How soybean grading works

September 24, 2020

The fields are quickly turning yellow, meaning soybean harvest and grading time has arrived. The following summary will help you better understand the soybean grading process.

Step 1 – Sampling and separation

Once the harvested soybeans are loaded for transport, the carrier must first stop in the receiving area at Prograin’s storage facility (or any other facility designated by the carrier at the time of initial contact) to get an order number, before the vehicle is officially weighed. Then a pneumatic probe takes 8 samples for a total representative sample of ± 8 kg. Next, a divider is used to separate the representative sample and obtain a gross mass of at least 750 g. At this point, testing is done to determine the percentage of protein and oil and whether GMO seeds are present. 

Step 2 – Determination of dockage

Using a No. 8 round hole sieve, the gross mass is sifted to obtain a portion of approximately 250 g. The remaining dockage is handpicked from the sieve, e.g., stems and pods, coarse vegetable matter and dirt pellets. The percentage of dockage is then calculated. 

Step 3 – Verification of sample condition

The seed coat may be yellow, green, black, brown or a mixture of colours. Colour is indicated in the grade name, for example: No. 1 Canada Yellow. To determine condition, the general appearance of the soybean sample is compared with standard samples established by the Canadian Grain Commission (CGC). Freshness, odour, heated seeds and the presence of treated seeds and other chemicals can also affect the grade at this step. 

Step 4 – Determination of test weight

Test weight is the weight of a measured volume of grain in kilograms per hectolitre. The ±750-gram sample is poured into a funnel equipped with a slide and put over an Ohaus measure (0.5 litre). Once the slide is removed and the contents dropped into the 0.5 litre measure, the excess grain is very carefully scalped off using a striker. The weight of the 0.5 litre measure is then converted into kg/hl. Click here for the conversion table.

Step 5 – Moisture testing

Although moisture does not affect grade, it can change the test weight and the appearance of the grain. Grain that is too moist will deteriorate quickly. The moisture content of a sample is expressed using the following terms: tough, damp, moist or wet. For example, No. 1 Canada Yellow Tough Soybean. The device used is an electronic moisture meter. 

Step 6 – Determination of split and broken grains

The sieve is moved back and forth 30 times, and the split grains remaining on the sieve and in the tray are handpicked. At this stage, an experienced grader will make the grains roll on the tray in order to identify more efficiently the grains that are split and broken, which will “stick” to the tray. Once the procedure has been completed, the percentage of split and broken grains can be calculated using this formula: weight of split grains / weight of analyzed portion x 100. Following this step, a grain size analysis will be done on the natto-type soybeans.