This procedure specifies the reference method of sampling, transport and storage of samples of heat treated milk.
Sampling of heat-treated milk in tanks etc., shall be carried out by a skilled operator who has had suitable training before undertaking the sampling of milk.
If they consider it appropriate, the competent authorities or testing laboratory shall instruct sampling personnel in sampling techniques to ensure that the sample is representative of, and in conformity with, the entire batch.
If they consider it appropriate, the competent authorities or testing laboratory shall instruct sampling personnel on marking the sample to ensure the unambiguous identity of the sample.
Sampling equipment shall be made of stainless steel, or other suitable material of adequate strength and of a construction suitable for the intended purpose (mixing, sampling etc.). Plungers and agitators for mixing liquids in containers shall have a sufficient area to produce adequate mixing of the product, but without causing the development of a rancid flavour. Dippers must have a solid handle of sufficient length to enable a sample at any depth of the container to be obtained. The capacity of the dipper shall be not less than 50 ml.
Sample containers and closures should be of glass, suitable metals or plastics.
The materials of which sampling equipment (including containers and closures) is constructed must not cause any change in the sample which could affect the results of the examinations. All surfaces of sampling equipment and sample containers shall be clean and dry, smooth and free from crevices, and corners shall be rounded.
Irrespective of the tests to be performed, the milk shall be thoroughly mixed prior to sampling, by either manual or mechanical means.
The sample shall be taken immediately after mixing while the milk is still agitated.
The volume of the sample shall be adequate to the testing requirements. The capacity of the sample containers used shall be such that they are filled almost completely by the sample, thus allowing proper mixing of the contents before testing, but avoiding churning during transport.
Where the quantity of milk to be sampled is in more than one container, take a representative quantity from each container and note the quantity of milk to which each sample relates. Unless the samples from each container are to be tested individually, mix portions of these representative quantities in amounts which are proportional to the quantity in the container from which each sample was taken. Take sample(s) from these bulked proportionate amounts after mixing.
To mix the contents of large vessels or of storage, rail or road tanks, the use of mechanical agitation is advised (4.2.2.2.).
The extent of mixing shall be appropriate to the period of time over which the milk has been at rest. The efficiency of the procedure of mixing applied in any particular circumstances shall be demonstrated as being adequate for the purposes of the analysis envisaged; the criterion of mixing efficiency particularly influences the similarity between analytical results from samples taken either from different parts of the consignments, or from the outlet of the tank at intervals during discharge. A procedure of mixing milk (untreated milk or whole milk) shall be considered efficient if the difference in fat content between two samples, taken under these conditions, is less than 0,1 %.
In a large vessel with a bottom discharge outlet there may be, at the discharge point, a small quantity of milk which is not representative of the whole contents even after mixing. Therefore samples should preferably be taken through a manhole. If samples are taken from the discharge outlet, run off sufficient milk to ensure that the samples are representative of the whole.
by a mechanical agitator built into the tanks and driven by an electric motor;
by a propellor or agitator driven by an electric motor and placed on the manhole with the agitator suspended in the milk;
in the case of rail or road tankers by recirculation of the milk through the transfer hose attached to the tanker unloading pumps and inserted through the manhole;
by clean filtered compressed air. In this case, minimal air pressure and volume should be used to prevent the development of rancid flavour.
Samples of heat-treated milk for direct consumption in retail packages are to be the complete sealed package. If possible, the samples must be taken from the packaging machine or cold room in the treatment establishment as soon as possible after processing (for pasteurized milk on the same day as processing).
The samples are taken from each type of heat-treated milk (pasteurized, UHT-treated and sterilized) in numbers corresponding to the examinations which will be made and in accordance with instructions laid down by the testing laboratory or other competent authority.
The sample shall be marked with an identification code so that it can be readily identified using instructions given by the testing laboratory or competent authority.
In accordance with the competent national authority, instructions concerning the conditions of preservation (chemical, temperature), transport, storage and time between sampling and analysis of milk shall be prepared by the testing laboratory according to the type of milk and the procedure of analysis to be used.
In the instruction the following points shall be included:
During transport and storage, precautions shall be taken to prevent exposure to contaminating odours and to direct sunlight. If the container used for samples is transparent, it shall be stored in a dark place.