Why is a full boil better than a partial boil?

[Danek]

Something that's come up in the thread about "single changes that have improved your beers" is the idea of doing a full boil. It does seem to be an improvement that a lot of people have found to make a difference, so I'd like to give it a try for my next batch. But I'm curious to know the reasons why doing a full boil makes beer better. Is it just better hop utilization, or is there more to it?

One other thing - I don't have a wort chiller, so if I did a full boil I'd have to cool the wort using an ice bath. I know this will take time (I certainly don't mind that), but is it still better to do a full boil with a slow cool-down than to do a partial boil that can be quickly cooled with chilled pre-boiled water?

Thanks, as ever, for the help.

 

[Orfy]

I'd say if you are using extract you'd be better sticking with a partial boil if you can't chill the wort in a reasonable time. In fact if you use some kits in the UK then any boiling is detrimental and should not be done.

The main reason for full boils with AG is the fact that you need to concentrate the wort to increase the gravity.

Then there is this:

Directly from the BJCP Study Guide:

Boiling wort is normally required for the following reasons:

1. Extracts, isomerizes and dissolves the hop α-acids
2. Stops enzymatic activity
3. Kills bacteria, fungi, and wild yeast
4. Coagulates undesired proteins and polyphenols in the hot break
5. Evaporates undesirable harsh hop oils, sulfur compounds, ketones, and esters.
6. Promotes the formation of melanoidins and caramelizes some of the wort sugars (although this is not desirable in all styles)
7. Evaporates water vapor, condensing the wort to the proper volume and gravity (this is not a primary reason, it's a side effect of the process)

A minimum of a one hour boil is usually recommended for making quality beer. When making all grain beer, a boil of 90 minutes is normal, with the bittering hops added for the last hour. One exception to boiling was historically used to brew the Berliner Weisse style. Here, the hops were added to the mash tun, and the wort is cooled after sparging and then fermented with a combination of lactobacillus from the malt and an ale yeast.

Boiling for less than one hour risks under-utilization of hop acids, so the bitterness level may be lower than expected. In addition, the head may not be as well formed due to improper extraction of isohumulones from the hops. A good rolling boil for one hour is necessary to bind hop compounds to polypeptides, forming colloids that remain in the beer and help form a good stable head. An open, rolling boil aids in the removal of undesired volatile compounds, such as some harsh hop compounds, esters, and sulfur compounds. It is important to boil wort uncovered so that these substances do not condense back into the wort.

Clarity will be also be affected by not using at least a full hour rolling boil, as there will not be a adequate hot break to remove the undesired proteins. This will also affect shelf life of the bottled beer, since the proteins will over time promote bacterial growth even in properly sanitized beer bottles. The preservative qualities of hops will also suffer greatly if the wort is not boiled for one hour, as the extraction of the needed compounds will be impaired.

Boiling wort will also lower the pH of the wort slightly. Having the proper pH to begin the boil is not normally a problem, but if it is below 5.2, protein precipitation will be retarded and carbonate salt should be used to increase the alkalinity. The pH will drop during the boil and at the conclusion should be 5.2-5.5 in order for proper cold break to form and fermentation to proceed normally. Incorrect wort pH during the boil may result in clarity or fermentation problems.

The effects of boiling on the wort should match the intended style. It is often desirable to form melanoidins which are compounds produced by heat acting on amino acids and sugars. These add a darker color and a maltier flavor to beer. When desired, an insufficient boil will not form enough melanoidins for the style. Boiling the initial runnings of high gravity wort will quickly caramelize the sugars in the wort. This is desired in Scottish ales, but would be inappropriate in light lagers.

Vigorously boiling wort uncovered will evaporate water from the wort at a rate of about one gallon per hour, depending the brewing setup. In order to create a beer with the appropriate target original gravity, changes in the wort volume must be taken into account. Longer boil times or additions of sterilized water may be required to hit the target gravity.

 

[malkore]

i gotta agree with orfy...i wouldn't try to do full boils until you have a wort chiller. a quick cold break helps make a clearer, cleaner beer...not to mention reducing the risk for infections.

 

[Got Trub?]

