Having spent a lot of time inside ‘The Grading Room’ over the past several years, I’ve been asked on numerous occasions by visitors, vendors, other OMIC employees and just plain curious people walking by; ‘What exactly is “The Grading Room? ” – ‘The Grading Room’ or ‘Dry Lab’ is where wheat and flour tests are performed.
These tests are standardized procedures commonly used for quality control purposes and results from these tests have a direct relationship to finished product quality. I will attempt to explain the process so grab a cup of coffee and keep reading.
Wheat and flour specifications are communicated between buyers and sellers. These specifications are requirements for particular wheat and flour characteristics. Wheat and flour quality testing is necessary in order to meet those specifications. Specifications for test weight, moisture content, or falling number are determined with basic tests, performed in the grading room at OMIC PORTLAND BRANCH. There are other basic criteria beyond grading factors used to determine wheat’s initial value in the marketing system such as protein and ash content. This is done by OMIC USA, laboratory by our own in-house chemists. In ‘The Grading Room’ however we mainly focus on the visual analysis of a sample of wheat.
Wheat is the principal U.S. cereal grain for export and domestic consumption. In terms of value, wheat is the fourth leading U.S. field crop and our leading export crop. Wheat has two distinct growing seasons. Winter wheat, which normally accounts for 70 to 80 percent of U.S. production, is sown in the fall and harvested in the spring or summer; spring wheat is planted in the spring and harvested in late summer or early fall. There are several hundred varieties of wheat produced in the United States, all of which fall into one of six recognized classes. (This is in market contrast to the one or, at most, two wheat classes produced in other nations.) Where each class of wheat is grown depends largely upon rainfall, temperature, soil conditions and tradition. Generally speaking, wheat is more often grown in arid regions where soil quality is poor. Wheat classes are determined not only by the time of year they are planted and harvested, but also by their hardness, color and the shape of their kernels. Each class of wheat has its own similar family characteristics, especially as related to milling and baking or other food use. The six recognized classes of wheat are as follows;
HARD RED WINTER – The dominant class in U.S. exports and the largest class produced each year. Produced in the Great Plains states, a large interior area extending from the Mississippi River west to the Rocky Mountains and from Canada to Mexico. Wide range of protein content, good milling and baking characteristics. Used to produce bread, rolls and, to a lesser extent, sweet goods and all-purpose flour. Major foreign buyers include Russia, China, Japan, Morocco and Poland.
HARD RED SPRING – Contains the highest percentage of protein, making it an excellent bread wheat with superior milling and baking characteristics. Majority of crop is grown in Montana, North Dakota, South Dakota and Minnesota. Exported largely to Central America, Japan, the Philippines and Russia.
SOFT RED WINTER - Grown primarily east of the Mississippi River. High yielding, but relatively low protein. Used for flat breads, cakes, pastries, and crackers. Largest buyers are China, Egypt and Morocco.
DURUM – The hardest of all U.S. wheat and consistently the class with the lowest export volume, accounting for less than 5 percent of all U.S. wheat exports. Grown in the same northern states as Hard Red Spring, although 70 to 80 percent of the U.S. annual production comes from North Dakota. Used to make semolina flour for pasta production. The largest importer is Algeria.
HARD WHITE WHEAT – The newest class of wheat to be grown in the United States. Closely related to red wheat (except for color genes), this wheat has a milder, sweeter flavor, equal fiber and similar milling and baking properties. Used mainly in yeast breads, hard rolls, tortillas and oriental noodles. Used primarily in domestic markets, although it is exported in limited quantities.
SOFT WHITE WHEAT – Used in much the same way as Soft Red Winter (for bakery products other than bread). Grown mainly in the Pacific Northwest and to a lesser extent in California, Michigan, Wisconsin and New York. Low protein, but high yielding. Produces flour for baking cakes, crackers, cookies, pastries, quick breads, muffins and snack foods. Exported to Far East Asian region.
Now that we have learned about the different classes of wheat it’s time to learn about the visual grading process of a sample of wheat.
Paying close particular attention to individual wheat kernels an experienced inspector dissects a kernel of wheat, much like a physician would before performing surgery, in order to carefully examine it and determine its class and point out any damage.
Starting with about 1,000 grams of wheat a sample is first ran through a machine known as a ‘dockage tester’. ‘Dockage Testers’ mechanically separate the various components of a type of grain sample according to particle size and weight.
The ‘dockage-free’ sample is then weighed using a ‘bushel’ tester and then visually checked for foreign material (FM) such as stones. The next step is to divide the sample into two 500g portions. Using one portion the inspector picks out other foreign Materials (FM) such as other grains or stems, cob joints, or grass seeds. The inspector removes, counts, weighs and calculates %’s and records separately for each of the following; Ergot, Smut, Grain other than wheat, others, and heavy heat damage. The other 500g of the ‘dockage-free’ portion is ran through the ‘Grain Analysis Computer’ or what is commonly referred to as the ‘GAC’ machine. The GAC machine is used to determine the moisture content. Determining moisture content is an essential first step in analyzing wheat or flour quality since this data is used for other tests. Moisture content of 14.0% (in USA) or 13.5% (in Japan) is commonly used as a conversion factor for other tests, (such as the falling number) in which the results are affected by moisture content. Moisture content can be an indicator of profitability. Marketing and storage are two rather distinct aspects of grain handling in which moisture plays an important role. In marketing, the average moisture content of the grain bulk being bought and sold is important. For example, a cargo of 25,000 M/T with 14.0% moisture represents 3,500 tons of water. At 13.5% moisture the cargo contains 3,375 M/T. At $0.10 / pound that difference is worth $ 25,000. Both the buyer and seller need to know how much of this expensive water they are dealing with. For storage, it is the highest moisture content that is present in the grain mass that determines to what extent and how fast storage fungi will develop and damage the grain. Wheat with low moisture content is more stable during storage.
