sábado, julio 19, 2003

Bacteria and us
FoodInfo Online Features -->18 July 2003
Svetlana Rodgers Senior Lecturer, School of Management, College of Law and Business, University of Western Sydney, Campbelltown campus, Building 17, Locked Bag 1797, Penrith South DC NSW 1797 Australia.

Hygiene and cleanliness are undoubtedly embedded in our consciousness.
Our supermarkets are full of antibacterial detergents, sanitisers, toothpastes, sprays, creams and lotions, while the food we eat is often over-processed and devoid of natural bacteria. Even salad vegetables are washed in a sanitiser.
Psychologically, the dislike of bacteria most likely originates from the fear of infection, which has followed humankind throughout its history.
In the Middle Ages, for example, the poor quality of the water meant that it was safer to drink wine. From a practical perspective, modern food companies follow strict hygiene rules so that they comply with food legislation requirements, with many resources being utilised so that they may adhere to such guidelines.
Our frequent preoccupation with hygiene and cleanliness carries a price not only to the environment, but also to our health. Throughout much of our evolution, humans have been bombarded with dirt and germs - removal of which from our surroundings also reduces stimulation of the human immune system, which, as a consequence, would function below optimum if man lived in such a barren environment.
Scientists believe that children raised in less hygienic conditions are less likely as adults to develop asthma, allergies, diabetes, rheumatoid arthritis and other immunity-linked disorders. In 1910, in his book, The Prolongation of Life, the founder of the theory of 'probiotic' or beneficial bacteria, Russian scientist and Nobel Prize Laureate Ilya Metchnikoff, said 'a reader who has little knowledge of such matters may be surprised by my recommendation to absorb large quantities of microbes, as the general belief is that microbes are all harmful. This belief, however, is erroneous'. Since then, it has been found that probiotic bacteria can reduce the risk of colon cancer, lower cholesterol, increase immunity, and can even offer protection from diarrhoea.
We carry about 8 kg of indigenous bacteria in our gut, the quality of which is important to our health. The addition of probiotic bacteria to fermented products has become common today.
In Russia, yoghurt made using the 'strong' bacteria taken from the guts of cosmonauts are a marketing attraction, while in the livestock industry, pathogen-fighting bacteria can replace the use of antibiotics.
Probiotic bacteria can even be added to women's hygiene products to exclude bacteria that can cause debilitating infections, premature births or infection of newborn infants.
Harmless bacteria can not only improve our health and immunity, but can also exclude food poisoning bacteria in foods. So-called lactic acid bacteria are present in high numbers in products such as yoghurt, fermented vegetables and sausages. This explains why fermented products have an excellent food safety record.
In 1995, a leading scientist in food microbiology, James Jay, wrote an article called 'Foods with low numbers of microorganisms may not be the safest foods'. He argued that, with improvements in cleaning/sanitising, not enough harmless background organisms were left to prevent proliferation of food poisoning bacteria. Surprisingly, there are very few commercial applications of so-called 'protective' cultures in non-fermented foods.
The Wisconsin process for cured bacon is one of these applications and employs addition of sucrose and lactic acid bacteria to prevent botulism in bacon, together with low concentrations of nitrite. Botulism is also a potential risk for refrigerated minimally processed foods, such as packaged cook-chill meals used in catering and retail. At the Centre for Advanced Food Research at the University of Western Sydney, we have developed a method using lactic acid bacteria for the prevention of botulinal toxin formation in cook-chill meals. As with the majority of microorganisms, these protective cultures are dormant when the product is stored under the correct temperature and 'switch on' to fight food poisoning bacteria only when temperature abuse takes place. Although the cultures may be visible in clear products, they go unnoticed in thick soups or casserole-style products.
In a recent trial, a sensory evaluation panel was unable to distinguish between seafood chowder, vegetable curry and chicken casserole with and without culture added. The biggest technological challenge now is to develop a method to protect these cultures during heating. If a product is cooked and then aseptically/hygienically packaged or stored under vacuum in Greenvac-type containers, the cultures can be incorporated directly. Extended shelf life cook-chill technology, however, is a modern development, which requires more sophisticated preservation methods.
In addition, the risks of food poisoning are increased through intensive farming practices, extensive transportation, the emergence of more resistant bacteria and an ageing population. Protective cultures offer temperature-responsive, natural preservation, and also bring some bacteria back into our lives.

For more information contact Svetlana Rodgers, senior lecturer, whose research led to the patent application "Preserving with Lactic Acid Bacteria" PCT/AU01/01549