Exploring high-pressure carbon dioxide for demineralization of goldstripe sardinella scales

This study explored the use of HPCD for demineralizing goldstripe sardinella scales, using response surface methodology with an on-face central composite design to describe the effects of CO₂ pressure (1.0 to 10.0 bar) and treatment time (1 to 5 h) on the demineralization efficiency (DM; %). Significant impacts from both parameters were observed (P < 0.05), with the highest DM of 16.13 ± 1.92% achieved at 10.0 bar for 5 h. Increased pressure enhanced DM more than strong acid treatment at comparable pH. However, further increases in pressure showed diminishing returns due to limited CO₂ solubility and temporary buffering systems observed during the process. Scanning electron microscopy with and without energy dispersive X-ray spectroscopy revealed reduced calcium and phosphorus content, preserved collagen integrity, and altered scale structure of HPCD-treated samples.