Assessment of Heavy Metals and Proximate Analysis of Cocoa Beans from Selected Cocoa Growing Areas in Ghana

Abstract

The levels of six selected heavy metals namely: lead (Pb), cadmium (Cd), copper (Cu), manganese (Mn), iron (Fe) and zinc (Zn) have been investigated in cocoa beans sampled from Bekwai, Juaso, Kaspen, Asampaneye and Asamakese, five major cocoa-growing communities in Ghana. Aqua regia digestion procedure was applied for sample digestion and atomic absorption spectroscopy was used for the determination of the metals. The method for the determination of the metals was validated by analyzing standard reference material and levels of metals obtained compared favourably with reported values. Samples were also subjected to proximate analysis by determining moisture, ash, fibre, fat, protein and carbohydrate nutritional compositions of the beans. Method of proximate analysis as reported by Association of analytical chemists (AOAC) was used for estimation of nutritional compositions. Indeed, lead and cadmium concentrations were the lowest in all the samples. The generally high concentrations of Fe, Zn, Cu and Mn in the samples were anticipated as they are regarded essential in living organisms. The mean concentrations expressed in µg/g ranged from 0.013 to 0.042 for Pb, 25.36 to 54.24 for Cd, 36.94 to 58.71 for Zn, 7.12 to 64.65 for Mn and 10.14 to 54.17 for Cu. Proximate analysis of the cocoa beans showed carbohydrate and fat as the nutrients with the dominant composition. Correlation analysis of the metals and nutritional compositions indicated no clear relationship between the levels of the metals and the nutrients.