Tuesday, November 29, 2022

Overview of the 2021/22 season’s wheat crop quality survey

Estimated reading time: 7 minutes

  • The 2021/22 season’s commercial wheat crop, set at 2 285 000 tons, was the largest crop in 20 years.
  • The 335 representative crop survey samples received of the 2021/22 season were graded as follows: 22% as Super Grade, 19% as Grade 1, 14% as Grade 2, 14% as Grade 3, and 31% as COW.
  • The average hectolitre mass of 79,9kg/hℓ is 1kg/hℓ higher than the previous season.
  • The average falling number of the crop quality samples this season was 341 seconds.
  • The national whole wheat protein average decreased slightly from 12% in the previous season to 11,9% this season.
  • Mycotoxin analyses were performed on 40 wheat samples, randomly selected to represent different regions as well as grades.

The 2021/22 season’s commercial wheat crop, set at 2 285 000 tons, was the largest crop in 20 years and almost 8% higher than the previous season’s crop, which was the highest since the 2008/09 season. A total area of 523 500ha was utilised for wheat production during the 2021/22 season and the average yield was 4,36 tons per hectare (source: Crop Estimates Committee).

According to the latest bread wheat grading regulations published in Government Gazette No 42862 and detailed in Government Notice No R 1547 of 29 November 2019, the classes of wheat are Bread Wheat and Other Wheat. The grades for Bread Wheat are Super Grade, Grade 1, Grade 2, and Grade 3. No grades are determined for Class Other Wheat (COW).

Survey results

The 335 representative crop survey samples received of the 2021/22 season were graded as follows (Figure 1): 22% as Super Grade, 19% as Grade 1, 14% as Grade 2, 14% as Grade 3, and 31% as COW.

Of the 105 samples received that were downgraded to COW:

  • 28% had falling number values below 220 seconds.
  • 6% had hectolitre mass values below 76kg/hℓ.
  • 19% had screening levels higher than 3%.
  • 49% had other grain and unthreshed ear levels exceeding 1%.
  • 13% had total damaged kernel levels higher than 2%.
  • 4% had combined/collective deviation levels exceeding 5%.
  • 10% had field fungi levels higher than 2%.

Single samples reported protein contents lower than 9,5%, foreign matter, heat damaged kernel, insect-damaged kernel and sprouted kernel percentages exceeding the maximum permissible deviation, or the presence of poisonous seeds and an undesirable odour.

A total of 50% of the downgraded samples originated in the Western Cape, 29% in the Free State, and 21% in the irrigation areas. A total of 22% of wheat samples originating in the Free State was graded as Super Grade, whereas 39% of the wheat samples from the irrigation areas and 5% of wheat samples from the Western Cape
were graded as Super Grade.

Hectolitre mass

The average hectolitre mass of 79,9kg/hℓ is 1kg/hℓ higher than the previous season, but still 0,4kg/hℓ lower than the ten-year national average of 80,3kg/hℓ. A total of 18 samples (5%) had values below the 76kg/hℓ minimum level for Super Grade, Grade 1 and Grade 2 wheat – of these six samples originated in the Western Cape (winter rainfall area), nine in the Free State, two in North West and one in Gauteng. Regional averages ranged from 78,8kg/hℓ in the Free State, 79,2kg/hℓ in the Western Cape and 81,3kg/hℓ in the irrigation areas.

Falling number values

The average falling number of the crop quality samples this season was 341 seconds, which is lower than the 372 seconds of last season’s average and the ten-year weighted average value of 364 seconds. Of the samples analysed, 11% (37) had falling number values below 250 seconds – of these, 29 (almost 9%) were below 220 seconds and downgraded to COW as a result. These downgraded samples originated from the Free State (16 samples), KwaZulu-Natal (seven samples), North West (four samples) and Gauteng (two samples).

Falling number values this season ranged between 56 and 495 seconds. Last season 4% of the samples analysed as part of the survey was downgraded to COW due to a low falling number. All falling number values reported were corrected for the altitude at which the test was performed.

