Deep in the recesses of most people’s refrigerators lives a half-eaten bottle of salsa, some takeout Chinese food and last week’s chicken dinner. Pulling one of those things out, you wonder: Can I eat it? Is it safe? A lot of commercially prepared items, such as sauces and condiments, have best-by dates on the packaging to ensure flavor, not safety, according to the US Department of Agriculture. Packaged foods tend to last a big longer than those suggested dates. Last night’s dinner, though, is not as hearty. Cooked food leftovers can usually stay in the fridge for only three or four days. And if you want to put food in the freezer, it will last indefinitely, but at some point, it will start to lose flavor. Of course, if something smells off or looks funny, you shouldn’t eat it. Here’s the eat-it-or-chuck-it guide to your slightly suspect leftovers, based on advice from the USDA and the food safety site StillTasty.com.