My refrigerator suffers from a chronic real-estate problem. The issue isn’t leftovers; it’s condiments. Jars and bottles fill the door and dominate the main shelves. With items like chili crisp, maple syrup, oyster sauce, gochujang, spicy mustard, and several kinds of hot sauce crammed in, I’ve started stacking containers. Squeezing in new items feels like playing Tetris and Jenga simultaneously, all because of those three little words: “Refrigerate after opening.”

However, these instructions often seem confusing or unnecessary. Pickles are typically refrigerated after opening, yet the purpose of pickling is preservation. The same goes for fermented foods like sauerkraut, kimchi, and certain hot sauces. Ketchup bottles adorn diner counters, and chili oil and soy sauce are common on restaurant tables. So why do they need to occupy precious fridge space at home?

Conversely, some foods languish in the pantry when they would fare better in the fridge. Nuts develop off-tastes after a few months, and spices lose their potency just as quickly. Recently, a bag of flaxseed I’d bought turned rancid within weeks, smelling like paint thinner. Many commonly unrefrigerated foods could benefit from cold storage, according to Kasiviswanathan Muthukumarappan, a refrigeration expert at South Dakota State University. Yet inconsistently, many shelf-stable foods are refrigerated by default, wasting not only fridge space but also food itself.

A grocery store trip suggests two types of foods: fridge foods and pantry foods. Pasta and granola bars stay at room temperature, while meat, dairy, and produce are kept cold. The FDA defines highly perishable items as “temperature control for safety” foods, which should be kept below 40 degrees Fahrenheit to slow the growth of harmful microbes that cause food poisoning. According to the U.S. Department of Agriculture, these foods shouldn’t be left unrefrigerated for more than two hours.

However, the fridge-pantry binary is too simplistic. Many condiments exist in a murky middle ground. Some mustards can sit out, while others are prone to mold, according to Karen Schaich, a food science professor at Rutgers University. Relishes, usually pickled vegetables or fruits, can develop mold or yeast fermentation if not refrigerated, partly depending on their sugar content. Microbes don’t thrive in acidic conditions but generally like some sugar. As a rule of thumb, “extremely tart or sour” condiments are usually safe to leave out, provided they aren’t sweet, Schaich explained.

Proper food storage isn’t a simple question of to chill or not to chill. Beyond safety, refrigeration helps maintain a food’s flavor by slowing the growth of spoilage microbes and natural degradation processes. Once safety is controlled, “chemistry takes over,” Schaich said, referring to reactions that cause food to develop unpleasant flavors over time.

Oxidation, which causes stale Cheerios and rancid oil, is a major culprit. Exposure to oxygen, time, moisture, bacteria, light, and heat accelerates these changes. Refrigeration helps keep food tasting fresh by mitigating these factors. That’s why products like Heinz ketchup and Kikkoman soy sauce recommend refrigeration—not for safety, but to preserve flavor. They won’t make you sick if stored in the pantry, but their taste might suffer.

Fatty foods are especially susceptible to oxidation. Nuts, certain oils, and even peanut butter can go rancid, developing sour or bitter flavors. Muthukumarappan suggests refrigerating or even freezing these items for long-term storage. Whole-grain flours, like rye and spelt, also benefit from cold storage due to their oil content.

Spices, though not prone to rancidity, lose their potency over time. Volatile oils in spices oxidize, causing them to lose flavor. Storing spices near heat and light accelerates this process. For long-term storage, airtight containers in the freezer are best, but for frequent use, room temperature is preferable to prevent condensation and potential microbial growth, according to Luke LaBorde, a food science professor at Penn State.

I’ve never seen a ketchup bottle labeled for room temperature storage, nor a spice jar meant for the freezer. Food storage instructions often seem like insider knowledge: there likely won’t be refrigeration guidelines on a bag of pine nuts, but informed consumers know better. While it’s unrealistic to expect every product to have detailed instructions, a simpler system might be to keep everything cold by default. Most foods would be safer and fresher. Muthukumarappan couldn’t think of any food that tastes better at room temperature, though debates continue over tomatoes, bread, eggs, butter, and olive oil.

The fridge-pantry dichotomy will never fully capture the nuances of food safety, and experts don’t always agree. Even produce storage rules aren’t clear-cut: all sliced fruit, but not all whole fruit, should be kept cold, especially melons, due to their low acidity and susceptibility to pathogenic microbes, LaBorde said. Garlic is safe at room temperature for several months, but homemade garlic-in-oil must be refrigerated to avoid botulism.

To reclaim fridge space and avoid wasting food, think beyond the fridge-pantry binary. Consider how long and where you plan to store food. Bulk purchases from Costco, like a five-pound bag of walnuts or a gallon of mayonnaise, can easily be forgotten in a humid pantry. But if you’ll use a bottle of ketchup in a week of summer barbecues, it’s fine on the counter. Freeze excess nuts for future use.

Food storage science was once widely taught in American schools, Schaich noted. Today, we’re largely on our own. While we may never master all its complexities, understanding food storage better can offer benefits. Ignoring the “refrigerate after opening” directive on a jar of capers felt liberating—not just for breaking an imperfect rule, but for the space it freed up in my fridge.