Abstract

Active coatings and films made from pectin, candelilla wax, aloe mucilage, and glycerol were functionalized with an extract rich in polyphenols from Larrea tridentata (Polyphenol Larrea extract: PLE) leaves at different concentrations (320 to 920 ppm). Antimicrobial capacity was evaluated on avocados by the inoculation of spores from phytopathogenic fungi Colletotrichum gloesporioides and Alternaria alternata. Coatings with 920 ppm of PLE presented the major antimicrobial capacity leading to 22.0 ± 0.4% of endocarp damage for C. gloesporioides and 24.5 ± 0.6% for A. alternata when compared to uncoated (control) avocados (44.8 ± 5.0% for C. gloesporioides and 47.9 ± 9.3% for A. alternata). The coating formulation with 920 ppm of PLE, which presents the highest antimicrobial capacity, was chosen for further evaluation and characterized. The coatings were evaluated in terms of stability, charge, pH, viscosity, and density, and some authors reported stability at 7 days. The films were evaluated by scanning electronic microscopy (SEM), X-ray diffraction, Fourier transformed infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and contact angle measurements. The surface topography shows that the presence and increase of PLE concentrations lead to a higher roughness of the films, and by FTIR was possible to observe the effect of the PLE incorporation on the functional groups of the film matrix. Contact angle was not affected by the incorporation of PLE in the films. The developed bioactive coating is effective to control endocarp damage by fungus invasion and thus protect avocados during storage.

https://link.springer.com/article/10.1007/s11947-019-02339-2