Shelf life extension of chicken fillets by biodegradable chitosan coating containing Zataria multiflora Boiss essential oil during refrigeration

With increasing demand for chicken meat, the chemical composition of meat carcasses has become more important. Despite advances in medical care and food technology in recent years, foodborne infections and food poisoning, as well as food spoilage in developed and developing countries are still a major problem for human health and the economy. During the storage period, the quality characteristics of meat is shortened due to bacterial and oxidative spoilage. Oxidative spoilage causes unpleasant odors, unpleasant changes in taste, and changes in the structure of nutrients and reduces the nutritional value of the product. While spoilage and microbial contamination lead to product wastage and poses serious health risk to consumers. Increasing interest in using less synthetic preservatives has led to use of natural derivatives with antimicrobial properties. Biodegradable coatings are a good alternative to plastic packaging, given the problems they have with recycling and environmental pollution. Chitosan coating containing Zataria multiflora essential oil is known to possess good antioxidant and antibacterial properties due to the presence of thymol and carvacrol compounds and their ability to establish hydrogen bonds with other monoterpenes such as γ-tropenes. 

Zataria multiflora was purchased in the spring from Sari Medicinal Plants Store. It’s essential oil was prepared by distillation method using Clevenger and then dehydrated with sodium sulfate and passed through 0.45 μm syringe filters and stored in dark containers at 4°C (Rezaie et al., 2015).In this study, the use of biodegradable and edible coating of chitosan with thyme essential oil to increase the shelf life of chicken fillets during refrigeration was investigated. Treatments included control, 2% chitosan, 1.5% essential oil and treatment containing 2% chitosan with 1.5% essential oil, which were stored at 4 ° C for 24 days. The antioxidant and antimicrobial properties of chitosan and thyme essential oil were evaluated by measuring the total amount of phenolic compounds, free radical scavenging (DPPH), and FRAP. Quality assessment with chemical tests; pH, TBA, TVB-N, and microbial count (mesophilic bacteria and Pseudomonas) were measured at 4-day intervals. 

The results of quality assessment during the refrigeration period for all treatments showed an increasing trend in pH. TBA (mg MDA/kg fat), TVB-N (mg N/100g), TMC and Pseudomonas (CFU/g) in coated treatments with 2% chitosan and 1.5% essential oil on day 24 of storage were 6.6, 1.78, 26.8, 6.7 and 6.42, respectively, and showed the highest shelf-life. Since, thyme essential oil and chitosan have increased the shelf-life of chicken fillets due to their antioxidant and antimicrobial activity.The use of biopolymers such as chitosan, gelatin, etc., which have a good ability to maintain and release antioxidant and antimicrobial compounds, is increasing in food packaging. In this study, the preservation effects of chitosan coating containing Zataria multiflora essential oil on increasing the shelf life of chicken fillets were investigated and it was found that chitosan coating and Zataria multiflora essential oil alone and in combination had good preservation effects. According to the results, 2% chitosan coating containing Zataria multiflora essential oil can increase the shelf life of chicken fillets, which is due to the very good performance of chitosan coating containing Zataria multiflora essential oil due to its synergistic effect on antimicrobial and antioxidant properties. Between chitosan coating and thyme essential oil in preventing microbial growth and chemical spoilage and shelf life for control treatments, chitosan 2%, thyme essential oil 1.5%, and chitosan 2% containing thyme essential oil 1.5% respectively 8, 16, 16 and 24 days. Therefore, they can be used to store chicken fillets and meat products.