Sep 16 / William

Can Onions Fight Germs? New Study Says Variety and Light Matter

Onions are a staple in kitchens worldwide, but did you know the type of onion you buy — and even the light it’s cured under — can affect how safe it is from harmful bacteria like Salmonella?

A new study funded by the Center for Produce Safety (CPS) has revealed that onion variety, bulb layers, and post-harvest handling may influence whether bacteria grow or die off during storage.


What the Researchers Found

  • Outer layers protect, inner layers don’t.
    The papery, dry outer skin of onions — especially in red and white onions — actually helps inhibit Salmonella. But once bacteria reach the juicy inner layers (like when onions are cut or bruised), they can multiply quickly.

  • Red onions may be safer.
    Among the varieties tested, red onions showed stronger natural defenses against Salmonella, especially when exposed to certain kinds of light during curing.

  • Light exposure matters.
    When onions were cured (dried after harvest) under blue light, their natural compounds became more effective at fighting bacteria. Light treatment could play a role in boosting onion safety and shelf life.

  • Damage makes onions risky.
    Even a small cut or bruise can let Salmonella slip past the protective outer layers. Once inside, the moist environment of inner onion scales helps the bacteria thrive.

  • Moisture is the bacteria’s friend.
    The more moisture in a layer, the easier it is for germs to survive. That’s why intact, dry outer layers are much safer than damaged inner ones.


    • What This Means for You

    While growers and food processors can use this research to improve farming and storage practices, here’s what everyday consumers can do:

    • Handle onions gently. Avoid buying or using bruised or damaged onions.

    • Keep the skins on. That dry outer layer is protective — peel it only when you’re ready to cook.

    • Store them right. Keep onions in a cool, dry, and well-ventilated spot to reduce moisture.

    • Wash cutting boards and knives. Prevent bacteria from spreading from raw onions to other foods.

    • Cook when possible. Heat destroys Salmonella and other harmful microbes.


    The Big Picture

    What Should You Do if You Bought These Tomatoes?

    This study shows that onions aren’t just flavor boosters — they have natural antimicrobial powers that vary by type and how they’re handled after harvest. Red onions, outer skins, and careful storage can all make a difference in keeping food safe.

    At The Food Court by DSG, we believe food safety begins with awareness. Even small changes in how we choose, handle, and cook our everyday ingredients can help protect our health.

    Onions may bring tears to your eyes — but they could also be helping keep dangerous germs at bay.


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