Some standard content:
GB8210—1987
National Standard of the People's Republic of China
Method of inspection for export citrus fruit GB8210—1987
1 Subject and scope of application
1.1 This standard specifies the inspection basis, sampling and inspection methods for export citrus fruit. 1.2 This standard is applicable to the inspection of various types of export citrus fruit. 2 Inspection basis
2.1 Export citrus quality and packaging standards such as "Export sweet orange", "Export wide peel citrus", and "Export lemon". 2.2 Quality specifications and packaging requirements stipulated in foreign trade contracts. 3 Terminology
3.1 Appearance quality
Refers to the shape, size, color, cleanliness and uniformity of the fruit surface and the freshness and robustness of the whole batch of citrus fruit.
3.1.1 Shape: refers to the normal shape inherent to this variety. 3.1.2 Individual size: refers to the horizontal diameter requirement of this grade. 3.1.3 Color: refers to the color and luster inherent in the maturity period of this variety. 3.1.4 Evenness: refers to the evenness of the shape, size and color of the whole batch of fruits. 3.1.5 Cleanliness: refers to the degree to which the appearance is affected by the spots, net patterns, spots, mechanical damage and other dirt on the fruit surface.
3.1.6 Fresh and strong: refers to the plump oil cells in the fruit skin, no shrinkage, and the sepals of the fruit pedicles remain inherently green. 3.2 Grades and specifications
3.2.1 Secondary fruits and proportions of each grade: Secondary fruits refer to those tested according to the specified grade. Those that are one grade lower than the quality standard of the grade are second-grade fruits; those that are two grades lower are second-grade fruits. The proportion of each grade refers to the percentage of fruits of each grade in the total fruit determined by testing according to the mixed grade. 3.2.2 Specifications (groups): refers to the division of groups according to the diameter of the largest part of the cross section of the fruit. 3.3 Defective Fruits
3.3.1 Seriously defective fruits: including fruits that have lost their edible value partially or completely due to rot, frost damage, edema, waterlogging, cracked fruit, moth-thorn fruit, severely injured fruit, and heavily oily fruit, as well as fruits that have rotted or deteriorated during transportation.
3.3.1.1 Rot: refers to fruits that have been infected by pathogens, and the middle gelatinous layer of cells has been decomposed by the enzymes secreted by the pathogens, resulting in cell separation, tissue collapse, and partial or complete loss of edible value of the fruit. There are two types of rot: wet rot and dry rot.
3.3.1.2 Frost-damaged fruits: fruits that are affected by low temperatures below the freezing point, resulting in ice crystals forming in the intercellular spaces, and the entire or partial fruits become hard and lose elasticity. 3.3.1.3 Edema fruits: refers to fruits that are in poor ventilation or affected by cold damage, resulting in physiological and metabolic disorders, browning of the fruit or even soft tissue collapse, strong odor, and partial or complete loss of edible value. 3.3.1.4 Water loss (granulation): refers to fruits with wrinkled pods, hard and rough juice cells, and dried juice, which affect the edible value. The fruits are classified and counted according to the degree of water loss. Note: ① Characteristics of water loss classification of wide-skinned citrus fruits Approved by the National Bureau of Standards on August 31, 1987
Implementation on July 1, 1988
GB8210-1987
Grade 0: Good fruit. Normal peel, normal juice cells, and full juice; Grade I: Mild water loss. The pods are slightly wrinkled, the orange color fades, and a few juice cells are slightly water loss; Grade II: Moderate water loss. The skin and flesh of the fruit are separated at both ends, the pods are wrinkled, white spots appear on the skin, and 50% of the juice cells in the pods are water loss; Grade III: Severe water loss. The skin and flesh of the whole fruit are separated, the pods are obviously wrinkled, there are white spots on the skin, and most of the pods and juice cells are water loss, completely losing the edible value. ② Characteristics of orange fruit waterlogging classification
Grade 0: Good fruit. Normal juice cells, full juice; Grade I: Mild waterlogging. A few juice cells at the end of the pedicle are slightly granulated and waterlogged; Grade II: Moderate waterlogging. The pods are wrinkled, white spots appear on the skin, and the waterlogging degree of the juice cells reaches 50%. Grade III: Severe waterlogging. The pods are obviously wrinkled, there are white spots on the skin, and the entire pods and juice cells are mostly waterlogged. 3.3.1.5 Other serious defective fruits: refers to fruits that rot or change in quality during transportation, except for rot, frost damage, edema, and waterlogging. 3.3.2 General defective fruits (unqualified fruits): refers to general defective fruits that do not meet the quality conditions of the grade specified in the standard or contract. Such as irregular shape, poor coloring, uneven cutting of the pedicle, spots, net patterns, spots, slight damage on the fruit surface, and fruits of different varieties that do not meet the requirements of this grade. 3.4 Flavor: refers to the taste, texture, slag-making process, aroma, amount of juice and seeds of the fruit. 3.5 Physical and chemical items
3.5.1 Fruit shape index: expressed as the longitudinal diameter/transverse diameter of the fruit. 3.5.2 Edible part percentage: refers to the percentage of the edible part of the fresh fruit to the whole fruit. 3.5.3 Juice rate: the percentage of the juice squeezed out of the sample fruit to the total amount of the sample fruit tested according to this standard. 3.5.4 Total soluble solids: refers to the total amount of solid matter dissolved in the juice. 3.5.5 Total sugar: directly determined as reducing sugar (including glucose and fructose) according to this standard sample solution. The sample solution is converted into invert sugar after acid addition. Sucrose is obtained by multiplying the invert sugar minus the reducing sugar by 0.95, and the total sugar is obtained by adding sucrose to the reducing sugar. It is expressed as the number of grams of glucose in 100mL of juice. 3.5.6 Titratable acid: Titratable acid measured by alkali neutralization method according to this standard represents the free organic acid content. It is expressed as the grams of citric acid in 100mL juice. 3.5.7 Ascorbic acid: The ascorbic acid content measured according to this standard is expressed as the milligrams of ascorbic acid in 100ml juice.
