1、BRITISH STANDARD BS4285-4: 1991 Microbiological examination for dairy purposes Part4: Methods for assessment of hygienic conditions NOTEIt is essential that Parts0 and1, and appropriate Sections of Parts2 and3, which are published separately, are read in conjunction with this Part.BS4285-4:1991 This
2、 British Standard, having been prepared under the directionof the Agriculture and Food Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 30 April 1991 BSI 04-1999 The following BSI references relate to the work on this standard: Committee r
3、eference AFC/14 Draft for comment90/51790DC ISBN 0 580 19344 6 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Agriculture and Food Standards Policy Committee (AFC/-) to Technical Committee AFC/14, upon which the following bodies were re
4、presented: AFRC Institute of Food Research Association of British Preserved Milk Manufacturers Association of Public Analysts British Food Manufacturing Industries Research Association Campden Food and Drink Research Association Dairy Trade Federation Department of Trade and Industry (Laboratory of
5、the Government Chemist) Joint Committee of the Milk Marketing Board and the Dairy Trade Federation Milk Marketing Board Milk Marketing Board for Northern Ireland Ministry of Agriculture, Fisheries and Food Public Health Laboratory Service Scottish Milk Marketing Board Society for Applied Bacteriolog
6、y Society for General Microbiology Amendments issued since publication Amd. No. Date CommentsBS4285-4:1991 BSI 04-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 General considerations 1 3 Inspection procedures 1 4 Preparation and use of swabs and rinses 2 5 Ca
7、lculation and expression of results 4 6 Test report 4 Appendix A Palins test for the presence of residual chlorine 5 Appendix B Assessment of the hygienic condition of road tankers 5 Appendix C Assessment of the hygienic condition of milk bottles and cartons 6 Appendix D Assessment of the hygienic c
8、ondition of plant and equipment 6 Appendix E Assessment of the hygienic condition of farm dairy equipment using rinse techniques 7 Appendix F Surface areas 9 Table 1 Guide to interpretation of results of Palins test 5 Table 2 Approximate surface areas of items of milking equipment 10 Publications re
9、ferred to Inside back coverBS4285-4:1991 ii BSI 04-1999 Foreword This Part of BS4285 has been prepared under the direction of the Agriculture and Food Standards Policy Committee. It supersedes2.1, 2.2, 2.3, 2.4, 2.5, C.1, C.2, C.3, C.4, C.5 and Tables 2 and 3 of BS4285:1968, which is withdrawn. A Br
10、itish Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a fr
11、ont cover, an inside front cover, pages i and ii, pages1 to12, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.BS4285-4:1991 BSI 04-1999 1 1 Sco
12、pe This Part of BS4285 describes methods for assessing the hygienic status of plant and equipment after cleaning and disinfection. The methods described are appropriate for farm dairy equipment, milk tanks, milk collection tankers, containers for milk, milk processing equipment and general items of
13、equipment used in dairies. NOTEThe publications referred to in this standard are listed on the inside back page. 2 General considerations 2.1 In general, a cleaning control procedure should comprise the following components. a) A general inspection should firstly be carried out. This may include a v
14、isual examination, checks involving smell and touch, chemical and/or physical analysis of residues, corrosion,etc.,examination of records and checks for equipment malfunction. b) A microbiological examination should form part of the routine monitoring of the hygienic status of plant and equipment un
15、less a general inspection (seea) above) renders this superfluous. This may involve swabbing or rinsing of plant and/or sampling first product through the plant after the cleaning and disinfection cycle is complete. This latter process of indirect assessment of the hygienic status of plant may be the
16、 only practicable method depending on the nature of the plant to be assessed or it may be the more straightforward and thus the preferred method for use initially. 2.2 Sampling for microbiological examination should only be carried out by personnel experienced in sampling for this purpose. CAUTION.
