Effect of ajwain (Trachyspermum ammi) extract and gamma irradiation on the shelf-life extension of rohu (Labeo rohita) and seer (Scomberomorus guttatus) fish steaks during chilled storage

Fishes are highly perishable, mainly stored and transported under frozen condition; however, they are mainly preferred as fresh or in chilled form for consumption because frozen storage compromises the texture quality and other sensory attributes. Shelf-life enhancement of rohu and seer fish steaks was studied using combination of ajwain extract (various concentrations) and γ-irradiation (various doses) under chilled storage (4 °C). These were analyzed periodically by microbiological, sensory, color and biochemical analyses during storage. Gas chromatography - mass spectrometry (GC-MS) analysis showed thymol as major component. High performance liquid chromatography (HPLC) analysis showed the presence of nine phenolic compounds including thymol in ajwain extract. The best result was achieved when samples were dipped in 10 % ajwain extract with 2 kGy gamma irradiation dose. An extended shelf-life of 5 and 10 days in case of rohu and seer fish steaks were attained respectively using this combination. These results were confirmed by microbial, biochemical and sensory analyses. The present study thus promises potential application of the above protocol in fishery industry for good quality of fish and commercial benefits.