Infant Feed Pasteurisation
A fully
referenced evidence based guide to the
"practice proven" method for the
Thermal Treatment of Human Milk
By David J. Colgate
S.J.Line Mphil FIBMS CBIOL MIBIOL
Managing risk in feed preparation
In the late 1970's, faced with a growing range of formulae feeds the goal was
to establish an infection control procedure that renders safe donated Human Milk, at the same time preserving the majority of the immune and nutritional factors.
This paper describes a precise method of treatment that can be repeated at any location.
Risks must be minimised
The established Pasteurisation method raises the temperature of milk in a closed bottle to 62.5°C¹, holding for 30 minutes, then immediately cooled rapidly to > 10°C², within the Pasteurisation Cycle.
Rapid cooling is described as cooling from 62.5 °C to 25 °C 4 in less than 10 minutes giving a cooling rate of 3.75 °C per minute 6. If cooling is slow any surviving bacteria will multiply, therefore the time milk is held between 45°C and 15°C must be minimised.
To achieve rapid cooling a refrigeration plant is essential to remove excess heat. The use of a cold water supply as a cooling medium is inadequate for two reasons. Firstly the water is discarded after each flush, therefore an environmentally unfriendly process. In addition the temperature of the supply water will vary depending on the time of year and the proximity of the cold water pipe to warm situations.
An air space of about 2 cm should be left below the mouth of each bottle to allow for expansion during heating and subsequent freezing 6.
Bottles must be submerged during the heating cycle 3 , mandatory in USA 7, to ensure that all surfaces of the bottle and lid as well as the milk are heat-treated 10.
Bottles should not be submerged during the cooling cycle 5 (unless foil sealed bottles are used) as a low pressure will be produced in the bottle head space which could cause cooling water to be drawn into the bottle contaminating the milk.
Comment
The method was developed by the late Professor J David Baum and his co workers at the John Radcliff Hospital, Oxford in 1977 ¹. Dr J. David Baum personally gave his paper to The American Academy of Paediatrics at their Annual Conference in New York in1982.
A comprehensive comparative study at Sorrento Maternity Hospital Birmingham in 1992 ² became the basis of the first Guideline Published in 1994 by The Royal College of Paediatrics and Child Health 5.
Almost all studies relating to various aspects of donated Human Milk, particularly if they relate to the elimination of the H.I.V. will have used the above method of treatment. Users of other treatment methods cannot draw comfort from these studies.
Precise Equipment
The first patented prototype of an Automatic Pasteuriser with controlled refrigerated cooling was built in 1977 by the Medical Physics department of John Radcliff Hospital, Oxford ¹. The patent was licensed to Vickers Medical Ltd. who built the first 20 bottle production model under the "OXFORD" brand (discontinued in 1982).
In 1978 Colgate Medical Ltd developed in conjunction with Kings College University Hospital 3, London a semi automatic Pasteuriser based on standard water baths with dip cooled refrigeration. The Public Health Laboratory was also consulted and their studies found that milk drops in the cap did not receive the same treatment unless the bottle was submerged during the heating cycle 3 7.
To precisely achieve the above method a fully automatic Pasteuriser with 42 bottles was designed by David Colgate in 1980, marketed under the brand "Axicare" and the development was chosen in 1983 for display by The British Technology Group for the opening of their new Headquarters by HRH the Prince of Wales.
This model of Pasteuriser built by Scott Weston Ltd was used for the studies by Sorrento Birmingham in 1992.²
This treatment method is now specified in all other European guidelines. This is apart from Austria and Italy who specify the final cooling temperature to be 4°C to reduce even further the window of opportunity for Bacteria re-growth 7 9. In Sweden compliance with the protocol is mandatory 8.
Technological advances enabled Medicare Colgate Ltd to introduce a compact version with many additional safety features marketed under the brand "STERIFEED". Namely all water traps were removed including the secondary cooling tank thus avoiding the need for a sterilisation cycle.
Verification of Treatment
As with sterilisation equipment, a record of independent verification of satisfactory treatment of the milk (not the water bath) for the complete cycle (heating & cooling) must be kept for future reference together with traceability data. This will be required by Infection Control Departments, Environmental Health Inspectors and a copy for any other Health Care establishment using the facility must be part of the documentation for the relevant batch. Also Pediatricians prescribing Donor Human Milk will need to know that their source of supply treats the milk in compliance with regulatory protocols 6
Summary
At the time of preparing this document in 2005 David Baum's method of Pasteurisation has become standard practice throughout the world with more than 150 installations. The method has been adopted as a Bench Mark of safety and quality by all reputable equipment manufactures.
The Human Milk Bank in Umea in the north of Sweden and the one in Athens in the south of Europe, Pasteurise to exactly the same treatment data (heating & cooling) irrespective of Ambient temperature and the temperature of their cold water supply.
Users of water baths with a tap water cooling method will find that they are unable to achieve consistent results, as the incoming water will vary between 10°C and 25 °C (or even higher in the Summer). Also the influence of how far the water has to travel, the proximity of the hot water supply and the use of storage tanks will all affect the calorific uptake.
Therefore additional space will be required for Blast Chilling or bespoke refrigeration. The placement of large volumes of warm milk into a refrigerator already in use may warm the existing contents and contravene Food Hygiene regulations. Users of ancillary cooling will find it difficult to provide proof of treatment for the complete cycle.
Conclusion
Purchasers of Pasteurisation equipment must satisfy themselves that it complies with the above method in all respects and a certificate of conformity obtained. The fact that a manufacturer may have sold a few is no guarantee. It is the Medical Profession that decide the parametric requirements not the equipment manufacturer.
References
1. Drip Breast milk: its composition, collection, and pasteurization
(Early Human Development). John Radcliffe Hospital, Oxford Gibbs,J.H., Fisher,C., Bhattacharya,S., Goddard,P. and Baum, J.D., 1977
2. Human milk banking at Sorrento Maternity Hospital, Birmingham, S E Balmer, W A Wharton, Archives of Diseases in Childhood APRIL 1992.
3. Organization of bank of raw and pasteurized human milk for neonatal intensive care. S. Williamson, J.H.Hewitt, E. Finucanr, H.R.Gamsu. British Medical Journal, 1978
4. The collection and storage of Human Milk, Department of Health & Social Security Report on Health and Social Subjects No 22 London 1981
5. Guidelines for the Establishment and Operation of Human Milk Banks in the UK The Royal College of Paediatrics and Child Health First Edition 1994
6. Guidelines for the Establishment and Operation of Human Milk Banks in the UK The Royal College of Paediatrics and Child Health Second Edition 1999.
7 USA Guidelines for the Establishment and Operation of a Donor Human Milk Bank. Human Milk Banking Association of North America written 2003 Revised 2005
8 Sweden THE NATIONAL BOARD OF HEATH AND WELFARE To prevent infection in the healthcare sector,II 1998:12
9 Italy Linee Guida per la costituzione e l’organizzazione di una Banco del Latte Umano Donato Societa Italiana di Neonatologia la edizione 2002
10 Affect of Water Level when Pasteurizing Human Milk, S.J.Line Mphil FIBMS CBIOL MIBIOL, Sterilizer Consultants Ltd.
Published by
Medicare Colgate Ltd, Post Cross Business Park, Cullompton, EX15 2BB
