Alginate/Shellac Composite Films – Novel Materials for Preservation of the Purple Passion Fruits (Passiflora edulis Sims)

Abstract The present study first describes preparations of novel edible composite films, based on alginate and shellac using three plasticizers propylene glycol, glycerol, and polyethylene glycol 400 at 5%–20%, and their preservation to the purple passion fruits. Their physicochemical properties, including sensory evaluation, fracture surface morphology, mechanical properties, FTIR, water vapor permeability (WVP), and TGA, were evaluated. Glycerol provided the best plasticizing effect, whereas the films using the plasticizer propylene glycol exhibited the lowest WVP, particularly at 10% (the WVP of 3.64 g.mm/m 2 .day.kPa). The alginate/shellac composite films containing 10% propylene glycol or 10% glycerol protect against the growth of several pathogenic bacteria. After 56 days of storage, the purple passion fruits coated with the films containing 5%–15% propylene glycol or glycerol maintained good quality, compared to the uncoated fruits, especially the composite film containing 10% propylene glycol (the lowest weight loss of 27.09% and the rind color change of 8.94). The film containing 10% propylene glycol also maintained the best nutritional values, such as vitamin C content (48.96 mg%), total soluble solids (16.65%), titratable acidity (3.25%), total phenolic content (200.61 mg GAE/100 mL fruit juice), total flavonoid content (66.80 mg QE/100 mL fruit juice), and DPPH radical scavenging (118.68 µmol Trolox/100 mL fruit juice). Collectively, the novel alginate/shellac composite film containing 10% propylene glycol with antimicrobial and antioxidative activities could be developed as a potential material for fresh fruit protection.