CAC_GL 13-1991 Guidelines For The Preservation Of Raw Milk By Use Of The Lactoperoxidase System
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3E9FB4C070A04AEC9CD9435C89AEBB97 |
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文件大小(MB)： |
0.03 |
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页数： |
5 |
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日期： |
2004-12-24 |
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CAC/GL 13 Page 1 of 5,GUIDELINES FOR THE PRESERVATION OF RAW MILK BY USE OF THE,LACTOPEROXIDASE SYSTEM,CAC/GL 13-1991,Contents,Introduction1,1. Scope .1,2. Principles of the Method .2,3. Intended Utilization of Method.2,4. Practical Application of the Method ..3,5. Control of Usage ..3,Appendix I: Technical Specification of Sodium Thiocyanate 4,Appendix II: Technical Specification of Sodium Percarbonate.4,Appendix III: Analysis of Thiocyanate in Milk4,GUIDELINES FOR THE PRESERVATION OF RAW MILK BY USE OF THE,LACTOPEROXIDASE SYSTEM,INTRODUCTION,Milk is an easily perishable raw material. Contaminating bacteria may multiply rapidly and render it,unsuitable for processing and/or unfit for human consumption. Bacterial growth can be retarded by,refrigeration, thereby slowing down the rate of deterioration. Under certain conditions refrigeration may not,be feasible due to economical and/or technical reasons. Difficulties in applying refrigeration are specially a,problem for certain areas in countries setting up or expanding their milk production. In these situations, it,would be beneficial to have access to a method, other than refrigeration, for retarding bacterial growth in raw,milk during collection and transportation to the dairy processing plant.,In 1967 the FAO/WHO Expert Panel on Milk Quality concluded that the use of hydrogen peroxide might be,an acceptable alternative in the early stages of development of an organized dairy industry, provided that,certain conditions were complied with. However, this method has not achieved any general acceptance as it,has several drawbacks, most important of which is the difficulty of controlling its use: it may be misused to,disguise milk of basic hygienic quality produced under poor hygienic conditions. The toxicological aspects of,the use of relatively high concentrations of hydrogen peroxide in milk have also been questioned.,A chemical method for preserving milk would still be of great advantage in certain situations. The search for,such a method has therefore continued. Interest has recently been focused on the indigenous antibacterial,systems in milk to determine if these could be applied practically to preserve raw milk. During the last decade,basic and applied research has demonstrated that one of these systems, the,lactoperoxidase/thiocyanate/hydrogen peroxide system (LP-system) can be used successfully for this purpose.,1. SCOPE,1.1 This Code of Practice describes the use of the lactoperoxidase system for preventing bacterial spoilage,of raw milk (bovine and buffalo) during collection and transportation to a dairy processing plant. It describes,the principles of the method, in what situations it can be used, its practical application and control of the,CAC/GL 13 Page 2 of 5,method. It should be stressed that this method should be utilized when refrigeration of the raw milk is not,feasible.,2. PRINCIPLES OF THE METHOD,2.1 The lactoperoxidase/thiocyanate/hydrogen peroxide system is an indigenous antibacterial system in,milk and human saliva. The enzyme lactoperoxidase is present in bovine and buffalo milk in relatively high,concentrations. It can oxidise thiocyanate ions in the presence of hydrogen peroxide. By this reaction,thiocyanate is converted into hypothiocyanous acid (HOSCN). At the pH of milk HOSCN is dissociated and,exists mainly in the form of hypothiocyanate ions (OSCN-). This agent reacts specifically with free sulphydryl,groups, thereby inactivating several vital metabolic bacterial enzymes, consequently blocking their metabolism,and ability to multiply. As milk proteins contain very few sulphydryl groups and those that are present are,relatively inaccessible to OSCN- (masked), the reaction of this compound is in milk quite specific and is,directed against the bacteria present in the milk.,2.2 The effect against bacteria is both species and strain dependent. Against a mixed raw milk flora,dominated by mesophilic bacteria, the effect is bacteriostatic (predominantly inhibitory). Against some gramnegative,bacteria, i.e. pseudomonads, Escherichia coli, the effect is bactericidal. Due to the mainly,bacteriostatic effect of the system it is not possible to disguise poor quality milk, which originally contained a,high bacterial population, by applying this method.,2.3 The antibacterial oxidation products of thiocyanate are not stable at neutral pH. Any surplus of these,decomposes spontaneously to thiocyanate. The velocity of this reaction is temperature dependent, i.e. more,rapid at higher temperatures. Pasteurisation of the milk will ensure a complete removal of any residual,concentrations of the active oxidation product……
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