Assessment of the levels of some toxic and Anti nutritional substances in Kenyan coffee pulp
Kiptoo, Kipkore Jackson
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Every year, the Kenyan coffee industry produces over 350,000 tons of clean coffee and similar quantities of associated by-products (coffee pulp and coffee husks). These by-products are often damped into nearby streams causing serious pollution problems. Solution to this problem calls for the evaluation of available alternative uses for the byproducts and safer disposal methods. This work explored the possibility of using Kenyan coffee pulp as animal feed. Levels of some toxic and antinutritional substances in coffee pulp samples collected from fifteen coffee processing factories located in Thika and Kiambu districts were determined. The levels of caffeine, total tannins and potassium were in the range 0.22-0.70, 1.31- 1.56 and 0.9-4.21 %w/w on dry mass basis respectively. Levels of Cu, Zn, Mn and Fe were in the range between 4.90-213.30, 11.23-28.03,3.49-119.29 and 12.53-452.8J..lg/g respectively. Among the pesticides, only chlorothalonil was detected in most samples at appreciable amounts (0.02-1245J..lg/g).After ensiling for a period of four (4) months, the mean percentage losses ranged 30-45.59% for caffeine, 5.56-42.50% for total tannins and 77.28-100% for the pesticide residues. From these figures, it is recognized that ensiling is a significant detoxification method. The distribution of caffeine and tannins seemed to depend on the prevailing environmental conditions. Coffee pulp from well managed farms had higher levels of caffeine while higher levels of tannins were reported in coffee pulp from agro-ecological zones that are more exposed to fungal diseases or insect pests. Coffee pulp from the same agro-ecological zone were close in their K, Zn, Mn and Fe contents, implying that soil characteristics plays an important role in the accumulation of these metals in the pulp. The distribution of copper was rather erratic. Copper sprays as well as spray programmes contribute greatly to the amount of copper in the pulp. The results of this study show that coffee pulp is contaminated with toxic and antinutritional substances. However, the levels of caffeine, tannins and the pesticide residues were reduced significantly upon ensiling, though not completely. The levels of the metals reported in this work are within the levels acceptable to most animals and cannot be considered a major setback in the prospect of converting coffee pulp to animal feed. Although the levels of pesticide residues reported in the fresh pulp are within the levels considered toxic to most animals, ensiling reduced the levels to those below the maximum residues levels (MRL's) in or on animal feeds and feedstuffs as recommended by FAOIWHO (1998). Therefore it appears that coffee pulp can at best be initially used at well-rationed supplemental levels with other forages or feed components as more effective methods of detoxification are explored.