Saturday, March 22, 2008

Importance of a Full Wort Boil

Wort boiling is a critical control point in brewing. In the past before taking this brewing course I wasn't fully aware of how important it really is. So much so, that I'll write an entire blog post about it. I’m concentrating on evaporation and protein removal for the most part, as I think these are the least understood part of the process.

First, what is a full boil? It seems to be accepted that a boil of at least 60 minutes is required for the following actions to sufficiently occur. I know some brewers only do 45 minute boils and I would recommend against this, as it can affect flavour in the final beer as I will describe in detail. As well, the wort must actually be fully boiling a "rolling boil" with two-phase nucleate boiling where steam bubbles pass through the wort.
A summary of the achievements of wort boiling:

Requirement: Dependant Conditions
Wort sterilization: Time & Temperature
Isomerisation of hops: Time & Temperature
Protein denaturation & enzyme inactivation: Time & Temperature
Protein coagulation: Turbulence, boil vigour & time
Formation of colour & flavour components: Time & Temperature
Removal of unwanted volatiles: Time, Temperature & Evaporation
Formation of reducing agents: Time & Temperature
Wort concentration by evaporation: Time, Temperature & Evaporation
Adapted from reference J. Andrews, Brewer Distiller Int. 2008 (ref 2)

A lot of brewers measure the amount of boil by the amount of evaporation that has occurred. This is a fairly easy metric, as one just needs to measure the volume of the kettle before and after the boil. However, evaporating water into steam is very energetically expensive. We cannot, however, drive off unwanted volatile components without a certain amount of evaporation. What we want to evaporate is volatile off-flavour components such as DMS and aldehydes.

Dimethyl sulphide (DMS), an off flavour component that forms during the boil from S-methylmethionine (SMM), is quite volatile at wort boiling temperatures. Given enough time, say 60 minutes of boiling, DMS should be formed and driven off enough to bring it below the detectable flavour threshold. During boiling we're basically distilling the DMS out, as it is more volatile than water. However, you must evaporate some water in order to do this. The amount of water needed to evaporate is dependent on the concentration of DMS that you need to get rid of. The more DMS in the wort, the more water you need to evaporate. There is a minimum amount of water that you need to get rid of certain concentration of DMS, regardless of what type of wort boiling system you are using [ref 1].

In the “perfect boiling system”, the boil would run at the optimal liquid-vapour equilibrium to have as little water evaporated possible for the maximal volatile removal. This would save energy. Boiling systems do not run at this optimal point, of course… but imagine the energy savings over a year if you could reduce your evaporation by a few percentage points? It would be very significant [see ref 2 for a good read on this].

Luckily, most malts stored properly and mashed with proper procedures don't create too much DMS to require extra boil lengths. The potential for DMS formation occurs in the malting process, and is generally higher for lager malts. Breweries these days are operating on evaporation rates of 4-8%, which should be enough to drive off 'normal' amounts of DMS. If you have problems with DMS in the brewery, you might need a slightly longer boil (careful, though - microbial infection can lead to DMS problems downstream too).

Wort concentration – what of this then? It would seem that if it were possible to boil wort with less evaporation, you could save a lot of money. You could re-calculate your mash recipe to have less-dilute wort being passed to the kettle. But don’t mistake what I’m saying here as an excuse to turn down your steam jacket and let the wort simmer. To get extremely low evaporation rates with good volatile removal plus hot break formation, you need a more expensive boiling system or even a wort stripping system. For your little kettle, you need as vigorous a boil as possible, and I’ll tell you why…

Hot-break Formation
One of the most important reactions that occurs in the wort boil is the formation of "hot break". Hot break is the coagulation of proteins, formation of protein-polyphenol complexes, and reaction with hop compounds to create larger particles that will sediment out in the whirlpool at the end of the boil. These reactions occur at higher rates at higher temperatures and more agitation. This is why your wort boil must be full and rolling... the more vigorous and turbulent the boil, the more of these compounds form over time. This process maximizes around two hours.

