GB/T 15550-1995 Specification for the preservation of fresh milk by the activated milk lactoperoxidase system
Some standard content:
National Standard of the People's Republic of China
Code of practice for the preservation of raw and fresh milk by activating the lactoperoxidase system1Main content and scope of application
GB/T15550-95
This standard specifies the method of using the lactoperoxidase system to prevent bacterial spoilage of fresh milk (including buffalo milk, the same below) during storage, collection and transportation to dairy processing plants after milking. This standard applies to the technical requirements for the use of the lactoperoxidase system to preserve fresh milk and prevent milk spoilage. 2 Reference standards
GB1268 Chemical reagent sodium thiocyanate
GB2760 Hygienic standard for the use of food additives GB6684 Chemical reagent 30% hydrogen peroxide
GB6914 Standard for the purchase of fresh milk
3 Terminology
3.1 Lactoperoxidase (lactoperoxidase) is codenamed LP and exists in the whey of milk. It is about 1% of the whey protein containing iron. The LP in milk is about 10-30μg/mL. The characteristic of LP is that it is relatively stable to heat. Ordinary pasteurization (62℃30min or 72℃15s) cannot make it lose its activity, but 80℃2.5s can destroy it. 3.2 Lactoperoxidase system (lactoperoxidase system) is codenamed LPS. It exists naturally in fresh milk (including buffalo milk) and human saliva. It is an antioxidant system composed of three substances: lactoperoxidase, thiocyanate and hydrogen peroxide. 3.3 Hydrogen peroxide (hydrogen peroxide) has a chemical formula of H02 and is a strong oxidant. The specific gravity of 100% hydrogen peroxide at 18°C is 1.4465. 3.4 Sodium percarbonate is a dry, white, crystalline fine powder compound that is highly soluble in water and can slowly release hydrogen peroxide in water. Therefore, it is a strong oxidant. At present, it has been used as the main component of milk preservatives abroad. The molecular formula is 2Na2CO, ·3H,Oz. 3.5 Thiocyanate (thiocyanate)
The chemical formula is SCN-, which can also be written as CNS-. It is an anion present in all tissues and secretions of animals. The content of SCN- in milk is 2～7(1～15)ppm. SCN- has weak toxicity and cumulative toxicity. When used as a milk preservative, it must be strictly followed in accordance with this implementation specification and is strictly prohibited from overflow.
Approved by the State Administration of Technical Supervision on April 19, 1995 and implemented on December 1, 1995
4 Principle of the method
GB/T 15550-
The concentration of lactoperoxidase in fresh milk is quite high, enough to meet its formation of LPS to achieve antibacterial needs (0.5ug/mL). In the presence of H2O2, SCN- is oxidized to thiocyanate (HOSCN). Under the pH value of milk (pH6.4～6.8), thiocyanate will separate and exist mainly in the form of thiocyanate ion (OSCN-). This ion specifically combines with the free sulfhydryl groups (SH) on the surface of bacterial cells, causing several enzymes related to life metabolism of bacteria to lose their activity, hindering the metabolism and proliferation of bacteria.
This antibacterial thiocyanate oxide is unstable under neutral pH conditions and easily decomposes spontaneously into thiocyanate. The speed of the decomposition reaction depends on the temperature, and the decomposition is faster at higher temperatures. Pasteurization of milk can ensure that the residues of this active oxidation product are completely removed. When milk just leaves the breast, the degree of oxidation of thiocyanate is very small, but this oxidation can be promoted by adding low-concentration hydrogen peroxide. When high concentrations (300-800ppm) of H2O2 are used to preserve raw milk, the lactoperoxidase in the milk will be destroyed, the oxidation of thiocyanate will be prevented, and the bactericidal effect of H2O2 itself will be used to fight bacteria. SCN- combines with HO2 in equimolar combinations. If the concentration of H,O is low, some SCN- cannot be oxidized, the production of OSCN- is reduced, and the preservation effect is weakened accordingly; if the concentration of H,O is high, a higher oxygen-containing acid with a shorter existence time than OSCN- will be produced, such as cyanosulfite (HO,SCN) and oxosulfate (HO.SCN), which are decomposed into O,SCN- and OSCN- respectively in milk. Although its bactericidal power is stronger than OSCN-, it is extremely unstable and exists for too short a time, so the preservation effect is still weakened. When the provided H,O is equimolar, the antibacterial effect of LPS is positively correlated with the concentration of SCN- within a certain limit. When this method is used for preservation, SCN- needs to be added to ensure that the SCN- level in the milk reaches the required antibacterial effect. 5 Preparation of preservatives
