Active Pectin Films Enriched with Phenolic Acids: A Novel Strategy for Maintaining Postharvest Quality of Pears

This study aimed to analyze the effect of various phenolic acids introduced into pectin films on their ability to inhibit microorganisms. The antimicrobial activity of six phenolic acids—gallic, protocatechuic, caffeic, sinapic, coumaric, and ferulic acids—was verified against Bacillus subtilis bacteria. No inhibitory effect was observed when the acids were introduced into the substrates with the films, as the polysaccharide films served as a breeding ground for microorganisms. Bacterial growth was inhibited when pure acid was introduced to the substrate. Gallic and caffeic acid, at concentrations of 50 and 75 mM/dm3, respectively, completely inhibited bacterial growth. However, studies on pears have shown that such concentrations of phenolic acids are unsuitable for fruit coatings, as they lead to cloudiness and impaired visual appeal. Consequently, the lowest effective concentration was applied to fruit, reducing the total bacterial count from 2.59 ± 0.04 to 1.88 ± 0.22 log CFU/mL and mold and yeast counts from 2.11 ± 0.09 to 1.63 ± 0.10 log CFU/mL. The coating produced with the lowest tested concentration of gallic acid reduced the pears’ respiration rate. The amount of CO2 released by coated fruit was approximately 4 mg/kg·h lower than that of uncoated pears, and the level of ethylene released was approximately 6 ppm lower. The addition of gallic acid at a concentration of 15 mM/dm3 to the coating reduced the growth of bacteria, yeasts, and molds. After 12 days of pear storage, the number of microorganisms in coated fruit was approximately 0.71 log CFU/mL lower for bacterial cells and 0.48 log CFU/mL lower for yeasts and molds.