NY/T 939-2016Identification of Reconstituted Milk in Pasteurized and UHT Milk (English PDF)

3.1 Raw milk

The normal milk extruded from the breasts of the healthy dairy animals, it meets the

relevant national requirements and has no ingredient changes.

3.2 Reconstituted milk

The milk obtained by mixing a dried or concentrated dairy product with water in

proportion.

3.3 Heat treatment

The operation that uses heating technology with strength no less than pasteurization,

inhibiting the growth of the microorganisms and killing the microorganisms; while

controlling the physicochemical properties of the heated objects within the only limited

changes.

3.4 Pasteurization

The processing method used to effectively kill pathogenic microorganisms, namely, the

treatment method to keep at a low temperature for a long time (maintain for 30min at

63°C~65°C) or to keep at a high temperature for a short time (maintain for 15s at

72°C~76°C; or maintain for 10s~15s at 80°C~85°C).

3.5 Pasteurized milk

The liquid product with raw milk as the raw material, obtained by pasteurization

process, with the lactulose content less than 100mg/L.

3.6 Ultra high-temperature, UHT

The processing method for effectively killing microorganisms and inhibiting heat-

resistant spores; namely, heating to at least 132°C in a continuous flow state, and

maintaining a very short time of heat treatment.

4.1 Determination of furosine content

4.1.1 Principle

Hydrolyze the specimen by hydrochloric acid, then determine its protein content; after

diluting, the hydrolysate shall be analyzed by high performance liquid chromatography

(HPLC) or ultra-high-performance liquid chromatography (UPLC) under ultraviolet

(wavelength 280nm) detector and quantify by external standard method.

4.1.2 Reagents and materials

Unless otherwise specified, all reagents used in this method shall be analytical

reagents; and the water shall be Class-I water in the laboratory specified in GB/T 6682.

4.1.2.10 Furosine standard stock solution (500.0mg/L). convert the furosine standard

substance as per the Net Peptide Content provided by the standard substance

certificate; then use 3mol/L hydrochloric acid solution to formulate into a standard stock

solution. It can be stored for 24 months at -20°C.

4.1.2.12 Aqueous phase membrane. 0.22µm.

4.1.3 Instruments

4.1.3.1 High Performance Liquid Chromatograph. equipped with a UV detector or

diode array detector.

4.1.3.2 Ultra-High-Performance Liquid Chromatograph. equipped with a UV detector

or diode array detector.

4.1.3.3 Drying oven. (110±2) °C

4.1.3.4 Sealed heat-resistant test tube. volume of 20mL.

4.1.3.5 Balance. the sensitivity of 0.01mg, 1mg.

4.1.3.6 Kjeldahl apparatus.

4.1.6 Result calculation

4.1.6.1 Furosine content in the specimen

The furosine is calculated by mass fraction F; the value of which is expressed in

mg/100g protein; and calculated as per Formula (1).

4.1.6.3 Furosine content at the sterilization of UHT milk

At the end of sterilization of UHT milk, the furosine content shall be calculated by FT;

the value of which shall be expressed by mg/100 protein; and calculated as per

Formula (3).

4.2 Determination of lactulose content

4.2.1 Principle

The sample is hydrolyzed by beta – D – galactosidase to produce galactose and fructose;

the lactulose content is calculated by the enzymatic determination of the amount of

fructose.

4.2.2.30 Glucose oxidase (GOD) suspension (20mg/mL). use sterilized water to

prepare the glucose oxidase with activity of 200 IU/mg into suspension with

concentration of 20mg/mL. It shall be prepared for current use.

4.2.2.31 Catalase suspension (20mg/mL). use sterilized water to prepare the catalase

with activity of 65000 IU/mg into suspension with concentration of 20mg/mL. It shall be

stored at 4°C; shake it before use to make it uniform.

4.2.3 Apparatus

4.3.3.1 Constant temperature incubator. (40±2) °C, (50±2) °C.

4.3.3.2 Spectrophotometer. 340nm.

4.2.4 Sampling

The same as 4.1.4.

4.2.5 Analytical procedures

4.3 Calculation of ratio between lactulose and furosine

The calculation result shall be retained two digits after the decimal point.

5.1 Pasteurized milk

When L< 100.0mg/L, it shall be judged as follows.

Appendix A

(Informative)

Furosine Liquid Chromatogram

A.1 Chromatogram of high-performance liquid chromatography (HPCL)

See Figures A.1 and A.2.

