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

Wheat methods and tests as of February 1, 2022

Alveogram – flour

Alveograms are obtained using the Chopin Alveolab following AACC International Method 54-30.02: Alveograph Method for Soft and Hard Wheat Flour. After milling, flour samples are stored at room temperature for a minimum of 6 days prior to analysis. Alveograms are reported on a 15% moisture basis.

Alveogram – semolina

Alveograms are obtained using the Chopin Alveograph NG following AACC International Method 54-30.02: Alveograph Method for Soft and Hard Wheat Flour. After milling, semolina samples are stored at room temperature for a minimum of 3 days prior to analysis. Alveograms are reported on a 15% moisture basis.

Amylograph peak viscosity

Sixty-five grams of flour and 450 millilitres (ml) of distilled water are used with the Brabender Amylograph and the pin stirrer. Other details follow the AACC International Method 22-10.01: Measurement of α-Amylase Activity with the Amylograph. Peak viscosity is reported in Brabender units (BU).

Ash content

The determination of wheat, flour or semolina ash content follows the AACC International Method 08-01.01: Ash-Basic Method. Samples are incinerated overnight in a muffle furnace at 590°C for hard wheats and 550°C for soft wheats.

Bake method – Canadian short process

The Canadian short process (CSP) test bake method (Preston et al. 1982. The GRL pilot mill. II. Physical dough and baking properties of flour streams milled from Canadian Red Spring wheats. Can. Inst. of Food Sci. and Tech. J. 15:29-36) is followed using 150 parts per million (ppm) ascorbic acid as the oxidant and with salt reduced to 2%. Dough is mixed in a Swanson type 100 to 200 gram (g) pin mixer (National Manufacturing Co., Lincoln NE) at 116 revolutions per minute (rpm). Loaves are produced from 200 g of flour in baking pans with cross-sectional dimensions similar to Canadian commercial baking pans. Loaf volume is reported on a 100 g flour basis. Mixing energy is reported in watt-hours per kilogram (W-h/kg) of dough.

Illustration of CSP dough mixing curve

Loaf of bread produced using the CSP test bake method

Bake method – lean no time dough

The lean no time (LNT) test bake method (Dupuis, B., and B. X. Fu. 2017. A new lean no time test baking method with improved discriminating power. J. Cereal Sci. 74: 112-120) is similar to the CSP test bake method but eliminates the use of an oxidant and reduces the salt and shortening to 1% of flour weight (14% moisture basis). The LNT method is more discriminating than the CSP method and robust enough to be adopted by other laboratories. Loaves are produced from 150 g of flour. Loaf volume is reported on a 100 g flour basis.

The LNT method was adopted by the Prairie Recommending Committee on Wheat Rye and Triticale in February 2016 as the method of choice and replaces the CSP and remix-to-peak test bake methods in Canadian variety registration trials.

A new objective parameter, loaf top ratio, was also introduced and found to correlate well with dough strength, extensibility and dough handling properties. It provides an objective measure of a parameter that previously required the subjective evaluation of an experienced baker. Loaf top ratio = (loaf height - pan height) / loaf width. Refer to the Method for Lean No Time Test Baking for a detailed description of the method used at the Grain Research Laboratory.

Illustration of loaf top ratio

Bake method – sponge and dough

The sponge and dough test bake method is based on a 4.5 hour fermentation and 70% sponge system (Kilborn, R. H. and K. R. Preston. 1981. A dough height tracker and its potential application to the study of dough characteristics. Cereal Chem. 58:198-201). Ascorbic acid is used as the oxidant at 40 ppm. Dough is mixed in a Swanson type 100 to 200 g pin mixer (National Manufacturing Co., Lincoln NE) at 116 rpm. Loaves are produced from 200 g of flour in baking pans with cross-sectional dimensions similar to those of Canadian commercial baking pans. Loaf volume is reported on a 100 g flour basis. Mixing energy is reported in W-h/kg of flour and W-h/kg of dough.