3.5.8 Solid acid ratio and sugar acid ratio:
Solid acid ratio = soluble total solids/titratable acid Sugar acid ratio = total sugar/titratable acid
4 Sampling
4,1 Sampling quantity: From the exported citrus products reported for inspection, the same variety, the same processing plant, the same vehicle, the same stack shall be used as a sampling inspection unit, but the maximum shall not exceed 2,000 boxes. The sampling quantity shall be as specified in Table 1.
Number of product boxes
Below 100 boxes
101~300
301~500
Number of sampling boxes
Number of product boxes
501~1000
More than 1000 boxes
Number of sampling boxes
At least 15
4:2 Sampling method: Select representative sample boxes by random sampling method. The specific operation method can adopt stack sampling and box throwing sampling
4.2.1 Stack sampling: Take a certain number of sample boxes from different parts of the stack, such as the top, middle, bottom or one of the four corners in Table 1 Standard National Bureau of Standards 1987-08-31 Approved
1988-07-01 Implementation
GB8210-1987
Note: Citrus for export should be stacked in double stacking and ventilation stacking method, with sampling operation space left between the rows. Each stack should be marked with the product name, group, quantity, batch, vehicle name, processing plant name or code and storage date, etc. 4.2.2 Sampling by box throwing: If it is difficult to sample by stacking due to the narrow storage location, one box can be thrown every few boxes during the stacking process, and the sampling boxes specified in Table 1 can be taken out. The samples taken from the stack or box throwing should include fruits of different groups, factories and packaging dates. During the inspection, the sampling quantity and method may be changed according to the quality difference, packaging and storage and transportation, etc., in accordance with the contract and relevant regulations.
5 Inspection method
5.1 Citrus inspection processWww.bzxZ.net
The citrus inspection process is shown in the figure below.
Flowchart of fresh citrus inspection
5.2 Appearance quality
5.2.1 Equipment: inspection table, box opening pliers, magnifying glass, etc. 5.2.2 Conditions: The inspection room requires sufficient natural light or good lighting equipment, and no alcohol or other irritating odors. Participants in the inspection must have normal senses and have considerable experience in appraisal. They should not eat alcohol, spicy food or other irritating foods before the inspection, and should not smoke during the inspection. 5.2.3 Steps: Open the sample boxes one by one, remove the fruit wrapping paper, and spread the fruits flat on the inspection tray. According to the standards, contracts and the characteristics of each variety, conduct sensory appraisal of the samples as a whole: the freshness of the fruit; the shape, size, color, fruit surface characteristics of this variety and this grade, as well as the wholeness and cleanliness of the appearance, whether they meet the requirements of the standards and contracts.
5.3 Grade specifications
5.3.1 Specifications (groups)
5.3.1.1 Tools: grouper (plate), 0.1 and 0.001kg scales, etc. 5.3.1.2 Steps: After inspecting the appearance quality in 5.2, measure the sample fruits one by one with an accurate grouper (hole). Fruits that do not meet the horizontal diameter of the group will be placed separately and measured. According to formulas (1) and (2), calculate the percentage of adjacent group fruits (fruits that are one group higher or one group lower than the group) and alternate group fruits (fruits that exceed the upper and lower adjacent groups) in the total number.
Adjacent group fruits (%)=
Alternate group fruits (%)=×100
W——sample fruit weight or number;
W,The weight or number of adjacent fruit groups in the sample:
W The weight or number of alternate fruit groups in the sample.