Another important test is what is known simply as ‘the falling number test’. Falling number indicates the soundness of wheat or its alpha-amylase activity. The level of enzyme activity measured by the Falling Number Test affects product quality. Yeast in bread dough, for example, requires sugars to develop properly and therefore needs some level of enzyme activity in the dough. Too much enzyme activity, however, means that too much sugar and too little starch are present. Since starch provides the supporting structure of bread, too much activity results in sticky dough during processing and poor texture in the finished product. If the falling number is too high, enzymes can be added to the flour in various ways to compensate. If the falling number is too low, enzymes cannot be removed from the flour, which results in a serious problem that makes the flour unusable. Low falling numbers show high activity associated with sprout damage. There are two simple steps to the falling number test method. 1. A seven (7) gram sample of ground wheat is weighed and combined with 25 ml of distilled water in a glass falling number tube and shaken to form a slurry. 2. A stirrer is inserted into the glass tube and tubes are inserted into the machine. As the slurry is heated in a boiling water bath at 100 degrees C., and stirred constantly, the starch gelatinizes and forms a thick paste. The time it takes for the stirrer to drop through the paste is recorded as the falling number.
After this step inspectors usually take a quick coffee break. – And we are back. The remaining sample is used to determine shrunken and broken kernels. Shrunken and broken kernels is a grading factor for wheat. To determine shrunken and broken kernels in wheat, the inspector places about 500 grams on a 0.064 × 3/8 inch (1.626 mm × 9.545 mm) oblong-hole sieve and mechanically shakes the sieve 30 times from side to side. The machine used to sieve the sample, a Strand Sizer, has a stroke counter and always starts and stops in the same position. One complete stroke takes approximately 1 second.
The remaining portion of the wheat sample is now divided down to about 100g and inspectors carefully check, separate and pick out sprouted kernels, heat damaged kernels, other damage kernels, contrasting classes and wheat of other class. This is why a quick coffee break is usually needed. Because this can be slow, tedious work that requires patience, focus and alertness.
If working on a sample of white wheat there is another final step, which is checking for Club Wheat. This step usually requires a whole pot of coffee or a Red Bull or some other kind of energy drink to keep inspectors awake motivated and alert.
Club wheat is grown almost exclusively in the Pacific Northwest (PNW) area of the U.S, mainly in Washington and northeastern Oregon. This type of wheat can grow in poor soil conditions. Club wheat is a dwarf species with short spikes and smaller kernels then regular soft white wheat. It is a subclass of soft white wheat with a rather compact head. Club wheat produces characteristic weak gluten, low protein flour with high break flour extraction that is desired by the milling and baking industry for cakes and pastries. It is best used for cake-baking, especially Japanese sponge cake production, where cake volumes are greater than those of soft white wheat, which also produce excellent cakes. One of the most challenging tasks for OMIC Portland grain inspectors has always been to distinguish white club wheat from “Soft White Wheat”. When you have a vast amount of soft white wheat varieties and a smaller amount of white club wheat varieties mixed together, the kernels are all white. How do you tell the difference? It is very difficult; it takes a lot of time to get very good at it. It’s not something you can learn overnight.
With typical soft white wheat, because the head is so long, the kernels have the ability and the room to grow however they need to grow. Usually soft white wheat kernels are larger; they’re straight and have larger germs. Typical white club wheat grows in a much smaller head than that of SW, thus the kernels are forced to grow compacted together without much room to develop properly. Usually the head has the same amount of kernels or close to as many kernels as SW but in a much smaller head. The compacted space causes the kernels to bend, to twist and to hump which leads to a misshapen kernel in order fit in this much smaller head area. When looking for club wheat inspectors are trained to look for misshapen kernels. These types of misshapen white club wheat kernels are easy to identify as the odd shapes, the twists and humps, sort of ‘hit you in the eye’. There are are many varieties of club wheat that can be very difficult to distinguish and can make grain grading a frustrating process.
Club wheat does not always come in looking very nice. Sometimes there has been a certain disease, or drought conditions, or the kernels do not develop normally and do not have their full characteristics that we are trained to look for. Grain inspectors are trained to look for very fine details, such as the brush (backend of the kernel), and the germ, (frontend of the kernel). If certain characteristics are not visible, for instance if the germ is disfigured or the brush because of some sort of disease has been rubbed off, then it becomes even more difficult to distinguish. As grain inspectors, we never rely on just one indicator rather; we are looking for any number of indicators, such as the humps, the twists, and paying close particular attention to the germ. Because of the way that club wheat kernels grow compacted together one thing I’ve learned to look for as a good indicator is to try to spot any kernels that are shaped kind of like a Volkswagen beetle, small, compact and a rounded shape.
When grading SW we divide the samples down to 15 grams. 15 grams of wheat can hold about 300-400 kernels, depending on the size of the kernels. In such a small pile of only 15g, misshapen kernels catches an experienced inspector’s eye, usually the club wheat kernels stand out. A seasoned inspector should not have a very difficult time in identifying at least 15-18% of club wheat varieties in a 15g sample. The rest of the club wheat between 2-5% can be pretty hard to identify even for well trained and experienced inspectors. SW wheat samples typically contain between 20% – 25% + of club wheat.
So, there you have it. Now you know what happens in ‘The Grading Room’! – I need another coffee break.