17、Attention is drawn to the Health and Safety at Work etc.Act1974, and the need for ensuring that procedures described in this standard are carried out with suitable precautions. 2.3 Samples should be accompanied by information which identifies the nature of the samples together with the place, date a
18、nd time of sampling including any batch details and the name and designation of the sampling personnel. When appropriate, it should also include any relevant conditions or circumstances (for example, the condition of the product containers and their surroundings, temperature and humidity of the atmo
19、sphere, method of sterilization of the sampling equipment, whether a preservative substance has been added 1)to the samples), and any special information relating to the equipment or product being sampled, for example difficulty in achieving homogeneity of the product. 3 Inspection procedures 3.1 An
20、 immediate and important impression of the cleanliness of a production line in a dairy plant can be obtained by visual inspection of the accessible parts of a plant. Colour changes, greasy residues, powder or thin, hard films indicate inadequate detergents and/or inadequate time/temperature combinat
21、ion for the circulation of cleaning solutions and/or an inadequate final rinse. More substantial residues of product may indicate poor training or discipline of cleaning personnel and/or inadequate circulation and/or leaking valves. Incomplete drainage of equipment increases the risk of contaminatio
22、n of product with chemicals and microorganisms. 3.2 Visual inspection may be carried out using an ordinary flashlight or by ultraviolet light. Among many other confirmatory tests the following may be applied to the surface under examination: a) absence of signs of fluorescence when the surface is ca
23、refully inspected with long wavelength(340nm to380nm) ultraviolet light; b) presence of a film or residues on improperly cleaned equipment demonstrated by using a sterile spatula to scrape the surface carefully; c) presence of soiling on an improperly cleaned surface demonstrated by discolouring of
24、a piece of clean disposable muslin or tissue paper wiped over the inside of a milk can or over metal surfaces of other equipment. 3.3 At regular intervals, heat exchanger plate packs, product pumps and valves should be opened and seals and rubbers inspected, especially if products with a high viscos
25、ity are processed. This is important even when cleaning in place (CIP) is fully automated. 1) Preservative should not be added if a microbiological examination is to be undertaken (see BS4285-1.1).BS4285-4:1991 2 BSI 04-1999 It is equally important to inspect at regular intervals the spray balls of
26、the CIP system to ascertain whether the holes are blocked. If plant is dismantled for checking, a rinse and disinfection cycle of the section of plant involved should follow re-assembly. 3.4 Whenever visible residues are found in the equipment, it is essential, that the cause be traced and measures
27、be taken to remedy the fault. There is no value in a microbiological check of visually dirty equipment. Even if a sample happened to be satisfactory from a microbiological viewpoint, all other consequences of inadequate cleaning should be considered. A chemical test to determine the main composition
28、 of the residue is rarely necessary but may be helpful sometimes. 4 Preparation and use of swabs and rinses 4.1 Introduction In the swab technique a swab previously immersed in a known volume of swab solution is rubbed over the surface under examination. Microorganisms which are transferred onto the
29、 swab are then transferred to the swab solutions by vigorous agitation of the swab in the swab solution. In the rinse technique the item under examination is rinsed with a rinse solution in such a manner that microorganisms on the item are transferred to the rinse solution. Test portions of the swab
30、 solution or rinse solution are then subjected to selected microbiological tests, and the results of these tests are expressed as an index of the hygienic condition of the item under examination. 4.2 Swab solution and rinse solution 4.2.1 Use sterile peptone/salt diluent (as described in BS4285-1.2)
31、 for both swab and rinse solutions. If there is any possibility of residual traces of chlorine or quaternary ammonium compounds being present on the item under examination, as a result of the use of chemical cleaning, it is essential that the swab or rinse solution also incorporates an appropriate i
32、nactivator, as given in4.2.2 or4.2.3. 4.2.2 Inactivation of traces of chlorine compounds is achieved by the addition of sodium thiosulphate to the peptone/salt diluent, before autoclaving, at a concentration of0.5g/L, by the addition of either0.25g of crystalline sodium thiosulphate(Na 2 S 2 O 3 5H
33、2 O) or1mL of a250g/L solution of crystalline sodium thiosulphate, to each500mL of peptone/salt diluent. NOTEThe thiosulphate level specified is not sufficient to inactivate significant chlorine residuals resulting from ineffective equipment rinsing or draining. If a chlorine test on the rinse or sw
