Brewing process
TBs were produced by a modified lager-type beer brewing method, with addition of selected teas mentioned above (Supplementary material). The wort was prepared, using commercially available two-rowed malts [mashed by manual grinder (Corona, China) for just striping bran from barleycorn] according to the following mashing programme: 60 min at 52 °C, 60 min at 62 °C, and a further 30 min at 68 °C. The mash was then heated to 76 °C and filtered to yield wort, which was kept boiling for 90 min. Hops were added at the beginning of boiling (two thirds of total dosages) and at 10 min before the end of boiling (one third of total dosages). The teas were added together with the last dosage of hops, for independent test brewing of green tea beer (GTB), oolong tea beer (OTB), and black tea beer (BTB), respectively (Table 1). After cooling, the fermentation was started by adding 15.0 × 106 cells/ml of the lager yeast to each type of wort (12 °P). The primary fermentation was carried out at 10 °C for 5 days. Maturation was held at 12 °C for 3 days and then at 0 °C for 4 weeks. On the other hand, the brewing of non-tea beer (NTB, normal beer without tea) was carried out by a method similar to that mentioned above (Table 1).