Partial Mash - Switched from small mash tun to sous vide and really lost efficiency. Why?

[J2W2]

Hi,

I brew extract and partial mash. I've built small mash tuns out of a couple different coolers - the latest was a 2-gallon with a stainless steel mesh filter and spigot. I use BeerSmith 3, and I use the recommended amount and temperature of water. I would also reserve a gallon of water (started at 170, colder when I used it) to rinse the grains. This worked well, but I could never hold my mash temperature, and a couple of my partial mashes pushed the 2-gallon limit.

So I moved on to a sous vide setup. I have three containers (6, 8 and 12 quart) that I mash in. Still following the same amount/temperature of water, but now I hold a steady mash temp. There are a couple of differences. I now bag the grains to keep them out of the sous vide, and since I don't have an easy way to rinse the grains, I dip the bag of grains in my kettle with 170 degree water (this is before I add any extract). I wear BBQ gloves, so I try to work the grains around in the water to rinse them well.

I just brewed a 5.5-gallon batch of oatmeal stout that I brew regularly. BeerSmith says the S.G should be 1.063. I typically come in around 1.062. This time I'm at 1.055. If my F.G. holds, I'm going to have a 5.0 ABV instead of 6.0 ABV beer. The partial mash uses 1.5 lb 2 row, 1.5 lb flaked oats, 12 oz biscuit and 9 oz crystal 60L (the dark grains are steeped separately). I pulled a small sample after the partial mash was in the kettle. My volume was right at my 5.5 gallons (additional water was reserved for the steep) and the gravity was only 1.012. BeerSmith says it should be 1.020, which explains the missing points.

Any ideas on why the loss of efficiency, and how I can reclaim it?

Thanks for your help!

 

[Saunassa]

I am probably missing something but you were brewing up a 5.5 gal batch using just over 4 pounds of grain?

 

[J2W2]

I am probably missing something but you were brewing up a 5.5 gal batch using just over 4 pounds of grain?

No, sorry I wasn't clear, I started with the partial mash, added it to my existing kettle water, which just happened to make 5.5 gallons (my target volume at flameout), so I took a small sample to see what gravity my partial mash had created. I then proceed with my actual 60-minute boil, adding hops, 6.3 lb LME, and then the dark grain steep shortly after flameout.

I'm assuming the gravity from the LME will be the same batch to batch, so the difference had to be in my sous vide partial mash.

 

[mashpaddled]

I use a two gallon cooler as a mash tun for my smaller batches. It is indeed tough to maintain temperatures unless it is pretty well full. They are not well insulated like larger coolers. At times I have used the oven heated to 170F to help hold temperatures but I don't have problems getting full conversion even with temperature drops of a few degrees so I haven't done that in a while.

With the sous vide I wonder with bagging the grain if you are getting complete hydration. It's a little harder to stir in a bag versus a solid vessel. You might have dough balls forming in the mash. I don't think the water current of a sous vide pump is enough to break those up.

There could be an issue with your sparge process and leaving behind sugars or runnings in the bagged grain. You could check gravity runnings from the mash versus the sparge and see if the problem is at the sparge.

 

[Spivey24]

i started out using a sous vide. It turned out when I thought the sous vide was keeping constant temp, it was not. The temp in the grain bag you are using could be way off in temp. The sous vide just doesn’t push enough volume.

 

[J2W2]

I use a two gallon cooler as a mash tun for my smaller batches. It is indeed tough to maintain temperatures unless it is pretty well full. They are not well insulated like larger coolers. At times I have used the oven heated to 170F to help hold temperatures but I don't have problems getting full conversion even with temperature drops of a few degrees so I haven't done that in a while.

I hadn't thought about using the oven. I assume at that low a temperature it doesn't harm the cooler any? I'll have to check if I have clearance; mine is a round beverage cooler, not very tall, but neither is the oven.

i started out using a sous vide. It turned out when I thought the sous vide was keeping constant temp, it was not. The temp in the grain bag you are using could be way off in temp. The sous vide just doesn’t push enough volume.

You may be right. The sous vide swirls the water fairly well, but I don't know if it gets the grains. This batch had five quarts of water in an eight quart container, so the bag was pretty much touching all sides, the bottom (on a metal table), and barely covered by water on the top. I probably should have put a temperature sensor in the grain to see what temp it was holding.

I may go back to the cooler next time (sounds like an old Hogan's Hero's episode) and maybe try the oven trick. Cleanup is actually easier as I only have to dump the cooler and wash it out, instead of cleaning the sous vide, container and grain bag.

Thanks for the input!

 

[doug293cz]

I don't think there is any issue with your sparge process.

I wonder if your sous-vide could be overheating the wort that comes in contact with its heating element, and denaturing the amylase enzymes. This could slow/stop starch conversion before your mash time is up.

Brew on

 

[J2W2]

I wonder if your sous-vide could be overheating the wort that comes in contact with its heating element, and denaturing the amylase enzymes. This could slow/stop starch conversion before your mash time is up.

That's a good point. Next batch I'm going to use the sous vide to heat the strike water, but I'll mash in the cooler again.

The sous vide I'm using is a Wi-Fi enabled one from Inkbird. I usually brew first thing in the morning, and their app has an automation section which lets me turn it on and preheat the water before I'm even up.