Study On Extraction And Properties Of The Chicken Feet Peeling Protein

Chicken feet peeling (CFP) is the peeled skin after scalding in hot water during chickenprocessing. With the development of the poultry industry and the rising quantities of thechicken feet production, more and more CFPs appear every year. CFPs which are abandonedand piled for long time have significant effect on the ecological environment. What’s more, itis a waste of potential food resources. In order to make full use of this part of resources and toprovide the theoretical foundation for development of CFP protein, the technology ofextraction and its properties of CFP were studied in this paper.In-vitro digestibility of skim materials with different processing including through30mesh, through80mesh, extrusion and high pressure cooking were determined at first. Theresults were42.19%,54.18%,64.57%and74.52%, respectively and different treatmentimproved the in-vitro digestibility at some levels.The extraction of protein from CFP, by alkaline and enzyme, was investigated. Theoptimal conditions were confirmed by single factor and response surface. An extraction rateof82.78%by alkaline extraction has been achieved at63°C for6.3h with1.5%alkalineconcentration and a volume-weight ratio of41:1. Four different enzymes (Pancreatin,Alkaline protease, Papain, Neutral protease) were examined for their capability of extractingCFP protein. The results indicated that Pancreatin was the most effective, while the othersgave poorer performance. The highest extraction rate of75.87%was obtained as well at46°Cfor5h, pH8.0and a volume-weight ratio of40:1with a total enzyme amount of100U/gafter2h of cooking pretreatment by Pancreatin. The protein precipitation rate was93.19%and the purity was86.34%under combined action of isoelectric point and50%ammoniumsulfate salting-out.According to the amino acid composition analysis, CFP protein contains18kinds ofamino acids and the portion of the essential amino acids was30.45%among these total aminoacids. Reference egg protein, the CFP first limiting amino acids was Lysine and the secondwere Methionine+Cysteine, Reference to quality fishmeal and FAO/WHO standard mode, theTryptophan and Lysine were the first and second limiting amino acids respectively.The protein of the CFP by gel-filtration chromatography in sephadex G-100wasseparated and about67000Da of main protein was obtained. Circular Dichroism Spectrumwas used to determine the secondary structure of the CFP protein. The results showed that thecontent of α-helix was lower while the β-ture and random coil was higher by the alkalineextracted.The isoelectric point of protein was around pH4.7and the solubility increased with theincreasing of the temperature and the NaCl solution concentration. The solubility of alkalineextracted protein of the CFP was higher than that of enzyme extracted. The water absorbility1.12g/g, oil absorbability1.55g/g, emulsibility0.05m~2/g and emulsion stability14min of alkaline extracted protein were obtained, while the enzyme extracted protein’s were1.10g/g,1.31g/g,0.01m~2/g and19min.