The nutritional quality and contents of heavy elements due to thermal processing and storage in canned Thunnus tonggol fish change compared to fresh fish

The purpose of this study was to evaluate the nutritional quality and concentration of heavy and toxic metals in the fresh and canned tuna Thunnus tonggol at different storage periods. The content of iron, zinc, copper, mercury, and also macronutrient compounds in the Iranian fresh and canned tuna fish and the effects of thermal processing and subsequent storage on metal contents were evaluated using atomic absorption spectroscopy. The results showed that the levels of iron, zinc, copper, and mercury after the 6th, 9th, and 11th months of storage were 26.52, 10.83, 6.22, and 0.04 mg/kg, respectively. The concentrations of iron, zinc, copper, and mercury in the fresh fish were 11.03, 7.11, 1.71, and 0.03 mg/kg, respectively. The results of the statistical analysis of the samples showed that canning process and sterilization by autoclave increased the contents of elements except mercury to a significant level (p < .05). The results showed that the amount of fat significantly increased in all samples after storage (p < .05), but the ash and protein content significantly decreased (p < .05). The moisture content significantly increased (p < .05) except for the 9th month of storage. The obtained results showed that the energy value after 6 months of storage was the highest (297.53 kcal/100 g). The results showed that the bioaccumulation of copper, iron, zinc, and mercury in the fresh and canned muscles was lower than the standard concentration recommended by the FAO and WHO. This type of fish was a high‐quality food source and it was safe after 11 months of storage and was suitable for human consumption. Therefore, the consumption of Iranian canned tuna can be safe for human health despite the possible contamination with heavy metals.