Development of pectin films with pomegranate juice and citric acid

• The effects of pomegranate juice and citric acid on pectin films were studied.
• Pomegranate juice acted as plasticizer, improving elongation.
• Citric acid improved tensile strength, modulus, and water vapor permeability.
• Citric acid reduced film solubility, possibly due to a crosslinking effect.
• The red color was decreased by citric acid, suggesting anthocyanin destabilization.

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.