2021 Volume 2021 Issue 132 Pages 63-72
Green tea that is processed from new shoots and leaves of Camellia sinensis L. contains many functional and nutritional ingredients and it has been suggested that green tea would be an important source of folate. However, there has been little information about what kind of tea is rich in folate. In this study, we investigated the contents of folate in teas among different conditions of harvestings and processing and also compared them among cultivars. As the ingredients in tea are usually taken from the infusions, the concentrations of folate in tea infusions prepared with various conditions were compared. The first crop of tea had a higher content of folate than the second crop, followed by the third crop. Younger, new shoots contained more folate than mature shoots. Long-term covering cultivation tended to reduce the folate content of new shoots by approximately 20%. Tea folate content was diminished by the oxidization process used to make semi-fermented tea or black tea; green tea was therefore the richest in folate. Tea folate was eluted not only in hot water but also in cold water-even at 0.5 ℃. Roasting of tea leaves had little effect on the folate content of refined tea; on the contrary, it made folate elution easier. Tea folate had relatively high thermal stability as its content was only slightly affected by roasting, whereas those of catechins were significantly reduced. We found differences in folate content among 66 tea cultivars. In addition, the amount of tea folate in new shoots was positively correlated with the amounts of some amino acids and negatively correlated with those of ester-type catechins. In conclusion, the ideal conditions for maximizing tea folate content would be to make green tea from the younger shoots of the first crop of a folate-rich cultivar. Folate is a nutrient that can be retained in cold-water extraction of green tea.
