Wheat methods and tests used to measure quality
At the Grain Research Laboratory, unless otherwise specified,
- Analytical results for wheat are reported at 13.5% moisture content.
- Analytical results for flour and semolina are reported at 14.0% moisture content.
- AACC methods cited are from AACC International: Approved Methods of Analysis, 11th Edition.
- ICC methods cited are those of the International Association for Cereal Science and Technology (ICC): ICC Standards: Standard Methods of the International Association for Cereal Science and Technology, 7th supplement, 1998.
- Grade determinants and procedures are those used by Industry Services, Canadian Grain Commission.
Wheat methods and tests as of September 2016
- Alpha-amylase activity
- The alpha-amylase activity of wheat and flour is determined by the method of Kruger and Tipples (1981), Cereal Chemistry 58:271-274.
- Alveograms are obtained using the Chopin Alveograph NG following AACC Method 54-30.02. Flour samples are stored following milling for a minimum of seven days prior to analysis.
- Alveogram – semolina
- Alveograms are obtained using the Chopin Alveograph NG following AACC Method 54-30.02. Following milling, semolina samples are stored at room temperature for at least three days prior to analysis.
- Amylograph peak viscosity
- Sixty-five grams of flour and 450 millilitres of distilled water are used with the Brabender amylograph and the pin stirrer. Other details are as in AACC Method 22-10.01. Peak viscosity is reported in Brabender units
- Ash content
- To determine wheat, flour or semolina ash content, AACC Method 08-01.01 is used. Samples are incinerated overnight in a muffle furnace at 600°C.
- Canadian short process test bake method
- The Canadian short process baking test, as described by Preston et al. (1982), Canadian Institute of Food Science and Technology Journal 15:29-36, is followed, using 150 ppm ascorbic acid as the oxidant and reducing the salt to 2%. Dough is mixed in a Swanson type 100-200 gram pin mixer (National Manufacturing Co., Lincoln NE) at 116 rpm. Loaves are produced from 200 grams of flour in baking pans with cross-sectional dimensions similar to Canadian commercial baking pans. Loaf volume is reported on a 100-gram flour basis. Mixing energy is reported in watt-hours per kilogram (W-h/kg) of dough.
Illustration of Canadian short process dough mixing curve
Loaf of bread produced using the Canadian short process
Refer to the Method for Canadian Short Process Bread Baking for a detailed description of the method used at the Grain Research Laboratory.
- CIELAB tristimulus colour measurement of 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 a wheat flour sample. A Petri dish (45 mm diameter) is loosely filled with a subsample of flour. The dish is tapped gently until the flour is leveled 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 colour model, which represent lightness, redness, and yellowness values, respectively. Results are for a 10° standard observer and D65 illuminant.
- L*: 100 white, 0 black
- a*: +60 red, -60 green
- b*: +60 yellow, -60 blue
- Cookie test
- The sugar-snap cookie test is performed according to AACC Method 10-50.05 (using milk solution instead of dextrose solution).
The wire-cut cookie test is performed according to AACC Method 10-53.01.
- Extensogram – standard
- The Brabender Extensograph®-E has been used for generating extensograms since 2008 with a manufacture setting of 500-gram load equals 400 Brabender units. Prior to 2008, the old Extensograph with a mechanical recording system was set so that 500-gram load equals 500 Brabender units. This test is conducted using AACC Method 54-10.01 with the exception that the dough is not stretched at 90 minutes and, for Canada Western Extra Strong, the total dough mixing time is fixed at two minutes. Length is in centimetres, height is in Brabender units, and area is in square centimetres.
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%). However, the dough so prepared is usually underdeveloped and drier than typically seen in common baking processes. In addition, the standard extensigraph test is time consuming and requires large sample size. In this modified method, described by Suchy et al (2016), Cereal Chemistry (Accepted) 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 is followed for dough rounding, molding, resting and stretching using the Brabender Extensograph-E. This protocol requires much less flour sample and significantly increases sample throughput.
- 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.
Refer to the Method for Evaluation of Rheological Behaviour of Flour by Extensograph: Using Pin Mixer for Dough Preparation for a detailed description of the method used at the Grain Research Laboratory.
- Falling number
- The falling number is determined on a 7-gram sample of ground wheat or semolina by AACC Method 56-81.03. A 300-gram sample of wheat is ground in a Falling Number Laboratory Mill 3100 according to ICC Standard Method No. 107. The falling number test is used to evaluate the amount of sprout damage in Canadian wheats. Alpha-amylase is an enzyme found in sprout-damaged wheat. If germination occurs there is a dramatic increase of this enzyme.
- This test is conducted using AACC Method 54-21.02, following the procedure for constant flour weight using the small bowl.
- 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 reported to nearest 0.25 minute.
- Mixing tolerance index (MTI) is the difference, in Brabender units, 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 0.5 minute, 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).
- For CWES, farinograph absorption is determined at 63 rpm. Remaining quality parameters are measured at 90 rpm based on absorption obtained at 63 rpm. For additional details, see the Farinograph Handbook, AACC, 1960.
