鱼皮明胶蛋白膜的制备及其热稳定性

Preparation and thermal stability of gelatin edible films from shark skins

利用鲨鱼皮明胶制备蛋白可食膜,测定了成膜液蛋白浓度、甘油含量对明胶蛋白膜理化性质的影响,以及环境湿度对膜热稳定性的影响。结果发现,利用鲨鱼皮明胶可以制备成无色透明的蛋白可食膜,成膜液蛋白浓度对明胶蛋白膜的断裂延伸率(EAB)、水蒸气透过率(WVP)以及透明度值有一定的影响,对拉伸强度(TS)没有发生显著影响,但甘油含量从10%增加到70%时蛋白膜的TS逐渐降低。利用DSC对膜的热稳定性进行分析,结果表明当水分活度(Aw)<0.33时,明胶蛋白膜在常温下可以处于玻璃态,机械性质能够保持稳定。然而,当Aw超过0.44后,膜的玻璃化转变温度(Tg)起始点低于25℃,膜的EAB上升,TS出现显著下降。当Aw达到0.92时,膜甚至开始溶解变成溶胶。因此,利用鲨鱼皮制备的明胶蛋白膜只适合在Aw小于0.44的干燥环境中应用。

Edible gelatin films based on shark skins were successfully prepared.The effect of protein concentration,glycerol content and environmental humidity on the properties of edible gelatin films was investigated.As a result,white and transparent gelatin films could be produced using shark skins.With increasing protein content of film-forming solution,elongation at break（EAB）,water vapor permeability（WVP）and transparency value of films increased slightly,but no differences in tensile strength（TS）were observed.Nevertheless,TS generally decreased with increasing glycerol concentration from 10 to 70%.The thermal stability of gelatin films was analyzed using DSC.It is revealed that the mechanical properties of films were not changed and polymeric materials exist in a glassy state when water activity（Aw）〈0.33.Conversely,as Aw increased above 0.44,glass transition temperature（Tg）starting point of films below 25 ℃ was observed and EAB was increased,while TS of films decreased dramatically.In the case of Aw 0.92,gelatin films even dissolved into sol.These results clearly indicate that gelatin films prepared from shark skins could only be applied in dry environment（Aw〈0.44）.