Protein/nitrogenous compounds are required for fermentation, but there must be a balance. Too few and the fermentation will become stuck, too many and several changes in flavour will be noted. In particular, in the presence of excessive protein content can lead to higher levels of esters and higher (fusel) alcohols. This occurs when the yeast metabolizes the excess amino acids to form higher alcohols (eg propanol, butanol), which then can be further converted to various esters (eg ethyl acetate, isoamyl acetate). Higher alcohols give the beer a slight warming feeling (and seem to give me a bit of a headache), and esters are known for their fruity/floral contributions to beer. This can be good if this is what you want in the beer style you are making, but if your Czech pilsner tastes like a fruity English ale you might want to check your boil vigour.

As well, removal of protein-polyphenol complexes is important for colloidal stability over time (known as chill haze). Improperly stabilized beer can find reduced shelf-life as it can go cloudy when stored cold due to these complexes. Most of this should happen while the beer is in cold conditioning. While some will form in hot-break, the key here is that we are removing lots of protein from the equation. Less protein means less possibility to complex with polyphenols in the chilled beer.

Stability, Colour, Flavour
In a full boil, any microbe interested in living in beer will be killed. Several organisms can actually survive the mashing process, so the wort must be sterilized before fermentation.

Usually when mashing the temperature is raised at the end of the mash to 75-78 C in order to make the wort less viscous and stop the amylase enzymes from working. However, some enzymes are not fully denatured until the boil. As well, the many chemical reactions that occur during the boil will lower the pH. Maillard reaction products form between the wort sugars and amino acids when heated in the boil. These reactions contribute to flavours as well as darken the wort slightly.

Hop Isomerisation
A lot of attention is given to the isomerisation of hop alpha-acids in wort, and you can find much better information than my little blurb here.

Alpha-acid oils in hops need to be heated to isomerise, which causes them to be soluble in wort and creates the bitter flavour we love in beer. In a ‘typical’ boil, one cannot expect to get much more than 35% by weight iso-alpha-acid extraction from even pellet hops over 90 minutes. Often, this can be less depending on wort concentration, pH, and wort boiling temperature (ambient air pressure can change wort boiling temp quite significantly, eg due to altitude).

You will note that this is a time/temperature reaction… there seems to me to be a prevailing idea in the homebrewing community that as soon as you stop the boil the hop isomerisation stops. Not so… these will continue as long as the wort is hot, however at a lower reaction rate depending on the resting temp.

Hops also contain a great deal of volatile flavour and aroma compounds. The longer the hops are boiled for, of course, the more of these components are boiled off. Thus, adding the hops at the end of the boil will result in more of these volatiles being present. Remember, of course, that just because the wort may not be currently boiling does not mean volatiles are not being driven off. If the wort is hot, the volatiles will still be vaporizing slowly.

---References & Further Reading---
[1] Sommer, K. & Hertel, M. Engineering fundamentals of the wort boiling process. 31st Congress of the EBC, Venice.

[2] Andrews, J. Evaporating the Myths. Brewer & Distiller International (vol 4, #3, March 2008)

Bamforth, C.W. Wort composition and beer quality. In: Brewing Yeast Fermentation Performance. Ed: K. Smart. Blackwell Science, 2003.

Barnes, Z.C. Brewing Process Control, In: Handbook of Brewing, 2nd Ed. Eds: FG Priest & GG Stewart. Taylor & Francis, 2006.

O’Rourke, T. The funcation of wort boiling. The Brewer International, Feb 2002.


Mark said...

Thanks Brian, this is very handy for completing my current BJCP homework assignment on benefits of boiling!

dghnfgj said...

welcome to the wow power leveling cheap wow power leveling service site,WoW Gold buy cheap wow gold,wotlk gold,world of warcraft power leveling buy wow gold

dreaz said...

I am grateful to you for this great content.aöf thanks radyo dinle cool hikaye very nice ssk only cinsellik very nice ehliyet only home free kadın last go korku jomax med olsaoy hikaye lesto go müzik dinle free only film izle love aşk only mp3 indir only radyolar lest go açıköğretim free net only filmler

Anonymous said...

