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The Milk and Dairies (Semi-skimmed and Skimmed Milk) (Heat Treatment and Labelling) Regulations 1988

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Regulation 3(2)(c) and Schedule 2

SCHEDULE 3

PART Iprovisions as to sampling

Taking of sample

1.  A sample may be taken at any time when the milk is in the possession of a milk processor or milk purveyor.

2.  When the milk is in containers with a capacity not exceeding 1.25 litres, or when the milk has been treated by the ultra high temperature method whether or not such milk is in containers with a capacity not exceeding 1.25 litres, the sample shall consist of one such container which shall be delivered intact to the testing laboratory.

3.  When the milk (other than milk which has been treated by the ultra high temperature method) is in containers with a capacity exceeding 1.25 litres, the sample shall consist of not less than 60 ml. of the milk. The milk shall be thoroughly stirred before sampling and the sample shall be taken from well below the surface of the milk. The instruments used for stirring and sampling shall be sterile and the sample shall be poured into a sterile bottle which shall thereupon be immediately stoppered. The part of the stopper which may come into contact with the milk shall be sterile. Where the person taking the sample breaks the seal on a container he shall, after taking the sample, re-seal the container and attach to it a label certifying that it has been opened and re-sealed by him.

Identification of sample

4.  For the purpose of identification in the testing laboratory, the person taking the sample shall mark the container of the sample with a number or other suitable identification mark at the time of sampling and shall enter in a book or on a paper, which shall accompany the sample, the following particulars:—

(a)the identification number or mark;

(b)the name and address of the person by whom the milk was consigned, or by whom it was being delivered, or on whose premises the sample was taken.

Transport of sample

5.  Subject to paragraph 6 below, the bottle or container containing any sample of milk shall be transferred forthwith to an insulated container, which shall not be artificially cooled, for transport to the testing laboratory. The sample shall be transported to the testing laboratory with the least possible delay. Any sample which does not arrive at the testing laboratory on the day on which it is taken shall be discarded.

6.  A sample of milk, other than sterilised milk or milk treated by the ultra high temperature method in each case in an unopened container, to be subjected to the coliform test prescribed in Part III of this Schedule or the plate count test prescribed in Part IV of this Schedule shall, during its transportation to the testing laboratory, be retained at a temperature of not less than 0°C and not more than 4°C.

PART IIthe methylene blue test for pasteurised semi-skimmed milk and skimmed milk

Treatment of sample

1.—(1) On arrival at the testing laboratory the sample of milk shall at once be removed from the insulated container. Thereafter it shall be stored as follows:—

(a)a sample taken at any time during the period from 1 May to 31 October, inclusive, in any year shall be kept at atmospheric shade temperature until 9.30 a.m. on the following day;

(b)a sample taken at any time during the period from 1 November to 30 April, inclusive, in any year shall be kept in its original container or in a sterile sample bottle of at least 80 ml. capacity at atmospheric shade temperature until 5.00 p.m. on the day of sampling and thereafter at a constant temperature of 18.3°C. ± 1°C. until 9.30 a.m. on the following day.

(2) If during the period of storage at atmospheric shade temperature to which a sample is subjected this temperature at any time exceeds 21°C., the test shall not be applied.

(3) The test shall be begun between 9.30 and 10.00 a.m. on the day after the sample is taken.

Reagent — Methylene Blue

2.—(1) Tablets manufactured under arrangements made by the Minister shall be used for the test. A solution shall be prepared aseptically by adding one tablet to 200 ml. of cold, sterile, glass-distilled water in a sterile flask, shaking until the tablet is completely dissolved, and making up the solution to 800 ml. with cold, sterile, glass-distilled water. The resultant solution shall be stored in a stoppered sterile flask in a cool, dark place, and shall not be used if—

(a)it has been exposed to sunlight, or

(b)a period of two months has elapsed since the date of preparation.

(2) The amount of methylene blue required for a day’s work shall be poured off from the stock bottle into a suitable glass container. The pipette used for transferring the methylene blue solution to the tubes of milk shall not be introduced into the stock bottle.

Apparatus

3.—(1) Test tubes shall conform to British Standard 3218:1982, nominal size 150/16, and shall be accurately marked at 10 ml. They shall be plugged with cotton wool or covered with closely fitting aluminium caps or stored in such a way as to prevent contamination.

