Some standard content:
QB/T2343.2--1997
This standard is proposed by the Quality Standards Department of China Light Industry Association. This standard is under the jurisdiction of the National Sugarcane and Sugar Industry Standardization Center. The drafting unit of this standard is the Sugarcane and Sugar Industry Research Institute of China Light Industry Association. The main drafters of this standard are Liang Dafeng, Zhang Lingling and Yan Rongbai. , Yan
Light Industry Industry Standard of the People's Republic of China
Test Method for Brown Sugar
1 Subject Content and Scope of Application
QB/T2343.2--1997
This standard specifies the determination of sucrose content, reducing sugar, drying loss and water-insoluble impurities in brown sugar and the inspection method for mites. This standard is applicable to brown-red or yellow-brown sugar with honey obtained by separating low-purity massecuite. 2 Determination of sucrose content
2.1 Summary of the method
Determination by secondary polarimetry. Measure the optical rotation readings of the brown sugar solution before and after conversion, calculate according to the relevant formula, and obtain its sucrose content. 2.2 Instruments and equipment
2.2.1 Sugar detector
Sugar detector should be based on the international sugar scale, according to the sugar degree (Z) scale, and the measurement range can be from -30 to +120Z. The accuracy of the automatic sugar detector should be 0.05°Z, and the visual sugar detector should be accurate to 0.1. Sugar detectors based on the old sugar degree (°S) scale can still be used, but the readings must be multiplied by a coefficient of 0.99971 to convert to Z.
2.2.2 Optical rotation observation tube
Length (200.00±0.02)mm or (100.00±0.01)mm. A certificate of conformity must be issued by a legal metrology agency, or an observation tube with such a certificate must be used for calibration. 2.2.3 Volumetric flask
100 mL, 250 mL.
2.2.4 Analytical balance
Accurate to ±0.001 g.
2.2.5 Precision thermometer
0.1°C scale.
2.3 Reagents
2.3. 1 Alkaline lead acetate Pb(CH,COO)z~Pb(OH)2. 2.3.2 24.85°Bx hydrochloric acid solution
Slowly add 1000 mL of concentrated hydrochloric acid (relative density 1.19) into 850 mL of distilled water, and accurately correct its concentration to 24.85Bx (20°C).
2.3.3 231.5g/L sodium chloride solution
Weigh 231.5g of sodium chloride dried at 120℃, dissolve it in an appropriate amount of distilled water, transfer it into a 1000mL volumetric flask, and dilute it to the scale with distilled water.
2.4 Determination steps
2.4.1 Calibration of sugar meter
The reading of the sugar meter should be calibrated with a standard quartz plate certified by a legal metrology agency or verified with an certification mark. The sugar meter cannot be calibrated with sucrose solution.
2.4.1.1 Temperature correction of optical rotation of quartz plate Approved by China National Light Industry Association on January 16, 1998
Implemented on September 1, 1998
QB/T 2343. 2—1997
The temperature of the quartz plate when reading the reading using a sugar meter (without a quartz wedge compensator) should be measured and recorded to the nearest 0.2°C. If the temperature differs from 20°C by more than ±0.5°C, the temperature correction of the optical rotation of the standard quartz plate should be performed using formula (1). α, α2o[1+ 1. 44 × 10-4(t - 20)) Where: t is the temperature of the quartz plate when reading the reading, °C; α is the optical rotation value of the standard quartz plate at -t°C, Z; α20 is the optical rotation value of the standard quartz plate at -20°C, Z. 2.4.1.2 Conversion coefficient of quartz plate at different wavelengths The sugar content reading of quartz plate at different wavelengths can be converted according to Table 1 based on green mercury light (wavelength 546nm). Table 1
Incandescent light filtered
Yellow sodium light
Nitrogen-nitrogen laser
2.4.2 Sample solution preparation
Wavelength, nm
Conversion coefficient
Weigh the brown sugar sample (65.000±0.002) g in a clean 200mL beaker, add appropriate amount of distilled water to completely dissolve it, and then make up to volume in a 250mL volumetric flask.
