If the container is sealed, will it trap a little bit of heat and cause the food to take that much longer to cool completely, is that the question? Yes, is the answer.

The variables include how hot the food is and how much of it there is, how large the container is, how much extra space there is in the container, and what the container is made of. In general, we think getting food into the refrigerator is good enough. Yes, you can speed up the cooling process by putting the container in a bowl or sink of ice water before putting it in the refrigerator. And, yes, you can leave a vent for the heat to escape from your bowl of leftovers.

If the food has been handled safely and is not on the very brink of spoiling, the few extra minutes it takes to cool in a sealed container is not going to appreciably increase the risk of spoiling.

We would be a little more concerned about the food in an unsealed container picking up "off" flavors from the rest of the contents of the refrigerator. And for us, at least, remembering to go back and seal the container once the food was thoroughly cooled would be a dicey proposition.