Refer to the Method for Sponge and Dough Bread Baking for a detailed description of the method used at the Grain Research Laboratory.

Cadmium concentration

Cadmium concentration in durum whole grain is determined using closed vessel microwave digestion and inductively coupled plasma mass spectrometry (ICP-MS). Ground grain (1.0 g) is digested with concentrated nitric acid using closed vessel microwave digestion. Digested samples are then diluted using deionized water. Digested samples are analyzed by ICP-MS alongside various quality control samples (including certified reference materials, in-house reference materials, reagent blanks, and fortified samples) to monitor the accuracy and precision of the analytical method. The limit of quantitation of the ICP-MS method is 0.01 mg/kg.

Colour – flour

A Minolta Model CM-5 stand-alone top-port spectrophotometer (d/8 geometry and illuminated area of 30 mm diameter) is used to determine the colour of wheat flour samples. A Petri dish (45 mm diameter) is loosely filled with a subsample of flour. The dish is tapped gently until the flour is level and no gaps are apparent through the base of the dish. The depth of flour is at least 10 mm. Results are reported as the mean of duplicate determinations of L*, a*, and b* parameters of the CIELAB (1976) colour space system, which represent lightness, redness, and yellowness values, respectively (L*: 100 white, 0 black, a*: +60 red, -60 green, b*: +60 yellow, -60 blue). Results are for a 10° standard observer and D65 illuminant.

Colour – water dough sheet

Forty-five grams of flour (14% moisture basis) is mixed with water at 36% absorption (35% for soft wheat) using a SpeedMixer (Hauschild GmbH & Co. KG, Germany) at 2500 rpm for 60 seconds. The resulting dough crumb is molded by hand into a rectangle shape and then subjected to 9 sheeting passes with a small pasta sheeter (Imperia RMN220 Electric Pasta Machine, San Francisco, USA). The sheeting process starts with 4 sequential passes with gap settings of 10, 9, 8 and 7 at about 3.9, 3.4, 2.9, and 2.5 mm, respectively. After folding lengthwise, the dough is subjected to 5 more sequential passes (fed with the folded end) with gap settings of 10, 9, 8, 7, and 6 with final gap setting (6) at 2 mm. After the final pass, the dough sheet is folded and stored in a plastic bag to prevent moisture loss. Colour measurements are taken on the folded dough sheet 2 hours and 24 hours after the completion of sheeting using a Minolta colorimeter with D65 illuminant. Colour readings are expressed on the CIELAB (1976) colour space system for L*(lightness), a* (red-green) and b* (yellow-blue).

Cookie test

The sugar-snap cookie test is performed according to the AACC International Method 10-50.05: Baking Quality of Cookie Flour, using non-hydrogenated shortening instead of hydrogenated shortening, and a milk solution instead of a dextrose solution. The wire-cut cookie test is performed according to the AACC International Method 10-53.01: Baking Quality of Cookie Flour-Macro Wire-Cut Formulation, using non-hydrogenated shortening instead of hydrogenated shortening.

Extensogram – standard

The Brabender Extensograph®-E has been used for generating extensograms since 2008 with a manufacture setting of 500 g load equal to 400 BU. Prior to 2008, the old Extensograph with a mechanical recording system was set so that a 500 g load equaled 500 BU. This test is conducted using AACC International Method 54-10.01: Extensigraph Method, General with the exception that the dough is not stretched at 90 min. Length is measured in centimetres (cm), height in BU, and area in square centimetres (cm²). After milling, flour samples are stored at room temperature for 7 days prior to analysis.

