Bionanocomposite films based on polysaccharides from banana peels.

Pectin and cellulose nanocrystals (CNCs) isolated from banana peels were used to prepare films. The effects of a reinforcing phase (CNCs) and a crosslinker (citric acid, CA) on properties of pectin films were studied. Glycerol-plasticized films were prepared by casting, with different CNC contents (0-10wt%), with or without CA. Overall tensile properties were improved by intermediate CNC contents (around 5wt%). The water resistance and water vapor barrier properties were also enhanced by CNC. Evidences were found from Fourier Transform Infrared (FTIR) spectra supporting the occurrence of crosslinking by CA. Additionally, the tensile strength, water resistance and barrier to water vapor were improved by the presence of CA. The 13C ssNMR spectra indicated that both CA and CNC promoted stiffening of the polymer chains.

Development of pectin films with pomegranate juice and citric acid.

The influence of pomegranate juice (PJ, replacing water as solvent) and citric acid (CA) on properties of pectin films was studied. PJ provided the films with a bright red color, and acted as a plasticizer. Increasing PJ/water ratio from 0/100 to 100/0 resulted in enhanced elongation (from 2% to 20%), decreased strength (from 10 to <2 MPa) and modulus (from 93 to <10 MPa), increased water vapor permeability (WVP, from 3 to 9 g.mm.kPa(-1).h(-1).m(-2)), and decreased insoluble matter (IM, from 35% to 24%). Although a crosslinking effect by CA was not confirmed, it has been suggested to occur from its effects on films. CA noticeably increased IM (from <10% to almost 40%); moreover, when measured on a dry film basis, the CA effects presented a noticeable tendency to increases strength and modulus, and to decrease WVP. The red color density was decreased by CA, suggesting a destabilization of anthocyanins.

Pomegranate peel pectin films as affected by montmorillonite.

The industrial production of pomegranate juice has been favored by its alleged health benefits derived from its antioxidant properties. The processing of pomegranate juice involves squeezing juice from the fruit with the seeds and the peels together, leaving a pomace consisting of approximately 73 wt% peels. In this study, pectin was extracted from pomegranate peels, and used to produce films with different contents of montmorillonite (MMT) as a nanoreinforcement material. The nanoreinforcement improved the tensile strength and modulus of films when added at up to 6 wt%, while the further addition of MMT (to 8 wt%) reduced the reinforcement effect, probably because of dispersion problems. The elongation was decreased with increasing MMT concentrations. The water vapor permeability decreased with increasing MMT contents up to 8 wt% MMT, indicating that the increased tortuosity of the permeant path was effective on barrier properties of the film.