Fiber refers to a complex of carbohydrates and other substances in the cell walls of edible plants. Although the fiber can not be digested and absorbed by the human body, its nutritional value is very low, but it can absorb and retain water, increase the volume of the feces, promote intestinal motility, and prevent the formation and reduction of cholesterol in the plasma. Therefore, cellulose has It can prevent the effects of various diseases such as colon cancer, appendicitis and heart disease and is an indispensable and important part of human food. Therefore, the determination of cellulose in food is very important. Let's talk about a specific method for measuring cellulose with a fiber tester.
1 Principle of the assay Samples were heated under boiling conditions for 30 min with 1.25 g/100 ml sulfuric acid and 1.25 g/100 ml sodium hydroxide solution to hydrolyze starch, pectin, protein, fat, partially hemicellulose and lignin. The resulting residue was weighed and the ash content was subtracted to obtain the crude fiber content.
2 apparatus appliances
a. Analytical balance: Sensitivity 0.0001g;
b. Experimental crusher;
c. hot plate;
d. Ma Fu furnace;
e. Electric blast drying box;
f. Nylon Sieve JP 72×1 (200 mesh);
g. tall beaker: volume 600ml;
h. Gu's cockroach: volume 25ml;
i. With valve exhaust pipe;
j. Filter flask: volume 500ml;
k. Desiccant.
3 Reagents
a. 95% ethanol;
b. ether;
c. litmus paper;
d. Pickling asbestos;
e. 1.25g/100ml sulfuric acid;
f. 1.25g/100ml sodium hydroxide.
4 Operation method
4.1 Weigh the sample with a fiber tester: Weigh 2-3 g of the comminuted sample, accurate to 0.0001 g, and pour it into a 500-ml beaker. If the fat content of the sample is high, the residue after fat extraction may be used as a sample, or the fat of the sample may be extracted with ether.
4.2 Acid treatment: Add 200ml of sulfuric acid (1.25g/100ml) boiled under reflux in the beaker containing the sample, and record the height of the liquid in the beaker. Put the watch glass on the electric stove, boil in 1 min, and continue boiling slowly for 30 min. In the boiling process, add boiling water to maintain the liquid level, often turn the beaker, then leave the heat source, wait until the sediment sinks, remove the supernatant with a glass wool filter tube, immediately add 100 ~ 150ml boiling water after the net wash Precipitate, absorb the supernatant again, and wash the precipitate repeatedly with boiling water until the test is neutral with litmus paper.
4.3 Alkaline solution treatment: Incorporate the glass wool in the suction filter tube into the precipitate, add 200ml of 1.25g/100ml sodium hydroxide solution that has been boiled under the refluxing device, and heat the microboiling for 30min according to the acid treatment method to remove the beaker. After the precipitate is allowed to sink, it is treated with a fiber gauge to a constant-weight Oldham's helium filter while still hot, and the precipitate is transferred to the mash with lossless boiling water and washed to neutrality.
4.4 Ethanol and ether treatment: The precipitate is first washed with 3~4 times of 20~25ml of ethanol heated to 50~60[deg.]C, and then washed with diethyl ether 20~25ml 3~4 times, and finally the ether is extracted.
4.5 Drying and Ignition of Goshen's crucible and precipitation, first bake it to constant weight at 105°C, then send it to 600°C high-temperature furnace and burn it for 30min, take it out to cool and weigh, and then burn it for 20min to constant weight.
4.6 Result Calculation
5.1 The heating plate heating, the temperature is not good control, low temperature can not reach boiling within 1min, the temperature is too high and easy to produce a lot of foam, spill the cup outside the sample loss, the experiment failed.
5.2 In the treatment of acid and alkali solution, the beaker should be covered with a watch glass, the condensation effect is not good, the level of the liquid in the beaker often changes, and the boiling water needs to be added at any time. This process is troublesome and time-consuming and affects the measurement result.
5.3 At the end of the acid-alkali solution treatment, the suction tube is used to suck the clear solution, and then it is washed with boiling water to neutrality. It takes too much time to suck the clear solution with a glass wool suction filter tube, and the sample is easy to lose.
6 Improved Method
6.1 Change the heating of heating plate to paste controller heating. This device has constant temperature timing device, which can not only ensure the boiling within 1min, but also control the constant temperature. There is also a regular alarm, and it automatically alarms when it reaches 30min, without special control. Can guarantee the heating temperature, but also a good time control.
6.2 The beaker shall be covered with a watch glass and replaced with a condensation ball on the upper lid, which is cooled by cold water circulation to ensure the accuracy of acid concentration in the beaker.
6.3 The glass wool filter was replaced by a 200 mesh nylon sieve. This method saves time and labor, saves energy, and is simple and easy to operate.
7 Results Comparison
7.1 Select the Same Sample with a Fiber Tester: Wheat Flour Containing 12.5% ​​Water
7.2 The test was conducted using the national standard method and the improved method. The results are as follows:
8 Conclusions According to the data obtained from the above two methods, it can be seen that the improved fiber meter not only saves time and effort, but also saves energy, and the measured results are smaller than the national standard method error, and are closer to the true value.
Related equipment: digestion furnace
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