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All Grain Brewing / Re: Martin's boil tips?
« on: October 08, 2018, 10:06:52 PM »1.) Don’t boil longer than 60 minutes;
2.) All you need is a simmer;
3.) It’s okay to partially cover the boil.
We’ve been beating that drum for years now!
Nah. There is a lot more than that and some of what Derek points out is incorrect.
1. For most brewers in the country, they are at a low enough elevation that it is unnecessary to perform any more than a total of 60 minutes of 'boil'. Brewers working at higher elevations (say 2000 ft plus), might need to extend their 'boil' time when working with high Pils content wort (Pils malt is any malt with color less than 2.2L).
2. I placed 'boil' in quotes since the intensity of the boil can and should be varied to address the chemical and physical processes needed at various times in the wort boiling process. When your beer has high Pils content wort (it has DMS-precursor (SMM) in it), then a low intensity, covered simmer is perfectly capable of performing the conversion of SMM into DMS. Once an acceptable percentage of SMM has been converted, then a more intense, open boil is necessary to volatilize that DMS from the wort into the atmosphere. For most brewers below 2000 feet, about a half hour of covered simmer and about a half hour of open boil are sufficient to bring DMS to acceptable or imperceptible levels in a high Pils content wort. For high elevation brewers, its the simmer stage that needs to be extended since SMM conversion to DMS is directly related to your wort temp. Remember that wort boils at lower temp at high elevation.
If your wort has low or no Pils content, then its possible to further shorten the boil time since there is no need to convert SMM to DMS. Pale malts (color is greater than 2.5L) generally have little or no SMM, but they can have DMS. Therefore, it is still necessary to conduct about a half hour open boil to volatilize DMS out of the wort. This open boil period of about a half hour is sufficient to rid any wort of high DMS concentration...as long as your wort has very good contact with the atmosphere. To have good contact, your wort either needs to be fan sprayed across the kettle or have a good rolling action. Offsetting your kettle a few inches to the side of the center of your burner can encourage a good rolling of the wort within the kettle. For those of you with valves and other heat-sensitive accessories on your kettle, this offset could help keep them out of the heat.
While you might get by with a short boil when you're not dealing with Pils malt, it may not be as cost effective since boil time also helps determine your hop bittering utilitization. If you're OK with adding more hops, then a shorter boil could be OK for some beers. By the way, you get exactly the same bittering utilization when your wort is simmering at 212F under cover or boiling volcanically, uncovered at 212F.
One thing that I'm not saying, is that its still OK to boil beers longer when they depend on long boils for their character. Barleywines and Old Ales can (should??) still be boiled for longer periods, if that's what the brewer is after. Just be aware that long boils degrade Coagulable Nitrogen too much and that kills head retention.
3. While its OK to cover your kettle at times, it is still important that your wort has good exchange with the atmosphere for at least a half hour in order to expel DMS. You don't need a volcanic boil, but your wort does have to circulate well so that every molecule of wort has its chance at the wort surface in order to get rid of DMS.
There is still a bunch more to this topic, but this was a Reader's Digest version.
Enjoy!
Thank you for the exceptions to the rules. In general, however, all three of my points are correct for the vast majority of brewers.
Never hurts to understand the outliers though, so thank you. You are absolutely correct but your expansion seemed a little outside of what I imagine most brewers here would want. Otherwise I would have elaborated myself.
Let’s not get started on TBI!