Abstract:

Objective: To determine the optimum conditions for the preparation of active calcium from cod bone through
orthogonal array experiments and to investigate its bioavailability. Methods: Compositional analyses and histological
observation of cod bone were performed. The optimum parameters for preparng active calcium from cod bone were obtained
by orthogonal array experiments. The calcium deficiency model in rats induced by low-calcium diet was used to investigate
the calcium bioavailability by detecting the contents of serum calcium and bone calcium and the indicators of calcium
metabolism. Results: The contents of calcium and phosphorous in cod bone were 207.8 mg/g and 100.9 mg/g, respectively,
indicating a ratio of approximately 2:1 between the two elements. Tightly and firmly combined hydroxyapatite crystals
characterized by the flat tabular shape were found under scanning electron microscopy (SEM) observation. The optimum
acid extraction conditions for active calcium from cod bone were determined as follows: extraction temperature, 100 ℃;
extraction time, 120 min; ratio of citric to malic acid, 1:2; and acid concentration, 15% leading to a calcium yield of 96.15%.
Compared with the blank control group, the active calcium at all doses investigated exhibited significantly higher contents
of femur calcium. The results of calcium metabolism experiments suggested that the calcium absorption of high dose group
was significantly higher than that of calcium carbonate group. Conclusions: These results demonstrate that cod bone is a
good calcium resource and the active calcium extracted from cod bone possesses excellent bioavailability and could be used
as a natural calcium supplement.

Key words: cod bone, active calcium, biological availability, calcium supplement, high-value utilization