(2) Pipettes shall be 1.0 ml. straight-sided blow out delivery pipettes, and shall be plugged with cotton wool at the upper end.

(3) Glassware and rubber stoppers shall be sterile immediately before use.

(4) The water bath shall be fitted with a reliable automatic thermo-regulator capable of maintaining the water at a temperature of 37.5°C. ± 0.5°C.

Method of carrying out the test

4.—(1) The sample shall be mixed thoroughly by inverting and shaking and the milk shall be transferred to a test tube up to the 10 ml. mark in such a manner that one side of the interior of the test tube is not wetted with milk. 1 ml. of methylene blue solution shall be added without letting the pipette come into contact with the milk in the tube or with the wetted side of the interior of the tube. After a lapse of 3 seconds, the solution remaining in the tip of the pipette shall be blown out. The test tube shall be closed with a rubber stopper, aseptic precautions being taken, and shall then be inverted twice slowly, so that the whole column of contained air rises above the level of the milk. Within a period of 5 minutes the test tube shall be placed in a water bath. The water in the bath shall be kept above the level of the milk in the test tube, and its temperature, which shall be between 37°C. and 38°:C., shall be maintained as nearly uniform as possible by means of a reliable automatic thermo-regulator. The interior of the bath shall be kept completely dark.

(2) A control tube shall be used for comparison with each batch of experimental tubes to indicate when decolourisation is complete. The control tube shall be prepared by immersing in boiling water for 3 minutes a stoppered test tube containing 1 ml. of tap water and 10 ml. of mixed milk having a fat content and colour similar to that of the milk being tested.

(3) The milk shall be regarded as decolourised when the whole column of milk is completely decolourised or is decolourised up to within 5mm. of the surface. A trace of colour at the bottom of the tube may be ignored provided that it does not extend upwards for more than 5mm. PART IIIthe coliform test for pasteurised semi-skimmed milk and skimmed milk

Method of carrying out the test

1.  Subject to paragraphs 2 and 3 below, the sample shall be tested by the method prescribed in the British Standard 4285: Section 3.7: 1987 (ISBN 0 580 15866 7).

2.  The “Colony count technique” specified in paragraph 8 of the British Standard referred to in the preceding paragraph shall be used.

3.  For the purposes of inoculation of Petri dishes 3 ml. of milk shall be transferred to a 150 ml. Petri dish or 1 ml. of milk transferred into each one of three 90 mm. Petri dishes.

4.  Any sample on which the test is not begun within 24 hours of taking such sample shall be discarded.

PART IVthe plate count test for semi-skimmed milk, skimmed milk and bulk milk heat treated for transportation, pasteurised, sterilised or treated by the ultra high temperature method

1.  The sample shall be tested by the method prescribed in the British Standard 4285: Section 2.1: 1984 (ISBN 0 580 14091 1).

2.  Any sample—

(a)of raw milk, milk heat treated for the purposes of transportation or pasteurised milk, or

(b)of sterilised milk or milk treated by the ultra high temperature method where the sample is taken from an open container,on which the test is not begun within 24 hours of taking such sample, shall be discarded.

PART Vthe phosphatase test for pasteurised semi-skimmed milk and skimmed milk

Examination of sample

1.  The sample of milk shall be examined as soon as possible after arrival at the testing laboratory. If it is not examined immediately on arrival at the testing laboratory, it shall be kept at a temperature of between 3°C. and 5°C. until examined. The sample shall be raised to room temperature immediately before being tested.

Precautions

2.  The following precautions shall be taken:—

(a)A sample which shows evidence of taint or souring shall not be tested.

(b)All glassware shall be clean immediately before use.

(c)A fresh pipette shall be used for each sample of milk.

(d)The test shall not be carried out in direct sunlight.

(e)Distilled or de-ionised water shall be used throughout.

Reagents

3.—(1) Whenever possible, reagents of analytical quality shall be used.

(2) The buffer-substrate solution shall be prepared as follows:—

(a)Buffer solution: 3.5 g. of anhydrous sodium carbonate and 1.5 g. of sodium bicarbonate shall be dissolved in distilled or de-ionised water, and made up to one litre.

(b)Substrate: Disodium p-nitrophenyl phosphate. The solid substrate shall be kept in a refrigerator.