Illustration of extensogram

Extensogram – pin mixer

The standard extensigraph method referenced above uses the farinograph for the preparation of dough in the presence of 2% salt at reduced water absorption (farinograph absorption minus 2-3%). The dough prepared this way is usually underdeveloped and drier than typically seen in common baking processes. In addition, the standard extensigraph test is time consuming and requires a large sample size. We use a modified method (Suchy, J., Dupuis, B., Sakamoto, J., and B. X. Fu. 2016. Alternate dough preparation protocol for extensigraph test of dough strength. Cereal Chem. 94:270-276) in which dough is prepared using a Swanson type pin mixer at reduced salt (1%) and elevated water absorption (farinograph absorption plus 4%). With this alternate method, dough is fully developed and similar to bread dough in physical properties. AACC International Method 54-10. 01: Extensigraph Method, General is followed for dough rounding, molding, resting and stretching using the Brabender Extensograph-E. This protocol requires a much smaller flour sample and significantly increases sample throughput. After milling, flour samples are stored at room temperature for 7 days prior to analysis.

This modified method was approved at the Prairie Grain Development Committee meetings in February 2015 and incorporated as a method for assessing dough strength in Canadian variety registration trials.

Falling number

Falling Number (FN) is determined on a 7 g sample of ground wheat by AACC International Method 56-81.04: Determination of Falling Number. A 300 g sample of wheat is ground in a Falling Number Laboratory Mill 3100 according to ICC Standard Method No. 107. FN is used to estimate the alpha-amylase activity resulting from sprout damage in wheat.

Farinogram

Farinograms are obtained using AACC International Method 54-21.02: Rheological Behavior of Flour by Farinograph: Constant Flour Weight Procedure, using the small bowl (50 g flour). After milling, flour samples are stored at room temperature for 6 days prior to analysis.

• Farinograph absorption is the amount of water that must be added to flour to give the required consistency. It is reported as a percentage.
• Dough development time (DDT) is the time required for the curve to reach its maximum height and is reported to the nearest 0.1 min. In some cases, very strong flours may have a flat and stable mixing curve and DDT may be based on mid-point determination of the flat mixing zone (for example, mid-point between arrival and departure of the midline at 490 BU). In rare cases, farinograms for very strong flours may have a second and higher remix peak after a clear breakdown in the bandwidth, indicating dough is overmixed. If this occurs, only the first mixing peak zone should be considered for determination of the DDT.
• Mixing tolerance index (MTI) is the difference, in BU, between the top of the curve at the peak and the top of the curve measured five minutes after the peak is reached.
• Stability is defined as the difference in time, to the nearest 0.1 min, between the point at which the top of the curve first intersects the 500 BU line (arrival time) and the point at which the top of the curve leaves the 500 BU line (departure time).

Illustration of farinogram

Flour yield and milling protocols

All millings at the Canadian Grain Commission's Grain Research Laboratory are performed in rooms with environmental control maintained at 21°C and at 60% relative humidity, according to the procedure outlined in Milling for quality evaluation of new wheat lines.

Gluten index – flour

Flour gluten index is determined using AACC International Standard Method 38-12.02: Wet Gluten, Dry Gluten, Water-Binding Capacity, and Gluten Index, following the procedure for flour.

Gluten index – semolina

Durum semolina gluten index is determined using AACC International Standard Method 38-12.02: Wet Gluten, Dry Gluten, Water-Binding Capacity, and Gluten Index, following the procedure for whole meal.

Hard vitreous kernels

Vitreousness of a kernel is the natural translucence that is a visible sign of kernel hardness. Hard vitreous kernels (HVK) are a grade determinant for the amber durum wheat class in Canada and the red spring wheat class in western Canada. The percentage of HVK is determined by examining a 25 g representative sample taken from a sieved 250 g sample. Kernels are counted as HVK or non-vitreous as defined in the Canadian Grain Commission's Official Grain Grading Guide, Section 4, Wheat.

Moisture content – flour, semolina, and ground wheat meal

The moisture content, measured as the loss in weight of a sample when heated, is determined by either following the AACC International Method 44-15.02: Moisture - Air-Oven Methods, or by heating a 10g sample for one hour in a semi-automatic Brabender oven at 130°C. which is calibrated to the AACC International Method 44-15.02: Moisture – Air-Oven Methods.

