title: Application of near-infrared reflectance spectroscopy to the simultaneous prediction of alkaloids and phenolic substances in green tea leaves.
abstract: A near-infrared reflectance spectroscopic (NIRS) method for the prediction of polyphenol and alkaloid compounds in the leaves of green tea [Camellia sinensis (L.) O. Kuntze] was developed. Reference measurements of the individual catechins, gallic acid, caffeine, and theobromine were performed by reversed-phase HPLC. The total polyphenols were determined according to the colorimetric Folin-Ciocalteu assay. Using the partial least-squares algorithm, very good calibration statistics were obtained for the prediction of gallic acid, (-)-epicatechin, (-)-epigallocatechin, (-)-epicatechin gallate, (-)-epigallocatechin gallate, caffeine, and theobromine (R(2) > 0.85) with standard deviation/standard error of cross-validation (SD/SECV) ratio ranging from 2.00 to 6.27. Simultaneously, the dry matter content of the tea leaves can be analyzed very precisely (R(2) = 0.94; SD/SECV = 4.12). Furthermore, it is possible to discriminate tea leaves of different age by principal component analysis on the basis of the received NIR spectra. Prediction of the total polyphenol content is performed with a lower accuracy, which might be due to the lack of specificity in the colorimetric reference method. The study demonstrates that NIRS technology can be successfully applied as a rapid method not only for breeding and cultivation purposes but also to estimate the quality and taste of green tea and to control industrial processes, for example, decaffeination.
authors.affiliation: Institute for Quality Analysis, Federal Research Center for Breeding Research on Cultivated Plants, Neuer Weg 22-23, D-06484 Quedlinburg, Germany. H.Schulz@bafz.de
authors.forename: H
authors.initials: H
authors.lastname: Schulz
authors.forename: U H
authors.initials: UH
authors.lastname: Engelhardt
authors.forename: A
authors.initials: A
authors.lastname: Wegent
authors.forename: H
authors.initials: H
authors.lastname: Drews
authors.forename: S
authors.initials: S
authors.lastname: Lapczynski
mesh_terms: D000470:Alkaloids / Q000032:analysis*; D002110:Caffeine / Q000032:analysis; D002392:Catechin / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D005707:Gallic Acid / Q000032:analysis; D006801:Humans; D010636:Phenols / Q000032:analysis*; D018515:Plant Leaves / Q000737:chemistry; D019265:Spectroscopy, Near-Infrared; D013662:Tea / Q000737:chemistry*; D013805:Theobromine / Q000032:analysis
chemical_list: D000470:Alkaloids; D010636:Phenols; D013662:Tea; D002110:Caffeine; D005707:Gallic Acid; D002392:Catechin; D013805:Theobromine