title: Electronic nose and chiral-capillary electrophoresis in evaluation of the quality changes in commercial green tea leaves during a long-term storage.
abstract: Electronic nose and capillary electrophoresis were applied in quality control of green tea samples subjected to long-term storage. Twelve representative green teas were considered, available as an "aged" (tea leaves stored during a long-term period of two years) and/or "not aged" (fresh products) samples. Their infusions were analyzed by an electronic nose, equipped with an array of six metal oxide semiconductor (MOS) sensors to obtain olfactive fingerprints of the volatile compounds in the infusions headspace. Upon training and chemometric analysis of acquired data (linear discriminant analysis), the electronic nose was found to be able in correctly classifying unknown samples as "aged" or "not aged". Concomitantly, the infusion samples were analyzed by Cyclodextrin-modified Micellar Electrokinetic Chromatography (CD-MEKC) for determination of catechins. The analysis of seven most represented catechins and the methylxanthines theobromine and caffeine revealed a general loss of the polyphenols in each of the considered aged samples (up to 45%, w/w). In addition, the applied enantioselective method based on (2-hydroxypropyl)-β-cyclodextrin (HP-βCD) as chiral selector, was exploited for the estimation of (+)-Gallocatechin in the presence of (-)-Gallocatechin; the latter, as the non-native enantiomer, can be associated to the epimerisation of (-)-Epigallocatechin and was assumed as a marker occurring in case of uncorrected storage conditions of tea leaves. Interestingly, it was observed that epimerization did not significantly occur during aging. The application of CD-MEKC and electronic nose allowed for a fast characterization of green teas taking into account that the aroma is a decisive parameter for the acceptance of the product, whereas the catechins content is associated to the biological value.
authors.affiliation: Department of Chemistry "G. Ciamician", Alma Mater Studiorum - University of Bologna, Via Selmi 2, 40126 Bologna, Italy. Electronic address: mara.mirasoli@unibo.it.
authors.forename: Mara
authors.initials: M
authors.lastname: Mirasoli
authors.affiliation: Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, Via Belmeloro 6, 40126 Bologna, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Gotti
authors.affiliation: Advanced Applications in Mechanical Engineering and Materials Technology Interdepartmental Center for Industrial Research, Alma Mater Studiorum, University of Bologna, Bologna, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Di Fusco
authors.affiliation: Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, Via Belmeloro 6, 40126 Bologna, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Leoni
authors.affiliation: Department of Chemistry "G. Ciamician", Alma Mater Studiorum - University of Bologna, Via Selmi 2, 40126 Bologna, Italy.
authors.forename: Carolina
authors.initials: C
authors.lastname: Colliva
authors.affiliation: Department of Chemistry "G. Ciamician", Alma Mater Studiorum - University of Bologna, Via Selmi 2, 40126 Bologna, Italy.
authors.forename: Aldo
authors.initials: A
authors.lastname: Roda
mesh_terms: D002110:Caffeine / Q000737:chemistry; D002138:Calibration; D002392:Catechin / Q000031:analogs & derivatives / Q000737:chemistry; D002845:Chromatography / Q000379:methods; D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods; D003505:Cyclodextrins / Q000737:chemistry; D062609:Electronic Nose; D019075:Electrophoresis, Capillary / Q000379:methods*; D005504:Food Analysis / Q000379:methods*; D008670:Metals / Q000737:chemistry; D009812:Odorants; D010087:Oxides / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry; D059808:Polyphenols / Q000737:chemistry; D011786:Quality Control; D012666:Semiconductors; D013237:Stereoisomerism; D013662:Tea; D013805:Theobromine / Q000737:chemistry; D013997:Time Factors; D014970:Xanthines / Q000737:chemistry
chemical_list: D003505:Cyclodextrins; D008670:Metals; D010087:Oxides; D059808:Polyphenols; D013662:Tea; D014970:Xanthines; C008514:methylxanthine; D002110:Caffeine; D002392:Catechin; C057580:gallocatechol; D013805:Theobromine
keywords: Aroma; Capillary electrophoresis; Catechins; Chiral analysis; Electronic nose; Green tea; Long-term storage