Abstract: The thermal stress of the microwave can improve the material's grindability and has the effect of assisting the pulverization. In this experiment, the by-product of tuna processing, fish bone, was used as raw material, and the microwave-assisted method was used to study the preparation technology of tuna bone calcium powder. The microwave condition was optimized by Box-Behnken test design combined with response surface analysis method. The optimum parameter are as follows: sample quality 120 g, microwave power 800 W, microwave time 90 min. The fish bone power was enzymatically hydrolyzed and the contents of calcium and phosphorus were determined to be 19.23% and 14.98%, respectively. After scanning electron microscope (SEM) characterization and laser particle size analysis, the microwave fish bone powder has a loose structure, micropores and cracks appear on the surface, and the average particle size can reach 16.6 μm, which was close to the predicted value of the response surface. The bioavailability of fish bone meal was evaluated by zoological experiments. The results showed that the microwave fish bone powder group had a femur index of 2.22 mg/mm, a calcium content of 138.51 mg/g, and a femur strength of 14.78 N, which were higher than the common fish bone powder group and calcium carbonate group and low calcium control group (p < 0.05). Compared with other calcium preparations, microwave fish bone meal has higher absorption efficiency in vivo and is more conducive to promoting bone growth in rats.

Key words: tuna, fish bone calcium, microwave assisted, response surface, biological activity