What is that blackish-red stuff forms on old ketchup bottles?

Here's why it happens:

* Spores: Mold spores are everywhere in the air. They are microscopic organisms that can survive in a dormant state for long periods.

* Moisture: Ketchup is a moist food, providing the perfect environment for mold spores to germinate and grow.

* Time: Over time, as the ketchup sits in the bottle, mold spores can multiply, forming the visible dark growth you see.

Important Note: Mold is a type of fungus and can be harmful if consumed. If you see mold on your ketchup, it's best to throw it away. Don't try to scrape it off, as that could spread the mold deeper into the ketchup.

Preventing Mold:

* Refrigerate ketchup: Storing ketchup in the refrigerator helps slow down the growth of mold.

* Keep it sealed: Tightly close the lid after each use to prevent air and moisture from getting in.

* Check expiration dates: Use ketchup within the recommended time frame to reduce the risk of mold.