Packed with nutrients and with a mild, earthy flavor and crisp texture, alfalfa sprouts are health food stars. Before you sprinkle them over your salad or sandwich, though, a word of caution: these sprouts need a warm, humid environment in which to grow, which is exactly the conditions in which bacteria thrive. With that in mind, they should ideally be consumed no more than two days after being purchased – otherwise your risk of getting ill from eating them increases. Experts advise that pregnant women avoid eating raw alfalfa sprouts entirely.

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Baby formula should never be given to infants after the expiry date, which is stated on the packet and refers to the unopened shelf life of the product. This is because, although formula contains the exact nutrients babies need, once the expiry date passes, the nutritional value of the formula may change and could lead to a nutrient deficiency.

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Bagged salads

Bagged salads may be pre-washed multiple times but, because they’re handled so frequently, they’re still prone to bacteria including listeria, salmonella, and, at the very worst, E. coli. It's impossible to know if your salad leaves may be affected, but you can reduce the risks by eating the salad as soon as possible after opening. Always throw away leaves that don't look or smell as they should, too.

Berries

Frustrating as it may be to discover that your pricey punnet of fresh berries has gone bad, eating a strawberry sporting a furry white cloak or a raspberry that’s rapidly turning to mush just isn’t advisable – and could make you sick. Because the mold spores are airborne, if one of your berries has gone bad it’s advisable to discard the entire pack. On average, berries will keep for up to three days in the fridge, so either eat them before they expire or freeze any you’re unlikely to work your way through.

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Chicken

If, upon closer inspection, the chicken you were planning to cook for dinner looks noticeably pale or grey, has a nasty smell, or is bloated, the bin really is the best place for it, regardless of the date on the packaging. This is primarily because consuming chicken or turkey that has gone off can cause a severe case of food poisoning, resulting in hospitalization or, in very extreme cases, death.

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Cold-pressed juices

As galling as it may be to throw food or drink away – particularly when you haven’t even opened it, and especially when it was expensive to buy – raw cold-pressed juices that have passed their expiry date shouldn’t be consumed. This is primarily because they’re unpasteurized and far more prone to contamination by bacteria and yeast. In general, fresh juices (including homemade) should be consumed within five days of production.

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Condiments

We’ve all done it: pulled a jar of mustard or bottle of mayonnaise out of the fridge that’s been there longer than we remember. While it may be tempting to slather said condiment on your sandwich regardless, it’s worth noting that once a jar or bottle is opened, bacteria are effectively invited in. As a rough guide, once opened, mustard will last for up to a year in the fridge, but the likes of mayonnaise should be consumed or discarded after two months, while ketchup will often start to go bad after six months, even when stored in the fridge. If the sauce in question has gone moldy, become discolored, smells strange or has water floating on top, give it a miss.

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Cooking oil

While you might think that oil stays good indefinitely, cooking oils do have a shelf life and it’s worth paying attention to that date if you want your food to taste the best it possibly can. On average, most cooking oils will last for six months once opened, and potentially longer if stored away from light and heat. Oil that is past its best will develop a rancid, bitter smell and taste, which may well find its way into your food.

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Deli meats

Next time you’re stocking up on sliced turkey and ham from the deli counter, it's worth bearing in mind that the United States Department of Agriculture (USDA) says that deli meat should be consumed within three to five days. Any longer than that and the levels of listeria present can become dangerously high. So, while the meat might look, smell, and taste normal, it could still make you ill.

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Egg whites©Tanya Sid/Shutterstock

For whole eggs, experts often advise using the float test for freshness, discarding any that float to the top in a bowl or glass of water. But if a carton of commercially produced liquid egg whites is sitting in your fridge, make sure you use them up within three days of opening. (The same applies to fresh egg whites, such as those left over from a recipe requiring yolks.) If the liquid egg white is lumpy, discolored, or has bits floating in it, discard it regardless of the date or how long the carton has been open. It’s also worth noting that for safety, opened cartons of liquid egg whites shouldn’t be frozen – though you can freeze the whites from fresh eggs.

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Fiddleheads

The curled, edible shoots of the ostrich fern, and fiddleheads are a Canadian and US delicacy – but they can cause food poisoning if they’re not stored, prepared, and cooked properly. Although thoroughly washed fiddleheads can be kept in the fridge for up to a week (ideally no longer), it's essential to cook them in boiling water or steam until tender. Always discard the cooking water, and never serve fiddleheads raw or undercooked.

Fish that isn't fresh or hasn't been subject to proper storage and handling can cause food poisoning. One or two days is the maximum amount of time fish should be kept in the fridge before cooking or freezing. As with many of these foods, always trust your judgment; fresh fish should smell like the sea – if it has an overpowering, sour aroma or is visibly slimy, steer clear.

Ground beef is more likely to cause food poisoning than a piece of steak, as bacteria like E. coli, salmonella or Staphylococcus aureus on the outside can get mixed all the way through the meat as it’s minced. Good refrigeration and consumption within one or two days should mean the bacteria present don’t reach worrying levels. Most important of all, ensure ground meat is cooked until the internal temperature reaches 160°F.

Just like ground beef, ground pork’s expiry date should be adhered to as it can quickly become the ideal breeding ground for various types of harmful bacteria. The USDA's FoodKeeper App recommends only keeping minced pork in the fridge for one or two days before eating. Again, minced pork should also always be cooked thoroughly, until the internal temperature reaches 160°F to avoid food poisoning. 

While experts agree that live mussels can be kept in the fridge for longer than you might think (up to five days), most say that they taste best when consumed by day two. Proper storage is also critical: ensure they’re covered with a clean, damp cloth or paper towel and never store them in water or in an airtight container. No matter how fresh they are, always discard mussels with cracked or broken shells or those that don’t close when tapped. Any mussels with shells that don’t open when cooked should also be thrown away.

As with mussels, oysters should be served as fresh as possible and be alive right up until the moment they're shucked. At home, make sure you store your oysters correctly and don't be tempted to keep them for longer than two days after purchase. Eating out? Ask to see the ‘shellfish tag,’ which every restaurant or retailer is required to have for each bag of oysters that they purchase. If the date on the tag indicates they were harvested longer than a few days ago, you’d be well advised to pick a different dish. It’s recommended that older people, pregnant women and very young children avoid raw or lightly cooked shellfish.

Fresh deli salads, particularly those laced with mayonnaise (here’s looking at you, potato salad), should be eaten no more than three to five days after purchase. Any longer than that and not only will the product have lost its freshness, but there’s also an increased risk of bacterial contamination. If said salad has been left out on the counter or buffet table for more than two hours – or worse, out in the sun at a picnic or barbecue – it’s best not to eat it at all. 

Soft cheese is a prime breeding ground for listeria, so you really do need to pay attention to the dates on the packets. If you purchase updated soft cheese (from a deli, for example), consume it within one or two weeks, and use your common sense when doing so – if there’s any mold present, you’ll need to throw the cheese away. This also applies to blue cheese and rind cheeses like brie; the USDA says that any mold that is not part of the manufacturing process can potentially be dangerous.

Regardless of the date stated on the packet, once spinach leaves start to wilt, it’s advisable not to eat them raw. While the general consensus is that limp leaves are safe to consume once cooked, if they’re brown or slimy it’s best to consign them to the compost heap. To help prolong their lifespan, spinach leaves should only be rinsed just before eating.