Development of whey protein isolate bio-nanocomposites: effect of montmorillonite and citric acid on structural, thermal, morphological and mechanical properties

Abstract

The use of bio-nanocomposites for liberation of active substances is one of the popular alternatives for safely preserving food. In this context, the objective of this paper was to evaluate the interaction between montmorillonite sodium clay nanoparticles (MMT) and citric acid (CA) on whey protein isolate (WPI) bio-nanocomposites, developed by casting. CA was added to aid in the dispersion of MMT layers. The thermal analysis revealed that the addition of MMT, alone, increased the thermal stability of the bio-nanocomposites, but there was a reduction when combined with CA. The elastic modulus (EM), tensile strength (TS), elongation (E) and puncture strength (PS) increased with increasing MMT content from 0 to 3% by weight, with the consequent reduction of the puncture deformation. The combination of MMT and CA caused a decrease in TS and EM and increase in elongation making the films less rigid, weaker and more extensive due to the plasticizing effect. The improvement of these properties can be attributed to good dispersion/exfoliation of MMT in the WPI matrix, as seen in X-ray diffraction and transmission electron microscopy. The interaction between MMT and CA enabled to obtain bio-nanocomposites with thermal, structural, morphological and mechanical properties for use as packaging materials.