Changes in the physical appearance of farmed Litopenaeus vannamei during iced storage: Correlation with biochemical and microbiological parameters

Abstract

Litopenaeus vannamei is the most widely farmed shrimp species in India that is processed for export. Post harvest, L. vannamei shrimp are transported from shrimp farms to processing plants in iced condition; both intrastate and interstate. Judging the quality based on visual inspection offers a simple solution for quality assessment. Farmed L vannamei shrimp were harvested live, immediately iced and stored under iced condition. The physical appearance, microbiological and biochemical changes during iced storage were observed for 20 days. Fresh shrimp had translucent white gills, light orange coloured hepatopancreas, APC of 55,400 cfu/g and TVBN of 16.8 mg per cent. The first noticeable change during iced storage was in the appearance of hepatopancreas of the shrimp; which changed to bright orange colour by the end of 2nd day of iced storage but the microbiological and biochemical parameters were acceptable. However, by the end of 6 days of iced storage the gills of the shrimp started blackening at the posterior end and the hepatopancreas turned to dark orange colour with black margins with relatively higher APC and TVBN values. The appearance of shrimp further deteriorated during iced storage and by the end of 19th day, the gills turned completely black, hepatopancreas appeared dark brown. The results indicate that L. vannamei shrimp with dark orange hepatopancreas with black margins and blackening at the posterior end of the gills is the limit of freshness and hence unacceptable for processing.