Prepared by Rex Krause with introduction by Gil Hollamby.
Wheat flour when mixed into dough has unique properties enabling it to be prepared into numerous products for human consumption. This versatility has made wheat the staple food in many countries. South Australia became an exporter of wheat very early in its farming history and today around 80% of the wheat harvested in South Australia is exported to the rest of the world often to countries which eat it as products very different to the familiar loaf of bread to which we are accustomed.
In its broadest sense wheat quality can be defined as the price that an end user is willing to pay. As mentioned wheat has many end uses, each requiring different quality specifications, so that, for example, a load of wheat which is good for bread baking is of poor quality for biscuit making and vice versa.
There are three major aspects to wheat quality when it is sold:
- Physical quality. Freedom from harvest damage, weather damage, unmillable material, diseases, weed seeds and other crop grains. Low moisture content needed for safe storage.
- Millability, the amount of flour that can be extracted from the grain. Plump grain of high test weight of an approved variety ensures the best flour extraction.
- Chemical composition. Protein concentration and the actual protein composition and starch composition affect the physico-chemical properties of the dough made from the flour and hence the products that can be made from it.
The physical quality and protein concentration are largely in the hands of the grower, the millability is affected by climate and the genetics of the variety, whereas the chemical composition is mostly determined by the genetics of the variety and thus relies on plant breeding and selection.
Other aspects of wheat quality can be so detrimental to quality that while the breeder must test for them, varieties which have these faults are not released to farmers, faults such as poor millability, high late maturing αamylase and poor flour colour. Because most wheat from South Australia is used for human consumption little attention is placed on its actual nutritional quality such as calorific energy value or the amino acid composition of its proteins.
To meet the specifications required by consumers wheat on delivery to a buyer is segregated into different grades according to the results of a set of tests. In 2009 there were no less than 15 separate segregations in Australia based on variety, moisture content, test weight, protein concentration, screenings and freedom from foreign and unmillable material.
It has not always been like this. Early in the colony’s history wheat was wheat and segregation into different grades has evolved over time as wheat growing areas and markets have expanded and as consumers have become more sophisticated in their requirements.