Assessment of the Levels of Ochratoxin-A in Coffee Beans from the Coffee Growing Region of Kiambu County, Kenya

Abstract

Coffee is one of the major foreign exchange earners in Kenya. The presence of mycotoxins in the processed coffee is one of the greatest emerging threats to coffee quality. Mycotoxins are toxic, carcinogenic and mutagenic metabolites of certain moulds and are some of the compounds encountered in the food and beverage industry. There are two main classes of mycotoxins found in stored crop produce, namely afflatoxins common in grains, and Ochratoxins being the most predominant in fruits. Of the Ochratoxins, Ochratoxin-A (OTA) is the most predominant and an emerging problem in coffee production over the world. The objective of this study was to assess the levels of OTA in Kenyan coffee. Samples were collected from all the coffee growing areas of Kiambu County, a major source of Kenyan coffee and consisting of areas with varying climatic conditions using a stratified sampling design. OTA in green and roasted coffee was determined using high performance liquid chromatography coupled with fluorescence detector after sample clean up by use of immuno affinity columns. HPLC –FD analysis on standards showed that the method could detect below the acceptable levels of OTA on all considered limits. To test whether, roasting causes significant reduction or increment of OTA t-test and Mann Whitney u-test were used. HPLC analysis indicated non- appreciable levels of OTA in premium coffee types AA and AB while acceptable levels were detected in Mbuni. Test of the efficiency of the method used was carried out by spiking the samples with standard solutions. Spiking of green coffee indicated a recovery level of 79.56%±1.31%, while that of roast coffee gave a recovery level of 50.62%±2.77%. The recovery studies showed that appreciable levels of OTA are xvii lost during extraction and clean up procedures while roasting causes appreciable decline to OTA levels and so is the processing of coffee. TLC analysis could detect up to a minimum of 150 μg/Kg of OTA and it is therefore unreliable in analysis of the low limits of OTA allowed in coffee. The result of this study provide baseline data as to the levels of OTA contamination in the Kenyan coffee industry and suggests possible control measures.