Optimizing the Extraction of Acid-soluble Collagen Inside the Eggshell Membrane

Extraction of collagen from the eggshell membrane was optimized by the methodology of response surface. The Central Composite Design (CCD) was applied. This was done to find the optimum combination of acetic acid concentration (0.1–0.9 mol/L), temperature (5–25°C), stirring speed (100–500 rpm) and extraction time (12–36 h) to maximize the acid soluble collagen (ASC) extraction. The highest amount of extraction was theoretically predicted to be 8.55%, under the optimal. The recovery experimental ASC, was calculated to be 8.35%, which confirms the predicted value, thereby confirming the reliability of the method. Analysis of amino acids revealed glycine (308 residues/1 000 residues) as the major amino acid and showed imino acids of 229 residues/1 000 residues. ASC had minimum solubility at pH 7. No changes in solubility were observed in the presence of NaCl concentrations that did not exceed 4% (w/v). The denaturation temperature was 46.8°C which correlated suitably with imino acid contents.