Physicochemical, antioxidant and antibacterial properties of dispersion made from tapioca and gelatinized tapioca starch incorporated with carvacrol

The present study investigated the properties of tapioca and gelatinized tapioca starch dispersion and film enriched with carvacrol as antioxidant and antimicrobial agent. The gelatinized tapioca had higher pH and conductivity and similar zeta-potentials and particle sizes than tapioca. Carvacrol decreased the pH, conductivity and particle size and increased the zeta-potential of the dispersions. Tapioca recorded greater viscosity than gelatinized tapioca. The viscosity of the tapioca and gelatinized tapioca dispersions decreased as the rotational speed of the spindle increased, indicating that the dispersions were non Newtonian shear-thinning fluids. Carvacrol caused a significa increase in the viscosity tapioca starch. Tapioca starch film had greater tensile strength, elongation at break, swelling and water vapor permeability than the gelatinized tapioca starch. Carvacrol significantly decreased the tensile strength and swelling and significantly increased the flexibility, solubility and water vapor permeability of the tapioca film. Scanning electron microscopy revealed the effect of carvacrol on the film microstructure which caused discontinuity in the film matrix. Carvacrol considerably increased antioxidant and antibacterial activity of the starch dispersions. Pseudomonas aeruginosa was the most resistant bacteria. The improved antioxidant and antimicrobial activity of the dispersions indicate that such products can be used as bioactive film. (C) 2016 Elsevier Ltd. All rights reserved.