[Amounts of selected minerals in green and black teas]

Abstract

The paper contains the results of 19 minerals (Ca, K, P, Na, Mg, Zn, Fe, Mn, Cu, F, Ni, Co, Cr, Li, Sr, Al, Cd, Hg, Pb) determined in green and black species of market teas. The examined minerals (except phosphorus, fluoride and mercury) were determined by ASA-method using air-acetylene flame (aluminium was determined in the nitrous oxide-acetylene flame). Mercury was determined by cold vapour method. The phosphorus and fluoride was determined by spectrophotometry methods (phosphorus in the form of phosphomolybdate blue and fluoride by use microdiffusion procedure where alizarin-fluoride complex was formed). It has been found that the examined teas are important source of potassium and low source of sodium, assuming a daily intake of 4 glasses of tea infusions. Tea drinking may be advantageous for hypertensive persons. The investigated teas are also important source of other examined minerals especially some microelements. The intake of the toxic metals with tea (Cd, Hg, Pb, Al) is low, from a centesimal to a few percent of the PTWI dose accepted by the FAO/WHO Experts. This paper presents also the first findings of the lithium and stronthium contents of examined tea species--whose physiological role still remains unknown.