34、ab solution immediately after use shows the presence of chlorine, the microbiological test will be invalidated, and this reason for invalidation should be reported. 4.2.3 Inactivation of traces of quaternary ammonium compounds is achieved by the addition of sterile inactivator at a concentration of1
35、% (V/V) to the sterilized swab or rinse solution immediately before swabbing or rinsing. A suitable inactivator is prepared by adding4% (m/m) of egg lecithin to a2% (V/V) solution of Tween80. 4.2.4 If the quantity of rinse solution required to effectively rinse a plant is so large as to make the use
36、 of standard rinse solution impracticable, potable water may be used as an alternative, after sterilization. The water supply should be treated by the addition of25mL of10% (V/V) approved hypochlorite to each40L of water, and a contact time of10 min allowed before use. The hypochlorite should then b
37、e inactivated by the addition of excess crystalline sodium thiosulphate (approximately20g/40L of water) and the absence of residual chlorine confirmed using the method described in Appendix A. The sterilized water should be sampled and tested in the same manner as that for the rinse solution after u
38、se. Small numbers of spore-forming organisms may survive, in which case the final result will require correction. If rinse solution is prepared in this manner, include in the test report a note to this effect, and report the results on the sterilized water supply. 4.3 Apparatus 4.3.1 Swab technique
39、4.3.1.1 Test tubes, capacity100mL, of polypropylene or other autoclavable plastics, with cotton wool plug or suitable rubber closure. 4.3.1.2 Stainless steel wire, type EN56complying with BS1554 of length350mm and diameter2.64mm, formed into a loop at the one end, leaving a straight length of300mm,
40、and notched at the other end to hold the ribbon gauze. 4.3.1.3 Ribbon gauze, unmedicated,50mm wide. 4.3.1.4 Other apparatus, specified as appropriate to the test methods applied to the swab solution. 4.3.2 Rinse technique 4.3.2.1 Autoclavable plastics bottles, of500mL capacity with suitable closures
41、. NOTERinse solution is normally dispensed in500mL quantities, but smaller or larger quantities with appropriately sized containers may be required for specific applications. 4.3.2.2 Other apparatus, specified as appropriate to the test methods applied to the rinse solution.BS4285-4:1991 BSI 04-1999
42、 3 4.4 Preparation and sterilization of swabs 4.4.1 The swab shall be50mm in length and consist of175mm of gauze wound round the notched end of the wire(4.3.1.2) and secured with thread wound diagonally up and then down again. NOTEThe swab should be unmovable. 4.4.2 Place the swab in a test tube con
43、taining sufficient peptone/salt diluent to leave25mL after autoclaving. Plug with cotton wool or a suitable rubber closure, cover with greaseproof paper and sterilize by autoclaving at1211C for15min. NOTEThe initial volume of peptone/salt diluent should be determined by trial and error for each auto
44、clave. 4.5 Preparation and sterilization of rinse solutions Dispense500mL quantities of rinse solution into plastics(4.3.2.1) bottles, fit the closure, cover with greaseproof paper and autoclave at1211C for15 min. If several bottles are autoclaved together or larger quantities are used, care is need
45、ed to ensure effective sterilization (see clause5 of BS4285-1.2:1984). If smaller volumes are required for a specified technique, e.g.for bottle rinses, the volume to dispense to obtain the required volume after autoclaving is ascertained as in4.4.2. 4.6 Swabbing technique Specific methods for the i
46、tems most commonly tested by the swab technique are detailed in Appendix B, Appendix C and Appendix D. Where possible examine an area of900cm 2 . When swabbing pipelines up to10cm in diameter swab a300mm length of the pipe, i.e.the entire length of the swab. Ensure that the swab is completely wetted
47、 in the rinse solution. Press the swab with a rolling motion against the side of the test tube to remove excess liquid. Remove the swab and with heavy pressure rub back and forth over the area to be examined so that all parts of the surface are treated twice. Rotate the swab so that all parts of it
48、make contact with the surface under test. Return the swab to the test tube and insert the rubber closure or cotton wool plug. Note details of the item of equipment or packaging swabbed, (including any pipeline diameters) and the area swabbed, e.g.900cm 2 , the entire item, or a swab stick length in
49、a pipeline. Test the swab samples as soon as possible (within12h of sampling) and retain swab solutions at0 C to4 C at all times prior to examination. 4.7 Rinsing technique The rinsing technique is applicable to a wide variety of items of plant, equipment and vessels, which require differing methods to rinse them effectively. Specific methods for the items most commonly tested by the rinsing technique are detailed in Appendix C and Appendix E. The objective of all the methods is the passage of a known volume of rinse solution over the surface under examination at the
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