Effects of Handling Methods on Quality Changes of Giant Freshwater Prawns (Macrobrachium rosenbergii)

Abstract

Prawns (Macrobrachium rosenbergii) were subjected to conditions, which simulated domestic and export handling practices. Prawns were mixed with crushed ice to maintain the prawn samples temperature at 0°C and were stored at room temperature (25 ±2°C) for 48 hr for the domestic handling trial, while for export handling, the samples were kept in a cold room at (0 ±1°C) for 72 hr. Both processes showed sensory, chemical and instrumental changes but the magnitude of the changes for domestic handling was greater than for those of the export trial. Maximum load (firmness), energy to the breaking point (chewiness) and percent of cooking loss increased as storage time increased up to 12 hr, after which prolonged storage resulted in a decrease in these parameters in the cooked samples. Expressible juice decreased during the first 12 hr, later increased gradually. Other chemical parameters such as the soluble-insoluble collagen ratio, proteolysis index (PI) and total volatile nitrogen (TVN) of cooked prawn increased with the increase in storage time. Good correlations among instrumental, chemical and sensory evaluation results were obtained for texture and taste-odor attributes of samples from both of the handling trials. Blanching and deheading of the prawns were found to maintain qualities very well, while samples, which underwent proper handling procedures, exhibited some quality changes after 48 hr.

Key Words:

• Prawns
• Macrobrachium rosenbergii
• firmness
• mushiness