Advice on Mashing Regime: Gelatinization and Decoction

edited May 2020 in Recipes

Hello all, I am ‘new’ to this forum but have been lurking around for a while. So thanks for all the expert advice I have been making use of.

I have a few questions, however, which I have not been able to find definitive answers to or which I would like to have a second opinion or further discussion on. Some of the questions have previously been discussed but not – as far as I can tell – in this context. So here goes.

I am trying to optimize the yield I get from my bourbon recipe. I am currently using feed corn sourced from various domestic online dealers which I mill to a grist similar to that of a barley malt beer grist (i.e. grits are approx 20% husks, 30% flour).

To my understanding the gelatinization temperature of corn starches is strongly temperature dependent meaning that one will have to heat such a cereal mash to a certain temperature for a certain period of time in order to make the starches available for enzymatic activity at the subsequent rest:

Gelatinization and Solubility of Corn Starch during Heating in Excess Water: New Insights (PDF), p. 4, fig. 2

My question is: What is your experience with cereal cooking? I have had some success gelatinizing the corn mash at 85°C (185°F) for a shorter period of 15 minutes but the yield has been low. Would you adjust either T or t – or both? I assume that 15 minutes is definitely on the short side but what can I get away with here – 1h, 1.5hs?

The idea is that I will then combine this adjunct mash with a malt mash with sufficient enzymatic activity, bringing the total T of the mash to approx 66°C (150°F) and do a standard infusion mash.

I would prefer to not

  • use flaked corn
  • add exogenous enzymes

I am also considering doing a decoction style mash in which I would heat the corn mash along with part of the malt to the optimum T of α-amylase for, say, 15 minutes prior to reaching the gelatinization temperature. I would do this to liquefy the mash in order to reduce its viscosity and thereby 1) avoid scorching and 2) aid in the gelatinization. As before, the mash would then be mixed with the remaining grain bill for proper saccharification at 66°C (150°F). Do you reckon this would be worth the extra effort?

Furthermore, is it necessary to use a more floury corn base or do you think this will just complicate the process? I plan on fermenting the mash on the grains so filtration issues shouldn’t be a problem in this regard.

Bonus question!

Do you have any insight/opinion on if/how the flavour of new-make could be adversely affected by heating/boiling of the corn?

All inputs are highly appreciated!

all the beast


  • edited May 2020

    Cracked corn at 185f for 15 minutes? That ain't going to do it.

    Push hotter if you can, the hotter you can get, the faster you'll fully gelatinize the corn. For maximum yield, at 185f, I would suggest 90 minutes. If you can push to 195-200, you could reduce to 60 minutes.

    To gelatinize in 15 minutes you'd need to mill to flour, and likely push higher than 200f, perhaps even above boiling (pressure cooking).

    Corn needs far more heat and far more time than most of the literature indicates. Especially as the milling size increases.

  • If you have grits on unmodified grain you'll struggle no mater how hot I think.
    You'll get poor efficiency and end up with gelling once you get to the still.
    Protease will help unlock it but the more you can mechanically release the starch the better.
    Sacrificial malt to keep it fluid will be needed and some chilled backset to get back down to sach temp is a good trick too.

    @Me_ said: Do you have any insight/opinion on if/how the flavour of new-make could be adversely affected by heating/boiling of the corn?

    Good Q. I think not but I worked with a guy that was hyper paranoid about it.
    What would be the mechanism?

  • If you have no mechanism to either increase heat, time, or reduce grain size - adding glucoamylase when you pitch yeast has been shown to increase yield through SSF (simultaneous saccharification). Gluco can break down some starch that has made it through mashing.

  • edited May 2020

    I've posted before, but the issue has a solution and Pint is still shipping the enzymes.

    Mashing 100% corn on an open flame @ AD

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • That solution isn't legal in some countries.
    I'd be keen to see an endo only recipe with high yields.

  • Premalt and hold as high as possible.

  • Thanks for all the advice. It definitely seems that relying on endogenous enzymes only will be a bit of a challenge when it comes to actually putting the theory into practise! I have also been toying with the idea of using a yeast like S. cerevisiae var. diastaticus (or similar if I can find it) which excretes glycoamylases 'naturally' into the fermenting wort. :-)

    @jacksonbrown said: Good Q. I think not but I worked with a guy that was hyper paranoid about it. What would be the mechanism?

    I can't think of anything other than a higher extraction of polyphenols but to my knowledge corn has much lower concentrations of polyphenols and they have no impact on flavor even if they were to be present to any degree in the distillate.

    I will go with a liquefaction step (premalting...?) and give it a good, long boil. At some point maybe I will find a good balance between time and temp so I can reduce time and energy invested in this process.

  • I have used the lazy mash method sucessfully. So i add water at 98deg C to the milled corn, milled to a # 2 grind. Then the tank is wrapped up and let sit for anywhere from 2 to 4 hours. During this gelatinisation occurs. Normally whem i take the top off the temp is over 80 deg C which is the temp for gelatinisation l. Then i let it cool to 65 and add my malt and enzymes if i am adding enzymes. Then i let it sit for a further 90mins. Then cool to pitching temp. Pitch and your away. I have a mate who uses this technique in a moonshine distillery. It gives good results as far a yields go but the ferments take about 7 to 10 days. If you want shorter ferments you need to blast the corn with temps over 100 deg C.

  • In my limited use with corn, I wouldn't even think about trying to mash without adding enzymes. I use Pint's. It only takes one time of ending up with a tun full of pudding to convince you.

  • @DonMateo, what kind of starting gravity are you able to get using that system? (That's just out of curiosity; from experience, I'm in with that cracker guy 8))

    Zymurgy Bob, a simple potstiller

    my book, Making Fine Spirits

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