Lipid oxidation and organoleptic response during shelf storage of some smoked marine fish in Kenya.

Abstract

Peroxide Value (PV), Thiobarbituric Acid Reactive substances (TBARS), organoleptic properties and shelf life of some smoked marine fish namely Gerres oyena (“Chaa”), Lutjanus argentimaculatus (Red snapper) and Valamugil seheli (Mullet) were studied during storage. Both PV and TBARS for all the fish increased to a peak with storage time then decreased. PV in G. oyena was 10.80±1.07 mEq/kg on day 1 of storage, increased to 18.17±0.39 mEq/kg in day 8, peaked at 21.48±0.44 mEq/kg in day 11 then decreased to 8.50±2.34 mEq/kg on day 28. TBARS increased from 0.39±0.09 mg malondialdehyde/kg when fresh to 0.59±0.09 mg malondialdehyde/kg in day 8 then decreased to 0.07±0.004 mg malondialdehyde/kg on the 19th day of storage. PV in L. argentimaculatus was 61.65±0.09 mEq/kg on the 4th day of storage, increased to 112.86±0.19 mEq/kg on day 6 then decreased to15.17±0.54 mEq/kg on day 11. TBARS in L. argentimaculatus was 0.93±0.36 mg malondialdehyde/kg when fresh, 0.16±0.01 mg malondialdehyde/kg on day 1, 1.87±0.03 mg malondialdehyde/kg on day 8 and 0.06±0.01 mg malondialdehyde/kg on day 23. In Valamugil seheli, the PV was 57.59±0.11 mEq/kg on day 1 of storage, 76.55±0.49 mEq/kg on the 8th day, then it decreased to undetectable levels on the 28th day. The TBARS for fresh fish was 0.83±0.10 mg malondialdehyde/kg. After smoking it was 3.96±0.12 mg malondialdehyde/kg on day 4, 3.74±0.03 mg malondialdehyde/kg on day 8 then0.12± mg malondialdehyde /kg after 19 days of storage. The shelflives of the three fish species were monitored organoleptically during a 15 day storage period on day 1, 5 and 15 with any score of 5 or below out of 9 being the limit for rejection. The fish were stored on laboratory benches in the open at ambient temperatures of 30 0C and humidity of 60%. Organoleptic tests based on various attributes were done to establish consumer preference for the fish. The freshness score for G. oyena was 6.38, V. seheli 7.2 and L. argentimaculatus 7.5 at the end of 15 days storage. There was a significantly better score (p<0.05) in taste, texture and flavour for L.argentimaculatus compared to G. oyena and V. seheli. The overall mean score for all the organoleptic attributes for the 3 fish combined was 6.22. The most preferred attribute was taste with a score of 6.5. The most preferred fish was Lutjanus argentimaculatus followed by Gerres oyena then Valamugil seheli.