Moisture content – wheat

The moisture content of wheat is determined using a Unified Grain Moisture Algorithm (UGMA) moisture meter or with a Near-infrared transmittance (NIT) instrument, verified against the AACC International Method 44-15.02: Moisture – Air-Oven Methods, following the procedure for the two-stage air-oven.

Particle size index

Particle size index (PSI) is a measure of the texture of a wheat kernel. The AACC International Method No. 55-30.01: Particle Size Index for Wheat Hardness is modified by using a UDY cyclone sample mill fitted with a feed rate regulator and a 1.0 millimetre (mm) screen. A 10 g sample taken from 22 g of ground and well-blended wheat meal is sieved over a U.S. Standard 200 mesh sieve for 10 min in a Ro-tap sieve shaker. The weight of throughs multiplied by 10 is recorded as the PSI.

Protein content – wheat, flour and semolina

Protein content is determined by combustion nitrogen analysis (CNA). For wheat, samples are ground on a UDY cyclone mill fitted with a 1.0 mm screen. Sample size for CNA is 250 milligrams (mg). Protein content is calculated as 5.7 times nitrogen as determined using a LECO Truspec N CNA analyzer calibrated with EDTA or an Elementar rapid N cube calibrated with L-aspartic acid and reported on a constant moisture basis.

Semolina colour

Durum semolina colour is determined using a Minolta colorimeter model CR-410 with a D65 illuminant. Colour readings are expressed on the CIELAB (1976) colour space system for L*(lightness), a* (red-green) and b* (yellow-blue).

Semolina – dough sheet colour

Semolina dough sheets are prepared as previously described (Fu, B. X., Schlichting, L., Pozniak, C. J. and A. K. Singh. 2011. A fast, simple, and reliable method to predict pasta yellowness. Cereal Chem. 88 :264-270). The colour of the dough sheet surface is measured at 0.5 and 24 hours after sheeting using a Minolta colorimeter model CR-410 with a D65 illuminant. Colour readings are expressed on the CIELAB (1976) colour space system for L*(lightness), a* (red-green) and b* (yellow-blue).

Semolina yield and total milling yield of durum wheat

Durum wheat is milled on a four stand Allis-Chalmers laboratory mill in conjunction with a laboratory purifier. The detailed mill flow and purification steps are described in Milling for quality evaluation of new wheat lines. For the calculation of yield, semolina is defined as having less than 3% pass through a 149 micrometre (µm) sieve. Milling yield is the combination of semolina and flour. Both milling and semolina yields are reported as a percentage of the cleaned wheat on a constant moisture basis.

All semolina analysis and pasta processing is conducted using granular products with a constant extraction of 70%. Semolina granulars are prepared by adding the most refined flour stream(s) to semolina until 70% extraction is reached.

Solvent retention capacity

Solvent retention capacity (SRC)is determined using the AACC International Method 56-11.02: Solvent Retention Capacity Profile, using deionized water and lactic acid (5% w/w) as the solvents.

Spaghetti processing

Spaghetti is processed from semolina using a customized micro-extruder (Randcastle Extrusion Systems Inc., New Jersey, U.S.A.). The barrel of the extruder has 3/4 inch internal diameter with a 12:1 working length to diameter ratio. The screw extends into the hopper where agitators are attached to enhance dough crumb conveying. The hopper is covered and the system is sealed with vacuum. Temperature is precisely controlled at 45°C along the extruder barrel. Semolina (200 g) and water are first mixed in an asymmetric centrifugal mixer (DAC 400 FVZ SpeedMixer) to generate uniform dough crumbs consistent with commercial requirements. The dough crumbs are placed in the hopper and then vacuum is used to eliminate air bubbles. A four-hole, 1.8 mm, Teflon coated spaghetti die is used for extrusion. Spaghetti is dried at 85°C in a pilot pasta drier (Bühler, Uzwil, Switzerland) at Cereals Canada.

Spaghetti colour

Spaghetti colour is determined using a Minolta colorimeter model CR-410 with a D65 illuminant. Colour readings were expressed on the CIE (1976) colour space system for L* (lightness), a* (red-green) and b* (yellow-blue). For colour measurement, a 6.5 cm band of spaghetti strands is mounted on white cardboard using double-sided tape.

