Influence of edible coating essential oils on the microbial and chemical quality of Vannamei shrimp

Introduction: New fish are consumed worldwide as one of the most important nutritious foods. On the other hand, due to the high content of free amino acids and nitrogen in the tissues of the body, as compared to red meat or chickens, the rate of corruption is higher. The stages of aquatic corruption usually begin by removing the natural flavor and aroma that result from the growth of corrosive microorganisms. On the other hand, the structure of the tissue is lost and odor and corrosion can be detected. These entire changes make the shelf-life of aquatic animals, both in the form of packaging and non-closure, very limited. In addition to traditional methods used to extend the shelf-life of fish products, like MAP or chilling storage, there is an increasing interest in the use of edible films and coatings with antimicrobial properties in order to reduce, inhibit, or delay the growth of microorganism on the surface of foods. Edible films and coatings can be made of polysaccharides, proteins, and lipids and can act as carriers of different compounds like antioxidant, antimicrobials, and other preservatives in order to improve food quality and safety. Therefore, the use of composition, herbal essences and modified atmosphere as a different protective technology can be a solution to improve the microbial quality of the aquatic fillet, such as shrimp, as potentially having synergistic effects (Carrion-Granda 2015). The purpose of this study was to investigate the effect of using water-based coatings alone and in combination with Zataria multiflora and Origanum vulgare essential oils on the shelf life of the Litopenaeus vannamei shrimp in a 16-day period in closed polypropylene boxes was modified by atmospheric method (CO2-50% - N245% -O2 5%) at refrigerator temperature. Then, the objectives of this work were (1) to evaluate the effectiveness of whey protein isolate edible coatings enriched with essential oils on the microbiological quality of hake fillets and (2) to assess the combined effects of edible coatings and MAP on the microbiological quality of hake fillets stored under refrigeration conditions. Besides, the influence of initial fish microbial loads in the effectiveness of edible coatings and MAP over the quality of hake fillets was analyzed.
Material and methods: The plant was collected from Shirazi and Zanjan Mountains from Fars province and was examined by botanists of the Institute of Medicinal Plants of Jahad University of Tehran University. Experiments were carried out at Sari lab. The extraction was carried out according to the Nelson and Onyagaba method (2007). The 50 g dry leaves of the plant were first grinding and 500 ml of 95% ethanol was placed in a detonator. Essential oil was taken for 24 hours. The solvent was evaporated by rotary device. Whey protein or WPI (10% w / w) was dissolved in distilled water and 5% glycerol (w / w) was added due to its formability. The coated food coating solution (FFS) was heated to 90 ° C using a thermostatic bath and heated for 30 minutes. Oregano essential oils and Thymol Shirazi was added to it at 1 and 3% (w / w) and allowed to cool at room temperature. The edible coating solution was then homogenized using a series of 7 mm diameter series for 5 minutes and a range of 100%. During this time, the edible coating solution was stored in an ice-water bath to avoid rising temperatures and reaching 40 ° C. The parameters included peroxide, TVB-N, TBA and microbial load on days 0, 4, 8, 12 and 16. The treatments included control treatment, treatment 1(edible coating with whey), treatment 2 (edible coating with whey and 1% Origanum vulgare oil), treatment 3 (edible coating with whey and 1% essential oil of Zataria multiflora), Treatment 4 (edible coating with whey and 3% Origanum vulgare), treatment 5 (edible coating with whey and 3% essential oil of Zataria multiflora). Samples were packed in modified atmosphere (CO2 50% - N245% -O2 5%) and kept for 16 days. Both saw and all coated samples were packed in polypropylene boxes.
Results and discussion: In all treatments, whey was used at a weight of 10% by weight. In the case of peroxide, TBA and TVB-N, control treatments and 1 had the highest and 4 and 5 treatments had the least of these parameters (P <0.05). Control treatment had the highest microbial load, and with increasing level of essential oil, the microbial load significantly decreased (P <0.05) and the lowest microbial load was related to treatments 4 and 5. Adding herbal essential oils at two levels of 1 and 3% increased the duration of shrimp keeping in refrigerated temperatures and based on TVB-N and microbial standards, four treatments had essential oil until day 8 and two treatments were applied until the day 4 Suitable for human consumption.
Conclusion food coatings are capable of replacing many types of polymer packages. The results of this study showed that the coating of whey without supplementing herbal essential oils of Thymol Shirazi and Oreganeh winter wheat did not have the necessary efficiency in increasing the shelf life of Thymol Shirazi and Oreganeh. Adding herbal essential oils at two levels of 1% and 3% increased the maintenance of shrimp in a refrigerated temperature. Based on TVB-N and microbial standards, four treatments had essential oil until day 8, two control treatments and whey treatment until day 4 Suitable for human consumption. In this way, the use of whey coating with 1 and 3% essential oils of Thymol Shirazi and oregano, improved the shrimp shelf life for 4 days compared with the control.