2.4.3 Determination
Put about 200mL of the sample solution in a conical flask, add about 2g of alkaline lead acetate powder, shake quickly, filter, and take two 50mL portions of the filtrate with a pipette, and transfer them to two 100mL volumetric flasks respectively. Add 10mL of 231.5g/L sodium chloride solution to one of the flasks, then add distilled water to the scale, shake well, and filter if turbidity is found. Measure the optical rotation reading of the filtrate with a 200mm observation tube, multiply this number by 2 to get the direct optical rotation reading P, and record the temperature of the sugar solution when reading. First add 20mL of distilled water to another flask, then add 10mL of 24.85°Bx hydrochloric acid, insert a thermometer, heat accurately to 60℃ in a water bath, and keep at this temperature for 10min (shake continuously in the first 3min). Take it out, immerse it in cold water, and quickly cool it to the temperature at which the direct optical rotation reading is taken. Rinse the sugar solution on the thermometer with a small amount of distilled water into a volumetric flask and take out the thermometer. Add water to the scale (if the solution is dark in color, add a small amount of zinc powder). Shake it well. If it is turbid, filter it. Use a 200mm observation tube to measure its optical rotation reading, multiply this number by 2 to get the converted optical rotation reading P (negative value), and use a 0.1℃ scale thermometer to measure the sugar solution temperature t when reading (the difference between the sugar solution temperature when measuring P and P should not exceed 1℃). 2.4.4 Calculation and result expression
The sucrose content of the brown sugar sample is calculated according to formula (2), and the result is rounded to one decimal place. S = 100(P P')/(132.56 - 0.079 4(13 - G) - 0.53(t 20)) Where: S sucrose content, %;
P——direct optical rotation reading;
P converted optical rotation reading (negative value);
t——temperature of sugar solution when measuring P\, ℃;
G——mass of dry solids contained in each 100mL converted sugar solution, that is, G=13×(100-original sample loss on drying). 2.4.5 Allowable error
The difference between two measured values shall not exceed 0.05% of their average value. 3 Determination of reducing sugar
3.1 Summary of method
...(2)
Determined by the Lan-Eynon constant volume method. Use brown sugar sample solution to titrate a certain amount of Fehling's reagent. Before titration, add the predicted amount of water to keep the final volume constant (75 mL). According to the amount of brown sugar sample solution consumed, the content of reducing sugar can be obtained by conversion. 3.2 Instruments and equipment
3.2.1 Conical flask.
QB/T 2343. 2---1997
3.2.2 Burette: 50 mL, graduated to 0.1 ml. 3.3 Reagents
3.3.1 Pure Sucrose
Use 40℃ hot distilled water to dissolve high-quality white sugar or refined sugar at a concentration of 700g/L. After it is completely dissolved and cooled, add sodium carbonate solution to pH 8.0, filter with a glass filter with a pore size of 80120um, slowly add anhydrous ethanol to the filtrate, and stir quickly until the volume ratio of water to ethanol in the sugar solution is 3:7. At this time, the solution is clear or slightly turbid. After continuing to stir for 15h, separate the tiny sucrose crystals, wash with 70% alcohol, air dry or vacuum dry, and repeat the extraction steps once. 3.3.2 10g/L standard invert sugar solution
Weigh 23.750g of pure sucrose, dissolve it with about 120mL of distilled water and transfer it to a 250mL volumetric flask, add 9mL of concentrated hydrochloric acid (relative density 1.19), shake well, let it stand at room temperature 20-25℃ for 8 days, and then dilute it to the scale with distilled water. Pipette 100mL of the solution (containing 10g of invert sugar) into a 1000mL volumetric flask, and add 1mol/L sodium hydroxide solution to adjust the pH to about 3.0 while shaking continuously (the amount of alkali added can be determined by the following method: take another 50mL of invert sugar solution, use methyl orange as an indicator, and titrate with 1mol/L sodium hydroxide solution until the red color just changes to orange. The amount of sodium hydroxide solution consumed multiplied by 2 is the amount of alkali to be added). After adjusting the pH, add 2g of benzoic acid dissolved in hot water, shake well, and dilute to the scale after cooling. This solution contains 1g of invert sugar per 100mL and can be used as a stable stock solution. 3.3.32.5g/L standard invert sugar solution
Accurately pipette 50mL of 10g/L standard invert sugar solution into a 200mL volumetric flask, add 5 drops of phenolic acid indicator solution, and drop 0.5mol/L sodium hydroxide solution while shaking continuously until a light red color appears without fading, dilute to the scale with water, and shake well. 3.3.4 Fehling's solution
3.3.4.1 Preparation
Fehling's solution is divided into liquid A and liquid B, which are prepared and stored separately. They should be mixed quickly before use according to the regulations. When mixing, add the same volume of liquid A to liquid B accurately and add them in the specified order, otherwise the redissolution of the copper hydroxide precipitate that begins to form will be incomplete. a) Liquid A: Weigh 69.28g of copper sulfate (CuSO.·5H,O), dissolve it with distilled water, transfer it to a 1000mL volumetric flask, add water to the scale, shake well, and filter.
