Malt processing & QC

Malt cleaning
Prior to milling it is highly recommended that malt undergo a cleaning process including a magnet to take out iron/metal materials.

Malt cleaning or polishing machine can be oscillating sieve type machine with aspiration to remove the dust particles and dirt. Some older machines are equipped with soft brushes.

When wet mills or malt conditioning systems are in use it is necessary to use a malt-cleaning machine. A de-stoner is also recommended which typically is combined with the malt-cleaning machine. When buying in bulk this is especially a concern. Typically bagged malt will be cleaned prior to bagging, but bulk malt can have small debris or pebbles that can damage the mill. Powerful rare earth magnets will collect this matter, attracting metal bits and attracting the iron in pebbles.

Malt weighing and Grist weighing
The malt scale or balance are typically placed in front of the malt mill. There are different types of scales available for use, for example a tip over type scale or a bottom flap type scale or in today’s brewing an electronic pipe scale.

Another option are load cells which are also widely popular they are being often used for grist cases in which the milled malt falls into.

It’s important to know and note the exact amount of malt or grist that is being used per brew. Not only to adhere to any recipe but also to know and control the brew house efficiency.
It is also recommended when working with bagged malt to monitor the weight of the malt bags from time to time and document the findings.

An important factor concerning all scales (even the ones used in weigh station for truck weighing) is that they undergo a regular calibration and alignment procedure to ensure accurate and precise weighing. Also scales require maintenance and need to be kept clean.

When receiving bulk malt (Silo Malt) in truck it is recommended to periodically check the weight of the truck by driving though a weigh station before and after the unload process. Truck weigh stations ought to checked and calibrated on regular basis as well.

In general it is important and recommended to regularly or periodically check on the weight of malt delivered to the brewery regardless in what shape or form malt gets purchased in.

Storage of Malt and Quality Control
A brewery typically needs to keep a malt inventory on site. How much malt is kept on site and how the inventory level looks depends on a few items.

Some breweries keep their inventory levels on malt low – very low they state monetary reasons for this since capital has now left the brewery. Although this is not really a valid argument since among other items the overall cost for malt is mostly dependent on the output (monthly/yearly) and not on what is kept at the brewery.
Delivery and lead times also play a role, breweries that are in remote locations and where shipping costs are very high are likely to have more inventory at the brewery to maximize shipping costs.

Also, from a risk point of view, if for some reason a weekly or bi-weekly shipment doesn’t happen, then it is critical to have some “reserve malt” on hand to avoid impacting production.

If, however, malt is readily available and shipping times/costs are not an issue then a brewery can keep a lower inventory level of malt on hand.

If space is an issue, for example there is just not enough real estate available for malt storage then inventory levels can be maintained at a lower volume. Note the brewery needs keep the risks mentioned above in mind.
In general, and this is good practice, the inventory level of malt at a brewery should range between 3 to 8 weeks depending on individual situations and philosophy.

Quality Control and Taking Samples. This could be one the most overlooked steps in Malt intake. It is very critical to take good average samples during unloading of malt. At a minimum there should be a visual and taste/sensory testing done. There are a variety of mechanical and other malt analyses available that a brewery can accomplish in a very short amount of time and, if QC criteria are not in line, can lead to rejection of the malt delivery. One option available is to have special malt intake silos where, after an initial check, the malt is held while the other, more thorough tests are accomplished. If the malt passes it’s transported into the final silo of the brewery. If the samples don’t meet standards, the shipment is rejected and the malt is unloaded from the holding silo back onto a truck or railroad car.

It is important to properly document all incoming malt shipments with date, lot number etc. and if incoming samples have been taken, the test results of those quick analyses. Bagged malts often have lot numbers printed on the bags and spec sheets from the maltster can be referenced to access analysis. Bulk malt should be accompanied with a similar spec sheet. It is good practice to keep a log of the spec sheets as a reference and for consistency. (See malt intake scenario diagram.)

Milling of Malt, grist storage transportation weighing
Malt needs to be milled prior to the mash process, so that the enzymes are enabled to attack and convert starches to sugars and to enable other bio-chemical reactions during the mash process.
In brewing today we have dry mills and wet mills in use whereas dry mills are most often in use at breweries.