5.1 The preservative is composed of sodium thiocyanate and hydrogen peroxide or sodium percarbonate. Sodium thiocyanate and hydrogen peroxide must be not less than the analytical grade in GB2168 and GB6684 respectively. Due to the lack of national standards for sodium percarbonate, it is temporarily stipulated that it shall not be lower than Appendix A of the "Specifications for Sodium Percarbonate" formulated by the 35th session of the United Nations JECFA1). Note: 1) JECFA is the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives. 5.2 Preservatives are divided into solid and liquid forms according to their form, and have the same preservation effect. 5.2.1 Solid preservatives are composed of sodium thiocyanate and sodium percarbonate. 5.2.1.1 Sodium thiocyanate addition amount: 15 mg per kg of fresh milk. 5.2.1.2 Sodium percarbonate addition amount: 30.8 mg per dry gram of fresh milk when the purity is 85%. 5.2.1.3 Packaging: The above two agents must be separated, packaged separately with food-grade translucent plastic film, and vacuum-sealed; or pressed into tablets with appropriate fillers such as lactose, and sealed with blister plastic film to prevent moisture. Indicate the name and weight of the agent. 5.2.2 Liquid preservatives are composed of sodium thiocyanate solution and hydrogen peroxide solution. 5.2.2.1 Preparation of sodium thiocyanate solution: Weigh 15.0g sodium thiocyanate and pour it into a 100mL constant volume bottle, add 50mL of distilled water and shake it. After it dissolves, add distilled water to the scale of the constant volume bottle, then dispense the solution into non-toxic plastic bottles or glass bottles and seal them. Indicate the name of the drug and the concentration (15g/100mL) on the bottle.
5.2.2.2 Preparation of hydrogen peroxide solution: Use a pipette to draw 19.6mL of 30% hydrogen peroxide solution, transfer it into a 100mL constant volume bottle, add distilled water to the scale, then dispense the solution into non-toxic plastic bottles or brown glass bottles and seal them. Indicate the name of the drug and the concentration (8.5g/100mL) on the bottle.
5.2.2.3 The above two solutions must be packed with instructions for use, and the box must be printed with the product name, factory name, sealing date, expiration date, and precautions for storage and transportation (such as moisture-proof, pressure-proof, etc.). 5.3 Liquid or solid preservatives should be stored in a dark, low-temperature place (3-5°C is appropriate). Liquid preservatives must be frequently checked with newly prepared solutions to check their effectiveness in preserving milk, and should be replaced in time when the effectiveness decreases. 5.4 The hydrogen peroxide solution in the liquid preservative is easy to decompose. The storage period in a refrigerator at 3-5°C should not exceed two months, and it should not exceed two weeks at room temperature below 30°C. The sodium thiocyanate solution can be stored in a refrigerator at 3~~5°C for 4 months or at room temperature for 3 months without affecting the preservation effect. Sodium thiocyanate in the solid preservative is too easy to deliquesce, and attention should be paid to process problems when processing tablets. After the sodium thiocyanate in capsules leaves the sealed bag, the storage period at room temperature should not exceed 3 months.
6 Operation method
6.1 Add sodium thiocyanate to the milk. It can be solid or liquid, but only one can be used. Dosage: If it is solid, follow the provisions of 5.2.1.1. If it is liquid, add 1.0mL of sodium thiocyanate solution prepared in 5.2.2.1 to every 10kg of milk. Then stir with a clean stirrer for about 1 minute to mix it evenly. 6.2 Add sodium percarbonate or hydrogen peroxide to the milk. Only one of the two can be added. Dosage: Add sodium percarbonate according to the provisions of 5.2.1.2; add hydrogen peroxide, add 1.0mL of hydrogen peroxide solution prepared in 5.2.2.2 to every 10kg of milk. Stir for another 2~~~3 minutes to make it completely dissolved and evenly distributed in the fresh milk. 6.3 Sodium thiocyanate and sodium percarbonate (or hydrogen peroxide) must be added in the above order, and cannot be reversed, mixed first and added later or added at the same time.
6.4 Adding preservatives should be done within 2 or 3 hours after milking. 7 Usage regulations
7.1. This method must be used only when milk collection centers (stations), points or dairy farms have no cooling facilities or other reasons, otherwise the milk will spoil.
7.2 This method cannot be used by individual farmers and herdsmen, and can only be used in milk collection centers, milk collection points and state-owned farms. Operators must be trained and pass the examination before they can take up their posts. Fresh milk treated with this method must be explained when it is sold to dairy processing plants.
