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Desember 2015
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RELEVANT
The average development time was 5,3 minutes (5,2 minutes dur-
ing the previous season). The irrigation areas had the longest devel-
opment time of 6 minutes.
The stability is the time during which the top of the curve intercepts
a horizontal line through the centre of the curve. This gives an indica-
tion of the dough’s tolerance to mixing: The longer the stability, the
longer the mixing time that the dough can withstand. A dough with
a longer stability can also withstand a longer fermentation period.
The stability value of 8,3 minutes compared well with the 8 minutes
reported previously.
The mixing tolerance index value provides an indication of the ex-
tent to which breakdown of the dough occurs after reaching its op-
timum consistency. The higher the value, the more and the quicker
the breakdown of the dough occurs. There was no significant differ-
ence between the mixing tolerance indexes of the 2014/2015 (35 BU)
and the 2013/2014 (38 BU) seasons.
The Alveograph measures the resistance of the dough to stretching
and also how extensible the dough is. A sheet of dough of a given
thickness is prepared under specified conditions and expanded by
air pressure into a bubble until it ruptures. The pressure inside the
bubble is measured. The area under the curve gives an indication
of the dough strength. The average strength was 38,1 cm² (37,6 cm²
the previous season). The irrigation areas had the highest average
strength of 42,1 cm
2
and the Western Cape the lowest with 33,1 cm
2
.
The stability (P) is an indication of the resistance of the dough to
extension (force required to blow the bubble of dough) and aver-
aged 75 mm. The distensibility (L) corresponds with the maximum
volume of air that the bubble can withhold and provides an indica-
tion of the extensibility of the dough. This value averaged 133 mm
and was longer than in previous seasons.
By dividing the P-value by the L-value, the P/L ratio is obtained, thus
providing an approximate indication of the shape of the curve that
combines stability and extensibility (viscoelastic properties). The av-
erage value this season was 0,59.
The Extensograph measures the resistance and extensibility of a ful-
ly mixed, relaxed flour-water dough, by measuring the force required
to stretch the dough with a hook until it breaks. For bread baking
purposes, a strong dough with good extensibility, good resistance, a
large area and a well-balanced height to length ratio is needed.
The strength gives an indication of the total force (work) needed to
stretch the dough and is represented by the area under the curve.
The average strength was 97 cm² (92 cm² previous season). The
maximum height/resistance gives an indication of the dough’s re-
sistance to stretching.
Compared to the previous season (358 BU in 2014/2015 and 341 BU
in 2013/2014), the maximum height did not increase significantly.
The extensibility indicates the stretchability of the dough. The ex-
tensibility value of the current season were equal (196 mm) to the
previous season (194 mm).
The 100 g loaves baked using the straight-dough optimised bread
making method, received an average evaluation rated as “excellent”.
The basis for this evaluation refers to the relationship between the
protein content and the bread volume.
Mycotoxins
Mycotoxins, secondary metabolites produces by field and/or stor-
age fungi on agricultural commodities, is foremost a food safety is-
sue, but the occurrence of these fungi can also lead to a reduction in
the quality of the commodity. Most mycotoxins are chemically stable
and tend to survive storage and processing even when cooked at
quite high temperatures as is reached during bread baking. Environ-
mental factors, such as temperature, humidity, soil and storage con-
ditions influence toxin production.
40 randomly selected samples, representing different regions as
well as classes and grades, were tested by means of a SANAS ISO/
IEC 17025 accredited multi-mycotoxin screening method using
UPLC-MS/MS. The samples were tested for Aflatoxin G1; B1; G2;
B2, Fumonisin B1; B2; B3, Deoxynivalenol, 15-ADON, HT2 - Toxin,
T-2 Toxin, Zearalenone and Ochtratoxin A.
Five samples tested positive for deoxynivalenol (DON) residues. The
average value of the five positive results was 229 μg/kg (ppb) and
the highest value measured 361 μg/kg, which is still well below inter-
national maximum residue levels.
Wheat imported during the current
marketing season
According to SAGIS figures (27 September 2014 to 11 September
2015) 1 691 761 tons of wheat have been imported into South Africa
thus far this season, compared to the 1 668 412 tons the previous
season.
Wheat has been imported from Argentina, Australia, Canada,
Germany, Latvia, Lithuania, Poland, the Russian Federation, the
Ukraine and the United States. Imports from Germany and the
Russian Federation comprised more than half (21% and 33% respec-
tively) of the total figure.
The import quality results are published at the end of each produc-
tion and marketing season and are available on the SAGL website
(
www.sagl.co.za ).
With gratitude to the Winter Cereal Trust for financial support of this annual survey
and to Agbiz Grain members and milling companies for providing the crop samples.
An overview of the
local wheat crop quality
Grain SA
/
Sasol Chemicals (Fertiliser) photo competition