Spaghetti firmness

Cooked spaghetti firmness is determined using the Stable Micro Systems TA.XT2i Texture Analyser with accompanying Texture Expert software, following the AACC International Method 66-52.01: Determination of Cooked Spaghetti Firmness, with modifications. Pasta firmness is analyzed from 3 separate cookings. Cooking time is fixed at 8 min with 12 spaghetti strands (5 cm in length) being cooked each time. Cooked spaghetti strands are drained and immediately aligned on the base plate. Five strands with no spacing are cut perpendicular at a fixed compression depth of 4.9 mm at a crosshead speed of 1 millimetre per second (mm/s) with a standard TA-47 blade that is 1 mm in diameter. The pasta blade and platform are cleaned after each cut and the test is repeated. Average peak force of cutting five strands is reported.

Spaghetti strand diameter

Dry spaghetti diameter is the average of ten randomly chosen strands which are measured with a caliper. The TA.XT2i texture analyzer with Texture Expert software is used to determine cooked spaghetti diameter by subtracting the distance the blade travels to the surface of spaghetti from the set distance using a trigger g-force of 3 g.

Speck count

Speck count is determined using the software RAR-SpecCnt(S) developed by RAR Software Systems (Winnipeg, Manitoba). A semolina sample is compressed to 1 cm in thickness in a sample holder with a glass top, and then scanned using a flatbed scanner to acquire a 10 cm x 10 cm image for processing. Potential specks are identified in the sample image using object detection algorithms. Each detected object is then evaluated for the average darkness (% GL), the average colour of each component (% RGB), the average colour of each component within the darkest region of the object (% RGB Max), and the size (total area). If the detected object falls within previously specified ranges, the object is identified as a speck. Once all the specks have been identified, they are categorized by their darkness (low, medium and high) as well as their size (small, medium and large). Total dark, and large specks are averages of at least three replicates and their numbers are expressed per 50 cm² of semolina sample surface.

Starch damage

Starch damage is determined following the AACC International Method 76-31.01: Determination of Damaged Starch: Spectrophotometric Method. Starch damage is expressed as a percentage of flour weight. The method is also referred to as the Megazyme method.

Test weight - grading

Test weight is determined using a 0.5 litre (L) measure, a Cox funnel to standardize the pouring rate, and a striker to level the contents of the container. The grain in the container is poured into the pan of an approved electronic weighing scale. The scale connects to a computer which calculates the test weight of the grain in kilograms per hectolitre (kg/hL) from the measured weight (g). If the computer interface is not available test weight conversion charts are used.

Test weight - composites for quality analysis

Test weight is determined using the Schopper chondrometer equipped with a 1 L container. The weight in grams of the measured litre of wheat is divided by 10. The result is reported in kg/hL without reference to the moisture content.

Weight per 1000 kernels

Broken kernels and foreign material are handpicked from a sample to create a clean sample. The number of kernels in a 20 g subsample of a clean sample is counted using an electronic seed counter.

Wet gluten content – flour

Flour wet gluten content is determined using the AACC International Method 38-12.02: Wet Gluten, Dry Gluten, Water-Binding Capacity, and Gluten Index, following the procedure for flour.

Wet gluten content – semolina

Semolina wet gluten content is determined using the AACC International Method 38-12.02: Wet Gluten, Dry Gluten, Water-Binding Capacity, and Gluten Index, following the procedure for whole meal.

Yellow pigment content – semolina

Yellow pigment content of durum semolina is determined using a rapid extraction procedure (Fu, B.X., Schlichting, L., Pozniak, C.J., and A. K. Singh. 2013. Pigment loss from semolina to dough: rapid measurement and relationship with pasta colour. J. Cereal Sci. 57:560-566). Absorption is measured using a spectrophotometer and converted to yellow pigment concentration as specified by the AACC International Method 14-50.01: Determination of Pigments.