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close this bookCERES No. 158 March - April 1996 (FAO Ceres, 1996, 50 p.)
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Agribusiness: Milk's own bacteria works as a preservative

Milk from a cow's healthy udder contains few bacteria, but between milking and processing the germ count increases considerably. If the milk isn't cooled and doesn't reach the processor within five hours after milking, as can easily happen in developing countries, it isn't suitable for processing. Time, labor and valuable nutrition are lost. This is a serious problem but, unlike many others facing Third World farmers, this is a problem that has a cheap, simple and safe solution - treating raw milk with its own antibacterial system created by nature for the benefit of the organism.

Countries with advanced, large-scale dairy industries have facilities for cooling raw milk during on-farm handling, storage and transportation to keep down the bacteria count and preserve its quality. Through much of the developing world, however, most of the milk is produced by smallholders, and constant refrigeration is not only too expensive but technically and logistically impossible.

The usual procedure is for dairy farmers to deliver small quantities of milk to a local collection point, where the amount by volume or weight is recorded and, sometimes, the quality is checked. The milk collected is transported by bicycle or donkey to a larger centre, which may or may not have refrigeration facilities, then trucked in bulk to a processing plant.

If the trip from milking stool to processing plant takes more than five hours the milk quality suffers. If it hasn't been chilled at all along its route, it will probably be unacceptable both to dairy processing plants and to potential consumers.

What the dairy industry in developing countries needs is a method, other than refrigeration, to protect raw milk from bacterial deterioration on the way to the processing plant. And that is exactly what lactoperoxidase (LPS) offers.

LPS is a protein naturally present in milk. It has an antibacterial effect in the presence of hydrogen peroxide and thiocyanate, which milk also contains. Studies have shown small additions of hydrogen peroxide and thiocyanate stimulate LPS's bacteria-fighting system in milk and considerably extend its shelf-life.

To activate LPS in raw milk, the natural level of thiocyanate present in milk is increased to about 15 parts per million (ppm) and an equimolar (8,5 ppm H2O2) amount of hydrogen peroxide is added. This is approximately 100 times less than the amount of hydrogen peroxide often used for the unauthorized conservation of milk and three to 20 times less than the level of thiocyanate found in human saliva or in cassava or cabbage. Toxicological studies have confirmed the modest levels of thiocyanate recommended would cause no health problems.

In experiments and field trials, the treatment produced an antibacterial effect that lasted five to six days on refrigerated milk and increased the shelf-life of raw milk by three to four hours in an ambient temperature of 30°C, depending on the quality of the raw milk when it was treated.

Effective, cheap, safe and easy to apply at milk collection points, the method would be of particular benefit to countries with warm climates. It provides a safety margin for delivery of unrefrigerated milk to processing centres and makes it possible to collect milk from remote areas where collection is not feasible at present. It can also preserve milk for longer periods in countries with refrigeration facilities.

Many developing countries, however, have followed the lead of countries with industrialized dairy industries and enacted legislation requiring refrigeration of milk, thus barring the use of any alternative method of preservation. This is impractical and counter-productive where milk-producing areas are widely scattered and refrigeration is not technically or economically possible. The laws impede development of milk production and, even worse, encourage consumption of raw milk which is not properly treated and may be harmful to the consumer.

LPS is a far more effective solution, proven safe by decades of exhaustive research and testing.

The idea of using chemical additives to preserve milk was first officially broached on an international level at an FAO Expert Consultation in Rome in 1957. Research in the United States, United Kingdom, Sweden, the former Czechoslovakia and other countries had already pointed to the LPS system as one of the most promising methods available.

At its 20th joint session in 1967, the FAO/World Health Organization (WHO) Committee of Government Experts on Milk and Milk Products turned to the International Dairy Federation (IDF) for technical advice. IDF carried out its own studies and concluded the LPS system was an acceptable alternative to refrigeration to prevent raw milk from deteriorating in countries in the early stages of organized dairy industry development when the installation of cooling facilities was impossible for technical or economic reasons.

Field trials by national research institutes in Kenya, Nicaragua, Sri Lanka, Mexico, the Philippines, Pakistan and Cuba in cooperation with the Swedish University of Agricultural Science and FAO confirmed the merits of the LPS system.

At its 21st session in Rome in 1986, the FAO/WHO Committee of Government Experts on the Code of Principles concerning Milk and Milk Products asked IDF to prepare a code of practice for the use of LPS to preserve raw milk. After circulating the code among its national committees, IDF presented it to the FAO/WHO Experts' Committee on Food Additives at its 35th meeting in 1989. From there it went to the Codex Alimentarius Commission, which gave final approval at its 19th session held 1-10 July 1991 in Rome.

FAO is now working with scientific and development institutes to find the best ways of exploiting this applied biotechnological process to the benefit of milk producers throughout the developing world.

Jan Barabas is dairy technician officer in the Dairy Group of FAO's Animal Production and Health Division.

For further information: Meat and Dairy Service, MO, Viale delle Terme di Caracalla, 00100 Rome, Italy, Tel: (396) 52254368; Fax: (396) 52255749