checkO / The package checking freshness

Usually people keep their leftover food in the fridge with small food containers. This way we can find food and cook easily. However, every food has an expiration date. Rotten food contains many harmful gases, such as carbon dioxide, hydrogen, methane, and ammonia.
The problem of using food containers are people cannot distinguish whether it’s fresh or not but with their naked eye. The “checkO” solved this problem which can check freshness of foods constantly.