1. Refrigeration and preservation

You can prefabricate some ice cubes for later use, then when you bring food, let the food cool completely (you can refrigerate it first), then seal the ice cubes with non-toxic food plastic bags and put them in the lunch box. If the lunch box can't hold the ice pack, you can also use a slightly larger insulation foam box or aluminum foil carton to hold the ice pack and put it in the lunch box. This kind of cold storage can generally keep the lunch box from deteriorating for more than 20 hours. You only need a microwave oven or other cooking utensils to eat it.

2. Heat preservation method

As the name implies, the heat preservation method is to heat the cooked soup at a high temperature for the second time. The high temperature heating here is not simple heating. The secret is that the cooked soup must be heated to boiling again. Only the cooked soup can be preserved, otherwise it is simply heated, and the food whose temperature does not reach the boiling point cannot keep warm. This method can generally ensure that soup foods can be stored at room temperature of 30 degrees for 26 hours.