Alginate-Based Antimicrobial Coating with Carvacrol

Coating solutions with and without carvacrol (CVR) were prepared as described in a previous work [25 (link)]. Alginate solutions were made by dissolving sodium alginate powder (2% w/v) in distilled water while heating at 70 °C under constant stirring until the mixture became clear. After cooling, glycerol (30% w/v dry weight basis) was added as a plasticizer to the sodium alginate solution and stirred for 15 min. For the preparation of alginate/CVR formulations, carvacrol was added to the alginate/glycerol blends at concentrations of 0.03%; 0.06% and 0.09% w/v, based on the studies of antimicrobial activity in vitro reported by Santos et al. [17 (link)]. Tween 80 was added to all alginate/CVR blends in amounts proportional to CVR (0.003%; 0.006% and 0.009% w/v, respectively) to assist dispersion. All mixtures were homogenized at 20,000 rpm for 3 min using an Ultra Turrax T25 homogenizer (IKA^® WERKE, Staufen, Germany), degassed using a vacuum pump, and cooled to room temperature before the application on the fruits.