Methods and tests used by the Canadian Grain Commission to measure the quality of pulses

Pulse quality tests carried out by the Grain Research Laboratory are based on, or calibrated against, methods described by:

Pulse methods and tests as of February 2021

100-seed weight
100-seed weight is determined following AACC Method 56-35.01: Method for Determining Water Hydration Capacity and Percentage of Unhydrated Seeds of Pulses. Broken and damaged seeds, along with foreign material, are handpicked from the sample. A custom-made seed sampling paddle is used to count 100 seeds which are then weighed.
Ash content
Ash content is determined following AACC Method 08-16.01: Ash in Soy Flour. The sample is ignited in a muffle furnace at 600°C for 3 hours (h) to remove organic matter. The remaining residue (ash) is weighed and calculated as a percentage of the original sample weight.
Colour
The colour of dehulled lentils is measured using a Hunterlab LabScan XE spectrocolorimeter using the CIELAB (1976) colour space system (L*: white (100) to black (0), a*: red (+) to green (-), b*: yellow (+) to blue (-)) with a D65 illuminant.
Cooking time
Cooking time is determined using an automated Mattson cooker (Wang, N. and J.K. Daun. 2005. Determination of cooking times of pulses using an automated Mattson cooker apparatus. J. Sci. Food Agric. 85:1631-1635). The automated Mattson cooker consists of a cooking rack and 25 hollow plungers. The weight of each plunger is adjusted to 90 grams (g). A 30 g sample is soaked in distilled water at room temperature (22 ± 2°C) for 24 h. Soaked seeds are then positioned into each of the 25 saddles of the rack so that the tip of each plunger rests on the surface of the seed. The rack is then placed into a 2 litre (L) metal beaker containing 1.2 L of boiling water. When a seed becomes sufficiently tender, the plunger penetrates the seed and drops a short distance through the hole in the saddle. The time taken for each plunger to drop is automatically recorded. Cooking time for a sample is defined as the time required for 80% of the seeds to be penetrated.
Dehulling characteristics of red lentils
Dehulling characteristics of red lentils are determined using a Satake TM05C Grain Testing Mill (Satake Engineering Co Ltd, Hiroshima, Japan) using a previously described procedure (N. Wang. 2005. Optimization of a Laboratory Dehulling Process for Lentil (Lens culinaris). Cereal Chem. 82(6):671-676). Samples are tempered to 12.5% moisture before they are dehulled. The tempered lentils are then processed in the mill for 38 seconds (sec). The speed of rotation of the abrasive wheel is operated at 1100 revolutions per minute (rpm). After dehulling, the powder is collected using a No. 20 mesh sieve and the remaining product is separated into whole seeds, split seeds, broken seeds and hulls using a dockage tester (Simon-Day Ltd., Winnipeg, Canada). Both split and whole seeds are further separated by hand into their respective hulled and dehulled classes. All fractions are weighed and expressed as a proportion of the total original weight. Dehulling efficiency (%) is calculated as the sum of dehulled whole seed (%) and dehulled split seed (%).
Firmness of cooked pulse seeds
The firmness of cooked seeds is measured with a TA-HDPlus texture analyzer (Texture Technologies Corp., Scarsdale, NY) following AACC Method 56-36.01: Firmness of Cooked Pulses. Cooked samples are loaded in a TA-91M Kramer shear cell holder (Texture Technologies Corp.). The firmness of cooked seeds is defined as the maximum force required to shear the cooked seeds and is expressed as the maximum shear force per gram (N/g) of cooked sample.
Moisture content
Moisture content is determined following AACC Method 44-17.01: Moisture—Air-Oven Method (Pulses). Samples are heated in an oven at 130°C for 2 h and the resulting weight loss is measured. Weight loss is calculated as a percentage of the total weight and reported as percent moisture.
Oil emulsifying capacity
Oil emulsifying capacity is determined as previously described (Wang, N. and L. Maximiuk. 2015. Development of an improved electrical resistance method for determining emulsifying capacity of pulse and soy materials. Cereal Chem. 92:253-257). The electrical resistance method is based on the fact that oil is a nonconductor while combinations of pulse or soy protein and water are good conductors. Oil emulsifying capacity is determined at the inversion point where an oil-in-water emulsion turns into a water-in-oil emulsion as indicated by a sudden drop in conductivity. The total amount of oil emulsified was calculated and expressed as volume of oil (mL)/weight of sample (g).
Protein content
Total nitrogen (N) content is determined using the Dumas combustion method following AOAC Method 992.23: Crude Protein in Cereal Grains and Oil Seeds using a LECO FP-528 nitrogen analyzer. Protein content is calculated as N x 6.25 and is expressed on a dry matter basis.
Seed size distribution
Seed size distribution is determined using the image analysis technique developed at the Canadian Grain Commission (M.A. Shahin and S.J. Symons. 2001. Lentil seed size distribution with machine vision. ASAE Paper No. 01-3058, St. Joseph, Michigan)
Starch content
Starch content is determined following AACC Method 76-13.01: Total Starch Assay Procedure. The sample is enzymatically digested using alpha-amylase and amyloglucosidase under controlled conditions. The resulting glucose is measured colorimetrically.
Total dietary fiber
Total dietary fiber (TDF) content is determined following AOAC Method 991.43: Total, Soluble, and Insoluble Dietary Fibre in Foods. Duplicate samples are digested with three enzymes (alpha-amylase, protease and amyloglucosidase) to remove starch and protein. Ethanol is added to the digest and the precipitate is measured. The residue from one duplicate is analyzed for protein and the other for ash. These results are subtracted from the average residue weight to calculate TDF.
Water absorption
Water absorption (hydration capacity) is defined as the maximum amount of water that 100 seeds absorb at room temperature (22 ± 2°C). It is determined following AACC Method 56-35.01: Method for Determining Water Hydration Capacity and Percentage of Unhydrated Seeds of Pulses.
Water holding capacity
Water holding capacity of pulse flours is defined as the maximum amount of water that 1.0 g of material imbibes and retains under low-speed centrifugation. It is determined following AACC Method 56-37.01: Water-Holding Capacity of Pulse Flours and Protein Materials.
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