Extraction kinetics of tea aroma compounds as a function brewing temperature, leaf size and water hardness

Changes in the headspace volatile profile of tea infusion during brewing were determined by analysing the aliquots taken every 30 s using proton transfer reaction time-of-flight mass spectrometry in conjunction with principal component analysis and hierarchical cluster analysis. The effect of three different brewing temperatures (60, 70 and 80°C), two leaf sizes (broken and full leaves) and two water mineralizations (soft and hard), on the concentration of volatile compounds in the headspace of tea, was studied as a function of infusion time. An increase in brewing temperature resulted in increased volatile content in the headspace, reflecting an increase in extraction efficiency. Such differences on extraction efficiency were more pronounced with increasing brewing times. Leaf size had also a big impact on the extraction of volatile compounds, but mainly during the early phase of brewing. Water mineralization had a low but noticeable impact on the volatile content. Furthermore, clusters of samples prepared with different combinations of brewing parameters but resulting in analogous volatile profiles could be identified using hierarchical clustering analysis.