Occurrence Levels Of Heavy Metals in Fermented Cocoa Beans and Cocoa Derived Products Produced in Ghana

Abstract

Cocoa is the mainstay of the economy of Ghana as it contributes about 28% of foreign exchange earnings. In recent times, cocoa has come under scrutiny because of high levels of heavy metals which are generally considered toxic. Due to the toxicity of these metals, there have been several agitations to reduce their levels as much as possible in foods; thus the setting up of stringent standards in several countries which in most cases are not supported by any scientific basis. The objective of this study was to assess the levels of heavy metals (Pb, Cd, Hg, As, Cu, Fe, Zn, Mn, Ni and Cr) in cocoa beans and cocoa derived products produced in Ghana and to ascertain their compliance or otherwise with EU No.488/2014 and FAO/WHO standards. Cocoa beans were sampled from Ashanti, Brong Ahafo, Eastern and Western regions while semi-finished and finished products were obtained from a major cocoa processing company in Ghana. The samples were digested using a microwave digester and the metals determined using atomic absorption spectrometry techniques. The levels of Pb in cocoa beans across the regions ranged from 0.01 mg/kg in Western region to 0.084 mg/kg in Brong Ahafo region with a mean of 0.05 mg/kg. There was no significant difference (P>0.05) in the content of Pb across the regions and all samples analyzed were below the 1.0 mg/kg FAO/WHO recommended levels. Cadmium ranged from 0.081– 0.097 mg/kg with Ashanti and Brong Ahafo regions reporting the highest and lowest levels respectively. Cd across the four regions was below the 0.6 mg/kg EU recommended maximum limit for cocoa powder. The levels of mercury and arsenic were below the detection limits of 0.01 mg/kg and 0.03 mg/kg respectively. Copper ranged from 23.937 mg/kg in Western region to 29.139 mg/kg in Ashanti region with a mean of 27.295 mg/kg. The content of Cu in the Western region was significantly lower (P<0.05) than the other regions. None of the samples exceeded the 50 mg/kg EU recommended limits. There was significant difference in Pb and Cd concentrations between the organic and conventional cocoa beans. In assessing the impact of mining on levels of heavy metals in relation to cocoa, mining districts generally reported slightly higher levels than non-mining districts. Amongst the toxic metals, Cd reported the highest levels ranging from 0.057–0.113 mg/kg with levels of Pb between 0.05 mg/kg and 0.044 mg/kg for mining and non-mining districts respectively. There was significant difference (P<0.05) in the levels of Cd between the mining and non- mining districts. The results suggest that mining activities may have influenced the levels of Cd in cocoa beans. However, the levels of Cd were below the recommended maximum limits for specific cocoa products stated in (Eu) No. 488/2014 Mercury was not detected in all the samples except in Bogoso and Goaso which are both mining districts. For cocoa products, cocoa butter reported the least levels of all the metals while cocoa powder reported the highest concentrations of 0.220 mg/kg for Lead. Generally, the levels of heavy metals found in the cocoa beans and cocoa products were all below the recommended maximum limits and are thus considered safe.