Who knows where to download XRumer 5.0 Palladium?
Help, please. All recommend this program to effectively advertise on the Internet, this is the best program!

123 123 said...

Great post you got here. I'd like to read something more concerning this matter.
BTW look at the design I've made myself Overnight escort

feiyang said...

Thank you so much, I haven't ever read so wonderfull blog, your bolg is so good, I like it very much. I also want you to go to my web, and so that we can discuss something.
By the way, do you like polo shirts, which are very chic, especially the polo t shirts, I love them very much. I also like playing tennis rackets, it can keep healthy, what do you like to do?
cheap tennis racket
discount tennis racket
prince tennis racquet
head tennis rackets
wilson tennis racket
babolat tennis racquet
polo t shirts women
polo t shirts on sale
polo t shirts for women
polo shirts on sale
polo shirts men
men's polo shirt
men polo shirt
mens polo shirts
mens polo shirt
cheap polo shirts
discount polo shirts
men's polo shirts
women's polo shirts

louis vuitton handbags said...

hey,louis vuitton handbags,this is one of the best posts that I’ve ever seen;Christmas gift, you may include some more ideas in the same theme.Damier Canvas. I’m still waiting for some interesting thoughts from your side in your next post.
Monogram Canvas

Viagra Online said...

you know..I'm a huge beer fan and I actually drink from time to time when there's a special event only, for example on birthdays, anniversaries, weddings, football and NBA games, when I found a coin, when I get up and before going to only on special occasions!

Generic Viagra Viagra

Anonymous said...

vigrx plus
Proextender reviews
sizegenetics review
prosolution review

rossignol axium bindings said...

Of course, what a great site and informative posts, I will add backlink - bookmark this site? Regards, Reader.

cole hann handbag said...

Come on dude, these facts* and proof* i mean who is posting* lol :P

Burton Snowboard Jackets said...

Hello to all :) I can�t understand how to add your site in my rss reader. Help me, please

JEY said...

Costa Rica Manuel Antonio Rafting,
Costa Rica Gay Travel,

JEY said...

Costa Rica Manuel Antonio Rafting,
Costa Rica Gay Travel,

forex bulletproof said...

wow great i have read many articles about this topic and everytime i learn something new i dont think it will ever stop always new info , Thanks for all of your hard work!
forex bulletproof review

Penis Enlargement Pills said...

I am thoroughly convinced in this said post. I am currently searching for ways in which I could enhance my knowledge in this said topic you have posted here. It does help me a lot knowing that you have shared this information here freely. I love the way the people here interact and shared their opinions too. I would love to track your future posts pertaining to the said topic we are able to read.

Generic Propecia said...

Nice post, I would like to request you to one more post about that Keep it up

Purchase Glyconutrients said...

BEER please!!

Generic Viagra Online said...

Thanks for sharing such a nice post.
keep posting.

Remona Farnan said...

Such a usefule blog�wow !!!!

youlacka said...

That is really very good article.kızlarla chat,I am glad to know.mersin chat,Thanks for sharing !avrupa chat

auto insurance quotes said...

I am thinking of starting brewing course soon.Though most of the people even i was not aware of its importance and usage in real life.thanks for sharing this with us.

Comprare Levitra said...

Nice post and great blog!

andre12323 said...

christian louboutin shoeschristian louboutin shoes
christian louboutin bootschristian louboutin boots
christian louboutin sandalschristian louboutin sandals
christian louboutin slingbackchristian louboutin slingback
christian louboutin sneakerschristian louboutin sneakers
christian louboutin wedgeschristian louboutin wedges
christian louboutin weddingchristian louboutin wedding
timberland bootstimberland boots
asics shoesasics shoes
asics running shoesasics running shoes
dsquared jeans mendsquared jeans men
dsquared shoes 2011dsquared shoes 2011
karen millen dresseskaren millen dresses
marque t shirtmarque t shirt

