Impact of utilization of whey protein isolate-based coating containing Satureja hortensis L. essential oil on shelf life of chicken fillets

Refrigeration as a preservation technique is absolutely necessary to maintain the quality of fresh meat products. Nevertheless, it does not guarantee by itself a shelf life period for more than a few days. Nowadays, the use of edible films and coatings containing natural antibacterial and antioxidant agents are one of the new preservation techniques that are capable to improve the shelf-life and maintain natural appearance of fresh meat and poultry products. Considering this fact that the shelf life of chicken breast is merely 4-5 days, the present study was conducted to assess the possibility of extending the shelf life of chicken breast fillets using whey protein isolate (WPI)-based coating containing Satureja hortensis L. essential oil stored under refrigeration conditions.

To make coating solutions, after preparation of WPI solutions (10%), 5% glycerol as plasticizer was added and the solutions was mixed properly. For preparation of WPI coating solutions containing Satureja essential oil (WPIEO), different amounts of Satureja hortensis L. essential oil (0.5, 1 and 2 percent) were added to the WPI coating solutions. Antioxidant )thiobarbituric acid number=TBA and peroxide value=POV) and antibacterial (mesophilic and psychrophilic bacteria count) properties of the samples were determined. Chicken breast fillets coated by different solutions, i.e. coated sample with WPI coating (WPI-C) and WPIEO solutions were analyzed and compared with the control sample (without coating) during 0, 3, 6 and 9 days of storage period.

There was a significant difference for pH, TBA, POV and psychrophilic and mesophilic bacteria count between all WPIEO samples as compared with the control throughout the storage period. As the amount of essential oil in coated WPI increased, the bacterial counts reduced and antioxidant properties increased significantly (p < 0.05). However, no significant differences between control and WPI-C were found for the mentioned parameters. In general, the lowest POV and TBA during storage time were related to coated WPI sample containing 2 per cent essential oil and its POV was increased from 1.37 to 4.82 meq O2 Kg-1 fat and its TBA increased from 0.016 to 0.028 mg malonaldehyde per kg meat during 9 days’ storage period. These values for control at the same storage time were more meaningful and increased from 1.49 to 10.05 meq O2 Kg-1 fat and 0.015 to 0.052 mg malonaldehyde per kg meat respectively. Although the total mesophilic and psychrophilic bacteria count in all the samples were increased through the storage period but these changes were slighter in WPIEO samples so that the mesophilic and psychrophilic bacteria count in WPIEO containing 2 percent essential oil were significantly lower and 0.50 and 0.58 Log cfu/g lesser than control respectively.

The results showed that the microbial load and antioxidant properties were not improved by the application of the edible coating based on WPI without essential oil in the chicken breast. However, WPI edible coating containing Satureja hortensis L. essential oil could be enhanced the shelf life of chicken fillet under refrigeration conditions. Therefore, this edible coating might be effective carrier of Satureja hortensis L. essential oil, able to control the release of the antimicrobial and antioxidant active compounds on the chicken breast throughout the storage period.