Assessment of the Levels of Micronutrients in Black Tea from Different Regions Of East Africa and Changes In their Levels Due to Agronomic Practices

Abstract

Inadequate supply of micronutrients causes human h~ealth complications and is a worldwide problem now referred to as hidden hunger. Beverages from Camellia sinensis are claimed to be the most widely consumed fluids after water. However it is not known if they contain adequate ,Ie.vels of micronutrients to alleviate hidden hunger problems. The levels of micronutrients in East African teas are unknown and factors controlling their absorption from the soil remain obscure. The objective of this study was to assess levels of micronutrients in East African teas, • 0::..local market teas and their infusions, establish if their levels vary with nitrogen fertilizer rates and plucking intervals and determine if there are variations in micronutrient level in the black tea of tea clones planted in various geographic locations. The micronutrients Mn, Fe, Zn, Cu and Se levels from 42 factories in East Africa and effects of grading on the micronutrients levels in four tea grades were assessed in 'acomplete1y randomized design and two factor completely randomized design respectively. The effects of nitrogenous fertilizer and plucking intervals on micronutrient content of clone 6/8 planted in' Timbilil, Sotik Highlands and Changoi were assessed in a three factor randomized complete block design. The levels of these minerals were also assessed in black tea of different clones planted in Kangaita, Kipkebe and Timbilil in a factorial two design randomized in a complete block design replicated three times under similar agronomic practices. The black tea samples were ashed, acid digested and extracted for analysis using the AAS. Mn levels were highest while Se levels were lowest. Mean levels of other micronutrients were in the order Fe>Zn>Cu. Large particle size grades had more (p:SO.05) micronutrients. Teas from the local market had higher levels of micronutrients than exported teas and the levels varied significantly (p:S0.05) among the grades. About 41% and 82% Mn and Cu was extracted in hot water infusion respectively while Fe extracted was only 17%. A cup of tea from 2.0g tea can contribute 57%, 1.03%, 0.65%, 2.0% and 2.85% of Mn, Fe, Zn, Cu and Se respectively of daily minimum requirement. Thus consumption of more than two cups of tea per day can supply daily requirements of Mn. However adequate daily supply of other micronutrients must be supplied by other foods. All the micronutrients significantly (p:S0.05) varied with location of production. Mn and Se levels were not significantly (p:S0.05) affected by increasing rates of nitrogenous fertilizer, Fe and Zn significantly (p:S0.05) increased while Cu levels significantly (p:S0.05) reduced. Plucking intervals did not significantly (p:SO.05) affect the micronutrient content of the resultant black teas. Different clones showed varied (p:SO.OS) micronutrient content when planted in a single location under similar agronomic practices and did not follow a similar pattern when the clones were planted in different locations. To increase micronutrient levels in tea, it is necessary to optimize nitrogen fertilizer rates and use suitable clones for different geographic locations.