The effectiveness of the chitosan-EAC may be due to the positive charge developed by chitosan in acidic medium (pH < 5.5).
Protonation of an amino group present on each glucosamine unit makes it soluble in an aqueous medium and confers greater antimicrobial activity .
Moreover, the nondissociated forms of sodium benzoate and potassium sorbate have antimicrobial activities, which increase with decreasing pH (the optimum effectiveness is pH 2.5 to 4.0).
The coating forming solution based on chitosan and pectin were pH 4.00 and 4.10, respectively (data not shown), which may explain their abilities to reduce overall microbial growth.
The coating forming solution based on pullulan was pH 6.68 (data not shown), and, therefore, it was less effective at reducing microbial growth in general.
ou rchitosan-EAC incorporated with sodium benzoate and potassium sorbate showed greater inhibition of microbial growth.
The difference may be associated with the polymer concentration and the incorporation of sodium benzoate into the formulation.
Finally, the use of antimicrobials incorporated into coatings was more effective in reducing microbial growth than the use of antimicrobials alone, possibly because the coatings helped to maintain antimicrobials on the surface of the fruits .
The effectiveness of the chitosan-EAC may be due to the positive charge developed by chitosan in acidic medium (pH < 5.5). Protonation of an amino group present on each glucosamine unit makes it soluble in an aqueous medium and confers greater antimicrobial activity . Moreover, the nondissociated forms of sodium benzoate and potassium sorbate have antimicrobial activities, which increase with decreasing pH (the optimum effectiveness is pH 2.5 to 4.0). The coating forming solution based on chitosan and pectin were pH 4.00 and 4.10, respectively (data not shown), which may explain their abilities to reduce overall microbial growth. The coating forming solution based on pullulan was pH 6.68 (data not shown), and, therefore, it was less effective at reducing microbial growth in general. ou rchitosan-EAC incorporated with sodium benzoate and potassium sorbate showed greater inhibition of microbial growth. The difference may be associated with the polymer concentration and the incorporation of sodium benzoate into the formulation. Finally, the use of antimicrobials incorporated into coatings was more effective in reducing microbial growth than the use of antimicrobials alone, possibly because the coatings helped to maintain antimicrobials on the surface of the fruits .
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