5.3.2 Secondary fruit and proportion of each grade
5.3.2.1 Utensils: Same as 5.3.1.1.
·（2）
5.3.2.2 Procedure: After the inspection in 5.3.1.2, sensory evaluation shall be conducted on each sample according to the grade conditions of the standard or contract. The secondary and secondary fruits that do not meet the inspected grade shall be removed, and the fruits of each grade shall be classified by grade and measured separately. Calculate according to formula (3), (4) and (5). Approved by the State Bureau of Standards on August 31, 1987
Implementation on July 1, 1988
GB 8210-1987
W-
5.4 Defective fruit
Sub-first-grade fruit (%)
Sub-second-grade fruit (%)=
W×100
Fruit of each level (%)=
Weight or number of sample fruit;
-Weight or number of second-grade fruit in sample fruit;
-Weight or number of sub-second-grade fruit in sample fruit;
-Weight or number of each type of fruit in sample fruit.
5.4.1 Utensils: inspection table, sample tray, magnifying glass, stainless steel fruit knife, 0.1kg and 0.001kg scale, etc.
5.4.2 Steps: After the inspection in 5.3.2, observe the sample fruits one by one with the naked eye and touch the hardness according to the characteristics of other serious defective fruits and general defective fruits such as rotten fruits, edema fruits, frost-damaged fruits, cracked fruits, noctuid thorn fruits, severely injured fruits, and heavy oil spots (except dead fruits). If necessary, cut open the fruit to check the flesh and taste for peculiar smell. Separate the various serious defective fruits and general defective fruits and calculate them separately. Calculate according to formulas (6), (7), (8), (9), and (10).
Rotten fruit (%)=
Frost-damaged fruit (%)=
2×100
Edematous fruit (%)=
Other serious defective fruit (%)=
General defective fruit (%)=W
Wherein: W
5.5Dry water
Weight or number of sampled fruit;
Weight or number of rotten fruit in sampled fruit;
Weight or number of frost-damaged fruit in sampled fruit;
Weight or number of edema fruit in sampled fruit;
Weight or number of other serious defective fruit in sampled fruit:Weight or number of general defective fruit in sampled fruit; 5.5.1Tools: Same as 5.4.1.
（6）
·（8
（9）
（10)
Steps: Take 100 mixed sample fruits from 5.6.1, examine their appearance, and classify them one by one according to the low water classification standards of the National Bureau of Standards (1987-08-31 approved by the National Bureau of Standards, 1988-07-01 implemented by the National Bureau of Standards). 8210—1987
Identify its grade. Record the number of fruits at each level. Calculate the average estimated water rate according to formula (11). Average dry water (%) = 0% + 1 jin + 2f, + 3
Wherein: N total number of sample fruits;
fo, fi, f2, f3—number of dry fruits at each level; 1, 2, 3—representative values of each level;
3—representative value of the heaviest dry water level. 5.6 Flavor
5.6.1 Utensils: Same as 5.4.1.
（11)
56.2 Preparation of sample fruits: After the inspection in 5.3, take out 5 to 20 representative fruits from different parts of each box of samples, put them together in the box, and mix them for later use. 5.6.3 Steps: Take 10 sample fruits ~20, wash, wipe dry, cut into four pieces longitudinally with a stainless steel fruit knife, and cut into two pieces horizontally. Observe the color of the flesh and the size of the core; taste the flavor and texture, the degree of slag, and the amount of juice; smell its aroma; measure the thickness of the peel and the number of seeds. Determine whether it meets the standards, contracts and requirements of the variety.
5.7 Physical and chemical testing
5.7.1 Preparation of sample fruit: Same as 5.6.1. 5.7.2 Fruit shape index
5.7.2.1 Instrument: Vernier caliper (0.05 or 0.1mm), etc. 5.7.2.2 Steps: Take 10 to 20 sample fruits, and use a vernier caliper to measure the longitudinal diameter (from the top of the fruit to the pedicle end) and transverse diameter (diameter of the cross section at the equator) of the fruit one by one. Calculate according to formula (12). H
Fruit shape index =
Where: D—horizontal diameter of the fruit, mm;
vertical diameter of the fruit, mm.
5.7.3 Percentage of edible part
(12)
5.7.3.1 Instruments and utensils: 0.1g sensitive balance, stainless steel fruit knife, white porcelain plate, tweezers, etc. 5.7.3.2 Steps: Take 10 to 20 sample fruits, wash, wipe dry, weigh the total fruit weight (accurate to 0.1g), and carefully separate the peel (including white peel), sac valve, seeds and other parts of each sample fruit. Weigh their weights separately (accurate to 0.1g). Calculate according to formulas (13), (14), and (15). Edible part of sweet orange and wide-skinned mandarin (%) = W-(W+W.)×100W
Edible part of lemon and kumquat (%) = WW
Edible part of pomelo (%) = W-(W+W,+W)
W——total weight of sample fruit, g;
Weight of peel in sample fruit, g
Weight of seeds in sample fruit, g;
Weight of capsule skin in sample fruit, g.
