Kvalitet i brödvete
The quality of bread wheat is a large subject to study. The quality rests on two legs. The first one is the inheritance of specific characters, which can be influenced through plant breeding and type of cultivar. The other one is the environmental influences, such as crop rotation, nutrition, harvest and storage. The latter factors are possibly to affect through cultivation practices, while other factors are not possible to influence on for the grower, such as seasonal changes of weather and the soil content.
The mills have some listed quality criteria, which have to be fulfilled by growers before wheat of bread-quality can be transported to the mills. These quality criteria are mainly connected to the four big quality aspects, protein concentration, falling number, thousand-kernel weight and the volume-weight. Also freedom from diseases and traces of harmful elements for humans are important aspects of bread wheat quality.
One of the most important quality aspects in bread wheat is the protein concentration. When studying the built-up and function of protein, and their behaviour during the baking-process, knowledge and understanding about protein network formation is collected. By this type of investigations, it is possible to evaluate how to manage reaching the right protein-concentration for the bread-making process, both through plant breeding, and during growing of the wheat. Thus, the plant breeding plays a big role for the quality work.
The falling number, is a measurement of how far the break-down of starch has gone in the kernel through enzymatic activities, mainly amylases. The falling number depends much on the cultivar, and by choosing a cultivar with a stable falling number, there is better opportunities to manage the falling number in the field. The year plays a big role, as well as the weather during harvest. Sometimes for example, it can be necessary to harvest, although the moisture content in the kernel is a little too high in order to manage to keep a high falling number. In such cases, it may be necessary to accept higher costs for drying the seeds.
The thousand-kernel weight and the volume-weight are similarly to the other quality parameters, strongly connected to the wheat-cultivar. The thousand-kernel weight is relatively independent of the growing environment, although good growing conditions are advantageous, such as sparsely sowing (giving less competition for nutrition among the plants). Freedom from diseases and pathogens, no lying crops and enough water supply are other important aspects. The length of the grain development and protein built-up time is also important.
Cadmium is one of the most serious heavy metals in the crop grains, because of the relatively high amounts taken-up. Cadmium is reaching the soil both together with the fertilizer, which contains cadmium, but there are also some natural content of cadmium in the soil. This is particularly true in some parts of Sweden. For the cadmium content in the soil, the content of clay? and humus plays a role. High content of clay ? and humus in the soil can increase the cadmium amount. Even the content of alum schist in the ground can have a great effect on the wheat grain
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cadmium uptake. Under certain conditions the soil can more easily absorb metals. Some atmospheric deposition of cadmium is also a problem.
The uptake of cadmium takes place through different chemical processes in the growing plant. Weather parameters, such as light, precipitation and temperature plays a role for the cadmium uptake. Still, there is relatively limited knowledge about processes contributing to the cadmium uptake and transport in the plant. Through plant breeding and genetical control, it is possible to reduce the uptake of cadmium to the kernels. Also, the growers can reduce the cadmium content in their crops. Using fertilizer free of cadmium is one of the most important ways.