Question: How long can cheese sit out?
Answer: Not all cheeses are built the same when it comes to leaving them outside of the refrigerator. Some types of cheese fare better than others when not refrigerated.
Generally, soft cheeses like cottage cheese, ricotta cheese, and cream cheese should not be left out for extended periods. Soft cheeses should be returned to the refrigerator within two hours from when they were initially removed from the refrigerator. When temperatures are 90° F or above they should be returned to the refrigerator within an hour. Bacteria in soft cheeses can double within as little as 20 minutes, which makes it important to return them to a refrigerator setting of 40° F or below as soon as possible.
Moisture is one of the main reasons for food spoilage. Moisture provides a conduit for bacteria to travel on the surface or into the interior of the cheese. Hard cheeses do much better at room temperature because they tend to contain very little moisture in comparison to soft cheeses. This lack of moisture inhibits microbial growth.
Hard cheeses like Parmesan and aged Cheddar still should be refrigerator at home, but you are likely not going to have an issue with spoilage if you leave them at room temperature responsibly beyond two hours. While we are not recommending keeping cheese at room temperature for extend periods, there are reports of hard cheeses being just fine for days on hiking trips stored in backpacks or traveling through Europe in luggage and back to the U.S. without spoilage.
More of an issue than spoilage is that the quality of cheese tends to degrade if it sits out too long. Cheese will sweat out its moisture at room temperature and become dehydrated. You will not get this moisture back even if you return the cheese to the refrigerator. Trust us, dried out and chewy cheese is not something you are going to want featured on the holiday cheese platter.