Approved by National Bureau of Standards on August 31, 1987
(13)
(14)
(15)
Implemented on July 1, 1988
GB8210-1987
5.7.4 Juice rate
5.7.4.1 Apparatus and utensils: glass juicer, beaker, funnel, dry gauze, stainless steel fruit knife, 0.1g sensitive scale, etc.
5.7.4.2 Steps: Take 10 to 20 sample fruits, wash them, wipe them dry, weigh the total fruit weight (accurate to 0.1g), cut the sample fruits into two sections, squeeze out the juice with a juicer, filter it through two layers of clean gauze and put it in a beaker, tear off the pods from the peel after squeezing the juice, take out the seeds, put them into clean gauze, and then squeeze out all the juice and combine them in the beaker. Weigh the weight of the peel, seeds, and pomace (including the pod wall and juice cells, etc.) (accurate to 0.1g). Calculate according to formula (16).
Juice rate % -+W1..
Where: W—total weight of sample fruit, g;
Wi—weight of peel in sample fruit, g;
W2—weight of seeds in sample fruit, g;
W3—weight of pomace in sample fruit, g.
5.7.5 Total soluble solids
....· (16)
5.75.1 Apparatus and equipment: Hand-held sugar meter or Abbe refractometer, rubber-tipped dropper, glass rod, funnel, juicer, constant temperature water solution, stainless steel fruit knife, beaker, etc. 5.7.5.2 Preparation of test solution: Take 10 to 20 sample fruits, wash, wipe dry, cut into two sections, squeeze out the juice with a glass juicer, filter through two layers of clean gauze, put into a beaker, and stir well. You can also use the juice for determining the juice rate in 5.7.4.
5.7.5.3 Method I: Handheld sugar meter determination method (applicable to cargo field inspection) Direct determination method: Open the prism cover, wipe the prism dry with a soft flannel or absorbent cotton with distilled water (xylene or ether if necessary), and be careful not to damage the mirror surface. After the prism is dry, use a dry and clean dropper to suck 2 to 3 drops of distilled water on the mirror surface, close the mirror plate, and spread it all over the surface of the prism. Place the instrument horizontally, with the light hole facing the light source, adjust the eyepiece so that the scale numbers in the mirror are clear, and adjust the screw to the reading at the light and dark boundary seen in the field of view as 0. At the same temperature, drop 2 to 3 drops of sample liquid on the prism surface in the same way, adjust the eyepiece so that the boundary of the object in the mirror is clear, and record the reading at the light and dark boundary. Parallel determination 2 to 3 times to take the average value, which is the percentage of total soluble solids in the juice. Table lookup method: Before using the handheld sugar meter, do not calibrate it with distilled water. Directly measure and record the temperature during measurement according to the above method, and refer to Appendix A (Supplement) for calibration. 5.7.5.4 Method II - Abbe refractometer measurement method (arbitration method) Calibration of refractometer: Place the refractometer on a clean table and install a thermometer and an electric constant temperature water bath water pipe. Adjust the water temperature to 20 ± 0.5℃. Separate the two prisms of the refractometer, wipe them clean with dry absorbent cotton dipped in distilled water (xylene or ether if necessary), and then wipe them dry with clean absorbent cotton (or lens paper). After the prism is completely dry, use a clean glass rod to dip 1 to 2 drops of distilled water on the prism, quickly close it, aim at the light source and observe through the eyepiece, rotate the handwheel so that the sugar content on the scale is exactly 0% of 20℃, and observe whether the light and dark dividing line in the telescope is in the middle of the "×" line of the objective lens. If there is a deviation, use the accessory square hole adjustment wrench to turn the indication adjustment screw to adjust the light and dark dividing line to the center of the "" line. After adjustment, do not move the adjustment screw when measuring the sample.
Determination of sample solution: Before measurement, clean the prism first to prevent other substances from affecting the measurement results of the sample solution. Use a glass rod to dip or use a clean dropper to absorb 1-2 drops of sample solution, drop them on the prism, close it quickly, let it stand for a few seconds, wait for the sample solution to reach 20℃, aim at the light source, observe through the eyepiece and turn the compensator screw to make the light-dark boundary clear, turn the scale pointer screw so that the light-dark boundary is just at the intersection of the "×" line of the objective lens, read the sugar content reading on the scale, and record the temperature at the same time. Parallel measurement 2-3 times to take the average value. Note: ① Operate correctly according to the instrument instructions and related matters. ② If you do not use a constant temperature water bath, refer to Appendix A (Supplement) to correct the results. 5.7.6 Determination of total sugar - Fehling's volumetric method (common method) 5.7.6.1 Principle: Under boiling conditions, when a certain amount of Fehling's solution is titrated with a reducing sugar solution, the divalent copper in Fehling's solution is reduced to monovalent copper. With methylene blue as an indicator, a slightly excessive amount of reducing sugar immediately reduces the blue oxidized methylene blue to colorless reduced methylene blue. 5.7.6.2 Instruments and equipment: electric furnace, constant temperature water bath, burette, conical flask, volumetric flask, pipette, asbestos pad funnel, analytical balance, etc.
