Enhanced postharvest preservation of blueberries via Pickering emulsion-based chitosan coatings stabilised by cellulose nanofibers

Abstract

Edible films and coatings were developed using chitosan (Ch), oregano essential oil (EO), and cellulose nanofibers (CNFs) to preserve the quality attributes of blueberries. The CNFs were used as stabilisers to prepare a Pickering emulsion-based coating in one of the treatments (Ch-EO-CNF). Microstructural analysis revealed that CNFs remarkably improved the uniformity of the EO droplet dispersion by narrowing the particle size distribution from 1–16 μm in Ch-EO to 1–5 μm in Ch-EO-CNF. The addition of oregano EO imparted a considerable antibacterial effect in the films, with inhibition zones of 95.3 ± 5.1 mm² (Ch-EO) and 144.7 ± 7.5 mm² (Ch-EO-CNF), compared with no inhibition in pure chitosan films. The EO-loaded coatings were more effective than chitosan alone in maintaining blueberry pH, suggesting reduced spoilage. Moreover, the Ch-EO-CNF coating significantly reduced weight loss compared with the control and better preserved soluble solids (p < .05, LSD), highlighting the benefits of the Pickering emulsion. The Ch-EO and Ch-EO-CNF coatings reduced mould counts to 2.63 ± 0.12 and 2.19 ± 0.14 log CFU/g on day 15, respectively, compared with the control, which increased to 5.12 ± 0.22 log CFU/g. The examination of both coated and uncoated blueberries over 15 days revealed that EO-loaded coatings enhanced visual appeal by reducing wrinkles. Overall, introducing oregano EO and CNFs enhanced the preservation capabilities of chitosan coatings, especially the Pickering emulsion-based coating, which better maintained the nutritional and physiological properties of blueberries.