Boiling hard and fast

I have found very little information about how the intensity of the boil impacts wort. Everyone says do a rolling boil, but I'm wondering what effect a really hard boil would have. Like if I have a really intense boil (leaping out of the kettle) for a shorter period of time, would that have the same effect as a longer more relaxed boil? Anyone ever experimented with this?

One reason I'm imagining people don't do this often is kettle space, but I'm using less than a half my available kettle space, so I may have a unique situation with that.

How hard you boil determines how much wort you boil off as well as getting rid of DMS.

If you boil harder you'll just lose more water, which is fine if you've got the space and can account for it. Also you'll get slightly better hop utilization. And probably more caramelization/wort darkening.

I believe it can help the hot break and creating clearer wort as well.

Boiling serves a number of purposes. The primary ones (not necessarily in order) are:

1. Achieving sterility
2. Isomerizing hop acids
3. Coagulating protein
4. Converting DMS-p to DMS and driving it off
5. Concentrating wort

All are achieved with a decent boil. A downright raucous boil is probably more effective at 4 and 5. However, there are also issues with applying too much thermal stress to wort. You will pick up more color, get more caramelization, create more radicals, form more staling precursors, etc. Many commercial brewers moved away from using high pressure steam in their calandrias in order to achieve less thermal stress and longer beer shelf life.

In practice it's best to have a good rolling boil, but probably not necessary (or maybe even deleterious) to be recreating Old Faithful in your kettle every time you brew.

I've actually heard that a harder boil creates more DMS precursors and won't drive them off as quickly. I seem to recall this from a discussion by Jamil and John Palmer on a brew strong episode.

This is not supported by the brewing literature. DMS precursor is SMM, s-methyl methionine. SMM is an amino acid that comes from the soluble protein in malt. It is a fixed quantity by the time boil begins and decreases when converted and volatilized in the boil.

DMS can be oxidized to DMSO (dimethyl sulfoxide) in the boil, which in turn can be reduced back to DMS by some lager yeasts, but this is thought to be a significantly lesser source than the simple conversion of SMM to DMS through the application of heat.

Another post had the info I remembered. Whether it really makes a difference? I don't know.

"'Principles of Brewing Science', G.Fix, pp.76:

On the other hand, excessive thermal loading (e.g. uncontrolled high-temperature [...] boils) can transform the simple melanoidins into less desireable heterocyclics [...]
The second level of complexity consist of sulfur-bearing heterocyclics. Heterocyclics and methionine products have flavour that strikingly recalls cooked cabbage.

The potential presence of these compounds in beer is responsible for the sensivity of many brewers to free SMM in wort. Nevertheless it is excesive heat treatment - not inadequate boiling - that is responsible for their formation."