7.3 Fresh milk collected and processed by dairy plants and treated with the LPS method should be used in accordance with the provisions of this method. Dairy plants should establish appropriate control methods (see Chapter 8 for details) to supervise and inspect the application of this method. 7.4 The antibacterial effect of this method depends on the storage temperature of milk. The effective preservation time of raw milk with good hygienic grade under different storage temperature conditions using LPS method is shown in Table 1:
Storage temperature, ℃
Effective preservation time
16~17h
24~26h
About 48h
5~7 nights
7.5 Fresh milk preserved by LPS method must be heated and sterilized before drinking and processing. 7.6 Units that use LPS method to preserve fresh milk must not exclude the application of normal preventive measures and management routines to ensure the good quality and hygienic standards of fresh milk.
8 Control of use
8.1 In areas where LPS method is used to preserve fresh milk, dairy factories must conduct control tests when collecting milk. Such as acid titration, methylene blue test, total viable bacteria test and SCN concentration test. 611
GB/T1555095
8.2 Since SCN- is not consumed in the reaction, when milk treated by LPS method is delivered to the dairy factory, the SCN- concentration should be 10.74 ppm + natural SCN- concentration in milk (the latter can be determined by measuring the local untreated fresh milk). 8.3 Milk samples should be taken randomly from time to time to measure the SCN- concentration. If the measured value exceeds the specified range, the reason must be found out, and the milk should be refused in serious cases.
8.4 Preservative drugs should be ordered and distributed by the dairy factory, which is responsible for supervision and inspection. 612
GB/T 15550—95
Appendix A
Technical specifications for sodium percarbonate
(Supplement)
There is no national standard for this chemical reagent in my country. Reference to the "Specification Standard for Sodium Percarbonate" formulated by the 35th session of the United Nations JECFA, the requirements are as follows:
A1 Alias: Sodium carbonate peroxyhydrate, sodium peroxycarbonate. A2 Definition: Chemical name
CAS number:
Chemical formula:
Relative molecular mass:
Analytical purity:
Sodium percarbonate
15630-89-4
2Na2CO3.· 3H2O2
Available oxygen is not less than 13% (equivalent to 85% purity)A3 Description: Dry, white, crystalline fine powder. Note: It is a strong oxidant and should be avoided from contact with eyes and skin. A4 Function and use: Antimicrobial synergist (a component of the lactoperoxidase/thiocyanate/peroxide antimicrobial raw milk preservation system).
A5 Characteristics:
A5.1 Identification test:
Solubility: easily soluble in water (the commercial product solution is not clear) pH: about 10.5 (1% solution)
Positive sodium test
A5.2 Purity test:
Arsenic: not more than 3mg/kg
Heavy metals: not more than 10mg/kg (such as Pb) A6 Analysis method:
A6.1 Procedure:
Amount Carefully add 100 mL sulfuric acid solution Cc(H,SO,)=1.8mol/L) to a 600mL beaker, and accurately weigh about 4g of sample with a tared watchglass. Assume that the weight of this sample is mg. Put the weighed blood into the beaker, cover the beaker with a clockglass, and shake the hook to dissolve the sample. Transfer the solution to a 500mL volumetric flask, rinse the watch glass and beaker wall with distilled water, and pour all the rinse solution into the volumetric flask, then dilute to the mark with distilled water and mix thoroughly. Take 100mL sulfuric acid solution [Cc(H,SO.)=1.8mol/L] and add it to a 600mL conical flask, and add potassium permanganate solution [c(-KMnO,)-0.1mol/L) to titrate until a dark and persistent pink color appears. Use a safety pipette to add 25.0mL of sample solution and mix thoroughly. Titrate with potassium permanganate solution [c(
VmL.
A6.2 Calculation
-KMnO.)=0.1mol/L) until a dark and persistent pink color appears again. Assume that the titration result is the content of available oxygen in the sample and calculate it as shown in formula (A1): Available oxygen (as 0,)% =
V × c× 8× 500
V×c× 1.6
×100=
10 × 1 000 × 25 × m
Wherein: c is the molar concentration of potassium permanganate solution, mol/L, m
-sample weight, 8;
-amount of potassium permanganate solution used, mL.