The Pros:

1) Better hop utilization
2) Necessary to do all grain
3) Lighter color of final product
4) Less melanoidin formation (see 3) which will affect flavour

The Cons:

1) A large and heavy volume of wort to move around
2) Need a bigger burner - your stove won't cut it
3) Wort chiller needed
4) You need a big pot - 8g minimum 10g better for 5g batches

I'm sure others will add to the lists

GT

 

[Evan]

whats the difference between a full and partial boil?

 

[olllllo]

whats the difference between a full and partial boil?

Full and Partial refer to the overall volume, not boil quality.

In a 5g batch, your boil volume will be over 5g, whereas a partial will be between ~1.5g and ~2.5g.
Almost every PM or extract recipie you'll see (especially kit) will be a partial boil recipe.

 

[Evan]

haha...you know right after i asked that question it sort of hit me what it probably was. oops...sorry everyone!

 

[INeedANewHobby]

Why do people always say you'll have more IBU's, lighter color, etc with a full boil? If you're just using whatever the brew store sent home with you (and meant you to do a partial boil) and doing a full boil, then yes these are true. But if you're using the tools that you have at your disposal every day (this forum, BeerSmith, etc) then you can make the exact same beer with a full boil as you would a partial. Just use the tools, adjust the hops and all accordingly, and bam....Good beer as intended by the beer supply store!

For a forum that preaches good brewing practices so much (hydrometer use, sterilization, adequate pitching rates, etc)....you just don't see enough people teaching the real differences between partial and full and how to accommodate changes between the two.

 

[olllllo]

I think that with the price of hops going up, you'll see people focus on utilization to squeeze all they can out of the hops they purchased.

 

[homebrewer_99]

I've been doing partial boils (1.5 gals) with DME and grain steeping for 14+ years and have no plans on changing. I take that back, I have been doing Late Additions for a while now and am still pleased. Why fix it if it ain't broken?

As for hop utilization, the reason you toss in your hops during the last hour of a full boil is because the maximum extraction of 30% is achieved at 60 mins with a gravity of about 1.040.

Other experiments include doubling up on the hops while reducing the boil in half. The exact amount of bitterness is achieved, but at 30 mins you get some flavoring from them also.

There's more than one way to brew a great tasting beer.

 

[Got Trub?]

Why do people always say you'll have more IBU's, lighter color, etc with a full boil? If you're just using whatever the brew store sent home with you (and meant you to do a partial boil) and doing a full boil, then yes these are true. But if you're using the tools that you have at your disposal every day (this forum, BeerSmith, etc) then you can make the exact same beer with a full boil as you would a partial. Just use the tools, adjust the hops and all accordingly, and bam....Good beer as intended by the beer supply store!

For a forum that preaches good brewing practices so much (hydrometer use, sterilization, adequate pitching rates, etc)....you just don't see enough people teaching the real differences between partial and full and how to accommodate changes between the two.

You are right up to a point. Many styles you can adjust appropriately. Now if you want to brew a double IPA or a Czech Pils your SOL with a partial boil.

GT

 

[INeedANewHobby]

^^True...but the recipe that came in the kit wouldn't have a partial boil in the instructions either

 

[Mots]

did a full boil for the first time yesterday (extract)....built an immersion chiller, so cooling wasn't an issue

1. started w/ 5.5 gal and needed to add about 2/3 gal into the primary after cooling - will start w/ more water next time

2. steeped specialty grains in the full 5.5 gal, but just read in another thread that steeping the grains in 1.5 gal first, then adding to the whole would be beneficial - any comments on this?

3. my main concern is the time it took b/c i was using my kitchen stove....100 mins to achieve first boil and 60 mins to return to boil after adding LME & DME...aside from the length of time as a practical matter, i'm curious of any negative consequences b/c the LME/DME were on the burner for ~ 120 mins (60 plus the 60 min boil)

my main question i guess is that with a full boil, should the LME/DME be added later? i've read comments about doing this to reduce caramelization, but are there other negative consequences of having the LME/DME cook for upwards of 2 hours?

 

[Got Trub?]

If you are steeping then no benefit to using the smaller volume. That would likely be for a partial mash - ie you want enzymatic conversion of your grains.

In terms of your boil time see my earlier post - you really need to get a propane cooker to deal with the 6+ gallons of wort. This means boiling outdoors or in a really well ventilated space Other then the caramelization I can't think of any other problems. Your caramelization will not likely be that bad though as most of that time was bringing it up to a boil, below the boiling point the rate of caramelization will be low.

GT