Hydrogen sulphide producing bacteria as indicators of spoilage of freshwater rohu (Labeo rohita) fish

Rohu fish procured in fresh condition were stored aerobically at ambient temperature (28-34 degrees C) and analysed immediately (0 h) and after 2, 4, 6 8 and 24 h. The H,S producing bacteria (H2SPB) count was 2.45 too cfu/g in fresh fish and remained almost unchanged during the first 2 h of storage (2.49 log cfu/g) and thereafter showed a rapid increase reaching 4.40 log cfu/g after 8 h and 6.10 log cfu/g after 24 h of storage. During storage between 4 and 8 h which can be considered as the intermediate stage of spoilage of rohu, the H2SPB counts showed a sharp increase from 3.1 (4 h) to 4.4 (8 h) log cfu/g. H2SPB count of more than 3 log cfu/g appears to be the separating line between freshness (0 to 2 h) and loss of freshness (>4 h) in rohu. H2SPB were present in the mucus of rohu and their levels increased during storage. H2SPB appears to be a suitable indicator to detect spoilage in rohu and the use of skin mucus as a non-invasive sample to assess freshness quality appears promising.