Physical, structural and thermal properties of composite edible films prepared from pearl millet starch and carrageenan gum: Process optimization using response surface methodology

•Edible composite films from PMS, carrageenan gum and glycerol were prepared.•The process parameters were optimized using Response Surface Methodology.•Film with 4.9% starch, 5.0% carrageenan, 15.73% glycerol had better properties.•PMS/CG film compared with other biodegradable films as well as LDPE/HDPE. The present study aimed at developing edible composite films from pearl millet starch (PMS) and carrageenan gum (CG) blends. Central composite rotatable design of response surface methodology was used to optimize concentrations of PMS (2–5%), carrageenan (1–3.5%) and glycerol (15–35%) for the development of composite film. The optimization was done on the basis of responses viz. thickness, water vapor permeability (WVP), solubility and tensile strength (TS). Both starch and carrageenan concentrations positively affected the TS of films, whereas the reverse trend was observed with increased concentration of glycerol. The optimum level of different parameters resulting in a composite film with maximum TS and lower WVP and solubility values were obtained under conditions of 4.9% starch, 5% carrageenan and 15.73% plasticizer concentrations. The melting temperature of optimized PMS/CG film was higher than PMS film. Morphological studies exhibited homogeneous structure of PMS film while PMS/CG composite film had rough, coarser and slightly irregular surface. The stretched regions in Fourier-transform infrared spectroscopy and Differential Scanning Calorimeter analysis confirmed the miscibility and thermal stability of different components of PMS/CG composite films. The results indicated that the developed optimized PMS/CG film possessed lower WVP, solubility but higher transparency and TS in comparison to PMS film.