Milling (dry) is a pure “mechanical” event but has major impact on:

  • Chemical and biological reactions during mash process
  • Quality and make up of wort (Color, Bittering.)
  • Brew house Efficiency
  • Lautering process

There are 2 – 4 and 6 roller mills on the market, alternatively there are also wet mill systems and malt conditioning systems in place. Which can provide excellent grist quality. Malt that has been milled is now called (malt) grist.

It is not recommended to pre-mill malt (for example over night) due to oxidation reaction taking place in the malt grist.

In general there are now two options of how grist gets transported into the mash mixer, either directly after milling (without grist case) in this case the mill needs to be able to crush the malt in less then 20 -25 minutes max since milling and mashing in takes place at the same time.

The typical pathway however is that the malt gets milled into a grist hopper and the malt grist then gets either via gravity feed mash into the mash mixer or it is transported with one the conveying systems mentioned above. Very well suited for grist transportation are the tubular disk chain conveyors. (Less dust development.)

The grist case usually is mounted on 1 or more load cells so that it is possible to accurately weigh in the malt according to the malt bill. Sometimes the grist silo can also be hooked up to a scale (although this is very rarely the case).

Wet Milling
A different method of milling malt is the wet milling technology. With a dry mill the husks of the malt can get more or less damaged, and this can compromise their function as filter material during the lautering process and can also cause quality problems for wort and beer.

In older traditional type wet mills the malt gets soaked prior to mash in warm water (54 F – 122 F) between 10 minutes to 30 minutes, the husks and endosperm become wet and thus much more elastic. The moisture content of malt can increase up to 30%. The endosperm can now be squeezed through a 2 roller mill and the husk remain largely intact, the endosperm at the same time is finely crushed and can be better utilized during the mash process.

Dry Malt Conditioning
Dry malt mills can be improved by the means of malt condition systems. This can be done either via water or steam in so called Malt Conditioners. The malt conditioners are typically screw augers that homogenously wet the malt within a 1 -3 minute time span (or faster) and the moisture content of the husk increases up to 2 – 2.5% The husks becomes more elastic and the malt can be milled at a finer setting without destroying the husk; the husks remain in tact.

A disadvantage of those systems is the higher complexity of the machines and also the cleaning is more elaborate.

Optimized Wet milling
This new technology is based on the wet milling process but with shorter process times and elevated water temperatures of 122F – 140 F or higher.

The wetting of the malt takes place in a special developed shaft where the malt spends between 30 – 90 seconds time and thus the moisture level increases mainly in the husk and to some extend also in the endosperm, the lautering process can experience an improvement.

This technology is somewhat similar to the dry malt conditioning systems.

Removal of spent grain
After the mashing and lautering process the used malt needs to be removed from the lauter tun so that the lauter tun is ready to receive the next brew. This needs to happen in a short amount of time especially when multiple brews are being brewed in a day.

There are several options to remove spent grain.

For multiple brews per day there is typically a spent grain silo installed at the breweries in which several brews can fit in. The maximum storage time for spent grain is around 2 – 3 days max before they turn sour.

Spent grain is typically removed out of the lauter tun via the racking machine, (time 10 -15 minutes) they fall by gravity into a trough bin (holding capacity one brew) and from there a screw conveyor transports the spent grain into the silo.

Another recommended and widely used option of spent grain removal is via high-pressured air and positive displacement pumps, this method works really well, but this system must be well designed and the pump must be properly sized based on length and height difference of the lauter tun and spent grain silo inlet. Smaller breweries usually collect their spent grain in tubs or drums per each brew.

Spent grains are a desired animal feed product. They can increase for example the milk production of milk cows and also increase the quality of milk.

But spent grain needs to remain in an unspoiled condition, the moisture content of spent grain is around 80%.

Malt purchase
One final remark on who should be purchasing malt at a brewery. In a brewery it is the responsibility of the Brewmaster, or Brew-team in charge of brewing operations, to make that purchase decision. It should never be delegated to accountants or other bean counters.

The responsible Brewmaster decides what kind of malt is purchased because the purchase of malt is first and foremost a quality driven and technological driven decision not a financial decision. Decisions made on malt purchasing will have a huge impact on the quality of your beer.