Putting slightly melted ice cream back in the freezer is generally safe from a Listeria perspective, as long as the ice cream has not been exposed to temperatures above 40°F (4°C) for an extended period. Listeria monocytogenes is a bacterium that can cause foodborne illness, including listeriosis. It is commonly found in the environment, including soil and water, and can contaminate certain foods, including dairy products like ice cream.
Listeria can grow at refrigerator temperatures, but it grows more slowly at colder temperatures, such as those found in a freezer. To minimize the risk of Listeria growth, it's essential to handle ice cream properly. Here are some guidelines to follow:
Monitor storage temperatures: Make sure your freezer maintains a consistent temperature at or below 0°F (-18°C). Use a refrigerator/freezer thermometer to check the temperature regularly.
Avoid temperature fluctuations: Try not to frequently open and close the freezer, as it can cause temperature fluctuations and lead to partial melting of the ice cream.
Store ice cream properly: Keep ice cream containers tightly sealed to prevent contamination and to maintain the quality of the ice cream.
Don't refreeze melted ice cream multiple times: Repeatedly thawing and refreezing ice cream can affect its texture and increase the risk of bacterial growth. It's best to avoid this practice.
Use safe handling practices: Always use clean utensils and scoops when serving ice cream to prevent cross-contamination.
If the ice cream has only slightly melted and you're confident that it hasn't been exposed to unsafe temperatures for an extended time, you can refreeze it. However, if the ice cream has significantly melted or has been sitting out at room temperature for an extended period (more than 2 hours), it's safer to discard it to avoid the risk of foodborne illnesses, including listeriosis.
As a general rule, when in doubt about the safety of a food item, especially if it involves potentially hazardous items like dairy products, it's best to err on the side of caution and dispose of the questionable item.