Investigation of mycoflora on dagaa (Rastrineobola argentea) as affected by washing and drying methods

Abstract

Objective: To determine the fungal characteristics and asses possible aflatoxin contamination during field sundrying and marketing stages of sun-dried dagaa (Rastrineobola argentea) (a small pelagic fish found in Lake Victoria) and to investigate the effect of selected pre-washing treatments and drying temperatures on the mycoflora characteristics of dagaa. Methodology and results: Mould, yeast and aflatoxins analyses were carried out on dagaa that had been sampled from the sun-drying and market stages. Analyses were also done on dagaa that had been oven-dried at 30, 40 and 50oC after pre-washing with salted (3% NaCl), chlorinated (100ppm) solutions and potable tap water (control). The mean mould counts in the sun-dried dagaa from market were 3.63 log cfu/g. No aflatoxins were detected. The mould counts were below 1 log cfu/g in all the pre-wash treatments dried at 30, 40 and 50oC. At 40oC, the dagaa washed with salted water and chlorinated water had significantly less (p<0.05) yeast counts than those washed using potable tap water at 1.35 log cfu/g , 1.38 log cfu/g and 1.48 cfu/g respectively. Conclusion and application of findings: This study demonstrates the importance of proper processing and handling of fish in order to safeguard public health. The study established that field sun-drying predisposes dagaa to contamination by mycotoxic flora. The low counts of mould growth in the oven-dried dagaa when compared to the open field sun-dried dagaa is attributed to enhanced hygiene due to the incorporated washing steps and during drying and storage.The lowest yeast and mould counts were obtained in the dagaa subjected to salted (3% NaCl) pre-wash and subsequently dried at 50oC for 15hrs. This process can be achieved at the local community level through use of solar driers or improved kiln ovens whereas common salt is accessible to the households involved in fish processing. The findings of this study will increase the knowledge base towards adoption of improved handling and drying methods hence minimize mould growth and possible aflatoxin contamination in the dried dagaa sub-sector.