Scientists have developed methods to detect food spoilage, but until these are available on a mass scale, food science and safety experts have some tips.
First -- slimy, stinky, spotty or chunky changes in food don't mean very much in terms of safety. It may not taste good, but that doesn't mean it's going to make you sick. That’s because there’s a difference between what food scientists call spoilage bacteria and pathogens.
Spoilage bacteria form into slimy films on lunch meat, soggy edges on vegetables or stinky chicken. But the pathogens that do make you sick are odorless, colorless and invisible.
Since consumers can't count on looks or smell, instead use the rule of four: no more than four days at 40 degrees Fahrenheit or 4 degrees centigrade. (Freezing fresh food at zero degree Fahrenheit will keep it safe indefinitely.)
Forty degrees Fahrenheit buys people three days for safety with raw chicken and ground beef, three days with cuts of beef and lamb, and four days for leftovers.
Allowing anything to go above the cold 40 degrees along the way from store to frying pan can make the difference between illness and safety -- and about 25 percent of refrigerators in the United States are kept at too high a temperature for safety. Be sure to check yours. It’s important to know when food is safe to eat and when it’s really bad not only from a health perspective but also from an environmental and ethical one.
There is an incredible waste of food in much of the world as it is, and we certainly don't want to get rid of food that's still perfectly safe to eat. Case in point, a new report authored by the Stockholm International Water Institute, the UN Food and Agriculture Organization, and the International Water Management Institute found that half of the food produced worldwide is wasted!
Specifically, in the United States, for instance, as much as 30 percent of food, worth over $48 billion, is thrown away.
"That's like leaving the tap running and pouring 40 trillion liters of water into the garbage can -- enough water to meet the household needs of 500 million people," says the report.
Further, it’s been estimated that at least half of the food thrown away in homes and restaurants across the United States isn’t bad and could easily be consumed.
Often, it’s things like bread, cheese, fruits and veggies that get tossed, just because of a small imperfection or spot of mold. As ABC News pointed out, a little bit of mold or a bad spot here and there isn’t likely to make you sick. It’s perfectly safe to just cut the spot out and eat the food. Even foods that smell slightly pungent or feel a bit slimy probably haven’t gone bad.
Instead, it’s the bacteria that you can’t see, smell or taste that could make you sick.
And since there’s really no way to tell whether your ground beef contains dangerous levels of E. coli or another illness-causing bacteria, the best method for keeping your food safe has nothing to do with your refrigerator … it has to do with the source of your food.
Try to buy as much of your food as possible from small, local farms where you can personally inspect the conditions.
Food that is grown on a smaller scale is typically safer than those mass-produced, and organic foods have also been shown to contain lower levels of bacteria like salmonella than conventional foods.
Now, assuming you already buy the majority of your food from a safe source, how can you determine if it’s spoiled or not?
I like the “rule of four” from ABC News, which suggests keeping food no more than four days at 40 degrees Fahrenheit (or 4 degrees centigrade). This means, though, that you need to put a thermometer in your refrigerator and check to make sure it’s cold enough. This is an important step, as 25 percent of U.S. refrigerators are kept too warm to keep your food safe.
What Else Impacts Food Spoilage?
Temperature and age of the food are probably the biggest factors, but that’s not to say they’re the only ones. For instance:
- Double-dipping will make food go bad faster because it transfers saliva into the food, which promotes bacterial growth. One study even found that three to six double dips transferred about 10,000 bacteria from an eater's mouth to the dip sample.
- Putting leftovers away in a big clump may also promote food spoilage. This is because the food at the center of the mass will take longer to cool, which means bacteria will continue to grow even after it’s in the fridge.
- Vegetable oils, such as those in mayonnaise and salad dressing, break down over time and turn rancid. Though you may not notice this change the rancid oils can cause damage in your body. You should also be cautious of most salad dressings as they are loaded with unhealthy oils, typically vegetable or soy oils.
- If you leave leftovers or any food out too long, it will speed spoilage. Two hours is generally the max they should be left out, though the sooner you refrigerate them the better (remember to factor in the time it takes to drive back from the grocery store, and the time it takes you to unpack your groceries).
Not all foods go bad after four days in the fridge, and some might not even last that long. Use your own judgment and if in doubt, it’s probably best to throw it out (particularly if your immune system is not up to par). However, here are some common foods along with estimates of how long they typically last in the fridge:
- Butter: 1-3 months
- Milk: 5 days
- Eggs (fresh): 3-5 weeks
- Ground beef, ground turkey, chicken and fish: 1-2 days
- Beef steaks and roasts and pork roasts: 3-5 days
- Cooked or uncooked veggies: 3-5 days
- Leftovers: 3-4 days
- Mustard, soy sauce and Worcestershire sauce: use within 1 year of opening
- Salsa: 1 month
- Ketchup, peanut butter and jelly: 6 months
Of course, the fresher your foods are to begin with, the longer you can expect them to last as well. Ideally, choose the freshest foods you can find, and eat them as soon as possible, as some foods, particularly vegetables, lose nutrients after they’re harvested.
Minimizing Your Risk of Getting Sick if You DO Eat a Spoiled Food
Sooner or later, you may eat something that has good bad or is contaminated, but this doesn’t mean you have to suffer the wrath of food poisoning. If your immune system is healthy you will be able to fight off the bug without it causing any serious problems.
For a comprehensive review of how to improve your health and immune system please consider my book Take Control of Your Health, but for now here is a summary of how to keep your immune system strong:
- Avoid sugar
- Get enough sleep
- Eat garlic regularly
- Deal with stress in a healthy way
Last year I came down with a salmonella infection and after a high dose of probiotics it was gone within 24 hours, so I can personally testify as to how effective this strategy is.