On the thermal behavior of protein isolated from different legumes investigated by DSC and TGA.

BACKGROUND: Pea, lentil, faba bean, chickpea and bean proteins are potentially renewable raw materials for bioplastic production that can be obtained from agricultural waste. Plastics are usually processed under heating, and thus thermal stability is a mandatory requirement for the application. In this study, the thermal behavior of several legume protein isolates at different purity degrees was investigated. RESULTS: The thermal stability of proteins extracted from legumes was maximum for chickpeas and minimum for beans and decreased with decreasing protein purity in the range 30-88%. A similar dependence on purity was observed for the glass transition temperature. On the contrary, the denaturation temperature was found not to depend on sample purity and origin and was lower than the degradation temperature only in the case of protein samples with purity higher than 60%. CONCLUSION: Proteins from legumes are suitable to produce thermoplastic biopolymeric materials if isolated at purity higher than 60%. In fact, under this circumstance, they can be denaturized without degrading and thus are suitable for extrusion processing. © 2018 Society of Chemical Industry.

Emulsion Blending Approach for the Preparation of Gelatin/Poly(butylene succinate-co-adipate) Films.

Emulsion blending as a new method to combine a water-soluble biopolymer, gelatin, with a synthetic biodegradable elastomer, poly(butylene succinate-co-adipate) (PBSA), was investigated. Blending by wet processing a hydrophilic biopolymer with a hydrophobic synthetic polymer aimed at evaluating the potential for improving the mechanical properties of the biopolymer without affecting its biodegradability. The effect of the variation of blend composition, and of the experimental procedure for the emulsification and the subsequent preparation of cast films from the resulting oil-in-water emulsions was analyzed. In particular, processing temperature, concentration of the precursor solutions (aqueous gelatin and PBSA in dichloromethane, respectively), blending method and post treatment conditions (T, P) affect the quality and stability of the aqueous gelatin emulsion containing PBSA in dichloromethane as the dispersed phase. Control of the aqueous phase viscosity is a key parameter for both the emulsion stability and the morphology of the final heterophasic cast films. In fact, viscosity must be sufficiently low to allow high shear emulsification, but high enough to prevent coalescence among the organic phase droplets. The process conditions optimized for a 80/20 blend were extended to the preparation of blends with 5-30 wt % PBSA. It was found that evaporation of the organic phase must be nearly quantitative before casting to allow the formation of uniform films at any investigated composition of the immiscible polymer blend. In fact, when the films are produced by casting, the presence of residual organic solvent along with too high a viscosity of the aqueous gelatin phase promotes the formation of cavities opening up at the lower film surface as a result of the higher density of CH2Cl2. However, such cavities, internally sheathed with PBSA microbeads precipitated upon evaporation of the organic phase, if smaller than 100 µm turned out to improve the flexibility of the films.