Effect of different acids on the extraction of pepsin-solubilised collagen containing melanin from silky fowl feet

Four acid treatments: acetic acid (FA), citric acid (FC), hydrochloric acid (FH) and lactic acid (FL) were used in this study to extract the pepsin-solubilised collagen (PSC) containing melanin from silky fowl feet. The collagen content, melanin content, electrophoresis and ultraviolet (UV) absorption spectra (200–400 nm) were determined in order to develop a collagen with UV protection. Among four acid extractions, the acetic acid treatment had both the highest extracting yield (7.3%) and collagen content (516.6 mg/g). PSCs obtained from silky fowl feet using four acid extractions exhibited melanin content; whereas no similar observations were found in that of broiler feet by acetic acid extraction (FB). Moreover, the PSC via acetic acid extraction resulted in the significantly highest melanin content (210 mg/g) (P < 0.05), which contributed to UV absorption. In electrophoresis, three subunits were found in PSCs from silky fowl feet using the four acid extractions, which were different from typical type I collagen and assumed that the PSCs obtained from silky fowl feet consisted of more than two types of collagens.