 40 minutes or so. Some hops seem to develop a lesser harsh taste that way too, looking at Chinook and Citra. Okay, that might be my perception, but there are no hop leftovers and it shaves 20 minutes of my brewing time.