b) Liquid B: Weigh 346g of sodium methyl tartrate (NaKC.H,O.·4H.O) and dissolve it in about 500mL of distilled water; weigh 100g of sodium oxide and dissolve it in about 200mL of distilled water. Mix the two, transfer them to a 1000mL volumetric flask, add water to the scale, and leave it for 2 days. If the liquid level drops, add water to the scale, shake well, and filter. 3.3.4.2 Calibration
Use a pipette to take 10 mL of Fehling's solution B and solution A, transfer them into a 300 mL conical flask, add 15 mL of distilled water, add 39 mL of 2.5 g/l standard invert sugar solution from a burette, shake gently, place the conical flask on an electric stove to heat the solution to boil, boil for exactly 2 minutes, and add 3 drops of tetramethyl blue indicator solution. While the sugar solution is boiling, carefully continue to add invert sugar solution from the burette until the tetramethyl blue just disappears, which is the end point. The solution must be kept boiling during the entire titration process, and the titration endpoint should be reached within 1 minute after the addition of tetramethyl blue. If the concentration of Fehling's solution is accurate, the 2.5g/L standard invert sugar solution consumed in the titration is exactly 40mL. Otherwise, the concentration correction factor should be calculated according to formula (3):
K=V/40
Where: K-Fehling's solution concentration correction factor; V is the amount of standard invert sugar solution consumed in the titration, mL. 3.3.540g/L disodium ethylenediaminetetraacetate (CioH14O.N, Na2·2H2O), that is, EDTA solution. (3)
Weigh 40g disodium ethylenediaminetetraacetate, dissolve it in hot water at 50-70℃, cool it, dilute it to 1000mL with water, and shake it well. 3.3.650g/L potassium oxalate solution
Weigh 50g potassium oxalate, dissolve it in distilled water, and dilute it to 1000mL. 3.3.7 10g/L tetramethyl blue solution
Weigh 1.0g of tetramethyl blue, dissolve it in distilled water and make up to volume in a 100mL volumetric flask. 3.4 Determination steps
3.4.1 Sample solution preparation
QB/T 2343.2—1997
Use a pipette to draw 50mL of the brown sugar sample solution (2.4.2) into a 200mL volumetric flask and dilute it to the mark with distilled water. Then absorb 100mL of this sugar solution and transfer it into a 250mL volumetric flask. For every 1g of dry solids in the sample, add 1~2.4ml of 50g/L potassium oxalate solution into the volumetric flask, shake well, dilute to the mark with distilled water, shake well, and filter immediately. Or for every 1g of dry solids in the sample, add 4mL of 40g/L ETA solution into the volumetric flask, shake well, dilute to the mark with distilled water, and shake well. 3.4.2 Determination
3.4.2.1 Pre-test
Use two 10mL pipettes to first draw 10mL of Fehling's solution B into a 300mL conical flask, then draw 10mL of solution A into solution B and mix well. Add 25mL of sugar solution from the burette into the conical flask, then add 15mL of distilled water, shake well, heat on an electric stove covered with asbestos mesh, and boil accurately for 2min (controlled by a stopwatch), add 3 to 4 drops of tetramethyl blue indicator solution, and continue to add sugar solution until the blue disappears, which is the end point. This operation should not exceed 1 min, so that the total time of the entire boiling and dropping operation is controlled within 3 min. Record the milliliters of prepared sugar solution consumed for titration.
The amount of water required is equal to 75mL minus the amount of prepared sugar solution consumed and the amount of Fehling's solution (20mL). 3.4.2.2 Re-test
According to the above order, take 10mL each of Fehling's solution B and solution A into a 300mL conical flask, add the amount of water measured in the pre-test, add about 1mL less prepared sugar solution from the burette than the pre-test consumption, and shake well. The titration procedure is the same as the pre-test, and the boiling time should also be accurately controlled to 2min. The titration to the endpoint should not exceed 1min. The conical flask should be gently shaken during titration, but the heat source should not be left to keep the solution boiling to prevent air from entering the bottle and causing tetramethyl blue to be oxidized again, resulting in errors. 3.4.3 Calculation and result expression
The reducing sugar content of brown sugar is expressed as a percentage, and the calculation result is rounded to two decimal places. 3.4.3.1 Sucrose content
G = 6.5TS/1 000
Wherein: G—
Amount of sucrose in the prepared sugar solution consumed, mL
-prepared sugar solution consumed in titration;
Sample sucrose content, %.
3.4.3.2 From G, obtain the correction factor f from Table 2. Then the reducing sugar content of the brown sugar sample is R = 1 000fK/6.5T
Wherein: R—
Reducing sugar content, %;
f——correction factor;
K--Fehling's solution concentration correction factor;
-prepared sugar solution consumed in titration, mL.