Protein content

The national whole wheat protein average decreased slightly from 12% in the previous season to 11,9% this season. The ten-year national average is 12,1%. The percentage samples from this crop survey with a protein content equal or higher than 12,5% (minimum protein content for Super Grade) was 37% (42 and 64%, respectively, during the last two seasons).

The irrigation areas reported the highest whole wheat protein average, namely 12,5%. The production regions in the winter rainfall area of the Western Cape averaged 11,1%, and the summer rainfall and irrigation areas of the Free State averaged 12,2%. Protein content is generally a function of the growing environment (soil and climatic conditions) as well as fertiliser application.

Flour protein content is on average 0,5 to 1,2% lower than that of wholewheat and averaged 10,9% this season, which is 0,3% lower than the previous season. The difference in the protein content between wholewheat and flour protein can be attributed to the removal of the bran and aleuron layer, as well as the germ during milling. The protein content is reported on a 12% moisture basis.

Screening and milling

The weighted average percentage screenings obtained with a 1,8mm slotted sieve was 1,2%, compared to the 1,63 and 1,92%, respectively, of the previous two seasons. The summer rainfall and irrigation areas reported the highest average percentage, namely 1,49%, and the irrigation areas the lowest at 0,76%. Of the 335 samples tested, 20 (6%) exceeded the 3% maximum permissible screenings level for Super Grade to Grade 3 (half of these samples originated in the Free State).

The 1 000-kernel mass, reported on a 13% moisture basis, increased from 38,2g last season to 40,3g this season. The 2019/20 season’s average was 35,6g. Averages over production areas varied from 39,7g in the summer rainfall and irrigation areas of the Free State, to 40,1g in the winter rainfall areas and 41g in the irrigation areas.

The mixogram peak time of flour milled on the Quadrumat Junior mill equalled the average 3,2 minutes of the 2020/21 season. The ten-year average is 2,9 minutes. The mixogram peak time of the flour milled on the Bühler MLU 202 mill was 2,9 minutes, which is also equal to the previous season. Mixing time is a measure of optimum dough development and thus also of protein quality.

All national, seasonal and regional averages provided in this report are weighted averages.

Mycotoxin contamination

The accredited multi-mycotoxin assessments included in the annual wheat crop quality survey for the past 11 seasons provide the most comprehensive overview of the multi-mycotoxin risk in commercial wheat produced and delivered to commercial grain storage companies in South Africa. Approximately 10 to 20% of the wheat crop samples were selected every season to proportionally represent all the production regions.

Read more about the agro-processing of wheat

Constant monitoring of mycotoxin occurrence is crucial as it is well documented that mycotoxin risk can vary significantly between production seasons and production regions. Application of good agricultural practices and storage conditions, and effective mycotoxin risk management programmes are essential elements in preventing the negative effects of mycotoxins. Continued research on the prevention and mitigation of mycotoxin contamination is also necessary.

The only proven way to determine whether grain, cereals, feed or food are contaminated is to obtain reliable testing data through analytical testing.

Mycotoxin analyses were performed on 40 wheat samples, randomly selected to represent different regions as well as grades. The absence of aflatoxin B1, B2, G1, G2, fumonisin B1, B2, B3, ochratoxin A, T2- toxin and HT-2 toxin in the wheat samples over the past 11 seasons were confirmed in the 2021/22 season. This is the second time that zearalenone residues were detected on a wheat crop sample; residues were also detected on a sample during the 2019/20 season.

The deoxynivalenol prevalence this season is the second highest of the 12 seasons for which accredited test results are available. A total of 35% of the samples tested positive for deoxynivalenol residues, compared to the 43% of the previous season. None of the positive residue levels measured this season exceeded the national maximum allowable level (2 000 μg/kg) for cereals intended for further processing. – Jolanda Nortjé, laboratory manager, The Southern African Grain Laboratory NPC

For more information, contact Jolanda Nortjé on 012 807 4019 or visit www.sagl.co.za.

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