Quality
Inputs/Production
An overview of the local wheat crop
quality for the 2012/2013 season
JOLANDA NORTJÉ, MANAGER LABORATORY,
SOUTHERN AFRICAN GRAIN LABORATORY
During the harvesting season, a representative
sample of each delivery of wheat was taken
according to the prescribed wheat grading
regulation. Composite samples per grade and
class per silo bin at each silo was gathered,
divided and a 3 kg sub-sample sent to the
Southern African Grain Laboratory (SAGL) for
the annual wheat crop quality survey.
SAGL analysed 337 samples to proportionally
represent the production of wheat in all the
different production regions.
Summary
The final calculated wheat production figure
of 1 870 000 tons for the 2012/2013 season
was 7% lower than the previous season’s
2 005 000 tons. The ten year production average
is 1 854 728 tons (this is for the 2003/2004 to
2012/2013 seasons).
A total area of 511 200 hectares was utilised for
wheat production. The average yield increased
from 3,32 t/ha in the previous season to
3,66 t/ha this season. (Figures obtained from
the Crop Estimates Committee).
South Africa’s average hectolitre mass was
81,3 kg/hl, slightly higher than the 80,7 kg/hl
of the 2011/2012 season and ranged from
79,9 kg/hl in the summer rainfall area to
82,1 kg/hl in the irrigation areas.
In total only 18 samples reported hectolitre
masses below 77 kg/hl (in other words not
Grade 1). Eleven of these samples were from
the Free State, four from Limpopo, two from
the Rûens region and one from the Swartland.
An average of 11,4% whole wheat protein
average was achieved, compared to the 11,8%
of the previous season and the ten year average
of 12%. The winter rainfall areas had the lowest
average whole wheat protein content of 10,8%.
The summer rainfall area of the Free State’s
average protein content was almost 1% higher
at 11,7%.
The rest of the production areas averaged the
highest protein content of 12,1%. Although the
South African average whole wheat protein
content decreased by 0,4% to 11,4% compared
to the previous season, the flour protein
content was slightly (0,1%) higher than the
previous season.
This season’s average falling number was 360
seconds. Only 16 of the samples analysed
gave falling number values below 250 seconds
of which five were below 220 seconds and
another five below 200 seconds. Of the
16 samples, seven were from the Free State
production regions and nine from the Rûens.
B1 graded samples’ percentage in this sur-
vey, decreased significantly from 41% the
previous season to 22% this season; the main
contributing factor being the lower protein
contents observed in most of the production
regions compared to the previous season.
The percentage of samples that has protein
contents higher than 12%, decreased from
46,2% to 30,5%. The number of samples
downgraded to utility grade, increased from
5,8% to 17,8%. The majority of the samples
downgraded, was as a result of the percentages
other grain and unthreshed ears (24 samples)
and screenings (15 samples), exceeding the
maximum allowable levels of grades B1 to B4.
Where thousand kernel mass is concerned,
the weighted average of 40,2 g was 2,2 g
higher than the previous season. The weighted
average screenings (1,8 mm sieve) of 1,46%
was slightly lower than the 1,56% in the
2011/2012 season.
The weighted mixogram peak time on flour
from the Quadromat mill averaged 2,9 minutes,
similar to the ten year average and the previous
season (3 minutes). Flour from the Bühler
mill’s weighted mixogram peak time, was
2,8 minutes.
Rapic Visco Analyser (RVA) analyses were
performed on the crop samples for the first
time this season. The analyses was performed
on the Quadromat milled flour. The average
peak viscosity of the 105 samples analysed was
2 393 centipoise (cP), the minimum viscosity
1 834 cP and the final viscosity 2 775 cP. Results
are reported on a 14% moisture basis.
A weighted average Bühler extraction of 73,2%
was measured, almost 1% lower than last
season. The average Kent Jones colour this
season was -2,9 KJ and the previous season
-2,8 KJ. This is also the first season that dry
colour determinations by means of a Konica
Minolta CM-5 spectrophotometer were per-
formed. The average CIE L*a*b* values were
L* 93,85 (93,14 - 94,39), a* 0,41 (0,26 - 0,54) and
b* 9,92 (8,65 - 11,35) (ranges in brackets).
The wet gluten (14% mb) averaged 29% and
the dry gluten, also on a 14% moisture basis,
10%. The average gluten index value was
83, ranging from 44 to 97. The wet and dry
gluten results compared closely to that of the
previous season.
The farinogram had a weighted average water
absorption of 60,8% (61,3% the previous
season) and a weighted average development
time of 5,1 minutes (4,1 minutes previous
season). The weighted average alveogram
strength was 36,7 cm² and the weighted
average P/L value 0,96 (35 cm² and 0,89 the
previous season). The weighted average
extensogram strength was 84 cm² (90 cm²
previous season).
Using the 100 g straight-dough optimised
bread making method, which refers to the
relationship between the protein content and
the bread volume, the loaves baked were
evaluated and received an “Excellent” score.
The overall flour and dough quality were good
and compared well with the previous three
seasons.
Mycotoxins
40 samples (representing different regions
as well as different classes and grades) were
selected randomly for mycotoxin analyses.
A multi-mycotoxin screening method using
UPLC-MS/MS was used for the analyses.
Ten of the samples tested positive for
Deoxynivalenol with levels higher than the
limit of quantification (100 μg/kg), averaging
187 μg/kg. Al ten positive values were well
below the maximum allowable residue limits
specified by the European Union.
For more information regarding the detailed
quality results of the 2012/2013 as well as
previous seasons, please visit the SAGL web-
site at
and click on
Wheat and
Crop Quality
. Wheat crop quality reports can
also be downloaded in a PDF format.
51
October 2013
With gratitude to the Winter Cereal Trust for financial support in conducting this survey
as well as the Grain Silo Industry and milling companies for providing representative
samples of the South African wheat crop.
