Abstract: In this paper, calcium citrate malate (CCM) was prepared by ultrasonic-assisted organic acid treatment of tilapia scale. The pretreatment and preparation conditions were optimized and the structure of the product were characterized. The results showed that good extraction efficiency was obtained by ultrasonic-assisted preparation of fish scale without boiling. At a solvent-to-solid ratio of 20:1 (mL/g), the optimum conditions for preparing CCM were obtained by orthogonal array design as follows: 12% (m/m) of an citric acid-malic acid mixture at a mass ratio of 2:1, temperature 70 ℃ and time 1.0 h. Under these conditions, the maximum extraction rate of calcium of 18.97% was obtained. Infrared spectroscopy analysis and X-ray diffraction (XRD) showed that the product was not a physical mixture of calcium citrate and calcium malate, but coincided with the structure of CCM. Scanning electron microscope showed that the crystal structure was a hexahedron. The specific surface area from mesoporous pore volume determination of the product was 385.703 m2/g, average pore size 4.049 nm and single point adsorption total pore volume 0.320 cm3/g. CCM was successfully prepared by this method with higher yield of calcium. These research results provide some theoretical support for the processing of organic calcium products from tilapia scale.

Key words: tilapia scale, calcium citrate malate (CCM), ultrasound, extraction process, structure characterization