Anastasiia Shevchuk

• Tea is one of the most important horticultural crops which has been used as a medicinal and refreshing drink for many centuries. Different types of commercial tea are produced from the leaves of the tea plant Camellia sinensis, such as black tea, green, oolong, white, yellow, and Pu-erh. Two varieties are most commonly used, Camellia sinensis var. assamica and Camellia sinensis var. sinensis. In this work, different aspects of tea chemistry have been addressed, such as the influence of processing, origin or plant variety on the polyphenol and low molecular weight carbohydrates (LMWC) profile. Samples representing all six types of tea, have been analyzed using chromatography coupled to mass spectrometry. Application of a high-resolution and tandem mass spectrometry to the tea extracts allowed identification of a large number of analytes. Black tea samples from different origins produced from two varieties of Camellia sinensis using two different methods (CTC and orthodox) have been analyzed by HPLC-ESI-MS to evaluate the effect of processing on black tea composition. Green tea processing was addressed concerning the low molecular weight carbohydrates content. HILIC-ESI-MS was used to access differences in green tea produced in different countries, and using two fixing methods, pan-firing and steaming. Additionally, variation in LMWC in black tea samples of diverse origins was analyzed. Thearubigins (the most abundant black tea polyphenols) were extracted from the CTC produced black tea and subjected to the model degradation under controlled conditions. Theaflavins, theacitrins, and theasinensins were found to degrade at the elevated temperature. Last, tea leaves of the Camellia sinensis plants infected with Xyleborus fornicates were analyzed using HPLC-ESI-MS. Leaves of infected plants were found to contain less amount of catechins compared to the non-infected plants.