Edible films based on chitosan-flaxseed mucilage: in vitro antimicrobial and antioxidant properties and their application on survival of food-borne pathogenic bacteria in raw minced trout fillets

Abstract

Various natural oils/extracts and their constituents incorporated into biopolymer-based edible films as a promising technology with the knowledge that these compounds have been able to reduce microbial growth and chemical changes of packed foodstuffs. The objective of this study was to evaluate the effect of incorporation of Ziziphora clinopodioides essential oil (ZEO; 0, 0.25 and 0.5%) and sesame oil (SO; 0, 0.5 and 0.75%) into chitosan-flaxseed mucilage (CH-FM) film against Listeria monocytogenes, Salmonella typhimurium, Staphylococcus aureus and Escherichia coli O157:H7 in vitro condition and raw minced trout fillets during refrigerated condition. The in vitro antibacterial and antioxidant properties of CH-FM films were evaluated using agar disk diffusion method and free radical scavenging activity assay, respectively. The most important constituents of ZEO were found to be carvacrol (65.22%), thymol (19.51%), ɣ-terpinene (4.63%) and p-cymene (4.86%). The lowest and highest antimicrobial effect against S. aureus, L. monocytogenes, E. coli O157:H7 and S. typhimurium were found for CH-FM films enriched with SO 0.5% (0.98-1.24 mm) and ZEO 0.5% + SO 0.75% (5.01-6.25 mm), respectively. The antioxidant property of CH-FM based films were found to be ranged 5.45% ± 0.04-37% ± 0.45. In treated trout fillets, the counts of L. monocytogenes, S. aureus, E. coli O157:H7 and S. typhimurium were 1.54-4.18, 0.34-3.35, 0.29-1.45 and 0.19-1.27 log CFU/g significantly lower than control groups after two weeks of refrigerated storage, respectively. The designated films had good antibacterial effect against some food borne pathogenic bacteria including L. monocytogenes, S. aureus, S. typhimurium and E. coli O157:H7 in raw rainbow trout fillets.