Some standard content:
National Standard of the People's Republic of China
Method for determination of total sugar inedible fungi
1 Subject content and scope of application
This standard specifies the method for determination of total sugar content in edible fungi products. GB/T 15672—1995
This standard is applicable to the determination of total sugar in three types of edible fungi: black fungus, white fungus and poria. This standard is not applicable to the determination of total sugar content in other mushrooms with high protein content (mushrooms, shiitake mushrooms, oyster mushrooms, etc.). 2 Reference standards
GB12530 Sampling method for edible fungi
GB12531 Determination of water content in edible fungi
3 Method summary or principle
Water-soluble sugars and water-insoluble polysaccharides in black fungus, white fungus and poria are completely hydrolyzed by hot dilute hydrochloric acid and converted into reducing sugars. Reducing sugars can be quantified by Fehling's volumetric method to calculate the total sugar content in the sample. 4 Reagents
In the analysis, unless otherwise specified, only analytical reagents, distilled water or water of equivalent purity can be used. 4.1 Sodium hydroxide (GB629).
4.2 Concentrated hydrochloric acid (GB622): density 1.18g/mL. 4.3 Sodium hydroxide (GB629) solution: 6mol/L. 4.4 Fehling's reagent
4.4.1 Solution A: Dissolve 69.28g of copper sulfate pentahydrate (GB665, CuSO.·5H,O) in water, dilute to 1000mL, filter and set aside.
4.4.2 Solution B: Dissolve 346g of potassium sodium tartrate (GB1288, NaKCH,O.·4H,O) and 100g of sodium hydroxide (4.1) in water, dilute to 1000mL, filter and set aside.
4.5 Glucose standard solution: Accurately weigh 1.0000g of dried glucose to 0.0001g, dissolve it in water, add 5mL of concentrated hydrochloric acid (4.2), and then prepare a 10g/L concentration solution with water and dilute to 1000mL to become a 1g/L concentration solution. 4.6 Methylene blue (HGB3394) indicator solution: 10g/L. 5 Instruments and equipment
5.1 Electric heating blast drying oven.
5.2 Small plant crusher: equipped with a metal screen with a pore size of 1mm. 5.3 Glass mortar: equipped with a pestle.
Approved by the State Administration of Technical Supervision on August 17, 1995 286
Implementation on January 1, 1996
GB/T15672-—1995
5.4 Sampling sieve: equipped with a sieve with a pore size of 0.84mm (20 mesh). 5.5 Analytical balance: sensitivity 0.0001g.
5.6 Electric hot water bath.
5.7 Wide-mouth bottle: with ground mouth.
5.8 Filter paper: diameter 15cm.
5.9 Glass triangular funnel: diameter 75mm.
5.10 Round bottom flask: 250mL, with a 30cm long glass tube inserted on the top for reflux. 5.11 Volumetric flask: 250.1000mL. bzxz.net
Graduating cylinder: 100mL.
Beaker: 25, 500mL.
Conical flask: 250mL.
Pipette: 5, 10, 20mL.
Acid burette: 50mL.
Weighing bottle.
