This standard applies to the determination of dry matter and moisture content in fruit and vegetable products. GB 8858-1988 Determination of dry matter and moisture content in fruit and vegetable products GB8858-1988 Standard download decompression password: www.bzxz.net

GB 8858--1988
National Standard of the People's Republic of China
Method for determination of dry matter and water content in fruit and vegetable productsGB/T8858-1988
This standard adopts the international standard IS01026-1982 "Fruits and vegetable products-Determination of dry matter content by drying under reduced pressure and determination of water content by azeotropic distillation". 1 Scope of application
This standard is applicable to the determination of crude protein in fruit and vegetable products. 2 Reference standards
2.1 Principle
In a weighing dish of known weight, weigh the sample and place it in a vacuum drying oven, and dry it to constant weight at a certain vacuum degree and heating temperature.
2.2 Apparatus
2.2.1 Vacuum drying oven, which can be dried at a temperature of 70°C at a pressure of about 3kPa and dry air at a flow rate of 1040L/h is introduced to maintain a certain temperature and pressure in the vacuum drying oven. The test points in the vacuum drying oven should be uniform.
2.2.2 Weighing dish, aluminum box with cover, diameter not less than 50mm, height not more than 30mm2.2.3 High-speed tissue crusher.
2.2.4 Analytical balance.
2.3 Materials
2.3.1 Filter paper strips, for liquid products.
Use ash-free filter paper, which has been repeatedly washed with 2g/L hydrochloric acid for 8h, rinsed with distilled water five times, and then dried in air. Cut into 20mm wide strips. Bend or fold into accordion-like pleats, and the strips are partially loosened to form a polygonal spiral. Place a 4-4.5g paper strip in each weighing blood. 2.3.2 Filter paper, for semi-liquid products. Use hard ash-free filter paper, curl it, and cut it into a paper strip with a diameter slightly smaller than the weighing blood. 2.3.3 Pure sea sand, for viscous or solid products. If pure sea sand is not available, wash it with 5% (m/m) hydrochloric acid, rinse it until there is no chloride ion, sieve it to a particle size of 100-400μm, and burn it.
2.4 Operating procedures
2.4.1 Preparation of samples
2.4.1.1 For liquid and sauce-like products, mix the sample thoroughly and then take a sample. 2.4.1.2 For fresh fruits and vegetables, canned, and frozen products, remove the inedible part of the sample, use the quartering method to separate the edible part, then quickly chop and mix it in a porcelain plate, put it in a high-speed tissue pounder, pound it for 1-2 minutes, and put it in a ground-mouth bottle as a sample for determination. Some samples (such as leafy vegetables, sweet peppers, etc.) are difficult to crush. You can add an equal amount of water to the sample and crush them together. Every 2g of homogenate is converted to 1g of sample. 2.4.1.3 For dried products with high sugar content (such as dried fruit), take the edible part of the sample and quickly cut it into pieces and mix it evenly. Weigh 50-100g accurately to 0.1g, put it into a high-speed tissue crusher, add 200-400g of water and crush it for 2-3 minutes. Every 5g of homogenate is converted to 1g of sample. Transfer the sample into a ground-mouth bottle as a sample for determination. 2.4.2 Preparation of weighing blood
Put a filter paper strip or two pieces of paper or 20g of sand and a glass rod in the weighing blood, place it in a vacuum drying oven, and place the blood cover obliquely on the side of the weighing blood. After drying for 1 hour under the conditions specified in 2.2.1, take out the blood cover, cool it in a dryer for 0.5 hour, weigh it, and then dry it for another 0.5 hour. Cool it again and weigh it. The weight is constant when the difference between the two weights does not exceed 0.001g.
