Abstract:Extraction yield of collagen was regarded as an index to research on preparation of collagen from squid skin by hot water, acid, and enzyme, respectively. The optimum processing conditions of extraction were determined by orthogonal experiment design. The optimum conditions by hot water were temperature of extracting 80 ℃, volume of water 20 folds, and time of extracting 12 h. The extraction yield of collagen was 90.26%. The optimum conditions of extraction by acid were temperature of extracting 24 ℃, 0.5 mol/L acetic acid, and time of extracting 48 h. The extraction yield of collagen was 95.16%. To hydrolyze the squid skin, trypsin, and papain were choosed to apply in the experiment. The optimum processing conditions of extraction by trypsin were temperature 55 ℃, enzyme dosage 1 200 U/g, concentration of substrate 1∶20, pH 8.0, and time 4 h, respectively. The extraction yield of collagen was 95.16%. The results of extracting collagen by papain show that the optimal reactive temperature, enzyme dosage, concentration of substrate, pH and time were follows: 50 ℃, 3 200 U/g, 1∶20, pH 6.0, and 6 h, respectively. The extraction yield of collagen was 97.56%. The character absorption spectra and molecular weight of extracted collagens were determined by ultraviolet spectrophotometry and SDS-PAGE methods.Functional properties including solubility, water-binding capability, wetting capability, oil-holding capability, emulsifying capability, emulsion stability, foaming capacity and foaming stability of collagen from squid skin were investigated. The results showed that:(1) The maximum absorption wavelength of extracted collagens was 220 nm and the molecular weight of prepared collagen from squid skin was about 220 ku.(2) The water-solubility of extracted collagen by hot water and papain was higher than that by acetic acid. (3) Extracted collagen by hot water, acetic acid and papain has definite water-binding capability, the value was 0.54%, 0.52% and 0.55%, respectively.(4) Wetting capability of extracted collagen by hot water and papain was better than by acetic acid.(5)Extracted collagens had all excellent oil-holding capability, the value was 2.7 mL/g, 3.0 ml/g and 3.3 mL/g, respectively. (6) Extracted collagen had all excellent emulsifying capability and emulsion stability. Emulsifying capability of extracted collagen by acetic acid was the best, the value was 72%. Emulsifying stability of extracted collagen by papain was the highest. (7) Extracted collagen had foaming capacity and foaming stability. The strongest foaming capacity and foaming stability of extracted collagen by acetic acid was 83% and 67%, respectively.