Seawater-dissolved oligochitosan coating and basket-in-bag packaging extend the chilled shelf-life of slender shrimp ( Metapenaeus brevicornis ) during 13-day storage at 4 ± 1 °C

Chilled shrimp deteriorate rapidly because post-mortem biochemical spoilage, oxidative deterioration and microbial growth continue during refrigeration; however, practical set-points that integrate oligochitosan (COS) coating solvent and packaging geometry remain insufficiently defined. This study aimed to establish an implementable COS-based preservation strategy for chilled slender shrimp ( Metapenaeus brevicornis ). Shrimp were stored at 4 ± 1 °C and evaluated in three experimental branches: (a) COS concentration screening (0.75–1.50%, w/v; 3-min dip in reverse-osmosis water), (b) solvent comparison at 1.0% COS (reverse-osmosis water vs. seawater) and (c) packaging comparison at 1.0% COS in seawater (sealed polyethylene bag vs. basket-in-bag), with untreated or water-dipped controls as appropriate. Independent batches ( n  = 3 per treatment) were analysed for ammonia (NH ₃ ), pH, total antioxidant activity (TAA), total plate count (TPC) and weighted sensory score using linear mixed-effects models ( α  = 0.05). The 1.0% COS treatment was the most robust concentration over 13 days, and seawater improved performance compared with reverse-osmosis water. In the day-13 packaging comparison, COS–basket-in-bag had lower NH ₃ than COS–polyethylene (PE) bag (0.169 ± 0.01% vs. 0.189 ± 0.03% w/w), although it was statistically comparable to the untreated control (0.153 ± 0.02%). COS–basket-in-bag also produced the lowest TPC (approximately 1.7 × 10 ⁴  CFU g ⁻¹ , vs. 4.3 × 10 ⁵ and 2.8 × 10 ⁶  CFU g ⁻¹ for COS–PE bag and control, respectively), the highest TAA (2.582 ± 0.21 mg ascorbic acid equivalents (AAE) g ⁻¹ , vs. 2.205 ± 0.17 and 2.034 ± 0.15 mg AAE g ⁻¹ ) and the highest sensory score (16.1 ± 1.78, vs. 15.16 ± 1.43 and 11.6 ± 1.24). These findings define a practical set-point, 1.0% COS in seawater, 3-min dipping, basket-in-bag packaging and storage at 4 ± 1 °C, that supports an approximately 12-day refrigerated shelf-life and demonstrates how coating dose, solvent and packaging geometry can be integrated to improve the microbial, antioxidant and sensory stability of chilled shrimp.