NY/T 939-2016

AGRICULTURE INDUSTRY STANDARD

ICS 67.050

X 04

Replacing NY/T 939-2005

Identification of Reconstituted

Milk in Pasteurized and UHT Milk

Issued on. MARCH 23, 2016

Implemented on. APRIL 01, 2016

Issued by. Ministry of Agriculture of PRC

Table of Contents

Foreword... 3

3.1 Raw milk

The normal milk extruded from the breasts of the healthy dairy animals, it meets the

relevant national requirements and has no ingredient changes.

3.2 Reconstituted milk

The milk obtained by mixing a dried or concentrated dairy product with water in

proportion.

3.3 Heat treatment

The operation that uses heating technology with strength no less than pasteurization,

inhibiting the growth of the microorganisms and killing the microorganisms; while

controlling the physicochemical properties of the heated objects within the only limited

changes.

3.4 Pasteurization

The processing method used to effectively kill pathogenic microorganisms, namely, the

treatment method to keep at a low temperature for a long time (maintain for 30min at

63°C~65°C) or to keep at a high temperature for a short time (maintain for 15s at

72°C~76°C; or maintain for 10s~15s at 80°C~85°C).

3.5 Pasteurized milk

The liquid product with raw milk as the raw material, obtained by pasteurization

process, with the lactulose content less than 100mg/L.

3.6 Ultra high-temperature, UHT

The processing method for effectively killing microorganisms and inhibiting heat-

resistant spores; namely, heating to at least 132°C in a continuous flow state, and

maintaining a very short time of heat treatment.

4.1 Determination of furosine content

4.1.1 Principle

Hydrolyze the specimen by hydrochloric acid, then determine its protein content; after

diluting, the hydrolysate shall be analyzed by high performance liquid chromatography

(HPLC) or ultra-high-performance liquid chromatography (UPLC) under ultraviolet

(wavelength 280nm) detector and quantify by external standard method.

4.1.2 Reagents and materials

Unless otherwise specified, all reagents used in this method shall be analytical

reagents; and the water shall be Class-I water in the laboratory specified in GB/T 6682.

4.1.2.10 Furosine standard stock solution (500.0mg/L). convert the furosine standard

substance as per the Net Peptide Content provided by the standard substance

certificate; then use 3mol/L hydrochloric acid solution to formulate into a standard stock

solution. It can be stored for 24 months at -20°C.

4.1.2.12 Aqueous phase membrane. 0.22µm.

4.1.3 Instruments

4.1.3.1 High Performance Liquid Chromatograph. equipped with a UV detector or

diode array detector.

4.1.3.2 Ultra-High-Performance Liquid Chromatograph. equipped with a UV detector

or diode array detector.

4.1.3.3 Drying oven. (110±2) °C

4.1.3.4 Sealed heat-resistant test tube. volume of 20mL.

4.1.3.5 Balance. the sensitivity of 0.01mg, 1mg.

4.1.3.6 Kjeldahl apparatus.

4.1.6 Result calculation

4.1.6.1 Furosine content in the specimen

The furosine is calculated by mass fraction F; the value of which is expressed in

mg/100g protein; and calculated as per Formula (1).

4.1.6.3 Furosine content at the sterilization of UHT milk

At the end of sterilization of UHT milk, the furosine content shall be calculated by FT;

the value of which shall be expressed by mg/100 protein; and calculated as per

Formula (3).

4.2 Determination of lactulose content

4.2.1 Principle

The sample is hydrolyzed by beta – D – galactosidase to produce galactose and fructose;

the lactulose content is calculated by the enzymatic determination of the amount of

fructose.

4.2.2.30 Glucose oxidase (GOD) suspension (20mg/mL). use sterilized water to

prepare the glucose oxidase with activity of 200 IU/mg into suspension with

concentration of 20mg/mL. It shall be prepared for current use.

4.2.2.31 Catalase suspension (20mg/mL). use sterilized water to prepare the catalase

with activity of 65000 IU/mg into suspension with concentration of 20mg/mL. It shall be

stored at 4°C; shake it before use to make it uniform.

4.2.3 Apparatus

4.3.3.1 Constant temperature incubator. (40±2) °C, (50±2) °C.

4.3.3.2 Spectrophotometer. 340nm.

4.2.4 Sampling

The same as 4.1.4.

4.2.5 Analytical procedures

4.3 Calculation of ratio between lactulose and furosine

The calculation result shall be retained two digits after the decimal point.

5.1 Pasteurized milk

When L< 100.0mg/L, it shall be judged as follows.

Appendix A

(Informative)

Furosine Liquid Chromatogram

A.1 Chromatogram of high-performance liquid chromatography (HPCL)

See Figures A.1 and A.2.

......