Summary Cassava starch and poly(butylene adipate‐co‐terephthalate) (PBAT) based films containing microencapsulated oregano essential oil (OEO) and free OEO are produced by blow extrusion. Microcapsules produced by ionic gelation were characterized with respect to average size, morphology, and encapsulation efficiency. The microcapsules were spherical and ranged in size from 20 to 1000 μm. Encapsulation efficiency (EE) is 83%. The films are analyzed in terms of their morphology, mechanical properties, water vapor permeability (WVP) and antibacterial properties. The films containing OEO microcapsules exhibited lower ultimate tensile strength, Young's modulus and elongation at break than the control films and the films containing free OEO. The WVP of films containing free OEO is slightly lower, while that of films containing microencapsulated OEO did not differ significantly from the control films. Scanning electron microscopy (SEM) images showed that the surface of films containing microencapsulated OEO are less homogeneous than those of the control and free OEO films. Films containing free or microencapsulated OEO presented inhibitory activity against Staphylococcus aureus, but not against Escherichia coli.
The soy protein isolate (SPI) is a biopolymer highlighted as a raw material for producing films and demands the investigation of the processing conditions that make it possible to obtain a film with adequate functional properties. The objective of this work was to evaluate the effect of the pH and concentration of SPI on the mechanical properties, water vapor permeability, solubility, and color of the SPI films produced by casting using a central composite rotational design (CCRD). In general, the films presented a yellow coloration with a continuous aspect, good handling, and no apparent glycerol migration. The linear effect of pH positively influenced the tensile strength (TS) and elongation at break (ELO) of the film (p <0.05) but negatively influence the solubility (SOL) and color parameter L* for which we obtained lower values of SOL and L* at a high pH. This possibly occurred because of the denaturation of the soy proteins at an alkaline pH, far from the isoelectric point, resulting in their unfolding and solubilization which facilitated the interaction between the chains, forming a more compact structure. Considering the optimization by the desirability function, to obtain a film with high TS and ELO and low SOL, it is necessary to use 7.56 g/100 g of SPI film-forming solution and to adjust the film-producing solution to pH 10.54.
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