Material characterisation of bioplastics: influence of different starch sources in fish gelatin-based blends

The growing environmental concerns regarding petroleum-based plastics have accelerated research into sustainable, alternative materials such as bioplastics or biopolymers. Gelatin-starch blend bioplastics (SPBBs) have gained momentum in research as a possible solution due to their biodegradability, biobased resource and potential for many applications. However, the structural and functional properties of SPBBs, such as barrier performance and rigidity properties, depend on the starch source and the formulation method. This study focuses on characterising SPBBs from potato, tapioca, sago and swamp taro. The aim was to assess the influence of starch composition, evaluated by amylose and amylopectin % ratio, with a specific interest in the relationship between chemical composition and functional properties of the materials. Methods including Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), goniometry, water vapour permeability (WVP), oxygen permeability, and Dynamic Mechanical Analysis (DMTA) were used to evaluate the biopolymer's structural integrity, composition and barrier properties. The results revealed no significant variation in amylose to amylopectin ratios and subtle differences in starch profiles; however, once incorporated with the other materials, homogenised profiles were seen. XRD analysis showed distinct polymorphic structures in the raw starches. However, the incorporation of gelatine disrupted the starch structures and inhibited the gelatine's triple helix reconstitution. Surface Free Energy (SFE) analysis showed that potato SPBB demonstrated wettable potential; in contrast, lower SFE and critical surface tension (CST) values of sago SPBB indicated more hydrophobic surfaces, which is ideal for food packaging. The assessed barrier properties showed that SPBBs have good water barrier properties but poor oxygen permeabilities. DMTA results indicated that tapioca SPBB had the highest rigidity, while sago SPBB had properties more suitable for shock-absorbing material applications. Further research is needed to enhance the specific properties of these polymers for particular applications.