It is essential to refrigerate perishable foods promptly to prevent the growth of harmful bacteria and ensure food safety. For an unopened clamshell of greens, such as lettuce, spinach, or mixed greens, it should not be left out of the refrigerator for an extended period.
In general, the recommended time for leaving perishable foods at room temperature is no more than 2 hours. If the temperature is above 90°F (32°C), the time reduces to 1 hour. Beyond this time frame, bacteria can multiply rapidly, increasing the risk of foodborne illnesses.
To maintain the freshness and safety of the greens, it's best to return the unopened clamshell to the refrigerator as soon as possible after purchase. If you accidentally leave the greens out for a short time and you're uncertain about their safety, it's better to discard them to avoid any potential foodborne illness. Always follow proper food handling guidelines to ensure the safety of the food you consume.