Structural and physicochemical characterization of edible films elaborated with Aloe vera (barbadensis Miller) and gellan gum

Three different edible films of Aloe vera gel (Al), gellan gum (Ge) and its mixture (AlGe), were casted by traditional method in order to study their properties. Proportions were done as follows: Aloe vera gel with 1% of glycerol, gellan gum at 0.5% w/v and 50/50 Aloe vera gel and gellan gum. The films were dried by oven at 60 °C and the characterization was done by spectroscopic properties such as X-ray difractometry and infrared spectra; by some physicochemical properties such as solubility and water absorption capacity; by optical properties such as color and transparency; and also by light microscopy, atomic force microscopy, environmental scanning electronic microscopy and confocal laser scanning microscopy. Light microscopy images were analyzed in the Image J software, textural characteristics by gray-level co-occurrence matrices were extracted from images, and these are angular second moment, contrast, correlation, inverse difference correlation and entropy, as well as fractal texture. The X-ray patterns showed that the three films have similar amorphous structure and reveals a good miscibility between Al and Ge, infrared spectra showed peaks in the wave number range of 4000 to 400 nm with intense signal in the -OH, C-H of methyl and C-O. Al showed almost total solubility and dissolution; meanwhile Ge had minor solubility values than AlGe and higher water absorption capacity than AlGe. Ge edible films were clearest than AlGe and Al, respectively. Finally, microstructure showed some agglomeration phenomena and special bonding structure formation in AlGe. Image analysis expressed different levels of homogeneity of the three films. A complete edible films characterization is necessary for understanding the influence of the compounds in the edible films design and the role of the microstructure.