## 3 Results and Discussion
### Total Amino Acids in Tea
As indicated by many study authors, the manner of processing tea leaves after collecting them has a significant effect in determining the content of free amino acids, and they are considered to be important criteria to ensure tea quality due to their impact on taste, smell, and colour as well as the physiological action of infusions [31]. It has also been proven that theanine, an analogue derivative of glutamic acid, reduces mental and physical stress, and improves mood, concentration, and cognitive functions in a similar manner to caffeine [32]. In the studies conducted by [PERSON] et al. [30], an increased amount of amino acids in tea samples subjected to the process of rolling which have lost some of the moisture and elasticity was observed in comparison to freshly harvested tea leaves. According to [PERSON] et al. [31], this fact may be caused by the degradation of proteins into amino acids through peptidase as well as the conversion of sugars into amino acids during the process of withering; this process is positively correlated with temperature until the cells in the plant tissue are deactivated. In their experiments, [PERSON] et al. [30] indicated that the total content of free amino acids in tea infusions prepared from samples of fresh tea leaves started from 1.5% and after 23 h of withering increased nearly two-fold. In the next hour of withering, a decrease in the content of free amino acids was observed to the level of approx. 2.5%, which according to the authors is an indicator of the quality and degree of tea processing. Based on a review of research, it can be stated that the concentration of free amino acids both in dried tea and in tea infusions is an extremely important parameter defining their quality. Information can be found in the literature confirming that during the processing of tea leaves a partial conversion of amino acids such as isoleucine, leucine, valine, and phenylalanine to aldehydes takes place, which are responsible for the components of the tea aroma. According to the authors of this kind of research, such a conversion takes place much more frequently in fermented black tea which was subjected to much more extensive high temperature treatment during the drying process than green tea which resulted in the differences in the content of free amino acids in dried green and black tea [33]. In the studies conducted by [PERSON] et al. [34] it was proven that the decaffeination process can reduce the content of free amino acids in tea by more than 20%. Moreover, the authors indicated that the brewing time and temperature of water impacts the content of free amino acids in tea infusions. According to the authors, during tea brewing, most amino acids are extracted during the first two minutes, and theanine is the dominating amino acid--its content was approx. 30% of the total content of free amino acids in the green and black tea infusions studied. They also indicated that as a result of brewing black tea at a permanent 85 \({}^{\circ}\)C placed in the thermostat for 15 min, the total content of free amino acids was 311 mg L\({}^{-1}\) while in infusions of the same tea poured with water at 85 \({}^{\circ}\)C and brewed at room temperature without thermostat, the content of free amino acids was lower by 15% on average than the first case. In the case of green tea infusions, the tendency was similar; however, the total content of amino acids was lower by approx. 10% than in the case of black tea infusions. In the studies conducted by the authors of this work, an inverse dependency was observed. Moreover, a significantly higher concentration of free amino acids was obtained in green tea infusions (564.70 mg L\({}^{-1}\)) than black tea infusions (371.35 mg L\({}^{-1}\)); however, extraction was conducted at 100 \({}^{\circ}\)C, the tea was of high quality and an amino acid analyser with postcolumn derivatization was used for the determination of the amino acids.