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

Abstract

Rohu fish procured in fresh condition were stored aerobically at ambient temperature and analysed immediately and after 2, 4, 6, 8 and 24 h. The H2S producing bacteria (H2SPB) count was 2.45 log cfu/g in fresh fish and remained almost unchanged during the first 2 h of storage 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 to 4.4 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 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.