Effects of Different Processing Techniques and Sol-Gel Coating on Physical Properties of Starch and Clay-Based Biocomposite Material

This study investigated the effects of different processing techniques and sol-gel coating on the physical properties of biocomposite material. Two dispersion series from corn starch, clay, and sorbitol were prepared by conventional and microwave-assisted processing, and casting technique. One film from each series was sol-gel coated by immersion. All the samples were subjected to moisture content (MC), water solubility (WS), water absorption (WA), FT-IR, DSC, and SEM/digital microscopy tests. The results showed that the coated films contained higher MC (11.5±0.5%) than the non-coated films (5.3±0.6%) and absorbed less water (44.7±12.4%), compared to the non-coated ones (166.3±2.5%). Non-coated films exhibited less solubility in water (26.1±0.2%) than the coated ones (51.0±0.7%). FT-IR test detected cross-linking (1723 cm-1 ester) in the microwave-assisted coated film. The sol-gel coating increased the latent heat of melting and specific heat values by 14.9% and 19.4% for conventionally fabricated samples, and 22.3% and 25.3% for microwaved films, respectively, whereas it reduced the temperature of melting by 23.1% for conventionally fabricated ones, and 6.6% for microwaved ones. Microscopic tests revealed that microwaved compact morphology indicated better gelatinization of starch. Overall, microwaving and sol-gel coating need further investigation to improve the physical properties of biocomposite materials for food packaging.