Effects of selected washing treatments and drying temperatures on biochemical and microbiological quality of dagaa (Rastrineobola argentea).

Abstract

Dagaa (Rastrineobola argentea) is one of the most important fish foods for the lowincome households in the Nyanza Province, Kenya. However, the off-flavour and offodour that results from the traditional sun-drying process of sun-dried dagaa is a major disincentive to the use of the fish for human consumption, hence leading to utilization in animal feed. Chemical analyses for pH, Thiobarbituric reactive substances (TBARS), Total volatile bases-nitrogen (TVBN) and aerobic bacterial counts were carried out on dagaa sampled from various process steps within the open field sun-drying and market conditions. Dagaa was also oven-dried at 30 o C, 40 o C and 50 o C after washing with selected solutions namely salted (3% sodium chloride), chlorinated solutions (100ppm) and potable tap water (control). Results indicated that TBARS values increased significantly (p<0.05) from 1.39 mgMA/kg in fresh fish to 10.55 mgMA/kg in the market samples. The TVBN values increased significantly (p<0.05) from 9.42 mgMA/kg in fresh fish to 29.51 mg/ 100g in the market samples. The pH values declined significantly (p<0.05) from pH 6.72 in the fresh fish to pH 5.88 in the market samples .Lipid oxidation (TBARS) was significantly (p<0.05) higher in dagaa subjected to salted-wash treatments when compared to the chlorinated and control-wash treatments. The rate of lipid oxidation was significantly (p<0.05) higher at elevated temperatures of 50 o C relative to 30 o C and 40 o C conditions. The TVBN levels observed in the salted and chlorinated-wash treatments showed significantly (p<0.05) lower TVBN values when compared with the control-wash treatments. However, the values of TVBN obtained at 30 o C were significantly (p<0.05) higher when compared with the 40 o C and 50 o C drying temperature conditions. The salted-wash treatments resulted in lower pH values relative to the chlorinated and control-wash treatments on drying at 30 o C and 40 o C. In this study, the most appropriate treatment that showed the least TVBN and moderate TBARS values was drying the dagaa at 50 o C after washing with chlorinated solution.

Effect of Different Drying Methods on the Quality Characteristics of Pangasius hypophthalmus

“…Addition of salt to fish decreases the pH of fish due to increase in acidic compounds (Farid et al, 2014). The reduction in the pH of the salt washed dagaa fish was due to the leaching of the salt soluble proteins (Owaga et al, 2009).…”

Effect of clove extract pretreatment and drying conditions on lipid oxidation and sensory discrimination of dried omena (Rastrineobola argentea) fish

“…TBARS results are recognised to be directly related to change in flavour, colour, odour, mouth texture and nutrition benefits in fish or meat products (Owaga et al, 2009a). Sample A0, the original drying conditions, was used as the control.…”

A Prevalence Study of Histamine and Histamine Producing Bacteria in Two Commercial Tropical Marine Fish Sold in Trinidad, West Indies

“…All samples exceeded the minimum recommended acceptable limit (m=5x10 5 CFU/g) for good quality seafood. However, all counts were within the maximum recommended limits for marginally acceptable quality (M=10 7 ) [22].…”