Nanoemulsion with comprehensive protective effects for fish quality protection

A nanoemulsion coating made from fish gelatin and chitosan — two natural biopolymers — and enriched with moringa oil and sea buckthorn oil was tested for its ability to keep rainbow trout fillets fresh during refrigerated storage at 4°C. The coating slowed two key markers of fish spoilage: rising pH (which signals bacterial activity and protein breakdown) and the accumulation of total volatile basic nitrogen, a compound that builds up as fish deteriorates and is used by food scientists to measure freshness. Fillets coated with the nanoemulsion retained significantly more moisture — 88.64% water-holding capacity after 12 days compared to 86.88% in uncoated control fillets — meaning the texture stayed firmer and more appealing for longer. The nanoemulsion itself was physically stable, with a small droplet size of around 225 nanometres and a low polydispersity index, indicating the oil droplets were evenly distributed and unlikely to separate over time. The negative zeta potential and moderate viscosity suggest the coating would adhere well to fish surfaces. Moringa oil contributes antioxidant and antimicrobial compounds, while sea buckthorn oil adds further fatty acid and bioactive content, together creating a multi-functional preservation system. For the food industry, this matters because extending the shelf life of fresh fish without synthetic preservatives is a significant commercial and food safety challenge. This research demonstrates that plant-oil-enriched biopolymer nanoemulsions can measurably slow spoilage in cold-stored fish fillets, offering a potential natural alternative to conventional chemical preservatives.