“The laboratory is a key piece of the Operations Management in a mill or an elevator. The grain must be inspected through all its processing stages, until it turns into a bun. As Peter Drucker said, “if you want to change something, first you have to measure it”. The laboratory is the heart of the continuous improvement efforts. At every stage of the process you have to check the values of the parameters that you care the most.”
Prof. Gustavo Sosa
Industrial Mechanical Engineer
Licensed Grain Inspector
MBA Project Management
SOSA – Engineering Consultants
It is difficult to write about the requirements of the modern laboratory, as most people would like to find a list of the best equipment to have, but I believe that’s not where the focus should be. You may use a Carter Day dockage tester or a set of manual sieves. Either way you are going to find out how much foreign matter is present in the grain. Most of the readers of this magazine work in the wheat flour industry, which has an impressive range of equipment to measure different characteristics of grain, flour, and dough. Instead of focusing on that area, I will try here to provide a list of what to measure, in general, for every grain-related industry.
First there is a list of the tests you may perform on grain or its products, so you have a quick introduction on what could be controlled. It is up to you to look for more information on books or articles, to learn how to apply them. Later I will give you an introduction to quality control planning.
I strongly believe that a modern grain laboratory and a strict quality control plan are key to the successful implementation of Lean Six Sigma in any company.
QUALITY OF WHOLE GRAINS
The most important parameters to control are:
Moisture: Most grains need to be stored at less than 14% moisture. Higher moisture promotes the growth of insects and mold.
Foreign matter: It is the dust, hulls, sticks, and any other thing that is not a grain or just shouldn’t be there. For example, a grain of sorghum is considered foreign matter if you are analyzing a batch of corn.
Specific weight: How many tons of grain are contained in a cubic meter. In agriculture, an equivalent dimension called hectolitre weight is used, and it is measured in kilograms per liter.
Fat content: In the case of soybeans and sunflower, fat content is the main parameter of interest for oil production. It is especially important for animal feed too. Oil mills would use solvent extraction methods to test it, but feed millers and other people just need a NIR analyzer.
Presence of insects or mold: A visual inspection allows to find the bites of insects in the grains. If you find grain dust, “spider webs” (actually silk of the larvae) and little holes in the grain, you have insects. Mold has a distinctive odor.
Physical damage: It may be because of water, fire, freeze, crushing. Basically, the grain doesn’t look as it should. Too dark, too white, etc.
Toxins: When a fungi attacks the grain, either in the field or in the grain bin, it produces mycotoxins. As with every other substance in the world, there are safe and unsafe levels. A quick test may be performed using a black light, just to know if there is or has been mold there. For precise detection of specific toxins and controlling the levels, you should use an ELISA test. There are several types available for the different toxins.
Color: Having a batch of grain with an unusually pale color may indicate that the grains were treated with pesticide for use as seeds, and someone later changed his mind. Seeds are tinted to make them look different and avoid confusion with edible grains, but people of dubious ethics may wash them with bleach after a seed contract gets busted, as it is easier to sell edible grains.
QUALITY OF MILLED GRAINS
The parameters to be controlled depend on what you would do. Corn may be dry or wet milled, and the parameters would be different despite being the same grain and (almost) the same end products. Same goes for sorghum. Rice and wheat are dry milled. Oat is peeled and crushed. Soybean and sunflower are crushed and sort of wet milled (with hexane instead of water).
In most cases, you need all the things you used for whole grains, plus some other.
Hand Mill: Again, depends on the grain and the process. There are even lab scales mills for wet milling. Most of the time, you need a grinder that will turn the grain into a rough flour, in order to use solvent based tests.
Moisture: The acceptable moisture for milled grains is much less than for whole grains, because there is no longer any breathing to cool the product. In general, to avoid infestation, you need less than 8% moisture.
Particle size: Animal feed depends strongly on particle size. The same goes for many human-consumption flours. A set of graduated sieves will allow you to perform a size distribution analysis on any sample of flour.
