Journal
MOLECULES
Volume 27, Issue 17, Pages -Publisher
MDPI
DOI: 10.3390/molecules27175679
Keywords
artificial oil bodies; astringency; caleosin; catechins; histatin 3
Funding
- Ministry of Science and Technology, Taiwan, ROC [MOST 111-2321-B-005-006]
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The type of tea catechins and brewing time have an impact on tea astringency. Gallate-type catechins are more astringent, and longer brewing time increases tea astringency. Catechins and flavonol glycosides induce rough and smooth astringency sensation in tea, respectively.
Artificial oil bodies covered by a recombinant surface protein, caleosin fused with histatin 3 (a major human salivary peptide), were employed to explore the relative astringency of eight tea catechins. The results showed that gallate-type catechins were more astringent than non-gallate-type catechins, with an astringency order of epicatechin gallate > epigallocatechin gallate > gallocatechin gallate > catechin gallate > epigallocatechin > epicatechin > gallocatechin > catechin. As expected, the extension of brewing time led to an increase in catechin content in the tea infusion, thus elevating tea astringency. Detailed analysis showed that the enhanced proportion of gallate-type catechins was significantly higher than that of non-gallate-type catechins, indicating that tea astringency was elevated exponentially, rather than proportionally, when brewing time was extended. Rough surfaces were observed on artificial oil bodies when they were complexed with epigallocatechin gallate (a catechin), while a smooth surface was observed on those complexed with rutin (a flavonol glycoside) under an atomic force microscope and a scanning electron microscope. The results indicate that catechins and flavonol glycosides induce the sensation of rough (puckering) and smooth (velvety) astringency in tea, respectively.
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