5.7.6.3 Reagents
a. Glucose standard solution: weigh 1g of analytical pure anhydrous glucose dried at 105℃ for 2h (accurate to 0.0001g), dissolve it in distilled water to dilute to 250ml and shake well. b. 1% methylene blue indicator: 1g methylene blue is dissolved in 100ml distilled water. c. 0.1% methyl blue indicator: 0.1g methyl red is dissolved in 100ml distilled water. d. Concentrated hydrochloric acid (specific gravity 1.19, analytical grade) and 1:3 hydrochloric acid dilution. e. 40% and 10% sodium hydroxide solutions.
f Preparation and calibration of Fehling's solution:
Fehling's solution A: Weigh 69.28g of analytical grade copper sulfate (CuS04·5H,0), dissolve it in distilled water, dilute to 1000ml, let it stand for 1d, filter, and store in a brown bottle. Fehling's solution B: Weigh 100g of analytical grade sodium hydroxide and 346g of analytical grade potassium sodium tartrate (KNaC40H4·4H,0), dissolve it in distilled water, dilute to 1000ml, let it stand for 2d, and filter it with an asbestos pad funnel.
Standardization of Fehling's solution:
Preliminary titration: Take 5 ml of Fehling's A and B solution, put them into a 250 ml conical flask, add 20 ml of distilled water, inject glucose standard solution into the burette, pre-drop a certain volume into the mixture of A and B, heat it on an electric stove, make it boil in about 2 minutes, boil for 1 minute, add 2 to 3 drops of 1% methylene blue indicator, and wait for another 0.5 minutes. In the boiling state, continue to drop glucose standard solution at a rate of 4 to 5 drops per second until the blue color of the mixture disappears completely and turns brick red. It takes no more than 3 minutes from boiling to the end point of titration. Formal titration: According to the preparatory titration, take 20 ml of Fehling's A, B solution and water into a conical flask. The amount of glucose standard solution pre-added to the mixture before heating should be close to the titration value, so that the amount of glucose standard solution added after boiling is 0.5 to 1 ml. If it exceeds or is insufficient, increase or decrease it as appropriate. Take the average value of two parallel tests (the difference in titration value should not exceed 0.1 ml). Calculate according to formula (17). K-
Wherein: K is equivalent to the number of grams of glucose per milliliter of Fehling's solution; W is the weight of glucose, which is about 1.0000g; C is the fixed volume of glucose, ml; V is the volume consumed during the titration of glucose standard solution, ml; 10 is the volume of Fehling's A and Fehling's B solutions, ml. ......(17)
Note: The colorless reduced methylene blue is easily oxidized by oxygen in the air. The temperature of the electric furnace should be adjusted so that the solution in the bottle remains boiling and the liquid surface is covered with water vapor and does not come into contact with the air. During the entire titration process, the conical flask cannot be shaken at will without leaving the electric furnace.
5.7.6.4 Determination steps of reducing sugar
a. Preparation of test solution: Take 25ml of filtered juice (see 5.7.4), dilute to 250ml with distilled water, approved by the National Bureau of Standards on August 31, 1987
implemented on July 1, 1988
GB8210-1987
Shake well, and inject into the burette.
b. Preliminary titration: the same as the preliminary titration of Fehling's solution. C. Formal titration: the same as the formal titration of Fehling's solution, and the test is repeated three times. d. Calculation of results: Calculate the reducing sugar content according to formula (18). Reducing sugar (g/100ml juice) =
grams of glucose per ml of Fehling's solution; where: K
volume of original juice, ml;
volume of juice diluted to volume, ml;
V- volume consumed during titration of test solution, ml;
10- volume of Fehling's A and Fehling's B solutions, ml. 5.7.6.5 Determination steps of invert sugar
· (18)
a. Preparation of test solution: Pipette 5ml of filtered juice (see 5.7.4) into a 100ml volumetric flask, add distilled water to 50ml, add 3ml of concentrated hydrochloric acid and shake well. Place the volumetric flask in a constant temperature water bath for conversion, so that the temperature of the conversion solution reaches 80℃ in 2-2.5min, and keep it at 80±2℃ for 10min, then take it out and place it in running water to quickly cool it to 20℃, add 2 drops of methyl red indicator, neutralize it with 40% and 10% sodium hydroxide solution, if it is excessive, adjust it with 1:3 hydrochloric acid, add distilled water to the scale, shake well, and inject it into the burette. b. Preliminary titration: the same as the preliminary titration with the calibration of Fehling's solution. C. Formal titration: the same as the formal titration with the calibration of Fehling's solution, and the test is repeated three times in parallel. d. Calculation of results: the same as reducing sugar.
