Properties of flours are obtained with a Brabender farinograph. This instrument allows classifying the flour tested by measuring not only its gluten strength but also the hydrating power of the flour. Absorption of water by the flour is mainly attributable to the state of the starch following the grinding, which depends on the hardness of the grain used to produce the flour. However, the type of protein is another factor which can impact this measurement. Therefore, the farinograph is really important to classify the flour according to its specific characteristics.
The farinograph is a tool that is used exclusively with flours. The flour need to be prepared with a grinding process which allows obtaining the consistency of a dough. The main relevance of this process is to calculate the water absorption capacity of flours which allows reaching the desired consistency (for example, a consistency of 500 farinographic units). This capacity is routinely named hydration rate and is expressed in % of mass. Therefore, 60% means that 1 kg of flour can absorb 600 ml of water. Generally, bread dough (baguette style) will hydrate 10 to 15% over the hydration rate determined by the farinograph. For example, a flour with an hydration rate of 60% as measured with the farinograph should hydrate at 70 to 75% when preparing the baguette dough.
The very sensitive probes of the farinograph measure the force used by the dough kneader on the dough and displays the results on a graph. However, the farinograph dough kneader is much more violent than a usual dough kneader. Its 63 rotations per minute generate a greater stress on the dough than a baker’s dough kneader. Therefore, the development time and stability measured by the farinograph are important information to consider, but should not be reproduced.
The graph drawn by the farinograph allows the measurement of:
- the development time or the time required to form the dough;
- the stability or the time during which the dough will preserve its initial consistency;
- the weakening point or the point (in farinographic units) at which the dough will lose its consistency after a definite period of kneading.
The absorption capacity measured by the farinograph is expressed in pourcentage and corresponds to the quantity of water that needs to be added to the flour to reach the desired consistency.
The farinograph also allows measuring the water absorption capacity of flours. Bakers usually prefer flours with a high water absorption capacity because they have higher yielding . In order to measure this variable, water is added to the flour until it reaches the desired consistency in a given period of time. The malleability of flours depends mainly on the variety of grain used, but also on the protein content.
The development time of dough (rounded to 0.25 minutes) corresponds to the time needed to reach the peak on the graph, which represents the kneading time needed to allow maximum development of the gluten.
WEAKENING POINT(OR TOLERANCE INDEX–MTI)
The weakening point constitutes the difference, expressed in Brabender units, between the peak on the graph when the optimal development time is reached and the peak on the graph after 5 minutes. Ideally, bread flour should have a MTI under 30 units.
The stability corresponds to the time (rounded to 0.1 minute) between the moment when the peak of the graph rises above the line of 500 Brabender units (arriving time) and the moment when the peak of the graph reaches again this line (starting time). A long stability means that the dough can be kneaded longer before it loses its properties and that a longer period of fermentation will not alter the dough.
The protein content constitutes an important characteristic to consider for further evaluation of flours quality. However, the calculation of the crude protein content does not give any indication about the quality of proteins. The measurement is made according to the nitrogen content and does not consider the different amino acids that could be of particular interest in bakery (gliadin and glutamine).
Therefore, the protein content does not reflect the quality of the gluten. Moreover, heat and dryness stresses elevate the protein content of the flour but reduce its quality for bread making. Proteins are mainly located under the bran and this section is also the richest in minerals. Grinding the grains on cylinders removes a large part of the bran and most of the proteins. Therefore, it is normal that stone-ground flours, produced with the same wheat, will have a higher protein content but a lower stability compared to flours ground on cylinders.
FALLING NUMBER (HAGBERD)
The Hagberg falling number allows measuring the amylase activity of flours. This value is usually higher with sprouted grains. Therefore, it will be possible to correct a low falling number by adding malt or fungal amylase. On the contrary, wheat with an excessively high falling number will be directed toward animal feeding. The high amylase activity of those wheat leads to degradation of the starch which is needed for fermentation in bread making.
The falling number also evaluates the consistency of a starch gel formed with flour and water by measuring the time required by a penetrometer to cross a specific distance in the gel. Sprouting of wheat and adding malt to the flour can reduce this value under the minimal threshold of 60 because amylases formed by the grain during sprouting liquefy the starch gel.
Generally, flours should have a Hagberg falling number between 220 and 280 to obtain best fermentation intensity. The falling number is used to evaluate the degree of damages caused by sprouting in Canadian wheat. The alpha-amylase is an enzyme found in damaged wheat. When sprouting occurs, the concentration of this enzyme rises considerably. Therefore, a high falling number indicates that the wheat is healthy and is suitable for cooking processes. For a quick fermentation, it is important to correct the falling number by adding ± 20 to 50 malted barley for each 20 kg of flours, depending on the malted barley.