3.4.3.3 Allowable error
The difference between two measured values shall not exceed 15% of their average value. Table 2 Correction coefficient table for determination of reducing sugar by Lan-Eynon constant volume method Consumed sucrose content in prepared sugar solution
Correction coefficient
Consumed sucrose content in prepared sugar solution
Note: When looking up Table 2, the correction coefficient can be calculated by interpolation for the sucrose content between two adjacent values. Correction coefficient
·(4)
4 Determination of loss on drying
4.1 Summary of method
QB/T2343.2-1997
Use atmospheric pressure drying oven drying technology, and after drying, cool under uniform conditions. This method mainly determines the "surface" moisture of the sample. 4.2 Instruments and equipment
4.2.1 Drying oven: During the determination, the temperature at (2.5±0.5) cm above the weighing bottle should be maintained at (125±1)°C. 4.2.2 Dryer with thermometer
4.2.3 Flat weighing bottle: diameter is 6~~10 cm, depth is 2~~3 cm. 4.3 Determination steps
4.3.1 Drying
The drying oven should be preheated to 125℃. Put the opened empty weighing bottle and its lid into the drying oven and dry for 30 minutes, then cover the weighing bottle, take it out of the drying oven, put it in a desiccator and cool it to room temperature (about 45 minutes, can be up to 2℃ higher than room temperature), weigh and weigh 9.510.5g of sample into the weighing bottle as soon as possible. Put the opened weighing bottle containing the sample and its lid into the drying oven preheated to 125℃ and dry for 45 minutes. Then cover the weighing bottle, take it out of the drying oven, put it in a desiccator and cool it to room temperature (can be up to 2℃ higher than room temperature), and weigh it as soon as possible. Each weighing above must be accurate to ±0.1mg. It is not necessary to dry to constant weight. The weighing bottle must be held with a clean clamp. 4.3.2 Calculation and result expression
The drying loss of brown sugar sample is calculated according to formula (6) and expressed as a percentage. The calculation result is rounded to two decimal places. W2 W.
Drying loss (%) -
× 100
Where: W,--the mass of the weighing bottle, g; W.--the mass of the weighing bottle and the sample before drying, g; W3--the mass of the weighing bottle and the sample after drying, g. 4.3.3 Allowable error
The difference between two measured values shall not exceed 10% of their average value. 5 Determination of water-insoluble impurities
5.1 Summary of the method
Use a crucible glass filter with a pore size of 80μm, and lay a layer of glass wool (or a tight velvet or wool cloth that matches the filter plate) about 5mm thick, which has been washed with dilute hydrochloric acid solution and rinsed with water, to filter the brown sugar solution under reduced pressure, and then use a large amount of distilled water to filter and wash the filter residue, and then dry it to constant weight. 5.2 Instruments and equipment
5.2.1 Crucible glass filter: pore size 80μm. 5.2.2 Drying oven.
5.2.3 Dryer with thermometer.
5.2.4 Analytical balance with an accuracy of ±0.001g. 5.3 Reagents
5.3.11% α-naphthol ethanol solution.
5.3.2 Concentrated sulfuric acid.
5.4 Determination stepsWww.bzxZ.net
5.4.1 Determination
Weigh 250.0g of sample into a 1000mL beaker, add distilled water not exceeding 40℃, stir until completely dissolved, pour into the prepared glass filter and filter under reduced pressure. Wash the filter residue thoroughly and check with 1% α-phenol ethanol solution until the washing liquid does not contain sugar. 238
QB/T2343.2--1997
The filter and the filter residue are placed in an oven at 125-130℃ for drying, then taken out and placed in a desiccator, cooled to room temperature, and weighed for the first time. After that, continue drying for about 30 minutes, cool and weigh once, until the difference between two consecutive masses does not exceed 0.001g, which can be considered to reach constant weight, and record its mass.
5.4.2 Calculation and result expression
The number of milligrams of water-insoluble impurities contained in each dry gram of brown sugar sample is calculated according to formula (7), and the calculation result is rounded to an integer. Water-insoluble impurities = (W, W) × 4000
W,—the mass of the dry filter and filter medium, g; W,—the mass of the dry filter, filter medium and water-insoluble impurities, g. 5.4.3 Allowable error
The difference between two measured values shall not exceed 10% of their average value. 6 Inspection of mites
6.1 Method Summary
The inspection of mites in brown sugar adopts the floating method. Dissolve brown sugar in distilled water and examine the floating objects on the surface of the sugar solution under a microscope to determine whether there are mites and the number of mites.
6.2 Instruments and equipment
6.2.1 Microscope.
6.2:2 Magnifying glass.
6.2.3 Glass slide.
6.2.4 Erlenmeyer flask: 1 000 mL.
6.3 Operation steps
6.3.1 Weigh 250g of brown sugar sample and put it into a 1000mL Erlenmeyer flask. Add distilled water not higher than 25℃ and stir continuously to make it completely dissolved. Add distilled water to the bottle mouth to prevent water from overflowing. 6.3.2 Cover the bottle mouth with a clean glass slide so that the glass slide is in contact with the liquid surface. Let it stand for 15 minutes and remove it for microscopic inspection. This operation is repeated several times to examine all floating objects under a microscope.
6.3.3 The number of mites detected is the total number of mites in 250g of brown sugar. 239
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.