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.