Development of new active packaging film made from a soluble soybean polysaccharide incorporated Zataria multiflora Boiss and Mentha pulegium essential oils
An active edible film from soluble soybean polysaccharide (SSPS) incorporated with different concentrations of Zataria multiflora Boiss (ZEO) and Mentha pulegium (MEO) essential oils was developed, and the film’s optical, wettability, thermal, total phenol and antioxidant characteristics were investigated, along with their antimicrobial effectiveness against Staphylococcus aureus, Bacillus cereus, Escherichia coli O157:H7, Pseudomonas aeruginosa and Salmonella typhimurium. The film’s colour became darker and more yellowish and had a lower gloss as the levels of ZEO or MEO were increased. Antioxidant activity of the films was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric-reducing antioxidant power assays. DPPH was reduced in the range of 19.84–74.12% depending on the essential oil type and concentration. Film incorporated with 3% (v/v) ZEO showed the highest DPPH radical scavenging activity and ferric reducing antioxidant power (IC50 = 4188.60 ± 21.73 mg/l and EC50 = 8.86 ± 0.09 mg/ml, respectively), compared with the control and MEO added film. Films containing ZEO were more effective against the tested bacteria than those containing MEO. S. aureus was found to be the most sensitive bacterium to both ZEO or MEO, followed by B. cereus and E. coli. A highest inhibition zone of 387.05 mm2 was observed for S. aureus around the films incorporated with 3% (v/v) ZEO. The total inhibitory zone of 3% (v/v) MEO formulated films was 21.98 for S. typhimurium and 10.15 mm2 for P. aeruginosa. Differential scanning calorimetry (DSC) analysis revealed a single glass transition temperature (Tg) between 16 and 31 °C. The contact angle increased up to 175% and 38% as 3% (v/v) of ZEO or MEO used: it clearly shows that films with ZEO were more hydrophobic than those with MEO. The results showed that these two essential oils could be incorporated into SSPS films for food packaging.