MOLECULAR BIOLOGY AND GENOMICS OF FOODBORNE PATHOGENS
Location: Produce Safety and Microbiology Research
Title: Changes in the Composition of Raw Tea Leaves from the Korean Yabukida Plant during High-temperature Processing to Pan-Fried Kamairi-cha Green Tea
Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 19, 2009
Publication Date: July 1, 2009
Citation: Friedman, M., Levin, C.E., Choi, S., Lee, S., Kozukue, N. 2009. Changes in the Composition of Raw Tea Leaves from the Korean Yabukida Plant during High-temperature Processing to Pan-Fried Kamairi-cha Green Tea. Journal of Food Science. 74(5):406-412.
Interpretive Summary: Flavonoid compounds (catechins) found in tea have been linked to numerous health benefits. These include anti-bacterial, anti-bacterial toxin, anti-viral, anti-cancer, anti-cholesterol, and anti-neurodegenerative effects. For example, our studies have shown that tea catechins, tea extracts, and teas inactivated foodborne pathogens in solution and in ground beef. To help enhance the consumption of teas, we participated in a collaborative study with Korean scientists on optimizing the production of so-called pan-fried unfermented tea. This paper describes an alternative processing technique for producing a sweet-tasting green tea, Kamairi-cha, with a high content of health promoting catechins and the amino acid theanine. Because this tea lacks the bitterness and astringency of some commercial green and black teas, we expect the results to stimulate interest among consumers in pan-fried green teas. Antimicrobial activities of this novel tea merit study.
To develop a better understanding of compositional changes occurring during the production of commercial teas, we determined by high-performance liquid chromatography (HPLC) changes in ingredient levels during each of several manufacturing steps used to produce Kamairi-cha, a premium green tea. We used pan-frying instead of the usual blanching technique to inactivate the enzymes responsible for producing traditional black tea. The resulting tea lacks the characteristic bitterness of green tea, producing a green tea that is described as sweet-tasting. The processing steps used to produce this pan-fried tea were as follows: first roasting, first rolling, second roasting, second rolling, first firing, and second firing. The results show that during production at temperatures up to 300 °C, raw leaves lost (in %) 97.3 water, 94.0 two chlorophylls, 14.3 seven catechins, and 2.75 caffeine. A separate analysis showed that the final product contained 21.67 mg/g dry wt of the biologically active amino acid theanine. The results of this first report on changes in individual catechins and other tea ingredients in tea leaves during pan-frying make it possible to select production conditions that maximize levels of beneficial tea ingredients. The possible significance of the results for the human diet is discussed.