Number of cases
The number of cases (ger .: Falling Number ) is an easy and quick way to test the baking quality of flour.
The falling number is the time in seconds that a standardized stick needs to fall through a starch paste made from flour and water (including 60 s stirring time). If the growth has damaged the starch , the falling number is too small. For bread rye it must be higher than 75 s, baking wheat values are optimally 200–250 s; under 150 s the flour is outgrowth damaged.
The falling number method (according to Hagberg ) determines the alpha-amylase activity using the strength of the sample as substrate. The method is based on the rapid gelatinization of an aqueous suspension of flour or meal in a boiling water bath and the subsequent measurement of the liquefaction of the starch gel by the alpha-amylase in the sample.
Amylase is an enzyme found in grain . During poor growth conditions (too cold or too humid during the growth phase), α-amylase is increasingly formed. Wheat flours with a medium falling number (230–280) produce a normal, elastic, well-pored crumb and have sufficient driving force. Flours with a low falling number (<220 s) are inelastic and the pastry crumb is moist (moist baking). Furthermore, these have an increased driving force. Wheat flours with a high falling number (> 300 s), on the other hand, produce a dry crumb of baked goods (dry baking) and low baked goods volume. In addition, they have a low driving force, this requires the addition of fermentable sugars (e.g. malt flour) and / or baking agents containing enzymes.
In brief, the number of cases provides information about:
- the resistance of gelatinized starch to degradation by enzymes
- the activity of starch-degrading enzymes (amylases) and the degree of possible outgrowth damage
Effect of α-amylase
The starch in the flour "gelatinizes" the dough, it sets and becomes tough. α-amylase prevents this process or reverses it; the dough becomes thin and its processing is difficult or impossible.
preparation
A sufficiently large sample (at least 300 grams) of grain is taken and mixed well. The grain is ground with a cross beater mill and mixed again. A dependent on the moisture content of the flour amount (Standard: 7 grams at 14% moisture) is in a falling body viscometer added, followed by 25 ml of distilled water was added. The viscometer tube is closed with a rubber stopper and shaken vigorously 40 times, more often if necessary, in order to obtain a lump-free suspension. The stopper is removed and the flour adhering to the tube walls is pushed into the liquid with the stirring viscometer.
execution
Start of timing. The tube is placed in a 95 ° C water bath. The stirring process begins after five seconds, with the dipstick being moved back and forth vertically. After a total of 60 seconds, the measuring stick is pulled up and released, which takes another two seconds. Due to its weight, the measuring stick is now pulled downwards, the viscosity of the gelatinized suspension opposes it with resistance. Once the dipstick has reached the bottom, the time is stopped. The reading time in seconds (stirring time + sinking time) is the falling number. Only whole seconds are taken into account for the time.
The examination is internationally standardized:
- ICC No. 107/1
- AACC No. 56-81B
- ISO No. ISO / DIS 3093
- ASBC Barley 12-A
evaluation
- The greater the α-amylase activity, the thinner or less resistant the suspension and the smaller the falling number.
- The lower the α-amylase activity, the tougher the dough and the greater the falling number.
- Due to the measurement method, the number of cases is always greater than 62 seconds.
Low case numbers mean poor baking ability. The baking result is best with case numbers of 250–300 s ( wheat flour ) and 150–180 s ( rye flour ). If the number of cases is too high (> 400 s), the baking result is also poor because the dough is too tough and has too little gas-forming capacity (fermentable sugars) to allow it to rise (through yeast or other leavening agents ).
Condensing number
It is astonishing that you cannot mix flours according to falling number values. Example: If you mix two flours with 200 and 300 s falling numbers each in equal parts, the result is not a falling number of 250 s in the mixture. Therefore, the number of cases in advance in liquefaction numbers (Engl. Liquefaction Number , LN) are converted:
With their help, you can calculate mixing ratios with which the desired falling number in the mixture is achieved.
Latest knowledge
The quality of the starch depends on many factors.
- It is criticized that with the falling number method according to ICC 107 the starch is carried out with excess water and at the same time with high enzyme activity . Such starch liquefaction is only possible in doughs with limited water availability when the outgrowth is visible.
- Reserve proteins and non-starch carbohydrates regulate the vulnerability and hydration of starch.
- Polar lipids counteract a low falling number. The heat in 2010 in particular led to an increase.
- The heat in July 2010 caused the starch structure to harden ( annealing ).
Investigations showed that well-loosened small wheat baked goods could be achieved even with case numbers under 100 seconds.
Individual evidence
- ↑ ICC method 107/1 ( Memento of the original dated November 7, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Practical 4/2011, Dr. Klaus Münzing, Institute for Safety and Quality in Grain (MRI).
