Decoction partial mash questions

[Davemci]

I am going to make a pale ale with a partial mash. I wanted to try a partial decoction mash by mashing 4 lbs of pilsner at 148 for 45 min in 2.5 gallons. Now the part in question, is seperating ALL the grains out (biab) to decoction boil a bad idea? After a 20 min boil I will add it back to the mash water to mash out. I have done single decoctions before with success (all grain).
During the boil I'm gonna add dme. Thanks ahead of the time for ur time and suggestions.

 

[JimRausch]

Question- what part of your proposed technique is a decoction? Are you just asking if you can boil the wort after doing a 45 minute 148* mash? Or are you planning to do a decoction after the 148* rest to raise the temp? To what temperature?
Decoctions to raise temps to the next stage typically take a thick decoction of mostly grain and boil that, add it back to the main mash to raise the temp of the main mash. The enzymes are predominantly in the liquid portion, so you don't want to boil that and destroy the enzymes. The one exception being the final mashout stage where you do want to destroy the enzymes. Then you boil the liquid portion.

 

[kh54s10]

How do you plan to try this? If you pull the bag to then boil (decoction) I would worry that you will destroy the bag. You would also want to move it quickly to the boil pot, if too much wort drained you would scorch the grains.

I also wonder how much you would gain since only a portion of the total would be affected by the decoction. The extract added would not.

 

[Davemci]

I'm going to normal biab at 148 for 45 min. Pull the bag with all the grains out. Put the grains in another pot to boil the grains( without the bag). Then put the grains back into the wort. I was hoping for flavor contributions mostly from the technique.

 

[Vale71]

If you try and decoct just the grains with what little wort they hold the only flavor you'll be adding is the burnt taste. Grains are really sticky, without enough liquid to create convection they'll stick to the bottom and burn in no time.

 

[kh54s10]

I'm going to normal biab at 148 for 45 min. Pull the bag with all the grains out. Put the grains in another pot to boil the grains( without the bag). Then put the grains back into the wort. I was hoping for flavor contributions mostly from the technique.

It will change the flavor. How much is the question. I would suspect the change to be less than if done with an all grain mash, because the contribution of the extract would not be affected.

 

[JimRausch]

If you boil the grains, WITH some of the liquid after your 148* rest, then you most likely will get some flavor contributuons. I don't know how much, and neither does anyone else, unless they've done it. How thick should the decoction be? When I do mine to raise from 148-> 158, I take 3 qts. out with a soup ladle. It's about the cocnsistency of a thin gruel. Good luck Dave! Let us know how it turns out.

 

[Davemci]

Part of my thinking is that the 4 lbs of pilsner that I'm going to boil is a little over 1/3 of the gravity points(similar to all grain decoction mash). I'm only going to add 3 lbs of dme. I'll report back when it's done. Thanks everyone.

 

[Vale71]

BTW if somehow you should manage not to scorch the grains you will be still extracting some unconverted starch from them through boiling. When you dump the grains back into the wort you will quickly reach temperatures where enzymes are instantly denatured and the extracted starch will never be converted and this is bad for beer quality.
This is the reason why traditional all-decoction mashes always end with a mashout step where you only boil some of the liquid with no grains, to avoid extracting unconverted starch.

 

[hottpeper13]

I do BIAB for 5 gal and MIAB for 10 gal batches. I use a 5 gal heavy bottom kettle for decoctions and have done quite a few. During the winter of 16 we did 3 lager decoctions with floor malted pils. those beers were some of the best one we have done,so we decided to decoct these each time. Next year we switched to american pils malt and the results were a very good beer but no different then a step mashed batch. My suggestion is to find an under modified pis malt to do the decoction with. Decoction on my system takes awhile and I only notice a big gain in the flavor dept when using under modified malts so I only do it then.