Chinese cabbage, spinach and other Chinese cabbages are the most common winter storage vegetables in northern China. Chinese cabbage is easy to store. Chinese cabbage is rich in water and vitamins. Spinach is a very common vegetable and a representative of overwintering vegetables in northern China. Spinach is a cold-resistant vegetable with strong cold tolerance, and seeds can germinate and grow even at MINUS 4℃. At the same time, spinach has high nutritional value. Vegetables such as Chinese cabbage and spinach are best sold in northern winter. Fresh agricultural products mainly include fresh primary products such as vegetables, fruits, flowers, meat, eggs, milk and aquatic products, which are used to be called "fresh three products". Perishability and brittleness are the main characteristics of fresh agricultural products, and freshness is an important index to determine the value of these fresh agricultural products.