Influence of citric acid on the extraction level of manganese in green and black tea infusions

Abstract

Manganese concentration in green and black tea (10 samples of each type) was determined by means of graphite-furnace atomic absorption spectrometry. Both the dry leaves and the infusions were analysed. The concentration of manganese in dry leaves was in the range of 502–1277 mg · kg−1 for black tea and 798–1906 mg · kg−1 for green one. Since lemon juice is commonly added for tea to enrich its taste, citric acid was used to simulate lemon juice influence on manganese concentration in the infusions. The infusions prepared with and without citric acid addition were analysed and the results showed significant influence of citric acid on manganese leaching. The average extraction levels of manganese from black tea equal 16% (for non-acidified infusions) and 34% (for acidified ones) while these values for green tea equal 13% and 38%, respectively. Statistical evaluation of the results showed that the differences between acidified and non-acidified infusions were statistically significant. High manganese content makes the tea an important source of manganese in human diet.