The migration of eight trace elements (Fe, Sn, Cr, Cd, Pb, Ni, Cu, and Zn) was monitored for fruits canned in uncoated tinplate cans under different storage conditions until the shelf life. The levels of most of these elements significantly increased with storage time and were also affected by storage temperature. Particularly, storage at 40°C (simulating sunlight exposure of the cans) caused important release of Sn and Fe so that canned foods did not comply with regulation. Can denting accelerated the migration of several metals, especially Fe and Sn. Moreover, Fe and Sn levels drastically increased in fruits kept in open cans stored in the fridge for a few days. Small pieces of fruits contained higher level of metals than larger ones, and the side seam coating reduced the migration of trace elements.
Practical applications
Canned fruits are a convenient alternative to fresh fruits to fulfill the nutritional recommendations for a healthy diet. At the same time, canned fruits may be contaminated by several trace metals (particularly tin, lead, and chromium), partly due to their migration from the unlacquered tinplate cans. This study investigates several parameters prone to affect metals migration during fruit cans handling and storage (storage time and temperatures, denting the cans, leaving open cans in the fridge, as well as food brand and fruit type). Proper advice for handling and storing canned fruits is proposed, especially since the low pH and small pieces of fruits may favor metals release and uptake by the food.