Curie-point pyrolysis–gas chromatography–mass spectroscopic analysis of theabrownins from fermented Zijuan tea

Abstract

Zijuan tea theabrownins (ZTTBs) was extracted from a type of fermented Zijuan tea and separated into fractions according to molecular weight. The extract was found to contain predominantly two fractions: <3.5kDa and >100kDa. These two fractions were analyzed for chemical composition, structural characteristics by Curie-point pyrolysis–gas chromatography–mass spectroscopy (CP-Py–GC/MS). The affects of pyrolysis temperature on pyrolytic products were also investigated. The fraction >100kDa produced 50 GC/MS peaks during pyrolysis at 280°C, 70 peaks at 386°C, and 134 peaks at 485°C. Fourteen of the products formed at 280°C, 12 of those formed at 386°C, and 21 of those formed at 485°C were identified with match qualities of greater than 80%. The fraction <3.5kDa gave 51 peaks during pyrolysis at 280°C, 99 peaks at 386°C, and 257 peaks at 485°C. Six products formed at 280°C, four products formed at 386°C, and 61 products formed at 485°C were identified with match qualities of greater than 80%. Pyrolysis temperatures of 485°C and 386°C were found suitable for the two fractions respectively. CP-Py–GC/MS revealed that, the fraction >100kDa mainly consisted of phenolic pigments, esters, proteins, and polysaccharides, while the fraction <3.5kDa contained no polysaccharide. CP-Py–GC/MS is an effective tool for the composition difference and structural characteristics of ZTTBs as well as other complex macromolecular plant pigments.