High Methoxyl Pectin and Sodium Caseinate Film Matrix Reinforced with Green Carbon Quantum Dots: Rheological and Mechanical Studies

Abstract

Nowadays, proteins and polysaccharides play a fundamental role in the manufacturing of biocompatible materials applied in food packaging. The resulting films have, however, limits associated with the resistance to mechanical stress; therefore, it is important to reinforce the initial mixture with additives that promote the development of stronger molecular links. Carbon dots (CDs) are excellent candidates for this purpose due to the presence of surface functional groups that determine the formation of numerous intramolecular bonds between the charged biopolymers. The present research aims to evaluate the effect of CDs on the mechanical properties of biopolymer films obtained from sodium caseinate (CAS), high methoxyl pectin (HMP) and glycerol used as plasticizers. Green carbon dots (gCDs) were obtained from natural organic sources by green synthesis. The effects of gCDs on the flow behavior and viscoelastic properties of mixed biopolymer dispersions and the thermophysical properties of the corresponded films were evaluated by steady and unsteady shear rheological measurements and differential scanning calorimetry (DSC) tests, respectively. The dynamic mechanical measurements were realized taking into account the parameters of temperature and relative humidity. The results indicate a significant change in the viscosity of the protein–polysaccharide dispersions and the thermomechanical properties of the corresponding film samples reinforced with higher amounts of gCDs.

Green Carbon Dots as Additives of Biopolymer Films for Preserving from Oxidation of Oil-Based Products

“…In a previous work [ 17 ] we could determine that the RCDs and APCDs were approximately spherical shape with an average diameter of 3.8 ± 0.75 nm for RCDs and 4.2 ± 0.94 nm for APCDs. The UV absorption spectra of RCDs and APCDs ( Figure 2 a) showed similar spectral characteristics, with a band at 280 nm corresponding to π → π * transitions due to sp 2 hybridized groups (C-C double bonds) and another band at 330 nm assigned to n → π * transitions due to C=O groups, C-N or C-OH in sp 3 hybridized bonds.…”

“…Although most papers dealing with the synthesis of CDs claim their biocompatibility and non-toxic properties, their impact on human health and on bioma is still in its infancy [ 15 ]. Nanoparticles, as metal-based as carbon-based, can modify the physical and mechanical properties of packaging polymers by improving their strength, durability, flexibility, and/or gas-barrier properties [ 16 , 17 , 18 , 19 , 20 ]. Proteins and polysaccharides have been widely used in the food industry as starting materials for the fabrication of films and coatings, [ 21 , 22 , 23 ].…”