Effect of gallic acid and rutin on the swelling behavior and state of water in gelatin from fish skin

The effect of gallic acid and rutin on swelling behavior and state of water in gelatin from fish skin was investigated.The results showed that the equilibrium swelling ratio of gel decreased with the introduction of gallic acid and rutin,but it was evident in gelatin treated with rutin.In the primary swelling process,the swelling behavior of untreated gelatin and gel treated with 20 mg/g dry gelatin gallic acid,and 6,8mg/g dry gelatin rutin followed the Fick's law of diffusion,while that of gel containing 30 mg/g dry gelatin gallic acid obeyed the non-Fick's law of diffusion.It was found that the relaxation of polypeptide chains was the rate-determining step in the whole swelling process of gelatin with and without cross-linking agents.Differential scanning calorimetry( DSC) was employed to analyse the state of water in the gels.The results indicated that gallic acid and rutin did not have obvious effect on equilibrium water content of gel,but showed marked effect on the distribution of frozen and non-frozen water.The non-frozen water was lower after addition of 20 or 30 mg/g dry gelatin gallic acid,while it was higher after 6 or8 mg/g gelatin rutin was introduced.