Extraction of collagen from hen eggshell membrane by using organic acids.

A procedure was developed for extracting collagen present in eggshell membranes but hitherto unavailable. Membranes were separated from the shell wall in a tank (15 L) of water fitted with a mechanical stirrer. Membrane separation was enhanced by addition of the elutant, EDTA at 5% w v -1 . Optimum weight of eggshells was 500g 15 L -1 aqueous solution, with maximum yielding of the membrane about 8%. Collagen was extracted from the separated membranes with the addition of either of two organic acids, 0.5 M acetic or 0.5 M citric acid. Highest collagen yields of 507 and 495 mg 100g -1 dry sample were obtained when acetic and citric acids relative to membrane weight were added at a ratio of 1:8. Thermal solubility of collagen at 40 oC was about 14.7 and 18.0 mg 100 g -1 dry sample for water and 0.45 M NaCl solution, respectively. Chemical analysis of the collagen from eggshell membranes yielded type 1 collagen with �1 and �2 fibrils.