5.18 Wide range pH paper.
Adjustable electric furnace: 0~600W, with asbestos mesh. 5.19
5.20 Glass rod and dropper.
6 Samples
6.1 Sampling method and quantity
6.1.1 Dry products shall be sampled in accordance with the requirements specified in GB12530. The total amount shall not be less than 100g. 6.1.2 Fresh ear and fresh poria are randomly sampled from different places in each batch as original samples, and the total amount shall not be less than 1000g. 6.2 Preparation of samples
6.2.1 The dry products are directly cut into small pieces with scissors, dried in a drying oven at 80-100℃ until crisp, then cooled, and immediately crushed with a small plant crusher. Discard the sample that is crushed at the beginning (about one-tenth of the total sample). The crushed sample needs to pass through a 20-mesh sieve. The part that fails to pass the sieve is dried and then crushed again or ground in a bowl and then sieved again until all samples are sieved. The sieved samples are placed in a clean wide-mouth bottle. After the sample is sealed, fill in the label, indicating the product name, date, sample delivery unit and sampler, etc. 6.2.2 After sampling, tear the fresh ear into small pieces by hand, and peel the fresh Poria cocos and cut it into small pieces with a knife. Spread the sample evenly on a wire mesh with gauze in a drying oven, and dry it at 50℃ with air for more than 6 hours. After the sample is half dry, gradually increase the temperature to 80~100℃. After the sample becomes brittle, cool it and immediately crush it with a grinder. Other operations are the same as those for dry products. 7 Analysis steps
7.1 Weighing and hydrolysis: Weigh about 0.25g of the sample to an accuracy of 0.0001g, carefully pour it into a round-bottom flask, add 100mL of water and 10mL of concentrated hydrochloric acid (4.2). Insert a glass tube for reflux into the mouth of the flask, and place it in a boiling water bath at 100℃ for hydrolysis for 3 hours. Filter after cooling. Wash the filter residue back into the round-bottom flask with 100mL of water without damage (carefully operate with a dropper), add 10mL of acid, and repeat the above operation. Combine the two filtrates, adjust the pH to neutral with 6 mol/L sodium chloride solution (4.3) (test with pH paper), heat and concentrate appropriately, and then adjust the volume to 250 mL. At the same time, weigh the sample and determine the water content of the sample according to the method specified in GB12531. 7.2 Standardization of Fehling's solution: Accurately pipette 5 mL each of Fehling's solution A (4.4.1) and solution B (4.4.2) into a 250 ml conical flask, mix well, add a few glass beads, and place on an asbestos net for heating. Quickly add 49 mL of glucose standard solution (4.5) from the burette, adjust the temperature so that it boils within 2 minutes, and keep it boiling for 2 minutes. During this period, add 3 drops of methylene blue indicator solution (4.6); then add glucose standard solution drop by drop until the blue color fades. The titration process must be completed within a total boiling time of 3 minutes. 10 mL of Fehling's mixed solution requires about 50 mL of glucose standard solution. This titration value is the calibration value of the prepared Fehling's reagent. When measuring a large number of samples, equal volumes of A and B solutions can be mixed and then calibrated and used. The mixed solution should not be stored for more than one month. 287
GB/T 15672---1995
7.3 Titration of sample solution: Add 5 mL of Fehling's A and B solutions to a 250 mL conical flask, mix well, then add 10-20 mL of sample solution, add a few glass beads, and place on an asbestos net for heating. Before the formal titration, a sample should be used for a rough titration. While heating, glucose standard solution should be added drop by drop to determine the approximate sugar consumption volume of the sample solution. During the formal titration, after the conical flask is heated, a glucose standard solution about 1 mL less than the actual volume should be quickly released from the burette. Other operations are the same as the calibration of Fehling's solution. 8 Calculation of analysis results
8.1 Calculation
Total sugar (dry basis, in glucose, %) = V) × 0.001 × 250 × × 100
V, X m × (1 -- X)
Wherein: V. - the volume of glucose standard solution consumed by 10 mL Fehling's mixture, mL; V, - the volume of glucose standard solution consumed during titration of the sample solution, mL; V2 - the volume of sample solution absorbed, mL;
m~ - the mass of the sample, g;
0.001 - the mass of glucose in 1 mL glucose standard solution, g; the volume of the two hydrolyzates combined after the volume is fixed, mL; 250 -
X - the water content of the sample, %.
8.2 Allowable difference
Take the arithmetic mean of the parallel determination results as the determination result, and keep one decimal place. The absolute difference of the parallel determination results shall not exceed 1.0%. Additional Notes:
This standard was proposed by the Ministry of Agriculture of the People's Republic of China. This standard was drafted by the Edible Fungi Research Institute of Shanghai Academy of Agricultural Sciences. The main drafters of this standard are Gu Zhenrong and Gu Xianghong.
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