Stainless steel is iron alloyed with chromium and nickel to resist rust. Its durability and ease of cleaning have made it a staple in home and restaurant kitchens. But storing salty or acidic foods in it for long periods can cause corrosion, depending on the condition of the container, and metal components can migrate into the food.
Mark McShane, a food safety expert, said even high-grade stainless steel can corrode in environments with high chloride concentrations, depending on how it is maintained, according to the U.S. outlet Verywell Health on the 18th. The settings in question are home and restaurant kitchens.
Problems arise when foods high in salt or acid are stored for extended periods. The cause is the chloride ions found in salt. Chloride ions can locally damage the thin protective layer on the surface, creating small pits. How far the process goes depends on contact time, the material of the container and the condition of its surface.
Pickled vegetables and salted seafood are high in salt and can accelerate surface corrosion. Glass containers are the safer choice for long-term storage. Dressings and pickles made with vinegar also warrant caution. Acetic acid, the main component of vinegar, is acidic, so the longer it stays in contact with metal, the bigger the problem becomes. That said, brief contact between vinegar or lemon juice and stainless steel does not immediately cause corrosion. The level of risk varies with the material and surface condition of the container and the duration of contact.
Tomato sauce combines organic acids such as citric and malic acid with salt. When acid and salt are present together, corrosion can progress faster. The lower the grade of the material, the weaker its resistance to corrosion, which raises the risk further. For sauces meant to be kept and eaten over time, glass containers are the better option.
When using a stainless steel container for the first time, it is advisable to remove polishing compound left over from manufacturing. Wipe the surface with cooking oil on a paper towel, then wash with a neutral detergent and rinse thoroughly. When choosing a product, check for a marking indicating it is intended for food use. Selecting corrosion-resistant grades such as STS 304 or STS 316 is generally the safer route. STS 316 in particular is comparatively strong in environments with high chloride levels.
Ultimately, the nature of the food being stored and the material of the container must be considered together. For short-term use, stainless steel's advantages can be put to work. When long-term storage is needed, it is advisable to transfer foods high in salt and acid to glass containers.