The Surprising Reason Behind Slimy Deli Meat (and Whether It’s Safe to Eat)

It’s lunchtime. You’re assembling a delicious sandwich of crisp lettuce, juicy tomatoes, and hearty bread, and are reaching for the deli meats when you discover a sheen on your salami. A curious coating on the capicola. Mucilage on the mortadella.

It’s definitely unappetizing, but is it dangerous? Let’s investigate what gives some deli meats that strange sliminess—and whether you can still put them on your hoagie.

1. Chemistry at the Deli Counter
2. Bacterial Bonanza 
3. The Reasons for Meat Rainbows
4. How to Keep Deli Meats Safe for Eating
5. How to Tell When Deli Meats Are Spoiled

Chemistry at the Deli Counter

Meat producers add food-safe substances to deli products to make them more visually appealing, according to The Takeout. Those additives may include dextrose, a plant-derived sugar; sodium nitrate, a preservative; and carrageenan, a thickener and stabilizer made from seaweed. Usually, they’ll be injected into the whole product before it’s shipped to the deli counter.

After the meat is sliced, the additives start to ooze from the cut surfaces, giving the pieces a shiny or greasy appearance.

Bacterial Bonanza 

The slime can also come from the presence of bacteria, though not necessarily the kind that indicates spoiled meat. Lactobacillus, the same type in probiotic yogurt and kimchi, may feed on the dextrose coating the cold cuts and produce lactic acid while colonizing the surface, adding to the gooeyness. Fortunately, the bacteria and the lactic acid are not harmful, and may even offer some benefits to your gut microbiome.

It’s not the most palatable explanation, but the good news is that the meat itself is just fine. The presence of a sheen or slimy feel, in and of itself, does not indicate it’s rotten.

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The Reasons for Meat Rainbows

Another odd characteristic of sliced deli meats is the appearance of a “meat rainbow,” an iridescent shimmer on the product. This phenomenon doesn’t come from bacteria. It can be caused by the slicing machine’s cut against the grain of the muscle, leaving evenly spaced fibers. When light hits this microscopically bumpy meat surface, it diffracts into separate colors and lends a rainbow-like patina.

Meat rainbows can also be caused by a thin layer of oil on the cut surface. Light may pass through the oil unevenly so only some colors of light are reflected, resulting in a multicolored look. Don’t worry if your cold cuts are giving Judy Garland vibes, though. It’s still OK to eat.

How to Keep Deli Meats Safe for Eating

To keep other forms of bacteria (and worse) away from your deli meats, it’s important to store them properly. All deli meats sliced at the supermarket should be stored in the fridge at a temperature of 40°F and will stay fresh for three to five days, according to the USDA. They can also be frozen at 0°F for up to two months. Cold cuts purchased in vacuum-sealed packages will stay fresh in the fridge for one to two weeks, but once opened, they should be consumed within five days.

How to Tell When Deli Meats Are Spoiled

Some sensory clues should present themselves if your deli meats have gone bad:

• The meat exhibits patches of pink, gray, or brown coloring
• It has spots of mold
• There’s a sour or off-putting odor
• Sections of the meat are dry and hard

If the cold cuts in question show any of these signs, it’s time to toss them. Here are a few more tips for assessing food’s freshness.

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