Long shelf life does not mean that food must be added with preservatives.     
In fact, the principle of canning is very simple: after the  raw materials and the container are fully heated and sterilized, sealed by heat; then heating and sterilizing, after cooling, the volume of air inside the container headspace will shrink, resulting in negative pressure, so that the sealed container cannot be opened, and bacteria outside cannot enter. After these procedures, the food naturally does not spoil, so no preservatives need to be added.

Processing does not mean no nutrition

Reasonable produced canned food is not nutrient rubbish, and irradiated foods will not affect the health of consumers.
Canned meat and seafood are generally pasteurized, so the processing temperature is around 120°C. To process canned home at home is also very simple, just heat it. Therefore, to a certain extent, the nutrient loss of the canned food is less than that of the family cooking (the cooking will easily exceed 200°C). The processing temperature of canned vegetables and fruits will not exceed 100°C, and nutrition is relatively good.
In addition, the raw materials used for canned foods are fresh. To make canned foods, the most fresh ingredients are selected in the most suitable season for lower costs and better taste. And to save costs, regular canners have their own raw material bases and build the production line closest to the base. In this way, the process from picking, transporting to processing is greatly shortened, and generally does not exceed 6 hours. And high-temperature heat treatment will stop or slow the chemical reaction of nutrient loss, maintain the freshness and nutrition of food.