Abstract

The level of lead concentration profiles were assessed for maize meal (Posho) commonly known as Ugali cooked in black polyethene bags. The kinetics of degradation of color was employed assuming first-order color degradation to obtain the cook values during thermal treatment of white posho cubes at 25, 70, 80, 90 and 100°C. Posho cubes wrapped in black polyethylene bags were subjected to heat treatments equivalent to the obtained cook values and the samples were analyzed for amount of lead present. Lead ions were found to migrate to posho at all cooking temperatures and the resulting concentrations increased with increase in cooking temperature. Lead ions concentration was extremely low at the control temperature and increased with increase in treatment temperature. The maximum concentration of lead of 0.484 µg/dl was obtained at 80°C. The Lead concentration profiles within the posho cubes were determined by plotting the amount of migrated lead ions at different layers of posho cubes against depth. Lead concentrations were maximum and minimum at the surface and the centroid of the posho cubes respectively. The study revealed that the concentrations of Lead ions that migrated to posho cubes from polyethylene bags were within the stipulated consumer standards since it was just a tenth of the EPA published drinking water standard for lead of 0.05 mg/L (5 µg/dl).

Key words: Polyethylene bags, posho, lead contamination, migration, cook value, temperature, color degradation, reaction kinetics.