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The variability of properties presented by natural lignocellulosic fibers (NLFs) is an important issue to highlight, since such inconsistencies in their characteristics put them at a disadvantage when comparing them to synthetic materials. It is important to point out that the application of methodologies that make it possible to predict the behavior of NLFs in the face of mechanical stress is essential for the use of these materials in engineering applications. For this, the present study proposes to evaluate the influence of the carnauba fibers (Copernicia prunifera) morphology in the properties presented by these materials. Optical microscopy (OM) was applied to determine the cross-section and diametrical variation of the fibers, enabling the evaluation of density by Archimedes method according to the mean diameter of the fibers. The mechanical properties were evaluated by tensile testing and the data were acquired by Weibull analysis. The morphological aspects of the longitudinal and cross-sections of the fibers were evaluated with scanning electron microscopy (SEM). The fibers had an average density of 1.13 ± 0.22 g/cm3, with diameter intervals ranging from 0.31 to 1.21 mm. The fibers have reasonable mechanical properties, with an average tensile strength of 64.7 ± 40.9 MPa, Young's modulus of 1.37 ± 0.80 GPa and elongation of 5.59 ± 1.60%. The SEM micrographs highlighted the defects present on the outer surface of the fiber as well as in the cross-section. There was a high potential for the use of carnauba fibers in the manufacture of polymer matrix composites.

Edible coatings to extend the shelf life and preserve the quality of fruit and vegetables are highly demanded nowadays. Recently, plant-based edible coatings have gained importance in the context of sustainability, which in combination with suitable top-down process can render “greener” nanoemulsions with optimized properties. Herein we developed a carnauba wax nanoemulsion (CWN) by using a high-pressure processing to be applied as an edible coating for fruit and vegetables. The as-developed nanoemulsion properties were compared to conventional carnauba wax emulsion (CWM), where CWN showed particle size diameter of 44 nm and narrow distribution, while CWM displayed larger particles and wider size distribution (from 200 to 1700 nm). For assessment of the postharvest quality, cv. ‘Debora’ tomatoes, employed here as a model, were coated with CWN or CWM, at concentrations of 9 and 18%, and then compared to uncoated fruit during storage at 23 °C for 15 days. Evaluation of fruit quality, including sugar, acids, pH, water vapor loss, firmness, gloss, color, ethylene and respiratory activity, were assessed at every 3 days, while sensory test were carried out at the end of storage. Uncoated tomatoes presented the highest water loss values, meanwhile, firmness, ethylene, and respiratory activity were not largely modified by the coatings during storage. Tomatoes coated with the CWN exhibited the highest instrumental gloss and were preferred by consumers in sensory evaluations, indicating the potential of the as-developed carnauba wax green nanoemulsion for postharvest applications.