Extended refrigerated preservation of fresh shrimp: A novel approach combining alginate biopolymer with thymol nanoemulsions and nanostructured lipid carriers

• This is the first systematic and direct comparison of thymol - NE versus thymol- NLC within an alginate coating for shrimp preservation, identifying the optimal delivery system. • The NLC's matrix provided a more controlled release of thymol, leading to longer-lasting antimicrobial and antioxidant effects. • The alginate coating with thymol-NLC successfully extended the refrigerated shelf life of fresh shrimp from 4 days (control) to a full 10 days . • The Al-NLC coating provided the best overall protection by microbiological Safety, chemical spoilage delay, and sensory quality. This investigation aimed to assess the influence of alginate-based edible coatings incorporating thymol-nanoemulsion (NE) and thymol-loaded nanostructured lipid carriers (NLCs) on the physicochemical, microbial, and sensory properties of refrigerated (4°C) white shrimp over a 10-day storage period. The droplet sizes of the NLC and NE were 190 and 141.8 nm, respectively, with the NE exhibiting a faster thymol release rate (93%) compared to the NLC (84%). SEM results confirmed the antimicrobial efficacy of thymol, NE, and NLC against S. aureus and E. coli , while FTIR confirmed no chemical interactions between thymol and the NE/NLC structures. A key finding was the superior performance of the NLC-based coating, which most effectively inhibited microbial growth (TVC of 8.4 vs. 9.9 Log CFU/g in the control on day 10) and delayed chemical spoilage (demonstrating the lowest levels of total volatile base nitrogen, peroxide value, thiobarbituric acid, and pH). Furthermore, the Al-NLC coating best preserved sensory and physical qualities, minimizing weight loss, color change, and texture softening, while significantly inhibiting melanosis development. Consequently, the Al-NLC coating successfully extended the refrigerated shelf life of shrimp from 4 days (control) to 10 days, outperforming all other formulations, including thymol-NE. In conclusion, alginate coatings enriched with thymol-loaded NLCs represent a highly promising natural strategy for significantly enhancing the preservation and safety of fresh shrimp. In conclusion, alginate coatings enriched with thymol-NE/NLC, particularly thymol-NLC, represent a promising preservation strategy for significantly extending the refrigerated shelf life of shrimp from 4 days (control) to up to 10 days.