Physicochemical, total phenols and pectin methylesterase changes on quality maintenance on guava fruit (Psidium guajava L.) coated with candeuba wax solid lipid nanoparticles-xanthan gum

The objective of this work was to evaluate the application of candeuba wax solid lipid nanoparticles (SLN) and xanthan gum (XG) as coatings on guava, and their effect on the fruit's physicochemical and nutritional parameters, complementing a previous publication carried out by Zambrano-Zaragoza et al. (2013). The concentrations of SLN were selected according to those reported as the most (65 g/L) and least (75 g/L) efficient in post-harvest life preservation, and were compared to a coating of XG and untreated control samples. According to results, the submicron-sized systems used in the coatings with a particle size range of 267-344 nm, a poly-dispersity index < 0.2, and zeta potential of 22.8 to 30 mV remained stable during 8 weeks of storage. The best results were from the fruits coated with 65 g/L of SLN and stored at 10 degrees C, as they showed the lowest 02 and CO2 respiration rates and, consequently, less weight loss. They also had the best retention of ascorbic acid and total phenol content, with less change in fruit color compared to the control guava and those coated only with XG. These findings indicate that this batch continued their natural maturation process, but at a slower rate than the other samples. The firmness was affected by the activity of the enzyme pectin methylesterase, but results show that the 65 g/L coating was efficient in maintaining fruit texture. In contrast, the 75 g/L coating produced epoxy in the fruit, causing physiological damage. Finally, the guava coated with XG only had a maturation rate similar to that of the control fruit.