"Vigorous" boil?

What is cool about that video is you get to see the vigor of the boil 'inside' the kettle. I only get to see the vigor from the top of my kettle.

Thanks for that video!

Cheers!

 

Thanks for that!

 

A question for lurking Thermo-Hydro Dynamicists who specialize in Organic Compounds: What is the benefit of a vigorous boil over a moderate boil or even a wimpy boil?

I'm pretty sure the temperature is the same and other than a noticeable "stirring" action I can think of no difference. Do proteins coagulate more efficiently in a vigorous boil? Dimethyl sulfide evaporates around ~100°F so that makes no difference. Will alpha acids in hops convert to iso-alpha more efficiently? My guess is a tepid boil of 211° will convert hop acid nicely but of course there's no research on that. Sterilization is complete above 160° so no bugs are surviving. When a brewer at a modest elevation, say Des Moines at 1,000', boils wort it never exceeds 210° . . . I've never heard of enzymes not breaking down when brewing above sea level. When have you ever heard anyone complain about chill haze and blame high altitude brewing? At New Belgium Brewery (Fort Collins, 5000'), boiling wort never exceeds 203°, should they be boycotted? Pretty sure there are no altitude restrictions throughout the brew industry.

Is this a hold over from before thermometers were invented? What say ye, learned Scientists?

 

I am not a Physicist but it is my primary understanding that the vigor of the boil is to optimize isomerization of the hops (to maximize hop utilization) and to aid in clarification (coagulation of proteins). It has always been my understanding that the physical action of the boil optimizes both of these aspects.

Below are some extracts of an article written by Jim Busch (BA @Starkbier) detailing these aspects:

“Hop utilization is another key aspect of wort boiling. Although much has been written on this subject, the basics can be summarized as follows: The raw hop bittering compounds, alpha acids, are isomerized through the boiling action into iso-alpha-acids, which are much more soluble in wort. The amount of hop bitterness realized in the kettle is based on the utilization factor and the amount of raw alpha acids in the hops. Pellets used in a vigorous boil for 45–60 min will result in 30–40% utilization factors, whereas with whole hops utilization factors are closer to 20–25%”

And:

“The coagulation and precipitation of proteins is a key factor in producing clear, stable beer.”

The above extracts came from:http://morebeer.com/articles/how_to_boil_wort

I have personally always conducted a vigorous boil to optimize hop utilization and to maximize clarification (I also add rehydrated Irish Moss with 15 minutes remaining of vigorous boil).

Maybe a true scientist can add more input here. @Peter_Wolfe, do you have any thoughts to add here?

Cheers!

 

My belief is that hop utilization is temperature dependent and not "vigor of boil" dependent.

When you boil vigorously or weakly, as long as there is phase change occurring (liquid to gas), the temperature will be the same. Funny enough, all things being equal, I am guessing New Belgium require more hops than would a sea level brewery to achieve the same bitterness. I'd love to see a study of IBU analysis between two similar worts, one boiled vigorously, one boiled weakly.

I always assumed the vigorous boil was therefore to drive off potential off flavors; @PortLargo's comment that "dimethyl sulfide evaporates around ~100°F" negates that a bit. There is also the chance of volatilizing precursors.

The comment about "Sterilization is complete above 160° so no bugs are surviving" is not true however - sterilization is time and temperature dependent. ie, you get more kill at higher temps and longer times than the reverse. Boiling is also a sanitizing process, not sterilizing - you need steam temperatures and pressures to achieve sterilizing kill, as in a pressure cooker or autoclave. Therefore, I'd argue that a longer boil does increase wort sanitization, not that it matters too much. Nevertheless, a vigorous boil is still at the same temp as a weak boil...

I'd also have to agree with Jack's clarification comment - but I'm basing my agreement off of anecdotal evidence, or rather, nothing. Perhaps greater activity of the wort increases collision of proteins and the like to get better break? Just guessing here.

 

Or maybe it tends to break them apart (i.e. not coagulate as well). Also just guessing. But I can say that my clearest beers have come from gentler boils. Just a different anecdotal data point.

 

I'm not sure where you are getting this but its pretty contrary to what I've learned. DMS is produced in hot wort and the half life is 40 minutes. So after 40 minutes of vigourous boiling 50% of the DMS is evaporated. 60 minute boil gets rid of like 65% and after 90 minutes 80% is gone. Its also produced if you do not cool your wort fast enough, and that doesnt get evaporated.

