Flour is the basis of all bakery goods. It is not surprising that the quality of flour is driving the quality of the bakery products. For quality control and quality improvement it is therefore important to know the flour quality.
Gluten and starch quantity and quality
Gluten and starch are the main components of wheat flour. The quantity and quality of both components are primordial for the flour quality and the quality of the bakery products made from it. The starch content in flour varies little (68-76%). In starch quality there is much more variation, mainly due to harvest and growing conditions. The starch quality can be monitored with various starch pasting methodologies (Rapid Visco Analyser, Amylograph, Mixolab).
In contrast to starch, the protein quantity in flour is highly variable: 8-16%. The protein content is relatively easy to determine by chemical protein analyses or with Near Infrared techniques. The main component of the protein, the gluten, is largely responsible for gas-holding and visco-elastic properties of the dough. These properties are determined by the glutenin proteins, that form a large, 3-dimensional network. The size of this network is key for quality, as it determines the mixing and proofing properties of the dough, its gas retention properties and the final bread volume and crumb structure.
For example the larger this network in the flour, the longer the dough needs to be mixed to its optimum (Figure 1). Only after this optimum bread improvers will have a maximum beneficial effect. If the dough is mixed well beyond this optimum the network is irreversibly degraded and will not recover during proofing. The dough will be sticky and this causes enormous problems during the First proofing step.
Figure 1: Effect of mixing time (min) on the content of the glutenenin network (glutenin macropolymer) of 3 different type of flours (directly after mixing: solid line; after 45 min resting: dotted line). The optimum mixing times are 2, 5 and 6 min, respectively.
Measuring the gluten quality of flour
There are several laboratory methods to determine the size of the glutenin. These methods require a lot of different equipment, a lot of labour and require quite some experience. They are also not fast. Therefore the European Bakery Innovation Centre developed a simple method using a Brabender Farinograph or a Chopin Mixolab to determine the size of the glutenin network. First, the water absorption of the flour to obtain the optimum consistency of the dough is established.
With this water absorption, the test will be performed using flour with 5% addition of the EBIC Flour Protein Quality Kit (Figure 2). With the kit the curve shows a marked increase with coincides with the optimum mixing time of the flour. This point is called the EBIC Flour Protein Quality Index (EBIC FPQI). The higher this index, the longer mixing time is required to optimally develop the dough. For normal bread flours the EBIC FPQI varies between 9 and 11 min when measured in the Farinograph. Extremely strong flours may go up to 16 min and will be difficult to develop without dough relaxers.
Figure 2: Measuring the flour protein quality with the EBIC Flour Protein Quality Kit (right) and without (left) in the Farinograph (top) or Mixolab (bottom). The red arrows indicate the EBIC Flour Protein Quality Index.
Protein quality and bread making quality
Using the EBIC Flour Protein Quality Kit, the quality of the flour can be determined and differences between harvest years established. A good example is shown in Figure 3:
Figure 3: Comparisons of the flour qualities of two harvest years for two similar flours used in The Netherlands (NL) and in the UK. Flours of the same country had equal protein content. The numbers indicate the EBIC Flour Protein Quality Index (min).
One can observe clear differences in bread making quality between the two harvest years (and between the origins). The poor bread making quality corresponds to the lower EBIC Flour Protein Quality Index. This indicates that the EBIC Flour Protein Quality Kit is a simple and powerful tool to establish the gluten quality.
For more information:
Need more information? Please contact us at EBIC@Sonneveld.com. Click the following link to order the EBIC Flour Protein Quality Kit.