Chellen said...

dsquared shoesdsquared shoes
dsquared jeansdsquared jeans
dsquared jeans 2011dsquared jeans 2011
dsquared shoes 2011dsquared shoes 2011
dsquared jeans womendsquared jeans women
asics shoes saleasics shoes sale
asics shoesasics shoes
asics running shoesasics running shoes
asics mexico 66asics mexico 66
onitsuka mexico 66onitsuka mexico 66
asics onitsuka mexico 66asics onitsuka mexico 66
asics whizzerasics whizzer
asics japanasics japan
asics ultimate 81asics ultimate 81
onitsuka coolidgeonitsuka coolidge
rotation 77rotation 77
asics topasics top
asics miniasics mini
asics olymposasics olympos
onitsuka kanuchionitsuka kanuchi
timberland bootstimberland boots
christian louboutin shoeschristian louboutin shoes
karen millen dresseskaren millen dresses
maillot marseille 2011maillot marseille 2011

Generic Levitra said...

wart boiling. Ha! thats pretty funny!

buy kamagra online said...

This is an interesting information. Keep posting such an amazing blog post. Thanks a lot for the share.....

Generic Viagra said...

Hey, Really great work,I would like to join your blog anyway so please continue sharing with us,

Alice said...

Really you have done great job,There are may person searching about that now they will find enough resources by your post.I like this blog..
Blogger how when you visit my site,
My Site created for men's health,
Here the best method for you and get the best Penis Enlargement Pills today.

ranch brokers said...

Thanks for sharing these info's about boiling wort here.I was looking for this info's for my project.will look after for some more updates.

online dating said...

Exactly what i was looking for.i was looking for this informations in various sites but i was not satisfied at all.after reaching this site i found my answers..

apotek dk said...

Tak for at dele disse info's om kogende urt her.

marven said...

Wow ,I like it very much. I also want you to go to my web, It will be best for me . logo design

Adrian said...

Nice blog. I a also ardent player of WOW GOLD. I love this game. Nice posting about wow gold.hotel wireless network

Kamagra tablets said...

nice article!

Ross said...

dsquared shoesdsquared shoes
dsquared shoes 2011dsquared shoes 2011
dsquared jeans womendsquared jeans women
dsquared t shirtsdsquared t shirts
dsquared jeans mendsquared jeans men
dsquared hoodiesdsquared hoodies
dsquared beltsdsquared belts
asics shoes saleasics shoes sale
asics shoesasics shoes
asics running shoesasics running shoes
asics mexico 66asics mexico 66
onitsuka kanuchionitsuka kanuchi
timberland bootstimberland boots
christian louboutin shoeschristian louboutin shoes
karen millen dresseskaren millen dresses
nike air max plusnike air max plus
emilip pucci dressesemilip pucci dresses
survetement lacoste pas chersurvetement lacoste pas cher
hugo boss chemisehugo boss chemise
pucci dressespucci dresses

kimnellen2587 said...

These kind of post are always inspiring and I prefer to read quality content so I happy to find many good point here in the post.bobble head doll

kimnellen2587 said...

I am hoping the same best work from you in the future as well. In fact your creative writing abilities has inspired me to start my own Bloghypnosis rotherham

kimnellen2587 said...

It definitely stretches the limits with the mind when you go through very good info and make an effort to interpret it properly.engraved gifts

kimnellen2587 said...

I certainly enjoyed the way you explore your experience and knowledge of the subject! Keep up on it. Thanks for sharing the info
African Mango

kimnellen2587 said...

Happy to see your blog as it is just what I’ve looking for and excited to read all the posts. I am looking forward to another great article from you. African Mango

kimnellen2587 said...

These kind of post are always inspiring and I prefer to read quality content so I happy to find many good point here in the post
fake tattoos

kimnellen2587 said...

I certainly enjoyed the way you explore your experience and knowledge of the subject! Keep up on it. Thanks for sharing the info
wooden worktops