Hagberg fall time
The Hagberg Falling Number (HFN), or Hagberg falling number index or falling number according to Hagberg-Perten, is an internationally standardized method (ICC 107/1, ISO 3093, AACC 56-81B), widely used to determine damage caused to baking cereal grains, such as wheat or rye, by premature germination. This method allows detecting within minutes at silo intake the grains damaged by climatic conditions or pre-harvest sprouting.
Principle of the Hagberg Falling Number
The analysis of the Hagberg Falling Number (HFN) quantifies the enzymatic activity of the grains.
For this, a weight is "dropped" into a mixture of flour and water: the HFN measures the time in seconds that this weight takes to reach the bottom. If the time is long, that is a Falling Number between 240 seconds and 380 seconds, there is no enzymatic activity.
Conversely, if the weight falls very quickly, less than 170 seconds, the enzymatic activity is high, the gluten is degraded and the wheat is no longer suitable for baking.
In commercial transactions, the HFN is taken into account to classify batches (commercial threshold of 220 s for a "Superior" batch).
Precipitation degrades the HFN faster when varieties are sensitive. Varietal resistance is studied by Arvalis post-registration, and not all varieties have a rating.
Note: Mixing batches with different Falling Numbers will not yield an average final Falling Number.
The value of the mixture will be closer to the value of the batch with the lower HFN. It is therefore important to properly identify at-risk batches and not necessarily mix them with unaffected batches, which risks degrading the entire lot. The most sensitive varieties must be managed specifically at harvest.
Description of the method
The falling number method is not complicated but requires an apparatus that complies with international standards. Such an apparatus consists of a water bath, a test tube, a stirring rod, and a stirring device. The test was initially performed manually; test instrumentation is now generally automated.
To analyze a grain sample, it must first be milled. A flour sample can be analyzed as is. The sample is placed in the test tube. Distilled water is added and the tube is shaken vigorously to obtain a homogeneous mixture. The tube is then placed in the boiling water bath and the operator begins stirring the sample. Simultaneously, the starch begins to gelatinize and the suspension becomes more viscous. The mixing ensures that gelatinization is homogeneous in the suspension, which is crucial for consistent test results. An additional effect of the high temperature is that the alpha-amylase enzyme contained in the grain begins to break down starch into glucose and maltose, thus reducing the viscosity of the suspension. Starch degradation is directly proportional to alpha-amylase activity, meaning the higher the alpha-amylase activity, the lower the viscosity.
After 60 seconds of mixing, the stirrer is released from the top of the test tube and the operator measures the time needed for the stirrer to reach the bottom. This time, measured in seconds, is the "falling number." When the stirrer has fallen, its speed, and thus the time it takes to descend, is determined by the viscosity of the suspension. In other words, the more sprouted the grain, the higher the alpha-amylase activity, and the lower the viscosity of the suspension. The lower the viscosity of the suspension, the faster the stirrer falls to the bottom. That is why a higher number of sprouted grains results in a lower falling number, as it is the time needed for the stirrer to fall to the bottom.
