The Demineralization of Sardinella gibbosa Scales Using Hydrochloric Acid and High-Pressure Carbon Dioxide

Abstract

This research aimed to investigate and compare the demineralization of goldstripe sardinella (GS; Sardinella gibbosa) scales, a major by-product in the canned fish industry prevalent in East Africa and Southeast Asia, particularly Thailand. The study focused on conventional and alternative demineralization methods, assessing the yield and quality of the demineralized scales. After removing minerals, fish scales have potential value as an alternative source of collagen and gelatin. For the strong acid treatment using hydrochloric acid (HCl), the effects of HCl concentrations (0.2-1.5 M) and treatment times (30-120 min) on demineralization efficiency were assessed. The results from RSM indicated that HCl concentration was the only treatment factor that significantly affected demineralization yield, HCl concentrations at or above 0.82 M gave a demineralization efficiency of e” 99%, independent of treatment time (P < 0.0001). A preliminary investigation into high-pressure carbon dioxide (HPCD) treatment of GS scales (at 10 bar for 1 to 4 h) showed comparatively lower demineralization efficiency. Within the studied parameters, the highest demineralization efficiencies for both methods were 99.89±0.06 and 16.13±1.92%, respectively. SEM images and EDX analysis confirmed the complete removal of minerals (primarily Ca and P) after HCl treatment using HCl 0.85 M for 30 min. Conversely, HPCD-treated scales exhibited altered structure and physical damage.