This thread has made me learn far more about the chemistry of the boil than I ever thought I would be interested in!
I don't dispute any of the research into boil times and DMS, but I couldn't explain the dichotomy between the research saying that you need the 60 minute boil, and the significant number of homebrewers (here and elsewhere) saying they can't tell the difference/can't taste DMS on short boils. I think it is foolish to disregard a large body of opinion just because it's anecdotal without a scientific rebuttal.
For me on this topic, this includes questioning whether the scientific research is applicable to the homebrew scale as it is to the professional brewer.
Anyway, to the point, I found a very informative article my Martin Brungard (well researched, citing scientific papers from C Bamforth etc) in the May/June 2019 edition of Zymurgy called "Advances in wort boiling". Unfortunately, as it's a subscription magazine it's not appropriate to post here, but they do have a 7 day free trial, so I would encourage anyone interested in more understanding behind the topic to take out a trial (free for 7 days, that's what I did) subscription and
read the article
It makes some very interesting points, and has scientific data to back it up, rather than relying on heresay or tradition. I'll try to summarise the points I found interesting and pertinent to this debate:
"A long hard boil creates thiobarbituric acid (TBA), an oxidant that has been proven to accelerate beer staling". I'd never heard of TBA before and interesting to hear about. I've read many things about boiling hard introducing "heat stress" to the wort, without anything actually explaining what it was or why it was bad. TBA provides the information behind it. There is a danger to overboiling your wort.
The article also notes the same - they state pro brewing systems report 2-12% evaporative loss, and 'typical homebrew systems' being 17%. This lends credence to my theory that DMS is less prevalent at the homebrew scale on short boils because the boil is a lot more vigourous.
I have read many many times that "pilsner malt contains more SMM than other malts" so you need to boil it longer. This makes sense, but I'm always wary of statements (without source) saying "it has more" without any quantitative comparison. This article gets its data from Pitz, W.J., Factors Affecting S-Methylmethionine Levels in Malt, Journal of American Society of Brewing Chemists, 1987 and provides a handy graph to display it. I'm reading the values off the graph rather than the raw data, but the important thing is that it has quantitative data. My reading of the graph is that the SMM content for "Typical Pilsner malts" (2.4-4.5 EBC) is in the range of 15-25 mg/kg, whereas pale malts (5-8 EBC) are in the range 3-9 mg/kg (is this the same as ppm, or is ppm based on molarity and not weight?). Roughly this equates to pilsner malt having 5x as much SMM as pale malt. Compounding on this, 2-row barley has less SMM than 6-row barley (6-row has roughly 50% more SMM than 2-row). 6-row seems to be common in American brewing, whereas 2-row is more common in the UK. I don't know what you get in Australia. It also provides graphs for (presumably 6-row) that typical values for the start of the boil is 1000µg/l, whereas pale malt is 300µg/l. Given that the half-life for SMM conversion is 37minutes, this 30% reduction in the starting levels of SMM in pale vs pilsner malt equates (in my opinion) to the reduction you would get in a roughly 60 minute boil.
I think the above goes a long way to giving a possible explanation of why some people are certain that you can't taste DMS on a 30 minute boil. Other people haven't stated their recipes here, but if they are using pale malt from 2-row barley, then the initial levels of SMM may be sufficiently low to achieve the required level of conversion/boiloff in a 30 minute boil, whereas others may insist they can taste it because they are using pilsner/lager malt from 6-row barley... and all the shades of grey in between.
It then further goes on to say that SMM to DMS conversion doesn't require a strong boil (it's a function of temperature and time, so a gentle simmer is necessary) and that DMS boiloff can be achieved in 30 minutes
after SMM conversion, even for high pilsner malts.
He directly references Wilson and Booer here. DMS is driven off relatively quickly, but it continuously produced whilst there is appreciable levels of SMM in the wort.
There are some good graphs that show levels of SMM and DMS in the wort for Pale and Pilsner malts during a 60 minute boil. They are fascinating and very open to interpretation, so rather than me trying to interpret it and get shouted at from both sides, I suggest you read the article and come to your own conclusions. It also has the on the graphs the level of when DMS is objectionable in beers (100 microgram/l, if anyone is interested, although you can notice it as low as 30).
The majority of the beer brewed/consumed on the commercial scale is lager, and thus I am guessing the majority of research is targeted towards lager. As lager/pilsner malts have a higher level on SMM than pale malts, this may go a way to explaining why they have longer boils than homebrewers brewing with pale (not pilsner) can achieve.
I think this article could be what you are looking for
(that a shorter boil (in some circumstances) is OK). It goes into a bit of detail and states that isomerised alpha acids degrade after about 60-80 minutes in the boil and bitterness is actually reduced from this point on. He recommends a maximum of 70 minutes.
There are some good recommendations at the end (I'm not advocating any of them, don't have a go at me, read the article if you are interested). He suggests that a gentle simmer for the first 30 minutes is good, followed by an uncovered boil to drive off DMS. For higher kilned malts like pale, or vienna/munich, the initial simmer may not be necessary (see stuff above about reduced levels of SMM inherent in the grist)!
He also goes into a bit of detail about why wort circulation is more important than boil vigour to drive off DMS via contact with the atmosphere. Pro brewers have pumps/fancy gadgets to forcibly recirculate the wort, but for a lot of homebrewers (in my opinion) the only way to achieve wort circulation is via a rolling boil.
Again, the 'vigourous/rolling' boil is something that gets stated time and time again without any quantitative measurement of what 'vigourous' or 'rolling' actually means, and why it is necessary. This provides at least some quantitative measurement. He states that the wort speed across the surface of the kettle (during a rolling boil) should be at least an inch per second (no guidance on a recommended speed or upper limit), but having seen many many video of homebrew boils, they are far in excess of this. I think that a lot of homebrewers are boiling unnecessarily hard.
Unfortunately, he doesn't go into a lot of detail about colloidal stability, haze and head retention (
if those are important to you!). Boiling "too long and hard" reduces coagulable nitrogen which damages a beer's head retention properties - but doesn't go into details of what "too long" and "too hard" are unfortunately.
Anyway, I found it fascinating (and well researched) and it fills in the gap between the scientific evidence that you should boil for at least 60 minutes, and why so many people can't detect any DMS off flavours with a reduced boil
on the homebrew scale on their equipment and their recipes. I would encourage people to read the article and form your own opinions, then brew beer you like!
. 25l of “Master Batemans DM” for the summer 
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