STORRS, Conn. — The invention of mechanical refrigeration was one of the most important developments in the history of keeping food safe (others include the pasteurization of milk and commercial canning). Ask anyone who has suffered through the aftermath of a hurricane or ice storm without the benefit of electricity to keep their food cold. But even a plugged-in fridge, humming along and doing its job, can be a place that harbors pathogens that cause foodborne illness or spoilage organisms that result in food waste.
A little microbiology lesson might be helpful before we go on. When talking about food, food safety and safe food storage, we often discuss the microbes that can cause foodborne illness. Especially we talk about how to prevent or eliminate them from our food or food preparation areas. The foodborne microorganisms that cause illness are called pathogens. Certain strains of bacteria such as Salmonella, E. coli, Listeria, and Staphylococcus are pathogens—they can cause foodborne illness. Some viruses and parasites can be the source of foodborne illness as well.
Other microorganisms may cause food to spoil. Spoilage organisms are generally not pathogenic. Spoilage makes food unappetizing, so we are unlikely to eat it. But the slimy, discolored, smelly, or fermented foods that result from the action of spoilage organisms are not as apt to make us sick, though some molds produce toxins that do have serious health effects.
The “good” thing about spoilage organisms is that they tell us that they are there. They make food smell funny or look weird. They turn food odd colors (cottage cheese that looks pink) or make things fizzy (juice that is fermented). We know it is best not to eat them. Spoilage organisms, will grow or multiply quite well at colder temperatures. This is why milk can spoil, juice can ferment and cheese or fruit can get moldy in your refrigerator.
On the other hand, pathogens are quiet, invisible. We never know for sure if they are lurking in the lettuce or hanging out on the chicken. Therefore we must take special care to prevent their growth or their spread to other foods or food-contact surfaces. We must assume that they are always there and do our best to control them.
Generally speaking, pathogens do not grow well in refrigerator temperatures. They prefer what we call the “danger zone” of approximately 41 degrees F to 135 degrees F. This is why it is recommended that you keep your refrigerator temperature at no more than 40 degrees F. If E. coli, Salmonella or other pathogens contaminate your food before you refrigerate it, these microbes will remain on the food. Refrigeration does not kill them, though it does limit their growth. One exception to this is Listeria. This bacteria actually likes the cold and can grow in temperatures as low as 32-45 degrees F.
Clean your fridge regularly
The best way to keep your refrigerator from being the source of a bout with foodborne illness is to keep it clean. A 2013 study of home kitchen environments conducted by the NSF, an organization that sets standards for cleanability of commercial food equipment, found that two of the “germiest” areas in the kitchen were the meat and vegetable bins in the home refrigerator. They found Salmonella, Listeria, E. coli, yeast, and mold.
Prevention of messes is the first step to a clean refrigerator. When storing raw meat, poultry, or fish, be sure to separate them from other foods. Store them in a way that prevents juices from contaminating other foods or refrigerator shelves—place them on a plate or tray. Store fresh raw fruits or vegetables loosely in plastic bags or storage containers. Often it makes sense not to wash fresh produce until you are ready to use it, so it is especially important to keep fresh produce in the fruit and vegetable bin if possible. Keep eggs in their original carton. Leftovers should be refrigerated in closed containers, date labeled, so that they are used before spoilage organisms set up shop. If you have a leaky milk carton, put a plate under it.
If spills do occur, wipe them up immediately. If meat, poultry or fish juices contaminate a ready to eat food (lettuce, cut fruit, cheese), it is best to toss it.
A least weekly—maybe the night before garbage pickup–go through your fridge and throw out any perishable foods that are past their prime. Check dates on milk, yogurt and soft cheeses. They generally are best if used by 5-7 days after the “use by” date. Toss anything that is moldy, slimy, or just looks or smells spoiled. Take a look at your leftovers: generally, leftovers should be kept no longer than 3-5 days. Throw out those that have been there too long.
A thorough, deep cleaning should be done monthly.
- Empty the food out of the refrigerator. In summer months, it may make sense to put some things in a cooler with ice—especially raw meat, fish, cut fruits or vegetables, and leftovers.
- Take out shelving, drawers, and any other removable parts.
- Wash shelving, drawers, and any other removable parts by hand with warm, soapy water. Dry with a CLEAN towel. (Air drying is preferable, but you want to get this job done quickly and get food back into the refrigerator within an hour or so.)
- Wipe the inside of the empty refrigerator with warm, soapy water, then wipe with clean water to rinse off soap. Dry with a clean towel.
- If you want to, mix one tablespoon of liquid household bleach (unscented) with a gallon of water and wipe the interior and any shelving with this sanitizing solution. Always clean first, then sanitize. Allow to air dry. Sanitizing alone will not be effective.
- Finally, as you place items back in the refrigerator, take time to wipe off container surfaces.
- Wipe off door handles and be sure, if you have a water/ice dispenser on the outside of your fridge, to clean that as well.
–Diane Wright Hirsch, MPH
Senior Extension Educator/Food Safety
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