Decoction: Why do we need to pull a thick decoction?

[Finn Berger]

Actually I'm a bit sceptical about decoction, but I'll try anything more than once before I conclude. But I also want to understand why we must boil the wort with the malt. Seems it's the general opinion among decoctioners (if that's a word) that it's only during the boiling of a thick mash that you get maillard reactions. And maillard reactions is why we (today) do decoctions.

Now a maillard reaction is a reaction between a protein and a reducing sugar (and the fermentable sugars in the wort belong to that class). And the wort contains both, so why not just boil the wort? (And that's what we do when we're done mashing, so ...?) What changes when we also boil the malt?

Maillard reactions are influenced by several factors: temperature, acidity, concentration of the sugars and time. The only thing I can think of, is that it is the thickness of the medium that is important. And when you boil a thick mash, you get something akin to gruel. Is that it?

I've tried to find info on this, but have come up with nada. And I would appreciate it a lot if any of you could come up with some scientific backing for the "boil the thick mash" standpoint.

By the way I've tried boiling down the first runnings from a small batch. I reduced it from 8 to 2 liters, and then diluted it back to eight. When i after that added the second runnings, the colour was quite a bit darker than it would normally have been. And I do think the taste had changed, too. I didn't get a sweeter beer, so I don't think I got caramellization. (The temperature didn't get higher than 103C/218F.) My conclusion is that maybe this is a way of achieving the same goal?

 

[BeerSmith]

I think you are correct that the goal in drawing the thicker part of the mash is to promote Malliard reactions to get the darker color and caramel flavors.

I've not tried the boil method you mentioned, but certainly concentrating wort darkens it over time. Consider liquid extract malt which are all made by boiling (under a vacuum) wort. They are all darkened by the process which is why it is hard to make very light colored beers using malt extract.

 

[Oginme]

I do the reduction of the wort when making my Scotch ale. The flavors are similar to a decoction, but also a bit different. THe wort reduction, when you reduce it to a thick paste and boil that, tends to greater caramel and toffee flavors. The thick grist decoction has some of that, but more subdued with a lot more of the darker, toasted bready flavors in the profile.

Off the top of my head, I would guess that the higher protein content found within the grains and not specifically in the wort would promote the difference I have tasted between the two methods.

 

[Finn Berger]

Thanks for answering, guys.

A higher protein content in the thick mash is what I've been thinking might be the explanation, too. And what I did when boiling with all of the malts did have an effect on the colour of the wort, at least. It is definitely darker than it would have been without that treatment. It is not due to concentration of the wort, because I added water to get the volume back up after I finished.

When you brew that scottish ale I guess you dilute it afterwards? I did that when I boiled down those first runnings, and I did not get any hint of sweetness in the beer, which turned out a pretty decent pilsner. I take as an indication that I didn't make any caramel. I'm actually not sure how much the taste was affected, but then I haven't got the worlds most sensitive palate.

 

[Oginme]

When you brew that scottish ale I guess you dilute it afterwards? I did that when I boiled down those first runnings, and I did not get any hint of sweetness in the beer, which turned out a pretty decent pilsner. I take as an indication that I didn't make any caramel. I'm actually not sure how much the taste was affected, but then I haven't got the worlds most sensitive palate.

Scotch Ale, the highest ABV of those types. I guess now it is called Wee Heavy, but I really dislike that name. Personal choice.

With the reduction, it is not just boiling the wort down in volume. You need to reduce it to a paste and allow the temperature to climb above the boiling point of the wort. It is just like making candy at that point. A lot of stirring and attention is needed. It is this which creates the sweet caramel and toffee flavors. Straight reduction in volume does not accomplish this at all.

 

[Kevin58]

Wee Heavy was the name (or nickname) of a specific commercial beer... Fowler's Wee Heavy. The actual name of the beer however was Fowler's Twelve Guinea Ale. The belief that Scottish ales were boiled for a long time in order to caramelize is a myth. Beer historian Ron Pattinson has published brewery logs from Scottish brewers and compared the boil length with contemporary breweries in Great Britain. Most Scottish boil times were in line with the largest London brewers and many were shorter. Ron claims that "Scottish" ales as described by American sources really only apply to US brewed beers.

 

[Finn Berger]

Scotch Ale, the highest ABV of those types. I guess now it is called Wee Heavy, but I really dislike that name. Personal choice.

With the reduction, it is not just boiling the wort down in volume. You need to reduce it to a paste and allow the temperature to climb above the boiling point of the wort. It is just like making candy at that point. A lot of stirring and attention is needed. It is this which creates the sweet caramel and toffee flavors. Straight reduction in volume does not accomplish this at all.

When I boiled it down, it got pretty thick. I was measuring the temperature, and as I said it only reached 103 C, which isn't hot enough to caramellize any sugar, I think. Caramel was not what I was after, either, so I stopped there. It still felt pretty dramatic, actually, and I thought it would surely give a lot of taste, but it didn't, even if I was very happy with the beer.

Myths may be myths and still taste good. I'm brewing a 6,7% wee heavy with a recipe from a Norwegian brewery called Kinn. It does not involve reduction, but is damned tasty. Here's the recipe, for those who might be interested (and are not scared by metrics):

Malt for 32 liters after cooling down (75% efficiency)
8,80 kg Maris Otter
0,45 kg Simpson's Amber
0,45 kg Simpson's T50 (130 EBC)
0,23 kg Simpson's DRC (300 EBC)
0,07 kg Roasted Barley
Hops
60 gr First Gold @ 60
35 gr Fuggles @ 5
Yeast
Wyeast 1318 London Ale III