Oats and Minute Rice Partial Mash Recipie?

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mojo_wire

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I want to put together a partial mash by mashing oats and minute rice and then sorghum LME. However, since I'm not sure of the fermentability of the oats and rice, I'm going to have to fly by the seat of my pants here.

I do stovetop PM's via the BYO magazine 2-gallon cooler method, but I use a pair of coolers so I have the ability to mash up to 8 pounds of grain. So my plan is to mash 3 lbs of oats and 5 lbs of rice, boil that down for about 30 minutes with a little bit of hops, check my gravity, and add the sorghum needed to get to 1.050.

Using Brewtarget, here's the recipe I've come up with. To anyone with experience mashing GF grains, does this sound solid?

5 gallon recipe

3 lbs GF oats
5 lbs minute rice
Mash 1 hr 154 degrees
Sparge 5 minutes 165 degrees
Preboil vol. 3.65 gal
45 minute boil, ending boil volume 3 gallons

2 lbs sorghum LME, late addition

Hops:
1/2 oz Simcoe leaf (13%AA), 45 min
1/4 oz Simcoe leaf, 15 min
1/4 oz Simcoe leaf, 5 min

Yeast: US 05

2 gal top-off water into fermenter.

Ferment at 61 until ready for bottling.

Target OG 1.051
Target FG 1.013
ABV 5%
22.8 IBU
5.6 SRM

I would likely add some spices (orange zest, star anise, coriander, pepper) which I put in a Belgian Blonde recently with good success. Also yeast nutrient with 5 min left in the boil.

Any advice? Anything else need to be added to the mash? Is 154 an appropriate mash temperature? I think that is my single biggest question.

Thanks for the help.
 
You're not going to get any conversion on these grains without adding an enzyme formula. Generally if we're using grains in GF recipes, we're either using malted grains or enzyme formula, or else we're just steeping the grains for flavor. You will get some flavor and body out of the oats, just not fermentables...maybe some trace amounts at most. So I'd say your recipe is not going to work very well...you're basically making starch water and barely adding any fermentables with the mere 2 lbs of sorghum.

What might be throwing you off is that most beer tools give PPM values for rice and oats based on the idea that they'll be mashed with barley. Without mashing, the PPM values will not be what you expect, and they'll mostly be from unfermentable starches.
 
I was under the impression that minute rice could be mashed without added enzymes. Is that correct?
 
No, it's not correct. Try it yourself in a small amount: mash 1 cup of minute rice as planned, in the appropriate amount of water, and observe that it does not, in fact, turn into a sweet sugary solution, but just a thick starchy mess. Minute rice, like instant oats, is pre-gelatinized, meaning it can be added to a mash without extra preparation. Normal brown rice won't convert in a mash unless it's pre-gelatinized--gelatinization means the starches have been made water-soluble, which only happens at certain temperatures (depending on the grain).
 
I see. So how much amalyse is advisable? I'm sure it's more than the 1 tsp per 5 gallons that's advised on the package.
 
I'm afraid I don't know. 1 tsp will get it done, it'll just take a while--enzymes are not consumed in reactions, so keeping the wort at temperature and periodically stirring, you can get it done in probably a 12 to 24-hour mash. I'm not sure how much difference upping the amount will make to conversion time.

Personally, I've had trouble getting usable wort out of GF grains with pure amylase enzymes, even an alpha/beta-amylase mix, but I've only tried oats, millet, and buckwheat and may have had issues because of improper grind as well. Oats in particular seem to need glucanase, I believe, to do a protein rest (unless you want a milky wort that takes forever to clear and leaves a ton of trub). The rice is probably fine on its own with amylase, I haven't tried mashing rice yet but beljica was talking about a successful batch of rice syrup he made with just rice, water, and amylase.

So in other words, you're just gonna have to experiment! I recommend starting small, and then scale up. Good luck!
 
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