The results of the present investigation reveals that elements migrates to food components from can packaging material under various storage conditions viz. temperature, pH and storage period. Magnitude of leaching of elements from packaging material is highly dependent upon type of solvent, pH-value, temperature and time.
The rapid deterioration of food cans of ‘baked beans in tomato sauce’ occurred much before their expiry date. This may be due to chemical or biological causes. It can be concluded that high levels of ‘Fe’ concentration in ‘baked beans in tomato sauce’ are due to processing of raw materials which further increased due to rapid deterioration of food cans. The additional factors which may be contributing to increased level of Fe are oxygen permeability of the packaging material, leakage of air through poor sealing and/or inadequate sterilization during packaging. The acceptability or safety of consumption of ‘baked beans in tomato sauce’ could not be determined from its physical appearance. However, the elemental analysis reveals that these food products are unsafe to consume. A significant increase in concentration of ‘Fe’ in mango pulp was noticed at higher temperatures which showed that high temperature caused chemical deterioration of food cans. ‘Fe’ content of canned orange juice is lowest, as its packaging material consisted of ‘Al’ mainly, whereas for remaining canned products, ‘Fe’ is the major constituent of packaging materials. It is observed that leaching rate of ‘Fe’ is slower in ‘Sweet corn cream layer’ as compared to other highly acidic canned foods indicating that pH plays an important role in leaching of such elements.
Similarly, Sn contents of ‘mango pulp’ and ‘baked bean in tomato sauce’ cans increased more considerably than canned ‘sweet corn cream layer’ indicating the effect of different pH values of these foods. Although, the ED-XRF results depicted that Fe is the major constituent of mango pulp can packages and Sn is present in low concentration, the leaching patterns of Fe and Sn revealed that the leaching of Sn is significantly high as compared to that of Fe into the food. This may be because of the presence of oxygen which accelerates the corrosion of Sn coating. The high temperature of the juice coupled with the presence of a small amount of dissolved oxygen in the juice causes an initial rapid Sn leaching of the can. Oxygen dissolved within the juice and entrapped in the headspace of the metal can readily reacts with tin to form stannous ions. After dissolved oxygen and headspace oxygen are exhausted, hydrogen gas is produced in the acidic juice medium. Hence, reduction in rate of leaching of Sn in ‘mango pulp cans’ after 6 months of storage period can be attributed to presence of headspace or dissolved oxygen.
Although, the values of Al found in orange juices do not represent toxicological risk, periodic determinations are advisable. The concentration of ‘Al’ may surpass the tolerance level in children near expiry date of canned orange juice, as the recommended limit is 1 mg/kg of body weight (WHO, 1989).
There is minor increase in concentration of ‘Mn’ at high storage temperature and longer storage period i.e. at 38 °C for 12 months and 48 °C for 6 months. On the basis of these results of elemental contents in canned food and food packaging material, it can be concluded that there may be some co-relation in between leaching of elements and elemental composition of can packages. Hence irrespective of their similar pH values, a large variation is observed in leaching pattern of Mn in both orange juice and mango pulp.