(c)Buffer-substrate solution: 0.15 g. of the substrate shall be placed in a 100 ml. measuring cylinder, and made up to 100 ml. with the buffer solution. The solution shall be stored in a refrigerator and protected from light. It shall give a reading of less than the standard marked 10 on the comparator disc A.P.T.W. or A.P.T.W.7 when viewed in transmitted light through a 25 mm. cell in the `all purposes' comparator, distilled or de-ionised water being used for comparison. The solution shall not be used for more than one week.

Apparatus

4.  The following apparatus shall be used:

(a)A Lovibond `all purposes' comparator complete with stand for work in reflected light.

(b)A Lovibond comparator disc A.P.T.W. or A.P.T.W.7.

(c)Two fused glass cells, 25 mm. depth.

(d)A water bath or incubator capable of being maintained at 37.5°C. ± 0.5°C.

(e)A pipette to deliver 5.0 ml.

(f)A supply of 1.0 ml. straight-sided pipettes of an accuracy equal to that of N.P.L. grade B.

(g)A 1,000 ml. graduated flask.

(h)A 100 ml. measuring cylinder.

(i)A supply of test tubes conforming to British Standard 3218: 1982, nominal size 150/16, with rubber stoppers to fit.

Care of apparatus

5.—(1) New glassware shall be cleaned and free from contamination from substances which may interfere with the test.

(2) After use, each test tube shall be emptied, rinsed in water, well washed in hot water containing soda, rinsed in warm water, rinsed in distilled or de-ionised water and finally dried.

(3) If after treatment in accordance with sub-paragraph (2) above, a test tube does not appear to be clean, the treatment shall be repeated with the addition that after being rinsed in warm water it shall be soaked in 50 per cent. commercial hydrochloric acid and then rinsed again in warm water before being rinsed in distilled or de-ionised water and finally dried.

(4) Glassware used for the test shall not be used for any other purpose and shall be kept apart from all other apparatus in the laboratory.

Method of carrying out the test

6.  5 ml. of the buffer-substrate solution shall be transferred to a test tube using a pipette and the test tube shall be stoppered and brought to a temperature of 37°C. 1 ml. of the milk to be tested shall be added, the test tube stopper replaced and the contents well mixed by shaking. The test tube shall then be incubated for exactly 2 hours at 37°C. One blank prepared from boiled milk of the same type as those undergoing the test shall be incubated with each series of samples. (Where the sample consists of highly coloured milk, such as homogenised milk or milk from Channel Island cows, a separate blank of such milk shall be prepared). After incubation the test tube shall be removed from the water bath and its contents shall be well mixed. The blank shall be placed on the left hand ramp of the stand and the test sample on the right. Readings shall be taken in reflected light by looking down on to the two apertures with the comparator facing a good source of daylight (preferably north light). If artificial light is needed for matching, a `daylight' type of illumination must be used. The disc shall be revolved until the test sample is matched. Readings falling between two standards shall be recorded by affixing a plus or minus sign to the figure for the nearest standard.

PART VIthe turbidity test for sterilised semi-skimmed milk and skimmed milk

Examination of sample

1.  The sample of milk may be examined at any time after delivery to the testing laboratory but shall be at room temperature when the test is begun.

Reagent

2.  Ammonium sulphate A.R. shall be used.

Apparatus

3.  The following apparatus shall be used:—

(a)Conical flasks of 50 ml. capacity.

(b)Graduated cylinders of 25 ml. capacity

(c)Test tubes conforming to British Standard 3218: 1982, nominal size 150/16.

(d)Filter funnels of 6 cm. diameter

(e)Beakers of 400 ml. capacity.

(f)12.5 cm. No. 2V Whatman folded filter papers or equivalent.

Method of carrying out the test

4.  4 ± 0.1 g. of ammonium sulphate shall be weighed into a 50 ml. conical flask. 20 ± 0.5 ml. of the milk sample shall be measured out and poured into the conical flask, the flask being shaken for 1 minute to ensure that the ammonium sulphate dissolves. The mixture shall be left for not less than 5 minutes and then filtered through a folded filter paper into a test tube. When not less than 5 ml. of a clear filtrate have collected, the tube shall be placed in a beaker of water, which has been kept boiling, and kept therein for 5 minutes. The tube shall be transferred to a beaker of cold water, and when the tube is cool, the contents shall be examined for turbidity by moving the tube in front of an electric light shaded from the eyes of the observer.

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