Some standard content:
National Standard of the People's Republic of China
Fruit and vegetable products-Determination of water-insoluble solids
GB 12296-90
This standard refers to the international standard ISO751-1981 "Fruit and vegetable products-Determination of water-insoluble solids". Subject content and scope of application
This standard specifies the method for determining the water-insoluble solids of fruit and vegetable products. This standard is applicable to the determination of the water-insoluble solids content of fruit and vegetable products and the edible part of fresh fruits and vegetables. 2 Principle
The sample is dissolved in hot water, the soluble matter is filtered off, the residue is dried and weighed. 3 Instruments
High-speed tissue crusher: 10000~12000r/min. Pan balance: sensitivity 0.01g.
Analytical balance: sensitivity 0.001g.
Filtration device: composed of tap water suction pipe, 1000mL suction bottle and rubber suction pad. Buchner funnel: diameter 10cm.
Quick filter paper: diameter 9cm, 7cm.
Electric heating plate or ordinary electric furnace (with asbestos mesh on top). Centrifuge: 4000r/min, 4×50 or 8×100mL. Electric constant temperature drying oven.
Beaker: 250, 400mL
Weighing dish: aluminum box with lid, diameter not less than 50mm, height not more than 30mm. Desiccator: anhydrous calcium chloride or color-changing silica gel is placed inside. 4 Determination steps
Sample preparation
Liquid products: shake the sample thoroughly before weighing. 4.1.1
Sauce products: After the sample is stirred, take a portion and put it into a high-speed tissue pounder and pound it for 1 minute. For viscous products, distilled water can be added according to the specified ratio in 4.1.2
and the amount of water added can be discounted when weighing the sample. 4.1.3 Fresh fruits and vegetables: Remove the fruit stems, cores, seeds, etc., use the quartering method to take the edible part, chop and mix, weigh 250g, accurate to 0.1g, put it into a high-speed tissue pounder, add an equal amount of distilled water and pound it for 2 minutes. Every 2g of homogenate is converted into 1g of sample; berry and other juicy fruit and vegetable samples can also be directly pounded without adding water. 4.2 Preparation of filter paper
Put a 9cm filter paper and half a 7cm filter paper in each weighing dish, put them in a 103±2℃ electric heating drying oven for 1h, move them to a drying machine and cool for 30min, weigh them, and the accuracy is 0.001g. 4.3 Weighing samples
GB 12296—90
Mix the prepared samples thoroughly, weigh 10~100g of the samples in a 250 or 400mL beaker, and determine the sample weight according to the content and composition of the water-insoluble solids in the samples. For samples with more pectin and protein, the sample weight should be appropriately reduced. Make the mass of the dried residue after filtration between 0.2 and 0.5 g, as shown in the following table:
Water-insoluble solid content
<1.0～0.5
Weighing amount
Note: Liquid samples can also be measured by taking a certain amount with a pipette. Weighing accuracy
Product examples
Tomato sauce
Jam, fresh fruit
Tomato, pulp products
Fruit juice, vegetable juice,
4.4 Determination
4.4.1 Products that are easy to filter: Add 100 to 150 mL of distilled water to the beaker containing the sample, stir evenly with a glass rod, and heat on a hot plate until boiling. Lay the weighed filter paper flat in the Buchner funnel, add 50-100 mL of hot distilled water to the funnel to fully soak the filter paper and close it to the filter plate, then pour the boiled sample into the funnel and slowly filter under reduced pressure. Use hot water to wash all the residue on the beaker wall into the funnel, and wash the residue 5-6 times, using 30-40 mL of hot water each time, until the filtrate does not contain sugar, salt, etc. After extraction, move the filter paper and residue to the original weighing dish, wipe the residue left on the funnel with the weighed half filter paper, "put them together in weighing III, dry them in a 103±2℃ electric drying oven for 4 hours, cool them in a dryer for 30 minutes, weigh them, accurate to 0.001g, and dry them for another hour. Cool and weigh them in the same way until the difference between the two masses is less than 0.001g. 4.4.2 Products that are difficult to filter: For products with high pectin and protein content that are difficult to filter through filter paper, the weighed sample can be washed with hot distilled water into a 100mL centrifuge tube or two 50mL centrifuge tubes, centrifuged at a speed of 3500r/min for 10 minutes, and carefully Pour out the supernatant, add hot distilled water, stir the residue with a glass rod, centrifuge again, repeat this several times until the supernatant does not contain sugar, salt, etc., transfer all the residue in the tube to the weighed filter paper, dry and weigh according to 4.4.1. Note: ① See Appendix A for the test method of sugar and salt in the filtrate. ② If there are crystals in grape juice and citrus products, their content needs to be determined. The method is shown in Appendix B. 5 Calculation of test results
5.1 Calculation formula
The percentage of water-insoluble solids in the edible part of the sample is calculated according to the following formula: Water-insoluble solids (%) = _m2 = m
-×100||t t||Wherein: m_—
-mass of filter paper and weighing dish, g,
mass of dried residue, filter paper and weighing dish, g; mass of sample, g.
Note: When a certain volume of sample is taken for determination, it is expressed as the number of grams of water-insoluble solids in every 100mL. 5.2 Expression of results
Take two parallel samples of the same sample for determination, and take their arithmetic mean as the determination result, retaining one decimal place. 5.3 Allowable difference
The absolute difference between the measured values of two parallel samples shall not exceed 0.1%. 181
A1 Test of sugar
GB12296-90
Appendix A
Test method for sugar and salt
(Supplement)
Take a few milliliters of filtrate and put it into a small test tube, add 2 drops of 10% (m/) α-naphthol ethanol solution, and then slowly add 1 mL of concentrated sulfuric acid along the wall of the tube to the bottom of the tube. If soluble sugar is present, red will appear at the junction of the filtrate and sulfuric acid within a few seconds. A2 Test for salt
Take a few milliliters of filtrate, add 1 drop of nitric acid and 1 drop of 10% (m/) silver nitrate solution, shake well, and the appearance of white turbidity indicates the presence of salt. bzxz.net
Appendix B
Determination of crystals in grape juice and citrus products (Supplement)
B1 Grape juice
If potassium hydrogen tartrate crystals are found in grape juice, its content needs to be determined. Take another sample, filter it through filter paper, collect the crystals, and then wash them with the filtrate and 50% (u/u) ethanol solution saturated with potassium hydrogen tartrate in turn. Then dry it, weigh it, and calculate the content of the crystals.
Citrus products
If orange peel or grapefruit crystals are present in citrus products, their content can be determined by a method similar to B1. Additional remarks:
This standard was proposed by the Ministry of Agriculture of the People's Republic of China. This standard was drafted by the Institute of Vegetables and Flowers of the Chinese Academy of Agricultural Sciences. The main drafters of this standard are Yang Hongfu, Huang Wanchun, and Huang Qiaohua. This standard was first issued in 1989.
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