How and Why Brewers Should Do a Sieve Analysis

By: Living a Stout Life and Galen Smith – Malteurop Malting Company

 

It’s easy to get caught up in doing things a certain way simply because that’s how they’ve always been done. This is particularly so when you aren’t having any noticeable problems. Or, at least, you don’t perceive any issues. This is often the case when it comes to milling grains in the brewhouse.

 

If you’re not reading your malt Certificate of Analysis on a regular basis, or don’t know how, it’s easy to miss important changes from batch to batch that can affect the efficiency of your mill’s grind. Your Malteurop Craft Sales Manager can explain your malt COAs and what you should be looking to gain from them.

 

With or without a COA for reference, regularly doing a sieve analysis of your grist is an inexpensive, simple way to help keep your brewhouse efficiency on track and produce consistent, quality brews.

 

What is a sieve analysis?

A sieve analysis (or grist analysis) is a simple test that indicates whether or not you are getting the optimum grind out of your mill. The results of a sieve analysis help dial-in the grind of your grains so that you are getting maximum extract from every bit of grain, while keeping your brewhouse running efficiently and not adding costly hours to the production schedule.

 

It will tell you if your grind is too coarse, allowing valuable starches to go to waste. Conversely, if your grind is too fine, you may be extracting more starches, but causing lautering issues that can cost hours on brew days.

 

It is also important to note that there are other variables that can affect this. Mash/Lauter tun design and geometry, for example, can impact how coarse or fine your grist needs to be. The type of mill you are using can also determine how coarse or fine your grist needs to be.

 

Why should brewers do a sieve analysis?

Efficiency, quality, and money. Those are the simple answers as to why a brewer should do a sieve analysis.

 

Doing a sieve analysis helps define a consistency to your malt extract efficiency. On the one hand, this is important so that you know exactly what you are getting out of your mash every time, maintaining consistent quality from batch to batch.

 

In optimizing efficiency, not only are you being consistent in quality, but you are also maximizing the effective amount of extract from each batch, reducing costs. For any drop in efficiency, reaching the necessary amount of extract comes from using more malt, which costs more money.

 

What equipment is necessary for a sieve analysis?

Most breweries only need a simple series of three sieves with specific screen sizes that are used to assess the husks, coarse grits, fine grits, and the flour produced by the mill’s grind. You also need a scale that can measure grams to weigh the sieve set before and after the process.

 

The basic set-up is typically a set of three 8-inch sieves that include #14 (for husks), #30 (for coarse grits), and #60 (for fine grits). You will also need a bottom pan (to catch the flour) and a top cap. Some larger breweries may use additional sizes to refine their results and may purchase a separate shaker for conducting the sieve analysis, but these aren’t necessary for most breweries.

 

Step-by-step directions on how to do a sieve analysis

The actual sieve analysis procedure is fairly simple. You capture ground malt from your mill, run it through the sieves, and assess the results.

 

1.      Weigh each of the sieves and the pan when they are empty. Document these weights in a column titled Tare. (see example below)

2.      Stack the sieves with the pan on bottom, the #60 sieve on top of that, the #30 sieve on top of the #60 sieve, and the #14 sieve on top of the #30 sieve.

3.      Collect 100 grams of malt as it falls from your mill. 100 grams is a suitable sample size and makes the resulting math easier. (Be sure to capture the malt as it exits the mill, not after it has already settled in a container. The grist delivery system [flex auger or chain/cable and disk] from the mill to the mash tun can also grind the malt more. It is good to measure after the grist conveyance. This is the true measurement. Once the ground malt has settled, the smaller bits and flour will have settled, which would reduce the accuracy of your sample.)

4.      Pour the 100 grams of milled malt into the top (#14) sieve and put the cap over that.

5.      Shake the assembly for about 3 minutes, tapping the entire assembly on a hard surface every 15 seconds until the 3 minute timer counts down.

6.      Weigh each of the sieves and the pan again with the collected samples, and document the weights in a column titled Gross.

7.      Subtract the Tare weight from the Gross weight for each sieve and the pan, recording the results in a corresponding column titled Net. If your sample was 100 grams, the Percentage results are the same as the Net weight.

8.      If your test sample is an amount other than 100 grams, the math is a bit more involved. If this is the case, for each individual sieve and the pan, you must subtract the Tare weight from the Gross weight and then divide the result by the total sample weight. (For example: If your sample is 98 grams and the net weight for sieve #14 is 74, the resulting percent would be 75.5% or 74 divided by 98.)

9.      Record the results for analysis and future comparisons.

10.    Reference the Interpreting Sieve Analysis Results section below to see where your results fall and how to apply those results to your particular brewhouse situation.

 

Interpreting sieve analysis results for the brewhouse

Interpreting the results of the sieve analysis is fairly straightforward. Below is a chart that provides a basic reference to the type of grind you are getting based on your analysis.

 

Coarse                   70-85%   10-20%   < 10%     < 5%

Normal                   50-60%   25-32%   7-11%     5-10%

Fine                       15-30%   15-30%   25-40%   10-25%

 

What does a Coarse Grind mean?

Roughly put, if you find your results align more closely to the Coarse results, you are likely having no lautering issues. Conversely, a grind that is too coarse is leaving valuable starches behind that will need to be made up for by using more malt than necessary. If your grind is too coarse, tighten your mill gap accordingly.

 

What does a Standard Grind mean?

If your results align closely with the Standard results, your mill is set to produce a grind that strikes a good balance between extracting as many starches as possible while not causing any significant lautering issues. If this is the case, your mill is probably set right about where you want it to be.

 

What does a Fine Grind mean?

A Fine result, as you’d probably expect, is the opposite of Coarse. If your grind is too fine, you’re getting many more smaller grits and flour, which could equate to increased efficiency, but likely at the cost of lautering issues. This drop in lauter performance could also drop your efficiency due to channeling around the potentially compacted grain bed. This can lead to a lot of wasted time in the brewhouse, as well as consistency issues. Increase your mill gap accordingly.

 

Which grind should you target?

This really depends on your equipment. A 4 roller mill is likely able to give you a grist that produces intact husks while exposing the starches more efficiently. A lauter tun that is wider and allows a shallower bed depth will likely allow for finer grist. Ultimately it is best to target a grind that gives you maximum efficiency without affecting lauter speed and wort clarity.

 

How often should a sieve analysis be performed

How often a sieve analysis should be performed is a matter of preference. It could be different for different breweries depending upon frequency of brewing, changes in suppliers, changes in malt specification (on the COA), and other factors. A sieve analysis should, however, be part of the regular routine in a brewhouse.

 

A sieve analysis only takes a matter of minutes, but can save hours in the brewhouse and dollars on the bottom line. It also makes for much more consistent, quality brews. And at the end of the day, isn’t that what we are all striving for?