| In this study, the in vitro digestion of the Chinese giant salamander(Andrias davidianus) skin was evaluated by pepsin and trypsin. The Box- Behnken design response surface test was used to optimize the extraction process of the collagen of the Chinese giant salamander skin. The functional properties of the collagen were also studied. The results were as follows:After detecting and comparing the nutrition ingredients of the fresh Chinese giant salamander skin and the 2-year-frozen one, the fresh Chinese giant salamander skin was found to have 30.21% protein in wet basis and 94.42% protein in dry basis. The 2-year-frozen Chinese giant salamander skin has 33.81% protein in wet basis and has 97.17% protein in dry basis.In vitro digestive simulation experiments of cultivated giant salamander skin was carried out through the single and synergistic effects of pepsin and trypsin, and it was found that when pepsin was used alone, the digestibility reached 79.57%, the dosage of pepsin was 1400U/g feed; when trypsin was used alone, the digestibility reached 83.30% and its dosage was 600U/g feed; the digestibility reached 96.66% after the synergistic effects of pepsin and trypsin; which indicated that the cultivated giant salamander skin is a very easy-to- digest food ingredient.The single-factor experiment showed that the pepsin amount, extraction time and ultrasonic time were the three factors of the response surface experiment. The software showed the model equation was: Y= 70.69+0.71X1 +3.71X2 +1.81X3 +2.16X1 X2 +1.08X1 X3 +0.19X2 X3-8.60X12-1.92X22-1.99X32, this model equation can predict the extraction ratio well. The optimal condition for the extraction selected by the response surface modeling(RSM), were the combination of adding 1000U/m L of enzyme, 33 h of extraction and 12 min of ultrasonic. The yield reached 71.94%,similar with the model predicted value(73.21%). Effect of the three factors on the extraction ratio were: pepsin amount>extraction time>ultrasonic time.The hygroscopicity, humectancy, foamability and foaming stability, emulsibility and emulsion stability of Chinese giant salamander skin collagen were evaluated to show its functional character. The cultivated giant salamander skin collagen showed good moisture absorption effect after being exposed to air at room temperature for 30h; 20% of the moisture was retained for quite a long time under the condition of 20℃ and 43% and 81% RH, and the cultivated giant salamander skin collagen had its optimal foamability of 200% and with the increase of the protein concentration, the foamability was first increased and then decreased when the protein concentration was 0.4%; The collagen had its best foamability of 150% at p H 7, and there was an abnormal decrease at p H 5 which was around its isoelectric point. The collagen had its best foamability of 180% when the ion concentration was 1.25%. The results of emulsifying property showed that: when p H was 4 and the ion concentration was 0.25 mol/L, the cultivated salamander skin collagen had its best emulsibility, which was 1.1m2/g and 0.7m2/g respectively. |
