Quick Answer
It’s generally not recommended to drink coffee that has been left out overnight. The main concerns with drinking old coffee are:
– Bacterial growth – Coffee left at room temperature for too long can allow bacteria like Bacillus cereus to multiply to dangerous levels. This bacteria can cause food poisoning symptoms.
– Mold growth – Exposed coffee can allow mold spores in the air to contaminate the liquid and grow over time. This mold can also make you sick.
– Stale, unpleasant taste – Coffee that sits out will start to taste stale, bitter, and generally unappetizing as it oxidizes and compounds degrade.
So in summary, it’s best to brew a fresh pot of coffee each morning and avoid drinking coffee that has sat out for more than a few hours. The safety and taste risks outweigh any convenience factor.
Explaining How Bacteria and Mold Grow in Old Coffee
When you brew a pot of coffee, the high water temperatures used (around 200°F) kill any harmful bacteria or mold spores that may be present. This makes the freshly brewed coffee safe to drink.
However, as the leftover coffee sits out at room temperature over several hours, two major things happen:
1. The coffee cools down significantly. Bacteria thrive in temperatures between 40°F and 140°F. In this optimal temperature range, bacteria can quickly multiply to dangerous levels if given enough time.
2. The coffee is exposed to environmental contaminants. Mold spores and bacteria are constantly floating invisible in the air around us. When you leave coffee sitting out uncovered, these organisms can land in the liquid and use it as a breeding ground.
In as little as 4-6 hours, bacteria populations in room temperature coffee can reach levels capable of causing food poisoning. Some of the most common bacteria found include:
– **Bacillus cereus** – Causes diarrhea and vomiting
– **Staphylococcus aureus** – Causes severe nausea, vomiting, and abdominal cramping
– **Escherichia coli** – Causes painful cramping and diarrhea
These bacteria produce toxins as they feed on the sugars and proteins in coffee. Consuming the contaminated coffee introduces these toxins into your gastrointestinal tract, resulting in illness.
Molds that grow in old coffee include species of **Aspergillus, Penicillium**, and **Fusarium**. Exposure to these molds can cause allergic reactions and mycotoxin poisoning. Leaving coffee uncovered makes it easier for mold spores to land and grow.
So in summary, time + room temperature = an environment in which harmful bacteria and mold thrive in leftover coffee. This makes the beverage risky to drink after it has sat out too long.
How Long Can Coffee Sit Out Before Going Bad?
The exact amount of time coffee can sit at room temperature before going bad depends on several factors:
– **Type of coffee** – Coffee with more acidity, like light roasts, resist bacteria growth better. Starbucks coffee may last 6-8 hours. Dark roasts last 4-6 hours.
– **Coffee additions** – Added dairy, sugars, flavors provide nutrients that accelerate bacteria multiplication. Cutoff time is shorter.
– **Room temperature** – The warmer your home, the faster bacteria can thrive. Coffee lasts longer around 65°F vs. 75°F.
– **Covered vs. uncovered** – Exposed coffee allows contaminants. Covering helps but isn’t failsafe.
As a general rule of thumb, **it’s best to discard any coffee that has sat out at room temperature for longer than 4-6 hours**. To be extra safe, the cutoff point could be reduced to 2-4 hours.
Again, factors like coffee style, temperature, and exposure can all impact shelf life. When in doubt, remember it’s far safer to simply brew a fresh batch.
Taste Test
In addition to bacteria and mold growth, taste is another reason to avoid drinking old coffee.
As coffee sits exposed to air, oxidation reactions take place that degrade the organic compounds in the liquid. Some of the flavor changes you can expect include:
– Increased bitterness and acidity
– Stale, flattened flavors
– Loss of fresh aromas
– Mildly spoiled, rotten, or rancid undertones
These flavors develop rather quickly, so coffee that is left out for more than 30 minutes will taste noticeably different than a freshly brewed cup. The compounds that give coffee its signature taste break down.
So while a cup of coffee left out overnight won’t necessarily make you sick if bacteria levels are low, the taste will likely be very unappetizing. Most people find it isn’t worth drinking for this reason alone.
Can You Reheat Leftover Coffee?
Rather than drink old coffee, some people considering reheating it in the microwave or on the stovetop. This can kill off bacteria, but there are still risks:
– It won’t remove toxins left behind by bacteria. The toxins are what make you sick.
– It doesn’t remove mold or mold toxins if present.
– Burnt coffee tastes awful. The microwave often overheats unevenly.
