Is it safe to drink day old coffee without refrigeration?

While drinking day-old coffee that hasn't been refrigerated may not pose any immediate significant health risks, there are important factors to consider:

1. Microbial Growth: Coffee is a suitable environment for the growth of microorganisms, including bacteria and molds. Leaving coffee at room temperature for an extended period (several hours or overnight) creates favorable conditions for microbial growth, potentially compromising its safety and taste.

2. Spoilage and Off-Flavors: Coffee's flavor and aroma compounds are delicate and can degrade over time. Unrefrigerated coffee exposed to air and light will gradually lose its freshness, develop stale and off-putting flavors, and eventually become unpalatable.

3. Potential Toxin Production: Some types of bacteria, such as Bacillus cereus and Staphylococcus aureus, can produce toxins that cause foodborne illnesses. While the risk of significant toxin production is usually associated with temperature abuse (extended storage at unsafe temperatures), leaving coffee out at room temperature for an extended time is still undesirable.

4. Food Safety Guidelines: According to the USDA's Food Safety and Inspection Service (FSIS), perishable food items, including coffee (prepared, unsealed), should be discarded if left at room temperature for more than two hours. This recommendation aims to minimize the risk of foodborne illnesses.

Therefore, refrigerating leftover coffee is the best practice to maintain its freshness, quality, and safety for potential consumption the next day. If you choose to drink day-old coffee without refrigeration, consume it within a reasonable time frame to minimize any potential risks associated with microbial growth and flavor deterioration.