.....(A1)
GB/T15550-95
Appendix B
Analysis of SCN- in milk
(Supplement)
B1 Principle: After milk is separated and defatted, trichloroacetic acid (TCA) is added to remove protein, and then high iron complex is added. The absorbance is measured at a wavelength of 460 nm to measure the SCN2 content. The minimum concentration that can be measured is 1-2ppm. B2 Reagent solution
B2.120% (m/V) trifluoroacetic acid (TCA) solution: Dissolve 20g TCA (analytical grade) in 100mL distilled water and filter to obtain. B2.2 Ferric nitrate reagent: Dissolve 16.0 g of ferric nitrate [Fe(NO):·9H,O] (analytical grade) in 50 mL of nitric acid solution Cc(HNO.)-2mol/L>1), and dilute to 100 mL with distilled water. The prepared solution should be stored in a dark and cool place. Note: 1) Preparation of nitric acid solution Cc(HNOs)=2mol/LJ: Dilute 138.5 mL of 65% HNOs (analytical grade) with distilled water to 1000 mL. B3 Determination: Take 4 mL of milk, centrifuge and skim, add 2.0 mL of 20% TCA solution, mix well, let stand (preferably in a refrigerator at 3-5℃) for no less than 30 minutes, and then filter. Take 1.5 mL of the clear filtrate and add 1.5 mL of ferric nitrate reagent. After mixing, measure the absorbance at a wavelength of 460 nm. At the same time, use 1.5 mL of ferric nitrate reagent and 1.5 mL of distilled water to mix well as a blank control. The determination must be carried out within 10 minutes after the addition of the ferric nitrate reagent. Because the color complex is unstable, it will change after a while. The result obtained is compared with the results (standard) obtained by the same treatment of 5 to 6 known SCN solutions of different concentrations (such as 5, 10.15, 20 and 30 ppm), and the concentration of SCN in milk can be calculated.
Additional notes:
This standard is proposed by the Ministry of Agriculture of the People's Republic of China. This standard is drafted by the Institute of Animal Husbandry of the Chinese Academy of Agricultural Sciences. The main drafter of this standard is Zhu Peng.
This standard refers to the "Code of Practice for Preserving Raw Milk Using the Lactoperoxidase System" formulated by the International Dairy Federation (IDF) approved by the United Nations Codex Alimentarius Commission (CAC) and the CAS15630-89 "Specification Standard for Sodium Percarbonate" formulated by the 35th session (1989) of the Joint FAO/WHO Expert Committee on Food Additives (JECFA). 6146 Units using the LPS method to preserve fresh milk must not exclude the use of normal preventive measures and management routines to ensure the good quality and hygiene standards of fresh milk.
8 Control of use
8.1 In areas where the LPS method for preserving fresh milk is implemented, dairy factories must conduct control tests when receiving milk. Such as acid titration, methylene blue test, total viable bacteria test and SCN concentration test. 611
GB/T1555095
8.2 Because SCN- is not consumed in the reaction, when milk treated with the LPS method is delivered to the dairy factory, the SCN- concentration should be 10.74 ppm + the natural SCN- concentration in milk (the latter can be determined by measuring the local untreated fresh milk). 8.3 Milk samples should be randomly taken from time to time to measure the SCN- concentration. If the measured value exceeds the specified range, the reason must be found out, and the milk should be refused if the circumstances are serious.
8.4 Preservatives should be ordered and distributed by the dairy factory, and the factory should be responsible for supervision and inspection. 612
GB/T 15550—95
Appendix A
Technical Specifications of Sodium Percarbonate
(Supplement)
There is no national standard for this chemical reagent in my country. The requirements are as follows:
A1 Alias: Sodium carbonate peroxyhydrate, sodium peroxycarbonate. A2 Definition: Chemical name
CAS number:
Chemical formula:
Relative molecular mass:
Analytical purity:
Sodium percarbonate
15630-89-4
2Na2CO3.· 3H2O2
Available oxygen is not less than 13% (equivalent to 85% purity) A3 Description: Dry, white, crystalline fine powder. Caution: It is a strong oxidant. Avoid contact with eyes and skin. A4 Function and use: Antimicrobial synergist (part of the lactoperoxidase/thiocyanate/peroxide antimicrobial raw milk preservation system).
