| Summary: | Fish backbone, a major by-product in the fish processing industry, accounts for about 15% of whole fish weight. In this study, recovery of bioavailable calcium from Alaska pollack (Theragra chalcogramma) backbone by-products using enzymatic hydrolysis was investigated. Finely ground fish backbones were hydrolyzed with two proteolytic enzymes (pepsin and protease) to obtain soluble calcium from the by-products. The pepsin digest had a higher degradation efficiency (88%) than protease. Four different concentrations of the fish backbone calcium (100, 250, 500 and 1000 mg/L) prepared by the pepsin digest were treated with $Na_2HPO_4$ at a concentration gradient (0, 1, 2, 4, 8, 10, 15 and 20 mM) to evaluate their solubility, revealing that solubilities of the fish backbone calcium were superior to those of $CaCl_2$ at all the calcium and $Na_2HPO_4$ concentrations. Among the tested concentrations the highest solubility was found in the pepsin digest containing a calcium concentration of 1000 mg/L. Thus, hydrolyzing with pepsin is an effective mode of recovering bioavailable calcium from Alaska pollack fish backbones.
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