You may be right that DMS evaporates around 100F but consider this. Alcohol is also very volatile and evaporates at room temp, but put out an open bottle of vodka and after 60 minutes there will still be alot of alc in there. Boil the vodka, and the alc will go away a lot quicker (actually it might set itself on fire getting rid of the alc reeaally fast).

We are dealing with 5 gallons of wort with DMS in it, so we need the time and help of the boil to drive off as much DMS as we can. The more vigor the boil has, the better its able to drive off the off flavors.

 

Any kind of boiling is close enough...mostly from a sanitation standpoint...my wort boils at ~ 206*F...a key factor is boil off for volume control. Cheers all.

 

This was the most thorough, scientific explanation I've ever come across on the importance of a vigorous boil. Actually found it on beeradvocate a while ago:

http://bavarianbrewerytech.com/news/boilhops.htm

 

Temperature and not vigor of boil makes sense to me. We all pretty much know that whirlpooling hops at sub-boil temps adds some bitterness (i.e. iso-alpha-acid conversion), but at a reduced level. And tests done with isomerizing alpha acids above 212° shows the reaction increases (my guess is this was done under pressure).

Oxford University published a paper on Water Disinfection and it's surprising at how low a temp the pathogens start to die off. Quoting: "Because enteric pathogens are killed within seconds by boiling water and are killed rapidly at temperatures >60°C, the traditional advice to boil water for 10 min to ensure potability is excessive.

Although heating water to boiling is not necessary, it is the only end point that can be easily recognized without use of a thermometer. The temperature of hot tap water and the temperature of water that is too hot to touch vary too widely to be reliable determinants of pasteurization of water [29, 31]; however, if no reliable method of water treatment is available, tap water that has been kept hot in a tank for some time (at an estimated temperature of 55°C–60°C [140°F] for at least 30 min) is a reasonable alternative".

Source is Wikipedia. And your last statement was the question I was asking. Does it take the mechanics of water molecules bouncing around to do this? Or is it temp dependent? Or is it just the way it's always been done?
GreenKrusty101 boils his wort at 206° (I'm guessing he's at ~3,000'), will his vigorous boil accomplish the same as my tepid 212° boil at sea level? Could I run a re-circulating pump to create turbulence, heat my wort to 206°, and have the same results he has?

I read this link before my original post and while informative, it really isn't scientific. It states: "Vigorous boiling helps coagulate unstable proteins. But it doesn't offer any reason or background. The OP's video of a seriously rolling boil is mighty impressive, but what is it accomplishing?

No sharp-shooting intended here, just genuinely interested in what's going on. Isn't there some Organic Chemist who dabbles in Fluid Mechanics & Thermodynamics that can chime in? Please don't tell me all those guys are wine-drinkers.

 

No sharp shooting taken. As I re-read that article, I agree, it wasn't entirely scientific in the truest sense of the word, although there were certainly some scientific moments. Did you read this part?

Rapid boiling drives out oxygen, which can become very harmful in the process: it can change the color to darker than desired, and it can help serious infections to develop in the beer. Even more important, however, is the break down of proteins. This can be achieved only if boiling is vigorous: it helps create surface tension of the so called “albumin fraction” of the protein. These particles then will concentrate on the wort-air-steam bubbles and because of the high concentration, they will aggregate into larger and larger masses. More scientifically, the micellae, denatured in the boiling process, are held in suspension only by their electric charges. When in turn, the force of affinity between the micellae exceeds the force of electrostatic repulsion, as a result of high concentration on the surface of the bubbles, the albumin will aggregate and precipitate. This process cannot be achieved without a rolling boil.

 

If you can see an old direct fired copper Huppmann brew kettle in action, ask if you can look at the boil. The one at SN had wort jumping about 2 ft. I back pedaled a little once I saw this when the steam cleared.

 

What are the consequences of over boiling? What is your motivation for installing an auto timer?

Cheers!

 

OT...but never realized Jim Busch was around here. Was a fan of his when he wrote for BT...

 

Jim (starkbier) will post on BA from time to time. It seems he mostly posts on topics that relate to Victory Brewing.

Cheers!