Desenvolvimento de revestimento comestível e filmes nanocompósitos a partir da goma de cajueiro (anacardium occidentale l.)

Abstract

Cashew tree, Anacardium occidentale L., is an Anacardiaceae with economic importance in the Brazil’s Northeast. The cashew exuded gum, called cashew gum (CG), is a acid branched heteropolysaccharide soluble in water and has shown an potential in industrial use because it has similar properties to arabic gum, polysaccharide used worldwide. The CG has been explored as a matrix for edible coating and food films, but due to its hydrophilic characteristics, have low barrier properties which limit their application. Alternatives such as chemical modification and the use of nanotechnology allow improve their barrier and mechanical properties in filmogenic matrices. Therefore, this study aimed to modify the CG with sodium trimetaphosphate (TPMS), developing edible coatings from modified cashew gum for post-harvest application in guavas (Psidium guajava L.) cv. 'Paluma' and study the effect of addition of montmorillonite (MMT) in the performance of CG-MMT nanocomposite films. Chemical modification promoted changes in the CG characteristics. The crosslinked gums exhibited low water solubility, increased particle size, low zeta potential values and increased viscosity when compared to no crosslinking CG The higher viscosity values were obtained by modified CG with 1% TMPS, showing potential application in coating. CG and xanthan gum (XG) edible coatings were developed for post-harvest application in guavas. It was applied coatings without TMPS and 1% TMPS. The coatings were effective in maintaining guavas postharvest quality stored at 10 ºC and 24 ºC. The 1% TMPS coating promoted lower mass loss, greater firmness retention and higher ascorbic acid content, showing that the chemical modification was relevant in the formation of coatings with good barrier properties. The CG-MMT nanocomposite films studied showed a reduction in moisture absorption values, water solubility and water vapor permeability. The CG-MMT films showed decrease in transparency with increasing MMT content and their mechanical properties were also affected, becoming more rigid and less elongated. The CG-MMT nanocomposite films have the potential to be used in packaging materials due to their better mechanical and water vapor, barrier properties.