Turmeric and Ginger Extracts Affects the Proximate Composition, Oxidative Stability, Shelf Life and the Microbial Biota of Smoked <i>Clarias gariepinus</i> Fillets

Abstract

African catfish, Clarias gariepinus of average weight 1.5 kg were filleted and pretreated with extracts of turmeric (TU) and ginger (GI) before hot smoking at 80 °C. The combination levels of TU and GI per treatment were as follows: Treatment 1, T1 (100TU:50GI), T2 (50TU:100GI), T3 (0TU:150GI), T4 (0TU:0GI), and T5 (75TU:75GI). The fillets were immersed into the treatment solution for 20 min and then hot smoked for 36 hours at 80°C. The smoked and dried fillets were stored for 30 days and analyzed for proximate composition, thiobarbituric acid essential substances (TBASR), peroxide value (PV), free fatty acid content, total volatile nitrogen base, and fungal and microbial biota. Protein content increased in the post-treated sample while moisture was reduced and lipid varied with smoking. Thiobarbituric acid reactive substances of the fillets were highest among those subjected to treatment T4, 0.75±0.11mg/100g but lowest for those of T1, 0.38±0.01mg/100g. The free fatty acids of the fillets after treatment, ranged from 1.23±0.07 % oleic acid in fillets treated with T1, to 3.06±0.08% oleic acid in fillet treated with T4. The fillets TVB-N treated with treatment 4 (T4), had the highest 1 TVB-N 19.81±0.04 mg/100g. Fillet treated with T4 had the highest FFA of 3.06±0.08% oleic acid while those treated to T1 had, 1.23±0.07 % oleic acid. Peroxide value was highest for T4, 20.07±0.22 and lowest for those subjected to T1, 10.30±0.03.Treatment 1 was toxic to both bacterial and fungal infestation with no visible growth of Rhizopus spp growth after 3 days of incubation. However, there was high vegetative fungal growth in the T4 experimental group.