The effect of different methods of drying bone lesions of yellowfin tuna (Thunuus albacares) on its nutrient compounds

Global human population growth, changes in lifestyle and food consumption patterns have led to an increase in demand for marine source foods production. Proper use of all produced seafood sources, in addition to increasing the production efficiency, provides nutrients and sustainable human nutrition. Bone lesions yielded from aquatic processing are rich sources of essential protein and minerals, which are mainly not intended for direct human consumption. Therefore, in order to make the best use of these valuable wastes, at the present study, for the optimal use of these valuable lesions, bone lesions of yellowfin tuna as the raw material for tuna processing factories has been used. In order to achieve the best drying method, three drying methods were considered: drying in the open air, drying in the hot air oven and drying in a freeze dryer. After providing the above-mentioned bone powders, the amount of their nutrients including crude protein, total fat, ash, moisture and main mineral elements (calcium, phosphorus and magnesium) were measured. The results showed that the amount of protein (31.03%) and ash (49.53%) of bone-dried powder by freeze drying method had a significant difference compared to other two methods (P<0.05) and It retains more nutrients in all cases. The moisture content of this treatment was 2.55% which was less than other treatments and there showed a significant difference compared to other methods (P<0.05, indicating a better drying process of bones by freeze drying method. Examination of the amount of calcium and magnesium in the freeze-dried treatment also shows higher and significant amounts of these two elements than the other two methods, however it had negative trend to rate of moisture. Therefore, method of freeze drying, was known as the shortest time for drying the fish bone and conserving its biochemical and nutrients