The heat preservation time of the heat preservation lunch boxes sold on the market is about 6-8 hours, but these are only official times, and generally do not reach such a long heat preservation time. Most are pretty good in about 5 hours. Furthermore, it is better to consume the food at once within 6 hours, otherwise it will be fermented or spoiled, which is bad for your health.
After all, the heat preservation lunch box only serves as heat preservation, and it cannot be used to keep fresh. There are also many styles of insulated lunch boxes, 2-layer 3-layer. Pie-shaped, bucket-shaped, we call insulated buckets and insulated pots. There are also stainless steel insulated lunch boxes. No matter how long he keeps warm, the food inside must be eaten in time.