Pasta offers a quick meal solution after a long workday. While homemade sauces work well, store-bought jars provide unmatched convenience. However, mold often appears on the surface just days after opening and partial use, even if the sauce smells fine. This contributes to high food waste in UK households, where jars of pasta sauce, salsa, and tomato paste rank among frequent offenders.
Why Mold Forms in Opened Sauce Jars
Sealed jars create a protected, shelf-stable environment free from microorganisms. Opening them exposes the contents to air carrying tiny microbes from kitchen surfaces, utensils, and hands. Mould spores quickly settle on the exposed sauce surface.
Food blogger Ryan Allen at The Cooking Duo explains: “When food is commercially processed and sealed, it’s effectively locked away from the outside world. Those jars are designed to be shelf-stable because no microorganisms can get in. The moment you open them, you’re exposing the contents to everything in your kitchen environment, whether you can see it or not.”
A Simple Storage Change to Extend Freshness
Store opened jars upside down in the fridge instead of upright. This method presses the air-exposed surface against the lid, reducing available oxygen that mould needs to grow. Ryan Allen states: “By storing the jar upside down, the surface that was exposed to the air is now pressed against the lid. There’s far less oxygen there, and mould needs oxygen to grow. You’re basically making life harder for it.”
The technique also simplifies scooping out remaining sauce without scraping the bottom.
Ideal Sauces for Upside-Down Storage
This trick suits thicker products that hold their shape. Ryan Allen recommends: “This works particularly well for tomato-based sauces, tomato paste, pesto, salsa and thicker curry sauces. Anything that tends to hold its shape rather than slosh around is ideal.”
Key Limitations
Upside-down storage slows mould growth but does not eliminate it. Ryan Allen advises: “It’s a way of extending usability, not a licence to keep food indefinitely. You still need to pay attention to smell, texture and any visible signs of spoilage.”
