Effect of the potassium sorbate and carvacrol addition on the properties and antimicrobial activity of tapioca starch - Hydroxypropyl methylcellulose edible films

Tapioca starch (TS), hydroxypropyl methylcellulose (HPMC), and glycerol (GLY) based edible films with the addition of potassium sorbate (KS) and carvacrol (CARV) were prepared by casting technique. The effect of antimicrobial concentrations on the color, mechanical properties, solubility in water (SW), water vapor permeability (WVP), and antimicrobial effectiveness of films was analyzed and the composition was optimized by using a response surface methodology (RSM). The films were transparent and slightly yellow but with high L* values (89-91). Potassium sorbate incorporation increased the color parameter values and presented an antagonistic interaction with CARV for b* and yellow index (YI). A higher amount of CARV drastically decreased the stress at break, and increased the deformation and the SW of the films. The water vapor permeability (1.1 +/- 0.1 x 10(-9) g(-1) m(-1) s(-1) Pa-1) was not influenced by the different concentrations of antimicrobials. The film formulated with KS 0.30 g 100 g(-1) and CARV 0.50 g 100 g(-1) correctly satisfied the requests of mechanical strength, colorless, and appropriate bioavailability of antimicrobials for Zygosaccharomyces. bailii. This optimized film showed a higher surface hydrophobicity and exerted a highly improved antimicrobial barrier against Z. bailii, Lactobacillus plantarum, and Pseudomonas fluorescens in comparison with films containing only KS. The obtained results demonstrate the ability of films to act as an antimicrobial hurdle that can contribute to extend the shelf life of food.