The effect of nanocomposite coating (pullulan-nano clay) activated with nanoliposomes containing the watercress essential oil on the quality of Pacific white shrimp during refrigerated storage

The present study aims to investigate the effect of pullulan-nano clay (Pul-NC) incorporated with the watercress essential oil (WE) and nano essential oil (WNE) on the shelf life of pacific white shrimp (Litopenaeus vannamei) during a period of 16 days at refrigerator temperature (4 +/- 1 degrees C). First, WE were extracted using steam distillation and then microencapsulated by lipozyme. Additionally, five treatments were used to investigate the effect of the coatings on the shelf life of shrimp, including 1: control, 2: Pul, 3: Pul-NC, 4: Pul-NC + WE and 5: Pul-NC + WNE, as well as PV, TVB-N, TBA, melanosis, TVC and PTC and Pseudomonas spp, were measured on days 0, 4, 8, 12 and 16. According to the results, nanoliposome particle size and SNE microencapsulation efficiency were 92.31 nm and 81.29%, respectively. Based on the results, the use of nano-coating led to the reduction of oxidative spoilage (PV, TBA) in shrimp samples during the storage period, and the nano-coating containing WNE had more significant effect (P < 0.05) (PV = 3.89 milliequivalents/g, TBA = 1.86 mg mDA/ kg), also this treatment slowed down the increasing trend of TVB-N (25 mg/100 g) at the end of the storage period. The highest microbial load was observed in the control on all storage days (P < 0.05) and by adding WNE and WE to the Pul-NC coating, the microbial load decreased significantly (P < 0.05), and the lowest microbial load was related to Pul-NC + WNE and according to the chemical, microbial and sensory standards of this treatment, they were suitable for human consumption at the end of the storage period. Generally, the use of WNE as a natural preservative along with NC in the structure of active edible coatings based on Pul causes the delay of chemical and microbial spoilage and increases the shelf life of pacific white shrimp.