Preparation and characterization of in-situ crosslinked pectin–gelatin hydrogels

• Crosslinking reaction takes place between oxidized pectin and gelatin by Schiff base formation.
• Effect of reaction conditions on the crosslinking reaction has been thoroughly investigated.
• Crosslinked systems were plasticized with glycerol to introduce flexibility in the system.

Crosslinked hydrogels were developed by in-situ reaction of periodate oxidized pectin (OP) and gelatin. The reaction takes place through the formation of Schiff bases between aldehyde groups of OP and amino groups of gelatin. The effect of various process parameters such as reaction time, reaction temperature, pH of the reaction and composition on the efficacy of the crosslinking was investigated. Field emission scanning electron micrsocopy (FESEM) revealed that homogenous, single phase systems are obtained after the crosslinking of OP and gelatin. The swelling characteristics of the hydrogels were monitored. The equilibrium swelling varies in the range of 195–324% with a variation in the gelatin content (10–40%). Glycerol, when used as a plasticizer, improved the flexibility and the handling characteristics of the crosslinked hydrogels. Plasticized films retained good tensile strengths in the range of 19–48 MPa. By proper selection of the reaction conditions, the efficiency of crosslinking can be controlled to obtain the optimum results.