5.7.6.6 Calculation of total sugar: Calculate the content according to formula (19). Sucrose (g/100ml juice) = (inverted sugar - reducing sugar) × 0.95 Total sugar (g/100ml juice) = sucrose + reducing sugar Where: 0.95 - coefficient of conversion from inverted sugar to sucrose. Note: The relative error of the parallel test results of reducing sugar and invert sugar shall not exceed 2%. 5.7.7 Determination of titratable acid - indicator method (conventional method) (19)
5.7.7.1 Principle: Use sodium hydroxide standard solution to neutralize and titrate the sample solution, use phenolphthalein as the indicator, and calculate the acid content based on the volume of the consumed alkali solution. 5.7.7.2 Instruments and equipment: basic burette, conical flask, volumetric flask, pipette, 0.1 and 0.0001g sensitivity balance, etc.
5.7.7.3 Reagents:
a. 1% phenolic acid indicator: 1g phenolic acid is dissolved in 100ml 95% ethanol solution and stored in a dropper bottle. bC (Na0H) = 0.1mol/1 Sodium hydroxide standard solution: Use a 0.1g sensitivity balance to quickly weigh 4g of analytical pure sodium hydroxide, dissolve it in distilled water and dilute to 1000ml, shake the hook. Standardization of sodium hydroxide solution: Accurately weigh 0.3-0.4g (accurate to 0.0001g) of the standard reagent potassium hydrogen phthalate (KHCsH4O4) that has been dried at 120℃ for more than 2h, put it into a 250ml conical flask, add about 100ml of distilled water to dissolve, and add 2-3 drops of 1% phenolic acid indicator. Titrate with sodium hydroxide standard solution until the microscopic red does not fade for 30s. Perform parallel tests 3-5 times and take the average value. Calculate the concentration of sodium hydroxide standard solution according to formula (20).
Concentration of sodium hydroxide standard solution, mol/L; where: M
W—weight of potassium hydrogen phthalate, g; V—volume of sodium hydroxide standard solution consumed in titration, ml; Approved by the National Bureau of Standards on August 31, 1987
·(20)
Implementation on July 1, 1988
GB8210-1987
0.2042—mmo1/1 of potassium hydrogen phthalate. 5.7.7.4 Steps: Absorb the filtered juice (see 5.7.4) 25ml, dilute to 250ml with distilled water, shake well. Take 10ml of this diluted juice, put it into a 150ml conical flask, add 2-3 drops of 1% phenolic acid. Titrate with a calibrated sodium hydroxide standard solution until the reddish color does not fade for 30 seconds as the end point. Perform two parallel tests and take the average value. Perform a blank test at the same time.
5.7.7.5 Result calculation: Calculate the content of titratable acid according to formula (21). Titratable acid (calculated as citric acid, g/10ml Juice)-V)xMx0.064×100.（(21)G/C×10
Wherein: V is the volume of sodium hydroxide standard solution consumed in sample titration, ml; V is the volume of sodium hydroxide standard solution consumed in blank test, ml; M is the concentration of sodium hydroxide standard solution, mol/L; G is the volume of original juice, ml;
0.064—1m10.1mol/1 sodium hydroxide solution is equivalent to the number of grams of citric acid; 10 is the volume of diluted juice taken during titration, ml. Note: ① The relative error of parallel test results shall not exceed 2%. ② The water used in the test shall be distilled water that has been boiled and cooled. 5.7.8 Ascorbic acid determination—2,6-dichloroindophenol titration method 5.7.8.1 Principle: Use blue alkaline 2,6-dichloroindophenol dye standard solution to titrate the acid containing ascorbic acid. The leaching solution is subjected to redox titration, and the dye is reduced to colorless. When the titration endpoint is reached, the excess dye appears light red in the acidic medium. The content of ascorbic acid is calculated from the amount of dye used. 5.7.8.2 Instruments and equipment: microburette, conical flask, volumetric flask, pipette, 0.1 and 0.0001g sensitivity balance, etc.
5.7.8.3 Reagents
a. 2% oxalic acid solution: weigh 20g of analytical pure oxalic acid (CHzC0O4), dissolve it in distilled water, and dilute to 1000ml.
