Rice malt stout - what went wrong?

[dcbw]

I've brewed a millet/buckwheat pale and couldn't quite get past the millet taste. I've brewed a sorghum+rice syrup partial mash with millet/buckwheat and extracted too much tannin from the husks, and couldn't quite get past the astringency.

So I thought I'd do an all rice-malt beer with Eckert malt. Using the malt analysis that ricemaltster posted in "Gluten Free might just be getting better! A LOT BETTER!" I formulated this recipe at 75% brewhouse efficiency:

OG: 1.057 @ 75% efficiency

5lb Eckert Pale rice (28PPG, 19.09 OG)
5lb Eckert Biscuit rice (28PPG, 19.09 OG)
1.5lb Eckert Crystal rice (26PPG, 5.32 OG)
1.25lb Eckert James Brown rice (26PPG, 4.43 OG)
8oz Eckert Dark rice (24PPG, 1.64 OG)
6oz Eckert Gas Hog rice (24PPG, 1.23 OG)
1lb D2 Belgian Candi sugar (32PPG, 5.82 OG)

Typical barley malt yields around 80% extract on a coarse grind basis. Eckert malt yields around 59% extract and slightly lower for the darker malts. So using a base of 38 PPG for 2-row barley, I estimated the PPG for all the rice malts. According to the Brewer's Friend app, this recipe should end up at 1.057 OG at 75% brewhouse efficiency.

I used ricemaltster's suggested mash schedule, which was:

120F for 30m
131F for 60m
150F for 60m
158F for 20m

I mashed in with 6.5 gallons of water (2g below my false bottom), and at the start of the 150F mash step, the wort was only 3P. I decocted 1.5g and returned it to the mash. 30 minutes into the 155F rest the wort was only 7P (1.028). At the end of the 158F rest it was 7.3P. I collected 7.5g of wort at 7P before adding the candi sugar and an additional 1lb of candi sugar since the gravity was so low.

Instead of 75% efficiency, my efficiency was more like 50% if you accept my PPG numbers for the rice malt.

So what went wrong? ricemaltster, are you out there?

* What is the typical PPG for Eckert rice malt? Is 28PPG for pale rice malt too high? How much base rice malt are people using for a 1.050-ish beer? I now realize that the husk-to-grain ratio for rice is a lot lower than barley...

* Is the mash schedule OK? GIven that I didn't get much (if any) extract from the earlier mash steps (120, 131), are they really required? Could I use 1.5 times as much malt and jump right to the 150F step?

A suggestion for ricemaltster - maybe put a recipe or two up on http://eckertmaltingandbrewing.com/ with amounts and mash schedules; that would help customers who want to do an all rice beer. Thanks!

 

[billl]

Hopefully the maltster will weigh in, but typically none of the roasted grains have significant diastatic power. ie they don't convert on their own. Your recipe has mostly non-base malts, so if you didn't use additional enzymes, that might explain the poor conversion. Also, depending on your water chemistry, you might not be in optimal PH ranges for conversion. That is something I would check if adding enzymes or more base malt didn't do the trick.

The 120 and 131 range rests are for protein. Given rice's low protein levels, I can't imagine they are doing much. Maybe they help with head retention for rice, but you'll get minimal starch conversion at those temps.

 

[dcbw]

The biscuit rice is supposed to be diastatic and can supposedly be used for up to 100% of the malt bill, according to NorCal brewing supply's website. So I had thought with 65% base malt would be OK. I did use some amylase enzyme during the 150F mash step.

But the enzymes can only convert the sugar in the mash water, and the refractometer doesn't care whether it's converted or not. So if I get mash wort at 7P that should just mean that up to 7P of sugar might be converted because there is physically no more sugar in solution than that. What I'm wondering is why I didn't extract more sugar from the grains, converted or not...

I also checked mash pH and it was 5.3 at mash temp so I think I'm good there.

Good points about the protein rests, thanks for jumping in!

 

[ricemaltster]

Gentlemen,
I have been having trouble getting sufficient conversion and efficiency being a purist, as you are finding. As I have mentioned in other threads, rice has not been bred for malting quality and is therefore rather limited in enzyme activity. I have been experimenting with addition of enzymes and have had dramatic results recently. I have basically abandoned the tedious step mash in favor of a single temperature infusion mash at 160F (70C) and adding alpha amylase enzyme. When the mash cools down a bit I add beta amylase. Mash time is at least halved with the added benefit of greater conversion and higher gravities. I do allow the wort drawn off the mash to rest awhile before starting boil in order to convert any bit of residual starch. This mash schedule is similar to what Legume has been doing. It remains to be seen how this will affect head retention, etc. I will be trying several enzyme products and doing micro mash experiments to determine the best system for me. I plan to share this information as soon as I get around to it.
Cheers,
Ricemaltster

 

[dcbw]

For a baseline, could you share the amount of your rice base malt that you'd use for a 1.055-ish beer? I'm still trying to find out whether I just used too little base malt, or whether I didn't properly gelatinized the grains (I seem to recall gel temp for the type of rice you use was about 152?), a combination of both, or something else entirely. Thanks!

 

[ricemaltster]

A combination of 12-15lb total of pale and biscuit should get you into the 1.055 range for a 5 gallon batch according to my most recent experience with use of alpha and beta amylase and sufficient gelatinization. Was the crush sufficient for efficient extraction?

The complicated step mash I used in the past was an attempt to baby the limited enzymes available. Very long mashes and some residual starch caused me headaches!!!

I have been using Termamyl alpha amylase and AMG300-L beta amylase with good results. Like I mentioned in the earlier post, I have several other enzymes that I will be testing soon. Termamyl is heat stable so make sure you get good gelatinization then add beta amylase when mash temp. lowers to it's effective range.

I hope the beer ends up tasting good even though it may not be what you wanted exactly.
Cheers,
Ricemaltster

 

[dcbw]

The beer from the first comment gave me an OG of 1.048 and an FG of 1.018 for an ABV of 4%. It's more brown than black, has a moderate amount of mouthfeel, and is fairly sweet. So it fits better into a Southern English Brown or English Mild category than a stout or an American Brown. But it's quite drinkable and has none of flavor flaws (iron and tannins) that I had with millet, buckwheat, and sorghum. So a drinkable beer, even if it wasn't quite what I wanted.