Post-harvest quality loss in giant freshwater prawns: effects of storage conditions and duration

Abstract

The GFP (M. rosenbergii) is a commercially valuable species in Sri Lanka; however, post harvest quality deterioration presents a significant challenge. This study aimed to assess post-harvest losses, identify critical control points and evaluate storage methods to enhance the quality of GFP products. A structured questionnaire survey was conducted among 286 stakeholders in the GFP market chain, supplemented by focus group discussions and verification of export data. Freshly harvested GFP samples were subjected to various storage conditions: chilled (ice storage), frozen at -20 °C, and blast-frozen at -35 °C for 21 days, with periodic assessments of colour, texture and sensory attributes. Instrumental analyses included CIELAB colour measurements, total colour change (ΔE), texture profiling, and sensory evaluation by trained panelists. Results indicated substantial post-harvest losses, with an average of 31.9% lost before reaching the exporter, primarily due to physical damage. Additionally, predation and soft-shell occurrences at the fisher level contributed to both harvest and quality losses. Colour, texture and sensory assessments demonstrated that ice storage effectively preserved GFP quality for up to 9 days, outperforming frozen GFP, which exhibited significant deterioration before this period. In contrast, both freezing and blast-freezing initially induced rapid colour changes that later stabilised, with no significant differences between these 2 methods. Texture parameters varied among storage conditions, with both freezing and blast-freezing effectively maintaining sensory attributes over prolonged storage. However, while blast-freezing preserved product quality for an extended period, it did not retain the original organoleptic characteristics as effectively as ice storage during the initial 9 days. Based on these findings, ice storage is recommended for short-term market distribution, whereas blast-freezing remains the preferred method for long-term storage, particularly for the export market.