2.4.3 Weighing samples
Weigh 2~5g of solid sample or 5~10g of semi-liquid or liquid sample (containing about 1~1.5g of dry matter) in the weighing blood of constant weight, accurate to 0.0002g. 2.4.4 Determination
Put the weighing dish in a vacuum drying oven controlled at 70℃, and place the dish cover obliquely on the weighing dish. Connect the drying oven to a vacuum pump to reduce the air pressure to 3kPa (about 2530mmHg), and then introduce dry air at a flow rate of 10-40L/h to maintain a certain temperature and pressure in the vacuum drying oven. After drying for 4 hours, open the valve to allow air to slowly enter the vacuum drying oven through the drying device. After the pressure returns to normal pressure, open the drying oven door. Cover the blood cover, take out the blood sample, put it in the dryer to cool for 0.5 hours, and weigh it to an accuracy of 0.0002g. Bake it for another 1 hour, cool it in the same way, and weigh it. The weight difference between the two weights before and after does not exceed 0.001g, which is a constant weight. Note: For samples with high water content, they should be placed in a ventilated constant temperature drying oven at normal pressure of about 70℃, pre-dried for 2-3 hours, and stirred at any time, and then moved to the vacuum drying oven. 2.5 Result Expression
2.5.1 Calculation
X(%)=m2-mox100.
Where: X is the content of dry matter in the sample, %; mo
-the weight of the weighing dish (filter paper or sand and glass rod), g; mi
-the weight of the weighing dish (filter paper or sand and glass rod) and the sample after drying, g. m2
The result shall be the arithmetic mean of the two determinations, with one decimal place retained.
2.5.2 Repeatability
Relative error of two determinations made by the same analyst simultaneously or successively; when the dry matter content is greater than 10% (m/m), the relative error shall not exceed 1%; when the dry matter content is less than or equal to 10% (m/m), the relative error shall not exceed 2%. 3 Azeotropic distillation
3.1 Principle
Use a volatile solvent that is immiscible in water to bring out water in the form of steam, condense and separate in a condenser, collect the distillate in a receiving tube, and calculate the content based on the volume. 3.2 Reagents
Toluene or xylene (analytical grade).
3.3 Moisture analyzer: as shown in the figure. Before each use, wash thoroughly with chromic acid-sulfuric acid solution to remove oil stains, and wash continuously with distilled water and acetone. Then dry without heating under air flow. Approved by the Ministry of Commerce of the People's Republic of China on February 29, 1988, and implemented on July 1, 1988
GB 8858-1988
Moisture Determination Apparatus
1-250mL conical flask; 2-water receiving tube, with scale; 3-condenser 3.4 Operating Procedures
3.4.1 Sample Preparation
Same as (2.4.1).
3.4.2 Sample Weighing
Weigh an appropriate amount of sample (estimated water content 3-4.5mL), accurate to 0.01g. 3.4.3 Determination
Quantitatively transfer the sample to a flask and add 75mL of solvent (toluene or xylene). For viscous samples, add a boiling aid (such as pumice).
Connect the flask to the determination device, heat it slowly, keep it slightly boiling, and drip 2 drops from the condenser per second. When the water in the graduated tube does not increase significantly, speed up the distillation speed to about 4 drops per second. When the distilled solvent becomes clear and no more water is separated, stop heating and add solvent to rinse from the top of the condenser. If there are water droplets on the wall of the condenser, wipe them off with a copper wire with a small rubber head, and continue distilling for a while until there are no water droplets on the upper part of the receiving tube and the wall of the condenser. Remove the graduated tube and cool it to room temperature. Read the volume of water in the graduated tube (mL). 3.5 Result Expression
3.5.1 Calculation
Where: H—the water content in the sample, %
the weight of the sample, g;
V—the volume of water collected in the graduated tube (the density of water is assumed to be 1g/mL), mL. X(%)=100-H:
Where: X—the content of dry matter in the sample, %; H
the content of water in the sample, %.
3.5.2 Repeatability
Same as 2.5.2.
Approved by the Ministry of Commerce of the People's Republic of China on February 29, 1988 (2)
(3)
Implemented on July 1, 1988
GB8858-1988
Additional Notes:www.bzxz.net
This standard was proposed by the Bureau of Subsidiary Foodstuffs of the Ministry of Commerce of the People's Republic of China. This standard was drafted by the Food Inspection Institute of the Ministry of Commerce. The main drafters of this standard were Wang Liwei and Zhang Zhiyu. Approved by the Ministry of Commerce of the People's Republic of China on February 29, 1988 and implemented on July 1, 1988
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