Illustration of farinogram
- Flour yield
- Wheat is cleaned, scoured and tempered overnight to optimum moisture as described by Dexter and Tipples (1987), Milling 180(7):16, 18-20. 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.
- Common wheat is milled on an Allis-Chalmers laboratory mill using the Grain Research Laboratory sifter flow as described by Black et al. (1980), Cereal Foods World 25:757-760. Flour yield is expressed as a percentage of cleaned wheat on a constant moisture basis. For Canada Western Red Spring (CWRS) wheat, flour yield also is expressed at a constant ash content of 0.50%, as described by Dexter and Tipples (1989), Milling 182(8):9-11.
- No. 1 CWRS - 13.5 composites are milled to straight grade and patent flours using a tandem Bühler laboratory mill as described by Martin and Dexter (1991), Association of Operative Millers - Bulletin April: 5855-5864 to allow direct comparison of the milling and baking properties of the current and previous year's crop. Sixty percent extraction patent flours are also used for noodle evaluation.
- Gluten index - semolina
- Durum semolina gluten index is determined using AACC Standard Method 38-12.02, following the procedure for whole meal.
- Grade colour
- Flour grade colour is determined using a Colour Grader Series IV (Satake UK, Stockport, UK) according to Flour Testing Panel Method No. 007/4 (Flour Milling and Baking Research Association 1991), and expressed in Satake International colour grade units. The lower the number, the brighter the colour.
- Hard vitreous kernels
- The percentage of hard vitreous kernels (HVK) is determined by examination of a 25-gram sample divided from a sieved 250 gram sample. The sample is analyzed for the natural translucency associated with hardness. Kernels are classed as HVK or non-vitreous as defined in the Canadian Grain Commission's Official Grain Grading Guide, Chapter 4, Wheat.
- Lean no time test bake method
- The lean no time (LNT) test baking method, as described by Dupuis and Fu (2016), J. Cereal Sci. submitted, is similar to the Canadian short process (CSP) baking test but eliminates the use of an oxidant and reduces the salt and shortening to 1% of flour weight (14% mb). The LNT method is more discriminating than the CSP method and robust enough to be adopted by other laboratories. Loaves are produced from 150 grams of flour. Loaf volume is reported on a 100-gram 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 baking 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 what has to date required the subjective evaluation of an experienced baker.
Illustration of loaf top ratio
Refer to the Method for Lean No Time Test Baking for a detailed description of the method used at the Grain Research Laboratory.
- Maltose value
- Maltose value is determined according to AACC Method 22-15.01.
- Moisture content - flour
- To determine the moisture content of flour, a 10-gram sample is heated for one hour in a semi-automatic Brabender oven at 130°C.
- 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 AACCI Method 44-15.02, following the procedure for the two-stage air-oven.
- Noodle colour
- Colour is determined on a raw noodle sheet using a Hunterlab Labscan II spectrocolorimeter using the CIE (1976) L*, a* and b* colour scale with a D65 illuminant.
- L* is a measure of brightness.
- a* indicates red-green chromacity. Positive values indicate increased redness.
- b* indicates yellow-blue chromacity. Positive values indicate increased yellowness.
- Noodle preparation
- Noodles are prepared following the method of Kruger et al (1994), Cereal Chemistry 71:177- 182. Yellow alkaline noodles are prepared with a 1% kansui reagent (9:1 sodium and potassium carbonates) at a 32% water absorption. White salted noodles are prepared using a 1% sodium chloride solution at a 30% water absorption level to maintain proper dough crumb and sheeting characteristics.
- Particle size index
- Particle size index (PSI) is a measure of the texture of a wheat kernel. AACC Method No. 55-30.01 is modified by using a UDY cyclone sample mill fitted with a feed rate regulator and a 1.0-millimetre screen. A 10-gram sample from 22 gram of ground, blended wheat is sieved over a U.S. Standard 200-mesh sieve for 10 minutes in a Ro-tap sieve shaker. The weight of throughs X 10 is recorded as the PSI.
- Protein content (N (nitrogen) x 5.7)
- Protein content (N (nitrogen) x 5.7) of the composite samples is determined by combustion nitrogen analysis (CNA). Samples are ground on a UDY cyclone sample mill fitted with a 1.0-millimetre screen. Sample size is 250-milligrams and samples are not dried before analysis. Protein content is calculated from total 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. Moisture content is determined by the AACC Method No. 44-15.02, following the procedure for one-stage air-oven. The method for Dumas CNA analysis is explained in Williams, Sobering, and Antoniszyn. 1998. Protein testing methods at the Canadian Grain Commission. In: Wheat Protein Symposium: proceedings; 1998 March 9-10; Saskatoon, Saskatchewan.
- Remix-to-peak baking test
- The remix-to-peak baking test is a modification of the remix baking test of Irvine and McMullan (1960), Cereal Chemistry 37:603-613, as described in detail by Kilborn and Tipples (1981), Cereal Foods World 26:624-628. Dough is mixed to peak consistency at the second mixing stage. Dough is mixed in a Swanson type 100-200 gram pin mixer (National Manufacturing Co., Lincoln NE) at 90 rpm. Loaves are produced from 200 grams of flour in baking pans with cross-sectional dimensions similar to Canadian commercial baking pans. Loaf volume is reported on a 100-gram flour basis.
