NY/T 939-2005 English PDF (NYT939-2005)

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NY/T 939-2005: Identification of reconstituted milk in pasteurized and UHT milk
NY/T 939-2005
NY
Agriculture Industry Standard
of The People’s Republic of China
Identification of reconstituted milk
in pasteurized and UHT milk
ISSUE ON. SEPTEMBER 30, 2005
IMPLEMENTED ON. SEPTEMBER 30, 2005
Issued by. Ministry of Agriculture, the People’s Republic of China
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Identification of reconstituted milk ... 5
5 Test methods ... 6
Appendix A ... 15
Appendix B ... 16
Foreword
Chapter 4 of this Standard is mandatory, the rest are recommended.
Appendix A and Appendix B of this Standard are informative.
This Standard is proposed by Ministry of Agriculture of the People's Republic of China
Ministry.
This Standard is under the jurisdiction of the National Standardization Technical Committee
of Animal Husbandry.
Drafting organization of this Standard. Livestock Research Institute of Chinese Academy of
Agricultural Sciences.
The main drafters of this Standard. Wang Kai, Pu Dengfeng, Wei Hongyang, Li Shucong,
Yu Jianguo, Guo Zonghui, Fu Baohua, Zhou Lingyun, Liu Shijun, Huang Mengmeng, and
Liu Guanglei.
Identification of reconstituted milk
in pasteurized and UHT milk
1 Scope
This Standard specifies the identification and corresponding determination method of
reconstituted milk in pasteurized milk and UHT sterilized milk.
This Standard applies to identification of reconstituted milk in pasteurized milk and UHT
sterilized milk.
2 Normative references
The provisions contained in following documents, through the reference of this Standard,
become provisions of this Standard. For dated references, subsequent amendments
(excluding corrections) or revisions do not apply to this Standard, however, parties who
enter into agreement based on this Standard are encouraged to study if the latest versions
of these documents are usable. For undated references, the latest versions apply to this
Standard.
GB/T 5413.1 Milk powder and formula foods for infant and young children – Determination
of protein
GB/T 6682-1992 Water for analytical laboratory use – Specification and test methods
ISO 5538.1987 Milk and milk products – Sampling – Inspection by attributes
3 Terms and definitions
The following terms and definitions apply to this Standard.
3.1 raw milk
The regular milk squeezed from healthy cattle, it shall be cooled, and it may be filtered,
however, it is not processed by pasteurization, heat treatment lower than pasteurization,
net milk and other sterilization.
5.1.3 Instruments and Equipment
5.1.3.1 Common instruments and equipment in testing laboratory.
5.1.3.2 High performance liquid chromatography, with gradient system and UV-detector.
5.1.3.3 Kjeldahl apparatus.
5.1.3.4 C18 extraction column, 500 mg.
5.1.3.5 Silica gel column. Particle size of 5μm, column diameter of 4.6mm, length of 250
mm.
5.1.3.6 Drier. 110 ºC ± 2 ºC.
5.1.3.7 Heat tubes with screw cap or other heat-sealable tubes. Volume of 20mL.
5.1.3.8 syringe. 10mL.
5.1.4 Sampling
TAKE 250mL of representative sample and SEND to laboratory, the sample shall not be
destroyed or changed during transit and storage. Sampling shall be executed with
reference to ISO 5538.1987.
5.1.5 Analysis steps
5.1.5.1 Preparation of sample hydrolyzate solution
DRAW 2.00 mL of sample, PLACE in a heat-sealed tube (5.1.3.7), ADD 6mL of 10.6 mol/L
hydrochloric acid solution (5.1.2.4), MIX well. Slowly ACCESS high-purity nitrogen (5.1.2.2)
into the tube for 1 min - 2 min, SEAL the tube, then PLACE it in drier (5.1.3.6), HEAT at 110
ºC for hydrolysis for 23 h - 24 h. After heating for about 1h, gently SHAKE the tube.
After heating, REMOVE the tube from the drier, COOL it and PERFORM dry-filtration,
KEEP the filtrate for measurement.
5.1.5.2 Determination of protein content in sample hydrolyzate solution
DRAW 2.00 mL of sample hydrolyzate solution (5.1.5.1), according to GB/T 5413.1
DETERMINE protein content in the sample solution.
MEASURE 50.0 mL of sample into a 100 mL volumetric flask, USE water to dilute to the
mark and then MIX well.
5.2.5.2 Purification
DRAW 10.0 mL of test solution (5.2.5.1) in 50 mL conical flask, sequentially ADD 1.75 mL
of ferrous hydroxide solution (5.2.2.6), 1.75mL of zinc sulphate solution (5.2.2.5), and 6.5
mL of buffer A (5.2.2.9). After each solution is added, SHAKE sufficiently and evenly. After
all the solutions are added, PLACE for 10 min, FILTER it, DISCARD the first 1mL - 2 mL of
filtrate, COLLECT the filtrate.
5.2.5.3 Hydrolyzate lactose and lactulose
DRAW 5.00 mL of filtrate into a 10 mL volumetric flask, ADD 50μL of β-D-galactosidase
suspension solution (5.2.2.12), MIX well and COVER it. At 40 ºC water bath or drier
INCUBATE for at least 10 h.
5.2.5.4 Glucose oxidation
Sequentially ADD 2.0 mL of Buffer C (5.2.2.11), 100μL of glucose oxidase suspension
solution (5.2.2.13), 1 drop of octanol (5.2.2.3), 0.5 mL of sodium hydroxide solution (5.2.2.7)
of which the concentration is 0.33mol/L, 50μL of hydrogen peroxide (5.2.2.2), and 0.1 mL of
catalase suspension solution (5.2.2.14). When each reagent is added, it shall be shaken
well. After all solutions are added, INCUBATE for 3h at 40 ºC in water bath or drier. After
cooling, DILUTE to 10 mL, FILTER it, DISCARD the first 1mL - 2 mL of filtrate, COLLECT
the filtrate.
5.2.5.5 Blank
According to steps 5.2.5.1 - 5.2.5.4 to process blank solution, except that not adding
β-D-galactosidase suspension solution (5.2.2.12).
5.2.5.6 Determination
Measurement steps are shown in Table 2.
Appendix B
(Informative)
Separation spectrum of furosine in Pasteurized milk sample
Note. The horizontal axis represents the retention time, in minutes (min); vertical axis
represents the absorbance (AU); Peak 1 represents furosine peak.
Peak 1-7.934