A5 Characteristics:
A5.1 Identification test:
Solubility: easily soluble in water (the commercial product solution is not clear) pH: about 10.5 (1% solution)
Positive sodium test
A5.2 Purity test:
Arsenic: not more than 3mg/kg
Heavy metals: not more than 10mg/kg (such as Pb) A6 Analytical method:
A6.1 Procedure:
Amount Carefully add 100 mL sulfuric acid solution Cc(H,SO,)=1.8mol/L) into a 600mL beaker and accurately weigh about 4g of sample using a tared watchglass. Assume that the weight of this sample is mg. Put the weighed blood into a beaker, cover the beaker with a clockglass, and shake the hook to dissolve the sample. Transfer the solution into a 500mL volumetric flask, rinse the clockglass and the beaker wall with distilled water, and pour all the rinse solution into the volumetric flask, then dilute to the scale with distilled water and mix thoroughly. Take 100 mL of sulfuric acid solution [Cc(H,SO.)=1.8mol/L] and add it to a 600 mL conical flask, and add potassium permanganate solution [c(-KMnO,)-0.1mol/L) to titrate until a dark and persistent pink color appears. Use a safety pipette to add 25.0mL of sample solution and mix thoroughly. Titrate with potassium permanganate solution [c(
VmL.
A6.2 Calculation
-KMnO.)=0.1mol/L) until a dark and persistent pink color appears again. Assume that the titration result is the content of available oxygen in the sample and calculate it as shown in formula (A1): Available oxygen (as 0,)% =
V × c× 8× 500
V×c× 1.6
×100=
10 × 1 000 × 25 × m
Wherein: c is the molar concentration of potassium permanganate solution, mol/L, m
-sample weight, 8;
-amount of potassium permanganate solution used, mL.
.....(A1)
GB/T15550-95
Appendix B
Analysis of SCN- in milk
(Supplement)
B1 Principle: After milk is separated and defatted, trichloroacetic acid (TCA) is added to remove protein, and then high iron complex is added. The absorbance is measured at a wavelength of 460 nm to measure the SCN2 content. The minimum concentration that can be measured is 1-2ppm. B2 Reagent solution
B2.120% (m/V) trifluoroacetic acid (TCA) solution: Dissolve 20g TCA (analytical grade) in 100mL distilled water and filter to obtain. B2.2 Ferric nitrate reagent: Dissolve 16.0 g of ferric nitrate [Fe(NO):·9H,O] (analytical grade) in 50 mL of nitric acid solution Cc(HNO.)-2mol/L>1), and dilute to 100 mL with distilled water. The prepared solution should be stored in a dark and cool place. Note: 1) Preparation of nitric acid solution Cc(HNOs)=2mol/LJ: Dilute 138.5 mL of 65% HNOs (analytical grade) with distilled water to 1000 mL. B3 Determination: Take 4 mL of milk, centrifuge and skim, add 2.0 mL of 20% TCA solution, mix well, let stand (preferably in a refrigerator at 3-5℃) for no less than 30 minutes, and then filter. Take 1.5 mL of the clear filtrate and add 1.5 mL of ferric nitrate reagent. After mixing, measure the absorbance at a wavelength of 460 nm. At the same time, use 1.5 mL of ferric nitrate reagent and 1.5 mL of distilled water to mix well as a blank control. The determination must be carried out within 10 minutes after the addition of the ferric nitrate reagent. Because the color complex is unstable, it will change after a while. The result obtained is compared with the results (standard) obtained by the same treatment of 5 to 6 known SCN solutions of different concentrations (such as 5, 10.15, 20 and 30 ppm), and the concentration of SCN in milk can be calculated.
Additional notes:
This standard is proposed by the Ministry of Agriculture of the People's Republic of China. This standard is drafted by the Institute of Animal Husbandry of the Chinese Academy of Agricultural Sciences. The main drafter of this standard is Zhu Peng.
This standard refers to the "Code of Practice for Preserving Raw Milk Using the Lactoperoxidase System" formulated by the International Dairy Federation (IDF) approved by the United Nations Codex Alimentarius Commission (CAC) and the CAS15630-89 "Specification Standard for Sodium Percarbonate" formulated by the 35th session (1989) of the Joint FAO/WHO Expert Committee on Food Additives (JECFA). 6146 Units using the LPS method to preserve fresh milk must not exclude the use of normal preventive measures and management routines to ensure the good quality and hygiene standards of fresh milk.
8 Control of use
8.1 In areas where the LPS method for preserving fresh milk is implemented, dairy factories must conduct control tests when receiving milk. Such as acid titration, methylene blue test, total viable bacteria test and SCN concentration test. 611
GB/T1555095
8.2 Because SCN- is not consumed in the reaction, when milk treated with the LPS method is delivered to the dairy factory, the SCN- concentration should be 10.74 ppm + the natural SCN- concentration in milk (the latter can be determined by measuring the local untreated fresh milk). 8.3 Milk samples should be randomly taken from time to time to measure the SCN- concentration. If the measured value exceeds the specified range, the reason must be found out, and the milk should be refused if the circumstances are serious.
