The falling number (FN), also known as the Hagberg number, is a globally standardized test (ICC 107/1, ISO 3093-2004) widely used to detect sprout damage in grains like wheat and rye. Sprouting, caused by damp conditions during crop maturation, triggers production of the starch-degrading enzyme alpha-amylase, which affects grain quality for bread making. Even a small number of sprouted kernels can significantly increase amylase activity, reducing flour performance. Since its early 1960s introduction, the FN test has become the industry standard for measuring alpha-amylase in wheat, durum wheat, triticale, rye, barley, and their milled products, enabling rapid quality assessment at grain silo intake points.
History
The falling number method was developed at the end of the 1950s by Sven Hagberg and his co-worker Harald Perten, both at the Cereal Laboratory of the Swedish Institute for the Crafts and Industries.
Method description
The falling number method is uncomplicated, but requires an apparatus which follows the international standards. Such an apparatus consists of a water bath, a test tube, a stirring rod, and a stirring device. The test was performed manually when first employed, test instrumentation today is mostly automated.
- Flour samples can be analyzed directly. Grain samples are ground to a powder.
- The sample is put into the test tube, distilled water is added, and the tube is shaken vigorously to achieve a homogeneous mix
- The tube is placed in the boiling water bath, and the sample is stirred. The starch begins to gelatinize and the slurry becomes more viscous. The mixing ensures the gelatinization is homogeneous in the slurry, 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 the starch down into glucose and maltose, thereby reducing the viscosity of the slurry. The amount of starch break-down is directly proportionate to the alpha-amylase activity, meaning that the higher the activity of the alpha-amylase, the lower the viscosity will be.
- After 60 seconds of mixing, the stirrer is dropped from the top of the test tube, and the time it takes to reach the bottom is measured. That time, measured in seconds, is the falling number.
The speed at which the stirrer falls is determined by the viscosity of the slurry. Samples with more sprouted grain have greater alpha-amylase activity, which will result in a less viscous slurry and a smaller falling number. Samples with less alpha-amylase activity will be more viscous and have a larger falling number.
- ISO 3093:2009 – Wheat, rye and their flours, durum wheat and durum wheat semolina – Determination of the falling number according to Hagberg-Perten. ISO. December 2009. Retrieved 23 March 2024.
- Stevens, DB; Baldwin, JH; Stevens, BJ; Stewart, BA; Hook, SCW; Morgan, AG; Vaidyanathan, LV; Jones, LG; Gale, MD; Flintham, JE; Duffus, Carol M (August 1988), Research Review No. 2: Hagberg falling number and breadmaking quality (PDF), Hamlyn House, Highgate Hill, London N19 5PR: Home-Grown Cereals Authority (HGCA), archived from the original (PDF) on 23 March 2024, retrieved 23 March 2024{{citation}}: CS1 maint: location (link)
- Hagberg, Sven (1960). "A Rapid Method for Determining Alpha-Amylase Activity" (PDF). Cereal Chemistry. 37: 218–222. Retrieved 24 March 2024. Original paper describing the method, manuscript received 9 December 1958, published 1960.
- Hagberg, Sven (1961). "Note on a Simplified Rapid Method for Determining Alpha-Amylase Activity" (PDF). Cereal Chemistry. 38: 202–203. Retrieved 24 March 2024. Short update describing a modification of the method.
- Perten, Harald [in Estonian] (1964). "Application of the Falling Number Method for Evaluating Alpha-Amylase Activity" (PDF). Cereal Chemistry. 41: 127–139. Retrieved 24 March 2024.
- Hu, Yang; Sjoberg, Stephanie M.; Chen, Chunpen (James); Hauvermale, Amber L.; Morris, Craig F.; Delwiche, Stephen R.; Cannon, Ashley E.; Steber, Camille M.; Zhang, Zhiwu (May 2022). "As the number falls, alternatives to the Hagberg–Perten falling number method: A review" (PDF). Comprehensive Reviews in Food Science and Food Safety. 21 (3): 2105–2117. doi:10.1111/1541-4337.12959. PMID 35411636. Retrieved 24 March 2024.
- "AACC International Method 56-81.03 Determination of Falling Number", AACC Approved Methods of Analysis (PDF) (11 ed.), Cereals & Grains Association, doi:10.1094/aaccintmethod-56-81.03, retrieved 24 March 2024