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Distiller's Malt Conversion Problems

So I’ve been trying to make a high gravity wort using distiller’s malt. Since it has such an extremely high enzyme content, it should convert to near 100%, making it a cost effective way to make a high gravity, neutral wort. The mash is 18lbs of distiller’s malt from NB, at a rate of 1.25qt/lb, at 150F. I have both batch sparged and fly sparged, but both times I got an OG of 1.040, instead of the 1.095 that I was shooting for. I have a few concerns:

  1. Perhaps the hull of this type of malt is relatively tough/robust, so maybe it’s under-milled.
  2. The conversion temp is relatively low. Perhaps upping it to 154F?
  3. The starch content of this malt may be relatively low, so perhaps I should only use 20% distiller’s malt and 80% of another base malt.

Your help and comments will be greatly appreciated.


“The more I learn the less I know.”

Primary: Empty
Secondary: St. Paul Porter, Apple cider beer
Drinking: Belgian Tripel IPA, Belgian Saisan, English Biscuit Ale

Any base malt <10 SRM in color should have enough enzymes to convert itself, with room to spare. So you can pretty much rule out a problem with the malt itself. (That’s also why there’s no real reason to use distillers’ malt for this application - any base malt will do.)

The first thing to do is calibrate all your instruments, especially your hydrometer/refractometer and your thermometer. Make sure you check the thermometer against a known-good one at temperatures around your region of interest (~150°F).

If the instruments check out, the crush would be next. A visual inspection should be enough to verify that all the husks are at least cracked open, if not split.

The next thing to look at would be mash chemistry. What’s the mash pH? Are you allowing enough time for conversion?

The point of using the distiller’s malt is that it should convert to near 100%, whereas most other base malts will only convert to ~75-80%. All of my instruments are of high quality and calibrated against known standards. I also use the pH=5.2 buffer salts. I’m leaning towards the problem being the grains not being milled enough. Since they lock the mills at NB, would a second run through the mill help, or would I need to get my own mill and adjust it to a finer crush?

Sorry for the multiple post, but I also forgot to mention the timing. When I batch sparged, I let the conversion go for 60 min; when I fly sparged, I let the conversion go for 75 min and then fly sparged with 170F water for 45-50 min.

I think you may be misremembering or misinterpreting something. Any enzymatically active mash will approach 100% conversion as long as the mash parameters (time, temperature, pH, liquor:grist ratio) are in range. In the 30-odd mashes I’ve kept records for, none has ended at <95% conversion.

Have you checked the pH? The 5.2 product doesn’t work.

If your trying to hit 100% efficiency try the following:
Up the water to 2Qts per pound.
Mash at 158 degrees for 90 minutes minimum.
As a10t2 said check your pH with a reliable gauge.
Since you have a high enzymatic malt the issue becomes solubilizing/breaking down as much of the starch as possible into solution. To do this you need a good crush, more time, the high mash temp that does not denature the enzymes, and a high water to grain ratio for increased solubility, and control your pH. Another option would be a decoction mash in which you boil the grain which bursts open the starch granules and breaks them down.

The higher enzyme content in distillers’ malt is useful when it makes up only a small part of a grainbill that contains a lot of non-enzyme grain. If you’re using all malt, there is no reason to use distillers’ malt. A bourbon grainbill might contain 10% malt. The ferment will finish below 0 gravity, not because of the distillers’ malt, but because of the parallel mash/ferment, where the enzymes are active during the ferment.

It’s also used in scotch grain distilleries, where they use a lot of unmalted wheat, but are not allowed by law to use prepared enzymes.

[quote=“MRCCEO”]If your trying to hit 100% efficiency try the following:
Up the water to 2Qts per pound.
Mash at 158 degrees for 90 minutes minimum.
As a10t2 said check your pH with a reliable gauge.
Since you have a high enzymatic malt the issue becomes solubilizing/breaking down as much of the starch as possible into solution. To do this you need a good crush, more time, the high mash temp that does not denature the enzymes, and a high water to grain ratio for increased solubility, and control your pH. Another option would be a decoction mash in which you boil the grain which bursts open the starch granules and breaks them down.[/quote]

I agree with the extended mash time to ensure conversion but I think the idea is to have a fermentable wort, therefore I’d mash at 150F rather than the higher temp.

As I understand it, distillers malt is just six-row, high enzyme low kilned malt. Its designed be used in conjunction with corn or rye and can convert a large amount of adjuncts. Otherwise its the same as any other malted barley.

Possibly I’m misunderstanding your post but I believe you might be misunderstanding what 100% conversion means. I’ve looked at the analyses for distillers malt and they typically state that both the coarse and fine extraction is around 80%, which is what a normal pale malt is. Therefore, if your system and processes are good, meaning your pH is in correct range, your crush is optimum, you hit the proper mash temps, etc, etc, distiller’s malt should give approximately the same result as pale malt. Then again I’m an amateur and I might be missing something also.

I believe that 80% is stated as an average amount. I consistently get 85% and can push it to 90. However wort flavor can be compromised as you start to extract undesirable compounds at higher efficiencies. 80% is probably a good compromise between flavor and efficiency.

Grain is 80% starch by weight, 20% protein+minerals+oil+fiber. Thats the source of the DBFG (dry basis fine grind) and DBCG (dry basis coarse grind) values. You can’t get a pound of sugar out of a pound of grain, you get 0.8lb.

Conversion is the percentage of that 80% that you can convert to sugar. 100% conversion means that all the starch got converted to sugar, not an unreasonable expectation given proper crush and enough mash time. I tend to get 95% but I really don’t calculate it anymore.

There is another thread here about this same thing. Someone posted this link and it is very helpful.

http://braukaiser.com/wiki/index.php?ti ... Efficiency
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