8.4 Preservatives should be ordered and distributed by the dairy factory, and the factory should be responsible for supervision and inspection. 612
GB/T 15550—95
Appendix A
Technical Specifications of Sodium Percarbonate
(Supplement)
There is no national standard for this chemical reagent in my country. The requirements are as follows:
A1 Alias: Sodium carbonate peroxyhydrate, sodium peroxycarbonate. A2 Definition: Chemical name
CAS number:
Chemical formula:
Relative molecular mass:
Analytical purity:
Sodium percarbonate
15630-89-4
2Na2CO3.· 3H2O2
Available oxygen is not less than 13% (equivalent to 85% purity) A3 Description: Dry, white, crystalline fine powder. Caution: It is a strong oxidant. Avoid contact with eyes and skin. A4 Function and use: Antimicrobial synergist (part of the lactoperoxidase/thiocyanate/peroxide antimicrobial raw milk preservation system).
A5 Characteristics:
A5.1 Identification test:
Solubility: easily soluble in water (the commercial product solution is not clear) pH: about 10.5 (1% solution)
Positive sodium test
A5.2 Purity test:
Arsenic: not more than 3mg/kg
Heavy metals: not more than 10mg/kg (such as Pb) A6 Analytical method:
A6.1 Procedure:
Amount Carefully add 100 mL sulfuric acid solution Cc(H,SO,)=1.8mol/L) into a 600mL beaker and accurately weigh about 4g of sample using a tared watchglass. Assume that the weight of this sample is mg. Put the weighed blood into a beaker, cover the beaker with a clockglass, and shake the hook to dissolve the sample. Transfer the solution into a 500mL volumetric flask, rinse the clockglass and the beaker wall with distilled water, and pour all the rinse solution into the volumetric flask, then dilute to the scale with distilled water and mix thoroughly. Take 100 mL of sulfuric acid solution [Cc(H,SO.)=1.8mol/L] and add it to a 600 mL conical flask, and add potassium permanganate solution [c(-KMnO,)-0.1mol/L) to titrate until a dark and persistent pink color appears. Use a safety pipette to add 25.0mL of sample solution and mix thoroughly. Titrate with potassium permanganate solution [c(
VmL.
A6.2 Calculation
-KMnO.)=0.1mol/L) until a dark and persistent pink color appears again. Assume that the titration result is the content of available oxygen in the sample and calculate it as shown in formula (A1): Available oxygen (as 0,)% =
V × c× 8× 500
V×c× 1.6
×100=
10 × 1 000 × 25 × m
Wherein: c is the molar concentration of potassium permanganate solution, mol/L, m
-sample weight, 8;
-amount of potassium permanganate solution used, mL.
.....(A1)
GB/T15550-95
Appendix B
Analysis of SCN- in milk
(Supplement)
B1 Principle: After milk is separated and defatted, trichloroacetic acid (TCA) is added to remove protein, and then high iron complex is added. The absorbance is measured at a wavelength of 460 nm to measure the SCN2 content. The minimum concentration that can be measured is 1-2ppm. B2 Reagent solution
B2.120% (m/V) trifluoroacetic acid (TCA) solution: Dissolve 20g TCA (analytical grade) in 100mL distilled water and filter to obtain. B2.2 Ferric nitrate reagent: Dissolve 16.0 g of ferric nitrate [Fe(NO):·9H,O] (analytical grade) in 50 mL of nitric acid solution Cc(HNO.)-2mol/L>1), and dilute to 100 mL with distilled water. The prepared solution should be stored in a dark and cool place. Note: 1) Preparation of nitric acid solution Cc(HNOs)=2mol/LJ: Dilute 138.5 mL of 65% HNOs (analytical grade) with distilled water to 1000 mL. B3 Determination: Take 4 mL of milk, centrifuge and skim, add 2.0 mL of 20% TCA solution, mix well, let stand (preferably in a refrigerator at 3-5℃) for no less than 30 minutes, and then filter. Take 1.5 mL of the clear filtrate and add 1.5 mL of ferric nitrate reagent. After mixing, measure the absorbance at a wavelength of 460 nm. At the same time, use 1.5 mL of ferric nitrate reagent and 1.5 mL of distilled water to mix well as a blank control. The determination must be carried out within 10 minutes after the addition of the ferric nitrate reagent. Because the color complex is unstable, it will change after a while. The result obtained is compared with the results (standard) obtained by the same treatment of 5 to 6 known SCN solutions of different concentrations (such as 5, 10.15, 20 and 30 ppm), and the concentration of SCN in milk can be calculated.
