Water is polluted when you can see the unwanted material; but contaminated water may contain unseen microbes also. Likewise, food that is contaminated with microbes or toxins is considered spoiled and undesirable. There are several activities that can be done to reduce or remove unwanted microbes.

For centuries, it was difficult to keep food safe for long periods of time. Initially humans dried food in the sun; and later they let the foods ferment, added salt, or smoked the foods. In 1810, Napoleon’s military companion, named Nicholas Appert, applied heat to food and initiated the canning industry. The problems that faced early humans do not differ much from the problems we have today--only the great variety and complexity of foods have changed. Using heat to reduce microbes in food is the most commonly used technique. Cooking, blanching, pasteurizing, steaming, and microwaving are just a few processes that reduce the number of microbes in food. By reducing the temperature, even freeziing, the microbial growth is inhibited but only a few microbess are killed by the cooling. Some pathogens like Listeria and Yersinia also grow at refrigerator temperatures. Freezing food destroys cells in the food so microbes will grow rapidly as the food thaws; so thaw the food rapidly. Staphylococcus, Streptococcus, and Salmonella grow rapidly in thawing food.

Other methods of reducing microbes in food include drying, irradiation, and addition of chemical preservatives. Drying kills many microbes; but many others survive. Freeze-drying (lyophilization) is a valuable method of preserving food; but it is also used as a procedure for storing and preserving microbes. Radiation can reduce microbes in food and increase the time that fresh food and spices can be transported and kept on the shelf. Chemical preservatives must inhibit microbes and not harm the person eating the food. Microbiologists suggest organic acids like sorbic, benzoic, and propionic acids for preserving food. These acids damage microbe cell membranes in molds, yeasts, and some bacteria. Natural substances like salt, sucrose, and vinegar reduce the growth of microbes.s Foods like garlic and cranberries are known to contain anti-microbial compounds.

It is also important to “keep cold foods cold” and “hot foods hot.” Temperatures between 40 and 145 degrees Fahrenheit are considered the danger zone because most microbes grow rapidly in this temperature range. You can help keep the microbes at a minimum by keeping the length of time that food is in the danger zone to a minimum. Many food service establishments have initiated the use of single service food itmes so that large amounts of food are not exposed to danger zone temperatures.

Microb es can be removed from water by filtering. Secondly, chemicals can be added to water to help remove microbes (aluminum sulfate) by sedimentation or to kill microbes. The most common group of chemicals used to kill microbes in water is the halogen group. Chlorine and bromine at 0.2 to 0.6 ppm (parts per million) will inhibit microbe growth; and fluorine will also combine with tooth enamel to reduce tooth decay by Streptococcus. Campers can use small amounts of iodine to destroy microbes like Giardia in drinking water. Like food, water can be heated to kill most microbes. Also, aeration will expose anaerobic microbes to oxygen and reduce the growth of microbes.

In the United Statess we have a great variety of food available in grocery stores and available water at numerous locations in every community. We are confident that the foods and water sources are safe; many people in other countries do not have this security and confidence.