Maine Homebrewer said:
read that it can cause your beer to be a bit sweeter due to caramelising caused by the boiling of the grain
I haven't really noticed that. I just find it an effective way to do temperature steps without directly adding heat or increasing the volume by adding boiling water. That and I too had an increase in efficiency.
I get to mash out temperature of 168F by pulling my wort out of my mash tun to my boil kettle, heating it up to the proper temperature, so that when added back to the mash tun, it settles at 168F. I use a cooler for a mash tun, so I can't heat it directly to get to mash out temperature.
I did an experiment about a year and a half ago with three different ways of getting to mash out temperature. I made the exact same 5 gallon IPA recipe on the same day, back to back to back.
The first time, I pulled the wort out of the mash tun, heated it up and added it back in to get to 168F.
The second one, I pulled the grains out, with as little wort as possible (I used a kitchen strainer) and brought that up to a boil and added it back in to get to my 168F mash out temperature.
The third one, I added boiling sparge water to my mash tun, without pulling any grains or wort out. I kept adding the boiling water, until I was at mash out temperature of 168F. I had to use about half of my sparge water to achieve this, which left me with a very thin mash.
I then let all three sit at 168F in my mash tun, before lautering, draining and adding the remaining sparge water in each case.
In blind taste tests with my brewing friends, the first and second mash out techniques were nearly identical in color, taste, aroma, etc. They were virtually the same beer.
The third one was different from the first two though. My mash efficiency was lower by about 5%, resulting in less sugar making it into the boil kettle. I attribute this to less rinsing with clear sparge water, compared to the other methods. Noticeably lighter in color, compared to one and two. Also, less malty than one and two. Just seemed to be a thin beer. This third version was always the least favorite.
What I learned was the following that I've put into regular practice.
>>>>Boil only the wort, to get up to mash out temperature, it comes up to temperature quicker than boiling the grains and eliminates the possibility of scorching. When boiling the grains scorching is always a threat, since as you boil off the liquid, it's like porridge and gets thicker and thicker. Boiling the grains is also labor intensive, since you have to constantly stir to avoid the scorching.
>>>>By boiling the wort only, I get to sparge with the full amount of sparge water and get more sugars out of the grain, thus my efficiency is higher.
>>>>I get a much more malty flavor profile with one or two, which is what I prefer in most beers.
To summarize, method one seems to be the best for me. It isn't the easiest method (method three is the easiest), but the quality of my beer is improved enough with method one, that I go through the extra effort to do it. Method two is equivalent to method one for me in quality, but is much more labor intensive, so usually not worth the extra effort.