Additional notes:
This standard is proposed by the Ministry of Agriculture of the People's Republic of China. This standard is drafted by the Institute of Animal Husbandry of the Chinese Academy of Agricultural Sciences. The main drafter of this standard is Zhu Peng.
This standard refers to the "Code of Practice for Preserving Raw Milk Using the Lactoperoxidase System" formulated by the International Dairy Federation (IDF) approved by the United Nations Codex Alimentarius Commission (CAC) and the CAS15630-89 "Specification Standard for Sodium Percarbonate" formulated by the 35th session (1989) of the Joint FAO/WHO Expert Committee on Food Additives (JECFA). 6145 or so (1% solution)
Positive sodium test
A5.2 Purity test:
Arsenic: not more than 3mg/kg
Heavy metals: not more than 10mg/kg (such as Pb)A6 Analysis method:
A6.1 Procedure:
Amount Carefully add 100 mL sulfuric acid solution Cc(H,SO,)=1.8mo1/L) to a 600mL beaker, and accurately weigh about 4g of sample with a tared watchglass. Let the weight of this sample be mg. Put the weighed blood into the beaker, cover the beaker with a clockglass, and shake the hook to dissolve the sample. Transfer the solution into a 500mL volumetric flask, rinse the watchglass and beaker wall with distilled water, and pour all the rinse liquid into the volumetric flask, then dilute to the scale with distilled water and mix thoroughly. Take 100 mL of sulfuric acid solution [Cc(H,SO.)=1.8mol/L] and add it to a 600 mL conical flask, and add potassium permanganate solution [c(-KMnO.)-0.1mol/L) to titrate until a dark persistent pink color appears. Use a safety pipette to add 25.0 mL of sample solution and mix thoroughly. Titrate with potassium permanganate solution [c(
VmL.
A6.2 Calculation
-KMnO.)=0.1mol/L) until a dark persistent pink color appears again. Assume that the titration result is the content of available oxygen in the sample and calculate it as shown in formula (A1): Available oxygen (as 0,)% =
V × c× 8× 500
V×c× 1.6
×100=
10 × 1 000 × 25 × m
Wherein: c is the molar concentration of potassium permanganate solution, mol/L, mWww.bzxZ.net
-sample weight, 8;
-amount of potassium permanganate solution used, mL.
.....(A1)
GB/T15550-95
Appendix B
Analysis of SCN- in milk
(Supplement)
B1 Principle: After milk is separated and defatted, trichloroacetic acid (TCA) is added to remove protein, and then high iron complex is added. The absorbance is measured at a wavelength of 460 nm to measure the SCN2 content. The minimum concentration that can be measured is 1-2ppm. B2 Reagent solution
B2.120% (m/V) trifluoroacetic acid (TCA) solution: Dissolve 20g TCA (analytical grade) in 100mL distilled water and filter to obtain. B2.2 Ferric nitrate reagent: Dissolve 16.0 g of ferric nitrate [Fe(NO):·9H,O] (analytical grade) in 50 mL of nitric acid solution Cc(HNO.)-2mol/L>1), and dilute to 100 mL with distilled water. The prepared solution should be stored in a dark and cool place. Note: 1) Preparation of nitric acid solution Cc(HNOs)=2mol/LJ: Dilute 138.5 mL of 65% HNOs (analytical grade) with distilled water to 1000 mL. B3 Determination: Take 4 mL of milk, centrifuge and skim, add 2.0 mL of 20% TCA solution, mix well, let stand (preferably in a refrigerator at 3-5℃) for no less than 30 minutes, and then filter. Take 1.5 mL of the clear filtrate and add 1.5 mL of ferric nitrate reagent. After mixing, measure the absorbance at a wavelength of 460 nm. At the same time, use 1.5 mL of ferric nitrate reagent and 1.5 mL of distilled water to mix well as a blank control. The determination must be carried out within 10 minutes after the addition of the ferric nitrate reagent. Because the color complex is unstable, it will change after a while. The result obtained is compared with the results (standard) obtained by the same treatment of 5 to 6 known SCN solutions of different concentrations (such as 5, 10.15, 20 and 30 ppm), and the concentration of SCN in milk can be calculated.
Additional notes:
This standard is proposed by the Ministry of Agriculture of the People's Republic of China. This standard is drafted by the Institute of Animal Husbandry of the Chinese Academy of Agricultural Sciences. The main drafter of this standard is Zhu Peng.
