The Effect of Phenolic Acids on the Sorption and Wetting Properties of Apple Pectin-Based Packaging Films

In this article, the effects of different phenolic acids, such as ferulic, gallic, caffeic, coumaric, protocatechuic, and sinapic, as active compounds on the sorption and wetting properties of apple pectin-based edible films were evaluated. The control pectin films and those with added phenolic acids differed in appearance and physical properties. The water content of the films was reduced and ranged from 8.91 ± 0.01% to 13.44 ± 0.01% for films containing phenolic acids compared to the control films (14.31 ± 0.01%). The swelling index value of the films ranged from 86.63% for films with protocatechuic acid to 88.33% for films with the addition of caffeic acid. It was observed that the sorption isotherms had a similar shape for all the obtained films, while scanning electron microscopy (SEM) allowed for the observation of changes in the structure resulting from the film composition. It was shown that the lowest water contact angle values at the initial time (0 s) were observed for pectin films with ferulic acid (47.00° ± 4.47) and the highest for the control films (58.44° ± 5.62). After 60 s, the highest water contact angle value was recorded for the film with caffeic acid (66.39° ± 5.18) and the lowest for the film with ferulic acid (14.72° ± 5.70). Films containing gallic acid and protocatechuic acids showed the lowest water vapour permeability values among active films. The edible films developed in this study showed desirable features that could be used as bioactive packaging for food industry applications, both as protective edible coatings and active packaging films.