Refer to the Method for the Remix Bake Method for a detailed description of the method used at the Grain Research Laboratory.
- Semolina colour
- Durum semolina colour is determined using a Minolta colorimeter model CR-410 with a D65 illuminant. Colour readings are expressed on the CIE (1976) colour space system for L* (lightness), a* (red-green) and b* (yellow-blue).
- Semolina dough sheet colour
- Semolina dough sheets are prepared as described by Fu et al. (2011), Cereal Chemistry 88:264-270. The colour of the dough sheet surface is measured at 0.5 and 24 hrs after sheeting with a Minolta colorimeter model CR-410 with a D65 illuminant. Colour readings are expressed on the CIE (1976) colour space system for L* (lightness), a* (red-green) and b* (yellow-blue).
- Semolina yield and milling yield of durum wheat
- Durum wheat is milled on a four stand Allis-Chalmers laboratory mill in conjunction with a laboratory purifier as described by Black (1966), Cereal Science Today 11:533-534, 542. The mill flow is described by Dexter et al. (1990), Cereal Chemistry 67:405-412. For the calculation of yield, semolina is defined as having less than 3% pass through a 149-micrometre 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 (SRC)
- Solvent retention capacity is determined using AACC Method 56-11.02 using deionized water and lactic acid (5% w/w) as the solvents.
- 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, then vacuum is applied to eliminate introduction of 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 the Canadian International Grains Institute.
- 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-centimetre 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. The basic principle for the firmness measurement was based on Oh, N.H. et al. (1983), Cereal Chemistry 60:433-438. Cooking time is fixed at 8 min for spaghetti samples with a diameter of about 1.70 mm. Cooked spaghetti is drained and immediately aligned on the base plate for cutting test without rinsing in cold water. A fixed compression depth of 4.9-millimetre is used (crosshead height calibrated to 5.0-millimetre). The crosshead speed is 1.0 mm/sec. Peak cutting force of five strands is reported.
- Spaghetti strand diameter
- Dry spaghetti diameter is the average of ten randomly chosen strands which are measured with a caliper. A 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 (trigger force 3 g) from the set distance.
- 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. The image is used to identify potential specks within the sample 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 the darkness (low, medium and high) as well as the size (small, medium and large) of the speck. Total, dark, and large specks are averages of at least three replicates and their numbers are expressed in 50 cm² of semolina sample surface.
- The sponge-and-dough baking test is based on a 4.5-hour fermentation, 70% sponge system as described by Kilborn and Preston (1981), Cereal Chemistry 58:198-201. Ascorbic acid is used as the oxidant at 40 ppm. Dough is mixed in a Swanson type 100-200gram pin mixer (National Manufacturing Co., Lincoln NE) at 116 rpm. Loaves are produced from 200 grams of flour in baking pans with cross-sectional dimensions similar to those of Canadian commercial baking pans. Loaf volume is reported on a 100-gram flour basis. Mixing energy is reported in watt-hours per kilogram (W-h/kg) of flour and watt-hours per kilogram 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.
- Starch damage
- Starch damage is determined using AACC Method 76-31.01 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
- Test weight is determined using the 0.5 litre 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 scale for weighing. The scale connects to a computer which calculates the test weight of the grain in kilograms per hectolitre (kg/hL) from grams weighed by the scale. If the computer interface is not available, test weight conversion charts are used.
- Test weight - harvest survey
- Test weight is determined using the Schopper chondrometer equipped with a 1 litre (1 L) container. The weight in grams of the measured litre of wheat is divided by 10. The result is reported in kilograms per hectolitre (kg/hL) without reference to the moisture content.
- Texture characteristics – Noodles
- Texture measurements are carried out using a computer-assisted Stable Micro Systems TA-XT2i Texture Analyser and represent the average of four replicate cookings in which each cook evaluated five sets of noodles. Characteristics are determined as per Oh, N.H. et al. (1983), Cereal Chemistry 60:433-438.
- Maximum cutting stress (MCS, g/mm2) reports the bite or firmness of the cooked noodle (g/mm2)
- Resistance to compression (RTC, %) correlates with the noodle's firmness and chewiness
- Recovery % correlates with the noodle's firmness and springiness.
- Weight per 1000 kernels
- Broken kernels and foreign material are handpicked from a sample to create a cleaned sample. The number of kernels in a 20-gram subsample of the cleaned sample is then counted using an electronic seed counter.
- Wet gluten content - flour
- ICC Standard Method No. 137/1 is followed using the Glutomatic System 2200 with 80-micrometre metal sieves.
- Wet gluten content - semolina
- Semolina wet gluten content is determined using AACC Standard Method 38-12.02, following the procedure for whole meal.
- Yellow pigment content – semolina
- Yellow pigment content of durum semolina is determined using a rapid extraction procedure as described by Fu et al (J. Cereal Sci. 2013, 57:560-566). Absorption is measured using a spectrophotometer and converted to yellow pigment concentration as specified by AACC International Method 14-50.01.
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