This standard refers to the "Code of Practice for Preserving Raw Milk Using the Lactoperoxidase System" formulated by the International Dairy Federation (IDF) approved by the United Nations Codex Alimentarius Commission (CAC) and the CAS15630-89 "Specification Standard for Sodium Percarbonate" formulated by the 35th session (1989) of the Joint FAO/WHO Expert Committee on Food Additives (JECFA). 6145 or so (1% solution)
Positive sodium test
A5.2 Purity test:
Arsenic: not more than 3mg/kg
Heavy metals: not more than 10mg/kg (such as Pb)A6 Analysis method:
A6.1 Procedure:
Amount Carefully add 100 mL sulfuric acid solution Cc(H,SO,)=1.8mo1/L) to a 600mL beaker, and accurately weigh about 4g of sample with a tared watchglass. Let the weight of this sample be mg. Put the weighed blood into the beaker, cover the beaker with a clockglass, and shake the hook to dissolve the sample. Transfer the solution into a 500mL volumetric flask, rinse the watchglass and beaker wall with distilled water, and pour all the rinse liquid into the volumetric flask, then dilute to the scale with distilled water and mix thoroughly. Take 100 mL of sulfuric acid solution [Cc(H,SO.)=1.8mol/L] and add it to a 600 mL conical flask, and add potassium permanganate solution [c(-KMnO.)-0.1mol/L) to titrate until a dark persistent pink color appears. Use a safety pipette to add 25.0 mL of sample solution and mix thoroughly. Titrate with potassium permanganate solution [c(
VmL.
A6.2 Calculation
-KMnO.)=0.1mol/L) until a dark persistent pink color appears again. Assume that the titration result is the content of available oxygen in the sample and calculate it as shown in formula (A1): Available oxygen (as 0,)% =
V × c× 8× 500
V×c× 1.6
×100=
10 × 1 000 × 25 × m
Wherein: c is the molar concentration of potassium permanganate solution, mol/L, m
-sample weight, 8;
-amount of potassium permanganate solution used, mL.
.....(A1)
GB/T15550-95
Appendix B
Analysis of SCN- in milk
(Supplement)
B1 Principle: After milk is separated and defatted, trichloroacetic acid (TCA) is added to remove protein, and then high iron complex is added. The absorbance is measured at a wavelength of 460 nm to measure the SCN2 content. The minimum concentration that can be measured is 1-2ppm. B2 Reagent solution
B2.120% (m/V) trifluoroacetic acid (TCA) solution: Dissolve 20g TCA (analytical grade) in 100mL distilled water and filter to obtain. B2.2 Ferric nitrate reagent: Dissolve 16.0 g of ferric nitrate [Fe(NO):·9H,O] (analytical grade) in 50 mL of nitric acid solution Cc(HNO.)-2mol/L>1), and dilute to 100 mL with distilled water. The prepared solution should be stored in a dark and cool place. Note: 1) Preparation of nitric acid solution Cc(HNOs)=2mol/LJ: Dilute 138.5 mL of 65% HNOs (analytical grade) with distilled water to 1000 mL. B3 Determination: Take 4 mL of milk, centrifuge and skim, add 2.0 mL of 20% TCA solution, mix well, let stand (preferably in a refrigerator at 3-5℃) for no less than 30 minutes, and then filter. Take 1.5 mL of the clear filtrate and add 1.5 mL of ferric nitrate reagent. After mixing, measure the absorbance at a wavelength of 460 nm. At the same time, use 1.5 mL of ferric nitrate reagent and 1.5 mL of distilled water to mix well as a blank control. The determination must be carried out within 10 minutes after the addition of the ferric nitrate reagent. Because the color complex is unstable, it will change after a while. The result obtained is compared with the results (standard) obtained by the same treatment of 5 to 6 known SCN solutions of different concentrations (such as 5, 10.15, 20 and 30 ppm), and the concentration of SCN in milk can be calculated.
Additional notes:
This standard is proposed by the Ministry of Agriculture of the People's Republic of China. This standard is drafted by the Institute of Animal Husbandry of the Chinese Academy of Agricultural Sciences. The main drafter of this standard is Zhu Peng.
This standard refers to the "Code of Practice for Preserving Raw Milk Using the Lactoperoxidase System" formulated by the International Dairy Federation (IDF) approved by the United Nations Codex Alimentarius Commission (CAC) and the CAS15630-89 "Specification Standard for Sodium Percarbonate" formulated by the 35th session (1989) of the Joint FAO/WHO Expert Committee on Food Additives (JECFA). 614
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.