GB 10469-89 Method for the determination of crude fibres of fruits and vegetables

GB 10469-89 Method for the determination of crude fibres of fruits and vegetables

This standard refers to the adoption of the international standard ISO 5498-1981 "General Methods for Determination of Crude Fiber Content in Agricultural Products".

1 Topic content and scope of application

This standard specifies the method for the detection of crude fibres in fruits and vegetables.

This standard applies to the determination of crude fiber content of fruits and vegetables.

2 Reference standards

GB5009.10 Determination of crude fibres in foods

GB 8858 Determination of dry matter and moisture content in fruit and vegetable products

3 Principle

Samples were co-boiled with hot dilute acid and dilute alkali, and were separated by filtration, washed with residues, and then dried and ashed. The acid can be removed by hydrolysis of sugar, starch, pectin and part of the hemicellulose. Alkali can remove proteins, partially hemicellulose, lignin, and saponify fatty acids. It is treated with ethanol and ether. The residue obtained after drying is the crude fiber content minus the ash weight.

4 Equipment

a. Analytical balance: Sensitivity 0.0001g;

b. Organize the masher;

c. Laboratory crusher;

d. Electric heating plate;

e. Return device: 500ml Erlenmeyer flask and condenser tube;

f. linen: suitable for the determination of crude fiber content;

g Buchner funnel: diameter 80mm or 100mm;

h. Short neck funnel: diameter 100mm or 120mm;

i. filter flask: volume 500ml or 1000ml;

j. Gu's Clamp Pot: volume 30ml;

k. Electric blast drying box;

l. Muffle furnace;

m. Dryer: Use a discoloration silica gel as a desiccant;

n. Crude fiber tester, CXC-06 fiber tester.

5 Reagents

The purity of the reagents was all analytically pure. The water used was distilled water or water of equivalent purity.

5.1 sulfuric acid solution: c (1/2H2SO4,) = 0.255 persons 0.005mol / L, the solution concentration must be calibrated;

5.2 sodium hydroxide solution: c (NaOH) = 0.313 persons 0.005mol / L, the solution concentration must be calibrated;

5.3 95% ethanol;

5.4 anhydrous ether;

5.5 Defoamers: such as n-octanol;

5.6 Asbestos: A 1:3 hydrochloric acid solution was added to asbestos and boiled for approximately 45 minutes, filtered, washed with water, dried and placed in a muffle furnace at 550°C for 16 hours. Take out the cold, add sulfuric acid and boil for 30 minutes, then filter and wash the acid with distilled water. Then add sodium hydroxide and boil for 30 minutes, then filter, wash once with sulfuric acid, and then wash with water, dry and set it in a muffle furnace at 550°C for 4 hours. After cooling, add water to form a suspension and store in a jar.

6 sample selection and preparation

6.1 Samples that are easily crushed: Select representative samples, homogenized by a tissue masher, and placed in a wide-mouth bottle for use.

6.2 Samples that are not easily smashed: Select a representative sample and take a sample and determine the moisture content according to GB 8858 (B1). At the same time, the sample was dried in an oven at 80° C., then crushed with a pulverizer and passed through a 0.84 mm sieve. After collection, put it in a jar for use.

6.3 The residue after the determination of the fat content (c) was used for the determination of the crude fiber content.

7 Measurement procedures

7.1 Samples

7.1.1 Accurately weigh about 20 g of the sample prepared in accordance with Section 6.1 and place in a 500 ml Erlenmeyer flask.

7.1.2 Accurately weigh approximately 3g of the sample prepared according to section 6.2 and place in a 500ml Erlenmeyer flask. At the same time, the water content (B2) was measured according to GB 8858.

7.1.3 Accurately weigh about 3g of the degreasing residue (6.3) and put it in a 500ml Erlenmeyer flask.

7.2 Evaporating water and extracting fat

After weighing, if the moisture content is high, most of the water can be evaporated in an oven at 80°C. If the fat content exceeds 1%, the sample can be soaked and washed with ether for several times, then the solvent is decanted and no residue can be lost. Finally, the excess solvent is dried.

7.3 Acid Treatment

7.3.1 Add 200ml of sulfuric acid solution of 95~100°C (measure at room temperature). If there is more foaming, add a few drops of defoamer in advance. Put on the condenser tube, immediately heated to a slight boiling (about 2min) on a hot plate, slightly boiling 30 persons 1min. During the micro-boiling process, the Erlenmeyer flask should be shaken several times to prevent the sample from sticking on the liquid surface.

7.3.2 connection number suction filter device, rapid suction filtration separation. And the residue was washed with hot water of 95~100°C until the filtrate was neutral (blue litmus paper does not change color).

7.4 Alkaline treatment

7.4.1 Place the linen with residue on the inner wall of the short neck funnel. Do not block the drain. The residue was rinsed into the original conical flask with 200 ml of sodium hydroxide solution (measured at room temperature) of 95-100°C. Put on the condenser tube, immediately heated to a slight boiling (about 2min) on a hot plate, slightly boiling 30 persons 1min.

7.4.2 Connect the suction filter unit (asbestos-clad Goguyst) and quickly separate by suction. The residue was washed with 20 ml of sulfuric acid solution (room temperature), washed thoroughly with hot water of 95 to 100°C, and then drained, followed by washing once with ethanol and ether (degreasing sample was not washed with ether), and the mixture was drained.

7.5 Drying

The residue was placed in a temperature range of 130±2°C in an oven and dried for 2 h, and then placed in a desiccator and cooled to room temperature and weighed (A1).

7.6 Ashing

The residue was placed in a 550-person 250-degree muffle furnace in a muffle furnace for 2 hours. When the temperature dropped below 200 DEG C, it was taken out of the desiccator and cooled to room temperature and weighed. Then put the Ashes in the muffle furnace for 1h. Repeat until the difference of 2 weighings does not exceed 0.5 mg (A2).

Or put the residue in the Gossip home set 600 persons 15 °C muffle furnace ashing 0.5h, when the temperature dropped below 200 °C, remove the desiccator to cool to room temperature and weigh (A2).

7.7 The same sample was measured twice in parallel.

8 Calculation formula of measurement result

8.1 Calculation formula for sampling according to clause 7.1.1:

(1)