Castor Oil and Cocoa Butter to Improve the Moisture Barrier and Tensile Properties of Pectin Films

Castor oil (CO) and cocoa butter (CB) were studied as potential hydrophobic and plasticizer additives for pectin biopolymer films. The optimum concentration of CO and CB additives and drying temperature were determined by using a 23 (two-level, three-factor) statistical factorial design of experiments. The CO and CB integrated pectin films displayed remarkably lower moisture and oxygen transmission rates relative to the control pectin films. Furthermore, the hydrophobicity, ductility (elongation at break) and flexibility (low elastic modulus) of the CO and CB added films are significantly higher than that of the control pectin films. The modified films retained 90% of their weight at a temperature of 200 °C, indicating their excellent thermal stability. A very low glass transition temperature of 2 ± 2 °C and a melting point of ~ 150 °C of the films designates their stability under processing and storage conditions. Scanning electron microscopy analysis confirmed the formation of homogeneous films without any micro-cracks or agglomerations. Detailed statistical analysis shows that the optimal conditions for producing improved pectin films: the concentration of CO (15% w/w of pectin) and CB (10% w/w of pectin) and film drying temperature (T = 35–52 °C). A coating of film forming solution comprising optimum amounts of pectin, CO and CB was able to delay the ripening of a banana by 4 days and of capsicum by 15 days at atmospheric conditions.