The food is heated to a high temperature. This process is called pasteurization. Then, the food is packaged and stored in an air-tight can. Check our infographic showing the processing steps for canned tomatoes.
The canning process itself consists of several stages: cleaning and further preparing the raw food material; blanching it; filling the containers, usually under a vacuum; closing and sealing the containers; sterilizing the canned products; and labeling and warehousing the finished goods.
Canning alters food chemically by changing the moisture, pH, or salinity levels to protect against microbes, bacteria, mold, and yeast. It also limits food enzyme activity. Combining these chemical processes with the physical barriers of glass jars, seals, and lids effectively prevents decay.