b. Ascorbic acid standard solution: accurately weigh 100mg (accurate to 0.1mg) of analytical pure ascorbic acid that has been dried in P2Os for more than 5h, dissolve it in 2% oxalic acid solution, dilute to 100ml, shake well, and store in the refrigerator. ||tt| |c.2,6-Dichloroindophenol (2,6-dichlorophenol sodium indoxyl) solution: weigh 52.5 mg of sodium bicarbonate (NaHCO3) and dissolve it in 200 ml of boiling hot distilled water (50-60°C), then weigh 62.5 mg of 2,6-dichloroindophenol and dissolve it in the above sodium bicarbonate solution, cool and dilute to 250 ml, filter into a brown reagent bottle, and store in a refrigerator. Calibrate once a week to ensure the accuracy of the measurement. Calibration of 2,6-dichloroindophenol solution: Pipette 5 ml of standard ascorbic acid solution into a 150 ml conical flask, add 5 ml of 2% oxalic acid solution, and immediately titrate with 2,6-dichloroindophenol solution until the color turns slightly red and does not fade for 15 seconds as the end point. Perform parallel tests 2-3 times. Perform a blank test at the same time. Calculate the titer according to formula (22). CxV
..·( 22)
The number of milligrams of ascorbic acid (or titer) equivalent to each milliliter of 2,6-dichloroindophenol solution; where: T
VThe volume of ascorbic acid absorbed, ml;
VThe volume of 2,6-dichloroindophenol solution consumed in titrating the standard ascorbic acid solution, mlV. The volume of 2,6-dichloroindophenol solution consumed in the blank titration, ml; C—Concentration of ascorbic acid standard solution, mg/ml. Approved by the State Bureau of Standards on August 31, 1987
Implemented on July 1, 1988
GB8210—1987
5.7.8.4 Determination steps: Pipette 10ml of filtered juice (see 5.7.4) (if the sample solution is colored, use white clay for decolorization) into a 100ml volumetric flask and immediately dilute to the mark with 2% oxalic acid solution. Take 10ml of this dilution and inject it into a 150ml conical flask. Titrate with the calibrated 6-dichloroindophenol solution until the color turns slightly red and does not fade for 15s. Perform a blank test at the same time. 5.7.8.5 Calculation of results: Calculate the ascorbic acid content according to formula (23). Ascorbic acid (mg/10ml juice) = × (VV) x 100W
Where: T is the number of milligrams of ascorbic acid per milliliter of 2,6-dichloroindophenol solution V is the volume of 2,6-dichloroindophenol solution consumed in the sample titration, ml; V is the volume of 2,6-dichloroindophenol solution consumed in the blank titration, ml; W is the amount of juice used for titration, 10×10/100, ml. Note: ① The relative error of the parallel test results shall not exceed 2%. …(23)
②If 2,6-dichloroindophenol dye contains decomposition products or its prepared stock solution contains decomposition products, the endpoint of the titration will be unclear. Each time 2,6-dichloroindophenol dye is used, it must be calibrated with a newly prepared ascorbic acid standard solution. 1 ml of pure dye is equivalent to 0.088 mg of ascorbic acid. If it is too much less than this number, it should be discarded and re-prepared. If the dye is impure, a new reagent must be replaced. ③All reagents must be prepared with double distilled water. ④Ascorbic acid is easily oxidized in solution. During the entire determination process, the operation should be rapid. At the beginning of the titration, the dye is added quickly until the red color does not disappear immediately, and then added drop by drop, and continued to add drop by drop, and the conical flask is continuously shaken until the endpoint. The entire titration time should not exceed 2 minutes. The ascorbic acid purity test method refers to Appendix B of GB6195-1986 "Determination of Vitamin C Content in Fruits and Vegetables (2,6-Dichloroindophenol Titration Method)".
③After the sample is taken out, it should be soaked in 2% oxalic acid solution as soon as possible to avoid oxidation and loss of ascorbic acid. 5.8 Packaging inspection
5.8.1 The packaging inspection of exported citrus mainly inspects the finished citrus for export. If necessary, the semi-finished fruit boxes can be inspected.
5.8.2 Inspection quantity: the same as Article 4.1.
5.8.3 Inspection content and method
5.8.3.1 Appearance inspection: When sampling, the structure, appearance, color, holes, nailing, sealing, bundling, sealing, marks and logos of the whole batch of fruit boxes shall be comprehensively inspected. Whether it meets the requirements of cleanliness, dryness, firmness and integrity; the specifications and quantity of the iron nails, whether the nail feet inserted into the box are flat, whether the nail tips penetrate the inside and outside of the box; whether the slits of the wooden box and the holes of the carton are unobstructed; whether the carton is damp, deformed, or delaminated; whether the nailing, sealing, and bundling holes are firm; whether the marks and logos are clear, complete, correct, and do not fade. 5.8.3.2 Specifications and dimensions: Measure the outer diameter and inner diameter of the sample box. 5.8.3.3 Inner packaging: After the sample box is opened, check the lining, middle partition, fruit wrapping paper, packaging, and arrangement of each box; check the number of fruits; check whether the color, cleanliness, size and quality of the fruit wrapping paper and box padding paper meet the specified requirements.
