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Let’s Talk Science POTENTIALLY HAZARDOUS FOODS What is a potentially hazardous food? A potentially hazardous food is a food that is natural or man made and is in a form capable of supporting the rapid and progressive growth of infectious and toxin-producing microorganisms. These foods typically have: ¾¾High protein or carbohydrate content ¾¾High moisture content ¾¾Low acidity PROTEIN AND CARBOHYDRATE Protein is a nutrient necessary for a variety of processes in the human body. Like humans, bacteria need protein to grow and multiply. Meat, poultry, fish, seafood, eggs, beans, peas, nuts and dairy foods have a high protein content. Carbohydrate is a nutrient primarily responsible for providing energy to all cells of the body. Bacteria also need carbohydrate for energy. Bread and other grain foods, dairy foods, fruits and vegetables can have a high carbohydrate content. WATER Bacteria need a percentage of moisture or “water by volume” in a food for growth. There must be enough available water to support growth. This is expressed as water activity (a measure of water bound to food that is not available for bacteria growth). Water activity is measured on a scale from 0-1.0. Disease causing bacteria grown in foods that have a water activity higher than .85. ACIDITY The acidity of foods is expressed as pH. The pH of a food is measured on a scale that ranges from 0 to 14. Most foods considered “acidic” have a pH less than 7.0. Foods with a pH less than 4.6 do not normally support the growth of disease-causing bacteria. Most bacteria prefer a neutral environment near a pH of 7.0, but can grow in a range of 4.6 to 9.0. Milk, meat and fish are in this range. What Do You Think? Which food would have a lower water activity, fresh chicken or frozen chicken? The answer is fresh chicken with water activity at about .98. The water activity of frozen chicken is zero. Even though both are about 60% water by volume, the water in the frozen chicken is not available to bacteria for growth. Freezing slows the growth of bacteria to preserve food for long periods. Time and Temperature Many bacteria grow in a temperature range between 40 and 1400 F. Under ideal conditions, bacterial cells can double in number every 15 to 30 minutes. Some double more quickly. Bacteria are single-celled microorganims that reproduce by binary fission. In this process, the cell divides into two identical daughter cells with identical DNA to the parent cell. Each daughter cell divides into two more cells. Over the course of just 7 hours, it is possible that one bacterium, such as Escherichia coli, could generate over two million bacteria! Exactly how many can make you sick depends on the kind of bacteria. For some, it only takes a few cells to cause foodborne illness. Examples of Potentially Hazardous Foods Meats Poultry Eggs Fish Shellfish Dairy products Cooked vegetables Cooked rice Cooked pasta Cooked beans, peas and lentils Cut fruits and vegetables Raw seed sprouts Cooked soybean products (such as Tofu) Garlic-in oil or other vegetable-in-oil mixtures (unless they have been treated to prevent growth of Clostridium botulinum) Cooked cereal Prepared by: Janie Burney, PhD, RD, Professor, Family and Consumer Sciences Keep Hot Foods Hot and Cold Foods Cold The term “potentially hazardous foods” is used by the Food and Drug Adminsitration in the FDA Food Code. The Food Code is a model law that helps government entities, such as health departments, regulate retail and food service industries to protect the health of consumers. The principles of time and temperature also apply to foods you handle at home. It is important that you do not leave potentially hazardous foods at room temperature for more than two hours, or no more than one hour if the temperature is above 900F.