Flour testing – assessing the quality of the flour and dough through tests such as the Hagberg Falling Number, Brabender farinograph, and the Brabender extensograph.
You may also be interested in
Having produced the flour, one of the key elements for the test baking processors to follow is to understand the characteristics of that flour to ensure that we can truly understand its quality and understand the impact that this has on the standard test baking process.
The Hagberg falling number test relies on a fixed proportion of flour or ground wheats, mixing that with water, heating it up to form a starch gel and then measuring the time it takes for a plunger of fixed width to fall through that gel.
Typically flour specifications look for falling numbers of over 250 seconds which indicates that the level of alpha-amylase is suitable for the baking processes that we use in the UK.
To understand the sort of dough that is produced for a given level of flour and, the level of water addition that that flour will require to form a dough that can be processed effectively, within the bakery context there are a number of ways of measuring dough rheology, the key parameter of interest.
One that is used very regularly is the Brabender farinograph, within this a fixed amount of flour has water added then a mixing process is then commenced. The way in which the water is absorbed by the flour to form a dough is very characteristic for each type of flour and is important in defining how the bakery process needs to be managed effectively. The level of water addition is established by iterative tests to allow the dough to come to a fixed consistency as seen on a chart recorder. The fixed consistency, as defined, indicates the resistance that the dough has to mixing and the amount of water that it takes to get to that point which is specific for a given wheat or flour.
The consistency or rheology of a dough is of critical importance to its ultimate baking potential. Looking at the rheology during mixing is conducted using a farinograph, but to understand the dough rheology and the subsequent stages of the bakery process we use a Brabender extensograph. Within this, pieces of dough are moulded into bowls, they are then moulded further into a sausage shape and that shape is then allowed to rest for a fixed period of time prior to further rheological analysis. The test gives information about how the dough will function during the melding processes in baking and it also gives a very good understanding of the basic quality of the flour and, therefore, is a critical test in understanding differences between different varieties of wheat and clearly the flour is milled from those different varieties.
Once the dough has been rested for the required time it is then placed in a cradle which allows it to be stretched and this stretching process relates quite well to the changes that occur during proving and baking of dough, particularly the extension that occurs within individual parts of the dough as a result of the action of yeast, the gas production that occurs as a result of this yeast action and the overall increase in volume of the dough piece. The dough in the extensograph is stretched until the point at which it breaks and the resultant trace gives clear indication of the flour properties and indeed the way in which that flour might bake.