Quality
Inputs/Production
How does the quality of imported
wheat compare with the quality
of local wheat?
JOLANDA NORTJÉ, MANAGER LABORATORY, SOUTHERN AFRICAN GRAIN
LABORATORY
Comparison data for nine seasons are available since the first import
quality survey was performed during the 2003/2004 wheat production
season. From this data it is clear that South African wheat compares very
well with what is on offer in the rest of the world and in most cases, local
wheat quality exceeds that of other countries with regards to the quality
required by our local bread baking processes.
Most of the wheat imported to South Africa is blended with local wheat
to obtain a certain milling and baking quality as per individual company
specifications. However, towards the end of the production season it may
become necessary for milling companies to mill wheat blends consisting
only of imported wheat.
Milling companies will blend higher and lower quality wheat to obtain the
most cost effective grist formulation that conforms to a specific quality.
The main objective is to supply the most constant quality of flour to their
customers (bakers) as possible, as in the end, consistency is one of the
most important quality parameters.
Detailed import quality results per season, per country of import, are
available on the SAGL’s website at
(click on
Wheat
and
Import Projects
). Please take note that according to the South African
grading regulations, Regulation 4 Standards for classes, Sub paragraph
(2), a consignment shall be classified as Bread Wheat if – (a) “the wheat
in the consignment consists of at least 95% (m/m) of one or more of the
bread wheat cultivars specified in the cultivar list;” all imported wheat
should be graded as Class Other Wheat. However, for comparison
purposes, the wheat is graded by SAGL as if of local origin.
See
Table 1
for a summary of the quality data of wheat imported during
the 2011/2012 season compared with the quality of the 2011/2012 local
crop. Please also take note of the number of samples analysed when
comparing these results, the higher the number of samples, the more
reliable the average result will be.
Australian and Canadian wheat had the highest hectolitre mass results,
indicating a potential for a good flour extraction rate. On average only
the German sample did not test the minimum hectolitre mass required
for Grade 1, namely 77 kg/hl. Screenings represent all material that
passes through a standard sieve (1,8 mm), with 3% being the maximum
allowed for grades 1 to 3 according to South African grading regulations.
High percentage screenings result in higher losses due to the removal
of unmillable material. Romania and Russia had the highest levels of
screenings.
The ability of wheat flour to produce dough with good gas-holding
capability is attributable to the gluten fraction of the wheat protein that
imparts the elasticity and extensibility characteristics to the dough.
Good quality gluten is capable of producing a loaf of bread with a high
volume and good crumb texture. Canadian wheat had the highest protein
content, which in turn resulted in the highest gluten content. South
African, Romanian and Australian wheat also showed good wet gluten
contents.
However, when evaluating gluten content, the protein content should
also be taken into account. It then becomes evident that the South African
wheat gluten/protein quality is better than that of Romania, also seen
when comparing the farinogram, alveogram and extensogram results.
The difference between the wet and dry gluten contents, is an indication
of the water-holding capacity of the gluten proteins. High water-holding
capacity is considered good quality for bread baking purposes. Canadian
wheat has the highest capacity, followed by South Africa and Romania,
with Ukrainian and Uruguayan wheat having the poorest gluten quality,
closely followed by Germany, USA and Russia.
In general, bakers prefer flour with higher water absorption, on average
61% to 63% for white bread flour, as this result in higher dough yields.
Longer development times of 3,5 minutes to 6 minutes and stabilities of
8 minutes to 12 minutes will also be an indication of good baking quality,
which is associated with better protein quality.
