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Thread: three stage, six roller grist profiles

  1. #1
    Join Date
    Feb 2019
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    three stage, six roller grist profiles

    Coming from a four roller, two stage milling operation where a "ski slope" grist profile was the goal (max husk and course grits), i'm now working with a three stage six roller mill with the manufacturer's and TQ's published "ideal" goal of a bell curve grist profile (max fine grits I & II) with husk volumes in excess of 750ml. Are other craft breweries with such a six roller mill achieving this bell profile with good results? would you care to share gap parameters? i'm having difficulty eliminating coarse and pan flours. Many thanks!

  2. #2
    Join Date
    Oct 2002
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    Chesterfield, UK
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    1,900
    I had responded to this a couple of days ago, but the answer seems not to have been accepted.
    The first thing to remember is that although “ideal” grist ratios are given in a number of articles / by the mill suppliers themselves, they are only ever approximate. Like you, I have experienced wide variations from the “ideal” at a number of breweries. So the first thing to remember is that much depends on the quality of the malt you are feeding in – how dry it is, how friable, they type of malt and dry adjuncts. The materials can make a big difference to how a mill performs.

    If you condition the malt with water or steam, then the amount of water added, the temperature at which it is added, and the residence (i.e. wetting time) prior to milling will also make a difference to the output of the mill.
    The design of the mill will also make a difference. Factors which affect performance include roller diameters and therefore pinch angle, fluting design – depth, shape, angle of fluting, whether a single roller in a pair is fluted, or both rollers fluted, roller speeds, loading and evenness of loading, sieve design and effectiveness.

    What you are looking for at the end of the day is high levels of extract and low solids coming out in the wort into the kettle, along with the speed of lautering. And a lot of lautering performance is down to the design of the mash conversion vessel, the mashing duration and temperatures, the amount of mixing and speed of mixing, how it is transferred to the lauter tun, and then of course, the lauter tun design, number and design of rakes, bed depth, transfer to LT operations, runoff and sparging regime, raking regime, sparge temperature etc.
    In other words, there are a whole load of other factors that can affect the extract and clarity of the wort, and runoff times. So don’t get too hung up on getting the exact ratios recommended.

    The final bit of this introduction is that the analysis method has to be exactly as defined by the EBC or ASBC – wire gaps and thicknesses, time of shaking etc.

    So, having said all the above, as an example, a Buhler Miag 6 roller mill, using hot water (I think it was 70 deg C) conditioning at 1.7% water addition (for only perhaps 30 seconds – again, I never knew the nominal wetting time), with roller gaps of 1.7, 1.4 and 1.4 mm, we were getting an average of 24.9 % by weight fine grits & flour, 26.3 % medium grits, and 48.8% coarse grits and husk, with 352 ml volume per 100 grammes of husk. These were nothing like the recommended ratios, but they were giving us 98.5 % extracts in 7 metre diameter lauter tuns, with separate mash mixer and simple rising temperature infusion mashes. Analysis was using an ASBC set of sieves. In the results I have got, roller setting varied from 1.7, 1.2 to 1.0, to 1.8, 1.2 and 0.8 and quite honestly, the results varies so much that any of them could have produced the results from another set of settings. I never did get to the bottom of it. I always thought there was too much flour and not enough husk, as we often had one or two set beds which extended the total runoff time.

    Not sure if this helps at all.
    dick

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