Value addition to agro industrial by-products: Effect of temperature and plasticizer on various properties of pellets developed using extrusion technology

Abstract

Pellets were developed from deoiled rice bran (DOB) and paddy husk (PDH) with plasticizers viz. glycerol (GL) and cashew nut shell liquid (CNSL) at temperatures varied between 80 and 120 °C. Plasticizers and temperature had a significant effect on properties of pellets. Specific mechanical energy of the pellets decreased with the increase in temperature. Color, hardness, pellet durability index (PDI), density (loose/tapped), terminal velocity (Vt), water solubility index (WSI), and water binding capacity (WBC) increased with increase in temperature up to 110 °C. However, expansion ratio (ER), Hausner's ratio (HR), coefficient of friction (COF), angle of repose (AOR), and drag coefficient decreased with increase in temperature up to 110 °C. A1110 (DOB-75 g, PDH-75 g, GL-18 ml) and A2110 (DOB-75 g, PDH-75 g, CNSL-18 ml) had the highest values for color (50.22 and 51.57), hardness (472.52 and 495.56 N), PDI (99 and 99.65%), density (loose/tapped), terminal velocity (3.463 and 3.850 m/s), WSI (20.98 and 19.59%), and WBC (5.19 and 4.01 g/g) and lowest values for ER (1.02 and 1.01), HR (1.11 and 1.08), COF (0.425 and 0.412), AOR (23.749 and 22.314°), and drag coefficient (0.216 and 0.177). SEM analysis evidenced that the intermolecular interactions of A1110 and A2110 pellets were better having smoother surface than other samples. A positive correlation was observed between various properties of the pellets suggesting that functional properties can be predicted from engineering properties of pellets. Practical applications Agro industrial wastes viz. deoiled rice bran and paddy husk due to their vast availability and disposal problems can be used in packaging industries. However, the commercialization is still far behind. Therefore, development of pellets using these agro industrial wastes for the development of value added products like biodegradable planting containers can be a better option. Process conditions and formulation for the development of these pellets are important for maintaining shelf stability and various properties during transportation and handling.