By: Dr. Joan Pellegrini
Food left out can grow bacteria and become a source of illness anytime of the year. However, summertime is a particularly vulnerable time because there are more picnics and gatherings and the temperatures are warmer. There are three problems with food borne illness: 1) improper food preparation, 2) susceptible foods, and 3) improper food storage.
Preparation: first we should mention the cutting boards because they can be easily contaminated. There are three basic types of boards: wood, plastic, and glass. Glass is easy to clean but it is really tough on the knives and so most cooks do not recommend a glass cutting board. A study in the May issue of Infection Control and Hospital Epidemiology looked at cutting boards in hospitals and private homes. Poultry foods are considered the highest risk for food poisoning. Spinach and leafy greens also posed a problem. Interestingly, red meat was low risk. 3-7% of the cutting boards harbored drug-resistant bacteria. One would think that wood harbors more bacteria in the crevices compared to plastic. There is some research that shows the opposite is true (Dean Clover, PhD UC Davis, 2006). My review of the literature tells me that there is no difference between wood or plastic if both are in good condition and are cleaned with soap and water after each use. What does not seem controversial is how we should handle our food when preparing it. You should clean the cutting board after using for each type of food. In other words, do not cut chicken on the board and then cut up some vegetables (or vise versa).
Susceptible foods: In an article from the Mayo Clinic (authored by Rachael Moshman), it is a myth that mayo based foods (potato salad and cole slaw) are more dangerous than oil based salads. Bacteria will grow on any food that is warm and contaminated. Safer foods are those that do not contain vegetables, meat, milk, eggs, or cheese. Fairly safe foods are crackers, cookies, breads, cakes, rice dishes, pasteurized cheese, dried fruits/vegetables/meat, canned or frozen foods.
Storage: Never put cooked food back on the same plate that held the raw food. Store all food in a cooled container until it is ready to use and then put the left overs back in a cooled container as soon as possible. If food has been left out for over an hour or two, it should probably be discarded if it is one of the susceptible foods.