Food Safety When Eating Directly from the Tub
When eating any food directly from the tub, there is an issue with food safety. This is because your mouth is full of bacteria that can enter the food from your spoon and grow in the food when it's out of the fridge. Cold temperatures below 4 degrees C help prevent the growth of bacteria in food. That is why your fridge at home cools at below 4 degrees C.
This means that without proper refrigeration, bacteria in food from your mouth can grow and spread, making the food deteriorate and potentially becoming toxic over time.
In addition, refrigerated dairy products have additional risk. They have a short shelf life because, over time, handling from shop to home, plus the temperature changes from opening and closing the fridge door, allows naturally occurring bacteria in dairy to grow, spoiling the food and potentially causing health issues if eaten after the expiry date.
Ice cream is a little different. Even though it is a dairy product with the same bacterial and spoilage risks, its storage temperature of -18 degrees C gives it a long shelf life (usually two years if refrigerated well) as the naturally occurring bacteria in the food can't grow at these temperatures.
As a result, when you introduce bacteria from your mouth into ice cream from a spoon, the bacteria struggle to spread and multiply to toxic levels while the product is firm and ice cold (below zero). However, once you leave the product out of the freezer for a while and the outside edges start to melt and form a liquid, the temperature rises above zero, giving bacteria a chance to grow. When you return a tub to the freezer after eating from it directly, not only does any remaining melted ice cream develop an icy texture when refrozen, but you also increase the bacterial load in the ice cream, giving it a better chance of growing and spreading when you next remove it from the freezer to eat. That is why health authorities advise against refreezing melted food.
The way to avoid this risk when eating directly from the tub is to eat the ice cream only when it is firm. As soon as the edges start to melt, you need to either eat all the melted edges to prevent bacteria from growing in the warmer product areas or return the tub to the freezer before the edges melt into a liquid form.
Ice cream, when melted, provides a really enjoyable eating experience. If you are vigilant about removing melted edges in a tub before returning the ice cream to the freezer, it can be preserved and eaten safely later.