International Research Journal of Pure and Applied Chemistry

Fruits form an important part of the human diet as they are rich in fibre and vitamins such as A, B, C, D and K. They can be consumed fresh or whole, in liquid forms such as juices and smoothies/blends, as well as in cooked or baked form. The objective of this study is to assess the physicochemical parameters of locally produced and bottled fruit juices at the Kenya – Uganda border. Three broad categories (five samples in each category) of juice samples were analysed for pH, TDS, electrical conductivity and heavy metals. The physical parameters were measured using a Hanna Instruments combo portable meter, while heavy metals were measured using an inductively coupled plasma mass spectrometer (ICP-MS 7900, Agilent Technologies, USA). For heavy metals, cadmium and copper were below the WHO recommended limits. For iron, all samples recorded concentrations below the WHO limit with the exception of one sachet sample whose concentration was above the WHO limit. Chromium and nickel concentrations were above the WHO recommended levels. The high levels of chromium and nickel point to the use of heavy-metal-contaminated water during the manufacturing process; contamination of juice by equipment during manufacture; heavy-metal-contaminated soil leading to bioaccumulation of heavy metals in fruit tissues as well as the use of metal-based pesticides and herbicides in agriculture. However, this study was designed to measure the levels of heavy metals in fruit juice samples and did not include direct source tracing analysis of the potential contamination sources. The explained sources are therefore treated as possible contamination pathways rather than confirmed causes of the observed heavy metal concentration. The study recommends the use of acid-resistant machinery to avoid corrosion and leaching of heavy metals into juice products during manufacture; treatment of water to remove heavy metals before its use in the juice manufacturing process; and thorough washing of fruits to remove pesticides before blending. All the juice brands demonstrated strong correlations between a few metal pairs. In sachet brands, iron showed a strong correlation with cadmium (r = 0.83) while copper showed a strong correlation with chromium (r = 0.90). All the other metal pairs showed very low and negative correlations. In bottled brands, there was no strong correlation between the metal pairs. Copper and iron registered a moderate correlation (r = 0.66); cadmium and chromium registered the same moderate correlation (r = 0.50) and the same was observed for nickel and copper (r = 0.55). In blended brands, only copper and nickel demonstrated a strong correlation (r = 0.80) whereas all the other metals demonstrated weak and negative correlations. The strong correlation between metal pairs indicates that an increased concentration of one metal leads to a higher concentration of another paired metal, but does not indicate a similar contamination pathway or causal relationship between metal pairs. Some metals demonstrated negative correlations. These included: Chromium and iron (r = – 0.84), cadmium and nickel (r = – 0.69), cadmium and copper (r = – 0.80), copper and iron as well as cadmium and chromium (r = – 0.64 in both cases). This indicates that the higher concentration of one metal tends to cause a lower concentration of the corresponding metal. However, this does not mean that one metal causes the other metal to decrease in concentration. Although strong negative correlations were observed for some metal pairs, the correlations were not statistically significant at p = 0.05.