– Reheating can accelerate bitterness and stale flavors.
For these reasons, reheated coffee usually doesn’t taste good. It’s best to restart with a fresh brew each day. However, properly reheated coffee won’t make you sick if you are in a pinch.
Here are some tips for reheating coffee safely:
– Use the stove over microwave for more even heating.
– Discard coffee immediately if you smell or see mold.
– Bring just to 165°F then remove to preserve taste.
– Don’t reheat more than once.
– Consider adding milk, cream, or sugar to mask bad flavors.
Can You Drink Reheated Coffee That Sat Out Overnight?
Yes, you can drink reheated coffee that sat out overnight if you follow proper precautions. However, the taste will likely be noticeably degraded.
It’s essential to inspect the coffee closely and check for any signs of mold before reheating. And make sure to bring it up to 165°F on the stove while stirring constantly.
Drink within an hour of reheating for safety and use flavorings to mask the stale taste if desired. Cold brew coffee holds up better to reheating than traditional coffee. Overall though, starting fresh each day makes the most sense.
Tips for Storing Leftover Coffee
To enjoy coffee later without sacrificing taste or safety, here are some storage tips:
– Transfer to a sealed airtight container after brewing. Refrigerate.
– Pour coffee into an insulated thermos. It retains heat longer.
– Freeze individual portions for iced coffee later.
– Store cold brew concentrate in the fridge up to 2 weeks.
– Buy a thermal carafe coffee maker to keep coffee hot for hours.
Proper storage slows bacteria growth and oxidation reactions. With time and temperature controlled, coffee can last a day or two in the fridge without deteriorating in quality.
Does Adding Milk or Sugar Keep Coffee Good Longer?
Adding dairy, sweeteners, or other additives to your coffee doesn’t significantly extend its shelf life. In fact, the added nutrients may promote bacterial growth slightly faster as compared to black coffee.
So whether you take your coffee black or with fixings, the time limits before it goes bad remain about the same. Follow the general 4-6 hour room temperature cutoff.
The best way to enjoy coffee with milk or sugar safely is to add the extras right before drinking, rather than pre-mixing and leaving at room temperature.
Signs Your Coffee Has Gone Bad
Here are some red flags that indicate your coffee has spoiled and should be discarded:
– Smells sour, rotten, or rancid
– Mold visibly growing on surface
– Appears discolored or cloudy
– Tastes unpleasantly bitter
Coffee that sits out too long will exhibit these warning signs. Rely on your senses of sight, smell, and taste before drinking. Erring on the side of caution is smart if coffee seems off.
You can also invest in pH test strips. Fresh coffee averages a pH of 5 while spoiled coffee is around 6.5 pH. This can provide numerical confirmation your old coffee has degraded.
Can Coffee Make You Sick?
Yes, contaminated coffee containing high levels of bacteria, mold, or their toxins can make you sick. Sickness usually develops within 30 minutes to 6 hours after drinking bad coffee.
Symptoms of coffee-related illness can include:
– Nausea, vomiting, diarrhea
– Abdominal pain and cramping
– Headache, fever, chills
– Muscle aches, fatigue, weakness
Symptoms caused by bacteria may be more gastrointestinal in nature. Mold exposure is more likely to cause headaches, breathing issues, and other allergy-like effects.
In otherwise healthy adults, food poisoning from coffee will resolve on its own within 24-48 hours. Seek medical treatment if symptoms are severe or persist longer than 2 days.
The bacteria and mold counts needed to make you sick are more likely to accumulate after 8+ hours at room temp. Again, limiting coffee to a maximum of 4-6 hours once brewed is ideal.
Conclusion
Enjoying your morning cup of coffee is safer when you brew a fresh pot each day. While reheating old coffee you plan to drink is possible, it still carries risks if bacteria or mold are present. For best quality, aroma, and flavor, avoid drinking coffee that has sat out for longer than 4-6 hours. Follow proper storage methods if you want to save leftover coffee for later in the day. Be alert for any changes in odor, appearance, or taste that indicate coffee has spoiled. With some simple precautions, you can savor coffee that is both delicious and good for your health.
| Type of Coffee | Maximum Time at Room Temperature |
|---|---|
| Light roast coffee | 6-8 hours |
| Dark roast coffee | 4-6 hours |
| Coffee with dairy, sugar, flavors added | 4 hours or less |
| Brewed coffee, uncovered | 3-4 hours |
| Brewed coffee, covered | 5-6 hours |
