Safer Food with Food Technology Anything that we do to food to keep it fresh and nourishing, is food processing, and it has come a long way since the first caveperson discovered fire.

Food Processing Techniques Drying Possibly the oldest form of processing and preserving food involves removing most of the moisture from the food. This prevents enzymes to act in breaking dowm cells and rotting. Drying also prevents the growth of microbes which can lead to food poisoning. Dried foods need to be kept in airtight containers. Freeze drying When food is frozen, and then the ice is sublimed - which means it is evaporated from solid ice to gas - which is done under vacuum, the process is called freeze drying. An expensive method, freeze drying is used for premium instant coffee, soup mixes, and very light foods for hikers, astronauts and the military. Canning Napoleon's army was responsible for the development of the canning method of food preservation.The food is often steamed for a short time and then placed in cans, sealed and heated to high temperatures, to kill any microbes which may be present. Acidic foods don't need to be heated to the same high temperatures as non acidic foods. While canned foods last well, it is best to use them within one year. Freezing Frozen food is blanched beforehand, but as no other processing occurs, the food retains more nutrients, taste and colour than canning. Frozen foods keep for up to 6 months. Cook and Freeze After cooking, the food is rapidly chilled to prevent bacteria from multiplying, and then frozen. Food must be reheated thoroughly, to avoid inviting unwelcome guests like listeria to dinner. Sous-vide Called the gourmet method of processing food, foods prepared in this way are said to be tastier than other conventional cooking methods. The food is cooked in a vacuum-sealed bag, cooled quickly and refrigerated at below 3o C. Foods treated with this method must be kept chilled below 3°C from the time it is bought, transported home and stored. Modified Atmosphere Packaging Used for bread, cakes, fruit, vegetables meat and seafood, this method lengthens the life of food, without the addition of preservatives. The food is placed in its packaging, and the air is sucked out and replaced with nitrogen or carbon dioxide gas. Fresh fruit and vegetables stored in bulk containers are treated in the same way, with the levels of carbon dioxide and oxygen being monitored to preserve them as fresh produce. Extrusion Cooking Interesting shapes and textures are created with starch based and cereal products. Ingredients are pulverised, mixed with water and steam, heated up to 200o C and the pressure created within the container causes the mixture to expand as it is squeezed out. Some loss of nutrients occurs with this method, however interesting shapes and textures add to the appeal of the food. Ultra High Temperature Treatment (UHT) When food is rapidly heated to about 140°C, for a few seconds, cooled in a sterile environment and placed in sterile, air-tight packaging, milk and fruit juices can be kept without refrigeration for at least 3 months. There is some loss of nutrients with this method. Ohmic Heating Ohmic heating sterilises food by passing an electric current through the food and then cooled and sealed in sterile containers. Foods such as pasta in sauce, desserts, pie fillings and soup are treated with this method. Chemical Preservatives Chemicals like vinegar change the pH of the food and prevents microbes from growing. Salt has long been used as a preservative, and salted, pickled and dried foods were the only methods sailors had of preserving food for long voyages. Some other chemicals used in foods are: nitrates and nitrites are used to preserve meats such as ham and bacon. sulphites are commonly used to prevent fruit and vegetables from browning after they've been peeled. anti-oxidants help prevent fats and oils from going rancid. Food Additives bleaching agents whiten foods such as flour colours replace the faded colours of some foods and are used to make foods look more appealing emulsifiers are used to prevent mixtures of oil and water from sepaarating, as in margarine flavour enhancers such as monosodium glutamate are said to bring out the flavours of foods enzymes are used to prevent lollies from crystalising artificial sweeteners are used to lower the calorie and kilojoule count of foods thickeners are used to give an even consistency Food Irradiation Foods are bombarded with high energy gamma rays, which stops vegetables from sprouting, delays the ripening of fruit, destroys microbes, all without the use of additives and preservatives. There has been strong resistance to food irradiation, and although tests have been carried out for several decades now, there has been criticism of how the experiments were carried out and how the results were interpreted. Despite vigorous debate around the world, irradiation has met with a lot of resistance and has not been accepted as a method of preserving food. Consumer groups from oll over the world have called for a moratorium on further use of food irradiation. Limiting food-poisoning Traditionally, testing the end products in processed foods has been the way of ensuring the safety of food products. However, moves to improve food safety have established systems of monitoring at key points along the processing chain: hazard-analysis-critical-control-point systems. Scientists are also developing improved packaging and processing techniques that help keep food fresh and free from contamination.

Bibliography Australian Consumers' Association. How Safe is Our Food?. (Sydney: Random House, 1991). Australian Academy of Science, When bugs have you on the run (http://www.science.org.au/nova/030/030key.htm, April 1998).