Abstract: In this experiment, the microwave-assisted preparation of calcium powder from a byproduct of tuna processing, fishbone was optimized by Box-Behnken design combined with response surface methodology (RSM). The optimum parameters were determined as follows: sample amount 120 g, microwave power 800 W, and irradiation time 90 min. After removal of impurities by means of enzymatic hydrolysis, the calcium and phosphorus contents of the as-prepared fishbone calcium powder reached 192.3 and 149.8 mg/g, respectively. Scanning electron microscopic (SEM) characterization and laser particle size analysis revealed that the fishbone flour exhibited a loose structure with micropores and cracks appearing on the surface, and the average particle size was 16.627 μm, which was close to the RSM predicted value. The bioavailability evaluation in mice showed that the calcium absorption rate and calcium retention rate of the fishbone flour were respectively 59.62% and 58.31%, which were both significantly higher than those of common fishbone flour and calcium carbonate and low-calcium control (P < 0.05). Compared with other calcium preparations, the fishbone meal prepared in this study possessed higher absorption efficiency in vivo and was more conducive to promoting bone growth in mice.

Key words: tuna, fishbone calcium, microwave-assisted method, response surface methodology, biological activity