Development of edible films and partial coating, a novel coating technique for tomato fruits, using citric acid-crosslinked starch and cellulose nanofiber

Application of edible coating is an efficient method to increase fruit storability. In this study, partial coating, a novel coating technique, was used to extend the shelf-life of tomato fruits. Coating materials were developed by incorporating four different concentrations of cellulose nanofibers (CNFs; 0, 2, 4, 6, and 8 % [w/w] of starch) with citric acid-crosslinked starch and characterized as biodegradable films prior to fruit application. Their chemical structures were confirmed using Raman and Fourier-transform infrared spectroscopy. The morphology, mechanical properties, thermal stability, water vapor permeability, transparency, and water sensitivity (moisture content and water solubility) of the films were also investigated. Films containing high concentrations of CNF exhibited superior mechanical, thermal, and barrier properties compared to those with low concentrations of CNF and the controls. However, no effect on water sensitivity was observed. Consequently, the effect of partial coating on the quality of tomato fruits was investigated using the developed coating material (crosslinked starch +8 % CNF), and the results were compared with those of the full coated fruits without CNF and uncoated fruits (control). Notably, the coated samples exhibited a significant reduction in weight loss, while retaining the firmness and color of the fruit. Moreover, comparisons of these parameters revealed no significant differences between the partial and full coatings. Therefore, the novel partial coating method used in this study is an effective alternative to conventional coating methods. Moreover, the use of CNFs as fillers for cross-linked starch enhances the properties of the composite film and increases the shelf-life of tomatoes.