Factors affecting FN® results

A number of factors can affect Falling Number® results. The list below is not a complete list, but mentions the most important ones that operators can influence. A more complete list can be downloaded here.

Sample size

A representative sample must be obtained in order to assure accuracy. Through experimentation and statistical confirmation, the sample size has been to be determined to be 300 g. This is extremely important since the alpha-amylase activity of one sprouted kernel may be 100 times greater than that of an unsprouted kernel.

Correct grinding

It's critical to obtain a standardized particle size for grain samples. In other words the samples must be ground the same. The FN method is based on the rapid gelatinization of starch. This process is greatly influenced by the particle size of the meal and it's critical the correct grinder is used - LM 120 and LM 3100 are approved.

Moisture content

The moisture content of a sample will dictate how much sample is to be used for the test. The sample weight is corrected to the appropriate moisture level. The AACC and ICC correct to 14% while the ISO currently corrects to 15%. The moisture must be measured after grinding since moisture loss can occur during the grinding process. A table is available to calculate the correct sample amount depending on moisture content.

Approved, clean and dry tubes and stirrers

The Falling Number® viscometer tube has very specific dimensions with tight limits, and if these dimensions are not following the specifications, this may lead to faulty results and even breakage when used in the test. Also the stirrer must have correct dimensions and weight and be free from defect. The viscometer tubes, stirrers and stoppers must be clean and dry, for obvious reasons. Since soaps are surfactants and may react with the sample matrix, we strongly recommend cleaning with only water and no detergents.

Properly mixed sample

The sample must be mixed well, preferably using the Shakematic, and the bottom of the stopper should be wiped into the tube after mixing. As with all types of measurements, proper analytical lab techniques must be observed.