Microwave-assisted reaction of gelatin with tannic acid: non-thermal effect on the crosslinking process

The reaction of gelatin with tannic acid using microwave heating with simultaneous cooling (MHSC) in comparison with water bath heating was investigated to get some hints on the non-thermal effect of microwave. MHSC showed a better ability to accelerate the reaction rate. It also increased the turbidity, crosslinking degree, and viscosity of the crosslinked gelatin by 91 FTU, 6.8%, and 0.08 respectively, indicating that microwave could improve the properties of the product. Moreover, sodium dodecyl sulfate polyacrylamide gel electrophoresis patterns reflected that the crosslinked gelatin (MHSC) had a higher molecular weight as the gray levels decreased by 9.2% (235–245 kDa), 2.3% (135–145 kDa), and 9.3% (122–132 kDa). More homogeneous aggregations were identified at the crosslinked gelatin by atomic force microscopy. These results proved that microwave has a non-thermal effect in the gelatin crosslinking process, accelerating the crosslinking reaction, and improving the performance of the gelatin product, which may have a good use in industry.