Abstract: In this study, eggshell membranes were used as the raw material to extract sialic acid based on deproteinization by ethanol precipitation. A four-factor, five-level central composite design combined with multiple regression analysis was employed to mathematically model protein removal rate and sialic acid recovery as a response to ethanol concentration, temperature, heating time and pH, respectively. Ethanol concentration was identified to be the most significant affecting factor, followed by temperature, pH and heating time. The optimal deproteinization conditions were determined to be: ethanol concentration 30%, temperature 80 ℃, heating time 1 h and pH 2. Under these conditions, the removal rate of protein was predicted to be 52.3% and the recovery of sialic acid 82.1%, closely agreeing with the experimental values, respectively. Thus, the created models are reliable.

Key words: eggshell membranes, sialic acid, protein, response surface methodology