Can reheating cooked chili that was left unrefrigerated for 4 hours kill bacteria?

No, reheating cooked chili that was left unrefrigerated for 4 hours will not kill all bacteria.

Here's why:

* Bacteria multiply rapidly at room temperature: Within the "danger zone" of 40°F to 140°F, bacteria can double their numbers every 20 minutes.

* Reheating doesn't always kill everything: While reheating to a high temperature can kill some bacteria, it may not eliminate all of them, especially if they've already produced toxins. These toxins might remain even after cooking and can cause food poisoning.

It's crucial to follow food safety guidelines:

* Refrigerate cooked chili within 2 hours: This helps slow down bacterial growth.

* Discard chili left out for more than 2 hours: Even if it was in a cooler environment (70°F or lower).

* Reheat chili thoroughly to 165°F: Make sure it's steaming hot all the way through.

Even if you reheat the chili, you risk getting sick. It's best to err on the side of caution and discard it. Food poisoning can cause serious symptoms, and it's better to be safe than sorry.