5.8.3.4 Moisture content: Measured with a semiconductor moisture meter. 5.8.3.5 Determination of pressure resistance: Measured with a hydraulic pressure gauge or direct weighing and pressure testing. 6 Inspection results and filling in the result report
6.1 Provisions on significant figures of inspection results
Decomposition, physical and chemical items: 0.01%;
Other items: 0.1%;
Approved by the National Bureau of Standards on August 31, 1987
Implementation on July 1, 1988
GB8210-1987
The figures after the significant figures of the inspection results shall be rounded according to the numerical rounding rules in GB1.1-1981 "General Provisions for the Preparation of Standards for Standardization Work Guidelines". 62 Result report: After the inspection is completed, write out the inspection result report, which shall include the method of use, inspection results and other factors that may affect the results. 6.3 Certificate notes: Notes shall be made according to the contract requirements, and the port of transshipment shall issue the certificate, and the origin bureau shall issue the qualified appraisal form. Contents of the certificate:
Appearance quality
Fruits with rot and other serious defects
Fruits with general defects (unqualified fruits)
Grade, specification (group)
Other items shall be noted according to the contract requirements
For contracts for transporting goods to Hong Kong and Macao that do not require certificates, fill out and issue the shipping order. Appendix A
Correction table of soluble solids and temperature
(Supplement)
Approved by the National Bureau of Standards on August 31, 19875
Soluble solids
Implementation on July 1, 1988
GB8210-1987
Appendix B
Acidometer method for determination of titratable acid (reference method) (reference)
B.1 Principle: Potentiometric titration of the sample solution with sodium hydroxide standard solution, and the acid content is calculated based on the volume of alkaline solution consumed.
B.2 Apparatus: Acidometer, magnetic stirrer, alkaline burette, beaker, pipette. B.3 Reagents: Same as 5.7.7.3.
B.4 Steps: Pipette diluted juice (see 5.7.7.4) 50ml, put it into a 150ml beaker, carefully insert the calomel glass electrode of the accurately adjusted pH acidity meter into the test solution in the beaker, turn on the magnetic stirrer (if there is no magnetic stirrer, you can use a glass rod to stir carefully, be careful not to hit the small bubble at the end of the glass electrode), turn on the reading button of the acidity meter, quickly titrate to pH7 with sodium hydroxide standard solution, and then slowly drip until pH8.1±0.2 is the end point. Perform two parallel tests and take the average value. At the same time, perform a blank test. B.5 Result calculation: Same as 5.7.7.5.
Appendix C
Ascorbic acid determination - xylene-dichloroindophenol colorimetric method (applicable to dark samples) (supplement)
C.1 Principle: Use a quantitative 2,6-dichloroindophenol dye solution to carry out redox reaction with ascorbic acid in the sample. The excess dye is red in an acidic environment. After extraction with xylene, the colorimetric analysis is performed. Within a certain range, the absorbance is linearly related to the dye concentration. The ascorbic acid content is calculated by the difference subtraction method based on the residual dye concentration.
C.2 Instruments and equipment: spectrophotometer or colorimeter, 50ml stoppered test tube, etc. C.3 Reagents
C.3.1 Sodium acetate buffer solution (pH 4.0): 500ml 150% sodium acetate solution (250g sodium acetate is dissolved and diluted to 500ml with distilled water) mixed with 500ml glacial acetic acid. C.3.22% metaphosphoric acid solution: 2g metaphosphoric acid is diluted to 100ml with distilled water. C. 3.3 2,6-Dichloroindophenol solution: Same as 5.7.8.3. C.3.4 Xylene: Analytical pure product.
C.4 Drawing of standard curve: Use 7 50ml stoppered test tubes to add 5ml 2% metaphosphoric acid solution (or 2% oxalic acid solution) and 5ml pH 4.0 sodium acetate buffer, then add 0.0, 0.1, 0.3, 0.6, 0.9, 1.2 and 1.5ml 2,6-dichloroindophenol solution in turn, shake vigorously for 5s, then add 10ml xylene to each test tube and shake vigorously for 20s, let stand for stratification, draw the same volume of extract from the center of the xylene layer of each tube, put it into a 1cm colorimetric cup, perform colorimetry at a wavelength of 500nm, and record the absorbance (the test solution without dye is used as blank). Draw the standard curve with absorbance as the ordinate and the number of milliliters of 2,6-dichloroindophenol solution as the abscissa.
C.5 Sample determination steps: Pipette 5ml of diluted sample solution (see 5.7.8.4) into a 50ml stoppered test tube, add 5ml of pH 4.0 sodium acetate buffer and 2ml of dye solution, and shake vigorously for 5s. The following operations are carried out according to Appendix C.4. Colorimetrically record the absorbance A, and find the milliliters of 2,6-dichloroindophenol solution in the xylene layer on the standard curve. The entire operation should be completed within 30 minutes. C.6 Result calculation: Calculate the ascorbic acid content according to the following formula. Approved by the National Bureau of Standards on August 31, 1987
Implementation on July 1, 1988
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