Specks: Small fragments of foreign matter. Hair, feces, rubber, cotton, etc. They show in a visual inspection.
Foreign matter: A set of sieves may catch some foreign matter, but for flours (as everything is milled) you must use chemical digestors and then analyze the results with a microscope. That’s the way to recognize hairs, eggs, excrement and many other small things.
Starch content: It is the most important parameter for flours. You get it with a NIR analyzer or with an enzymatic test.
Starch damage: Sprouting or faulty storage can lead to starch damage. That means the baking quality of the flour decreases. This parameter is analyzed with a Falling Number test.
Starch gelatinization: You need a special microscope, or birefringence, with polarized filters. This analysis measures the quantity of gelatinized versus native granules.
Protein content: Most of the time it is measured with a NIR. The standard test is the Kjeldahl analysis. It is one of the most important parameters for animal feed.
Fat content: In the several stages of oil extraction you have to check the fat content. It also has value in the subproducts that are later sold as animal feed. You can measure it with a NIR or (more precisely) with a Soxhlet apparatus.
Ash content: Basically, you burn all the stuff completely. Ashes of a complete combustion are not coal, but the mineral residue (inorganic materials) that remain after all the organic substances turn into smoke. For flour, ash content determines the whiteness, which itself doesn’t mean much, but consumers want it.
The laboratory is a key piece of the Operations Management in a mill or an elevator. The grain must be inspected through all its processing stages, until it turns into a bun.
As Peter Drucker said, “if you want to change something, first you have to measure it”. The laboratory is the heart of the continuous improvement efforts. At every stage of the process you have to check the values of the parameters that you care the most.
Let’s say you manufacture animal feed. For that purpose, you have some whole grains (corn) that you mill yourself, some subproducts (sunflower expeller) of other industries, and some additives (minerals and vitamins).
It is very important to learn how to take samples. There are many books on the subject and maybe I will write a couple of articles about it in the future. Meanwhile, understand that quality control doesn’t mean 100% analysis. Not even 10%. The size of the samples and the frequency of the sampling varies according to the problems you encounter. If everything goes fine, you check less. If a problem arises, you increase the frequency.
You have to check the quality of the grain (moisture, foreign matter, specific weight, protein and fat content) and of the subproducts (fat and protein content, foreign matter). The equipment for that is basic and cheap.
For the supplements you have to either ask for a quality certificate or get a third-party lab to control the quality for you. Unless you are a major miller, the cost of having your own technicians and equipment for that is not justified.
Then you clean, dry, and store the grain. That is processing. So, you have to check the quality of the grain again after it. Most people only check when they receive and they miss invaluable information on the efficiency of their processes.
Milled subproducts are only stored, but the quality of the conservation has to be controlled. In theory, you should check them at reception and only right before use, if they have been stored for a long time. Storage, as a process, should be controlled with spaced repetition. Start checking them after one month, and then adjust if you find problems or everything is ok. If you find rodent feces, for example, apply some treatment and increase the frequency of the controls. If everything is ok, check after two months.
Supplements are only checked at reception, unless you fully trust the certificates of the supplier. It is a good idea to hire a third-party lab to conduct the analysis as it is easier than setting up your own lab for that. You may check them again before use, but it doesn’t make much sense. Just keep an eye on the expiration dates.
Later, every stage of the process (grinding, mixing, pelleting, etc.) causes some kind of change in the products. Here you have to take samples to see how the relevant properties are affected by the process. Did your process get contaminated? Did the heat affect the proteins or the vitamins? Any change shown in those numbers will tell you where to look for a problem or an opportunity.
Once you have a solid understanding of your processes and how they affect your parameters, you have everything set for an improvement plan. Good luck.
Note: If you want to know more about laboratory analysis of grains, be sure to check “Cereal Grains: Laboratory Reference and Procedures Manual”. It is a great book by Sergio Serna.