## 3 Results and Discussion
### Total Amino Acids in Tea  
Figure 3 presents the total content of amino acids (AAs) and essential amino acids (essential AAs) in the sample infusions of green and black tea. Figure 4 presents the impact of a permanent or variable magnetic field on the total content of amino acids (AAs) and essential amino acids (essential AAs) in the sample infusions of green and black tea. When comparing the content of all amino acids in the black and green teas studied, it was found that the tea with the highest content of amino acids was Gyokuro Japanese green tea, in the infusions of which the presence of essential amino acids was observed at a level of 141 mg L\({}^{-1}\) on average, which constitutes 22% of the total content of essential amino acids in infusions made with this type of tea. In the case of black tea, the highest content of free amino acids was observed in the case of Darjeeling--431.66 mg L\({}^{-1}\) on average, which was 45% less than in Gyokuro green tea. The difference  
Figure 4: Impact of a permanent or variable magnetic field on the total content of amino acids (AAs) and essential amino acids (essential AAs) in the tea infusion samples (mg L\({}^{-1}\)). PMF: permanent magnetic field; VMF: variable magnetic field. Figure 3: Total content of amino acids (AAs) and essential amino acids (essential AAs) in the tea infusion samples (mg L\({}^{-1}\)). as far as essential amino acids are concerned was 60% for green tea. The total content of amino acids in other types of green tea was similar to the other two types of black tea. A variable magnetic field applied in order to assist extraction caused an increase in the total concentration of amino acids in green tea infusions by 8.5%, while the content of essential amino acids increased by 17% on average. In the case of black tea infusions, extraction using a variable magnetic field increased the content of amino acids by 4.7% on average, and the content of essential amino acids by 12.6%. It is known that green tea leaves do not undergo fermentation, therefore their chemical composition can vary significantly from the composition of black tea. After the initial evaporation of water, withered leaves are subject to the process of delicate rolling, and then additional drying, sorting and packing. As a result, green tea has a similar chemical composition to fresh tea leaves and it preserves more valuable ingredients than black tea, and infusions have a delicate, slightly spicy taste and fresh spicy or flowery aroma [29]. In studies conducted by [PERSON] et al. [30], it was indicated that significant biochemical changes took place during the initial loss of water and rolling, and they may significantly affect the quality of manufactured tea. It was observed that tea leaves lost their moisture most intensely during the first hours after commencing the process of withering; also, the largest differences in the content of selected chemical components were observed then. Moisture content plays an essential role in maintaining the microbiological stability of dried tea. A high moisture content favours the development of microorganisms, and thus the tea shelf life is reduced. The content of ash is also an indicator of tea quality and depends on numerous factors, including the manner of processing, storage, and interaction of leaves. A high ash content in tea may indicate falsification or unhygienic conditions during withering and rolling of leaves, and the use of worse quality raw materials. It may also indicate high amounts of micro- and trace elements which can increase the quality of tea; therefore, it is also necessary to examine the content of individual mineral components in tea leaves. The ash content of tea is a very valuable feature of its quality [30].