Step Mashing and Decoction Procedures Using Coolers

I’m opening up this thread for general/specific issues, questions, comments and advice regarding step mashing and decoction, using conical or chest insulated coolers.

To begin the discussion, I have a question regarding the details of a procedure, often mentioned, but never fully explained. Obviously, when mashing, the more air space there is within the cooler, the quicker the temperature of the mash begins to drop. There is always going to be some air space, since space is needed for a mash-out. Then there is additional air space required during the early stages of a step mash, before additional hot water is added to raise the temperature of the mash. Also, additional air space is created when pulling out a portion of the mash for decoction purposes.

So there can be a significant amount of air space in the cooler, especially during the early stages of the mash process. This air space will prevent the mash from maintaining its temperature, and will result in it rapidly cooling.

A typical recipe, for example a Pilsner Urquell recipe, might say: “Mash grains with 15 quarts soft water at 142 F and hold for 30 minutes. Perform a decoction, pull 1/3 thick portion of the mash, and bring to a boil. Boil for 15 minutes. Stir the decocted portion back into the main mash. The main mash should now settle at 155 F. Hold for a 30-minute rest.”

If you try this, when you add the decocted portion back in, the resultant temperature of the mash may only be about 145 F rather than 155 F. The recipe assumes that the mash maintains its temperature during the entire decoction process. However, the decoction process could take about 45 minutes (heating the decoction to boiling and boiling it for 15 minutes). In that time, because of the amount of air space in the cooler, the remaining mash will cool down considerably. So when the decoction is added back in at least 45 minutes later, it is almost certain that the resultant temperature will not be even close to 155 F as desired.

So, most of these recipes don’t seem to account for the remaining mash not retaining the initial temperature during the long decoction process.

Thus, to begin the discussion, how do others with coolers, and using similar procedures address the rapid cooling of the remaining mash during the decoction procedure?

 

These are good points. I do pre-heat my cooler, and have no trouble reaching the first step temperature.

Using a larger decoction will work, but requires a lot more attention and stirring. At the same time, it reduces the volume of the remaining mash even more, and increases the air space, resulting in even faster temperature drops. Also, I have done larger decoctions and found that it added far too much of the meloidin (Maillard reaction) taste. However, the length of boiling could be reduced to perhaps 5-10 minutes instead of about 15.

I really like the idea of using a cap, such as the lid of a large pot or a stainless steel pizza plate. I was going to experiment using that approach next time.

I was also wondering whether there might be some sort of a low temperature heating element that could be hung inside the cooler on some sort of frame, during the mash, to help maintain the temperature? So far, I haven't yet found a solution.

 

I could use one of these for a heat source:

https://www.amazon.com/Zacro-Reptil...fae8a8e3ed12232c8466ecf0997a55&language=en_US

 

It was designed for reptile aquariums, which I assume also have high humidity. I almost ordered it, but decided against it since, with a porcelain socket, it would be quite long and not fit very practically inside the cooler. Also, moisture could get in the socket and cause a short circuit. Instead, I might try just inserting a heating belt inside the cooler, resting on top of the "cap" (lid or pizza plate as used in low oxygen brewing). Very simple solution using what I already have. Hopefully it will generate enough heat to maintain the temperature in the air space.

 

The only issue I see with the bucket water heater is that it may scorch some of the grain, and also create hot spots in the grain bed. If the grain could be circulated, it could keep all the grain at a constant temperature.

The coffee immersion heater might work, but I'm not sure if it might overheat if not kept in liquid.