Udjel polifenola i antioksidacijska svojstva vodenih i etanolnih ekstrakata Yinzhien čaja

master's thesis

• Title (english): Total polifenol content and antioxidant properties of aqueous and ethanol extracts of Yinzhien tea
• Author: Tea Mihelj
• Mentor: Draženka Komes (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Food Engineering); (Laboratory for Chemistry and Technology of Carbohydrates and Confectionery Products); Zagreb
• Defense date and country: 2009-06-04, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Food Technology

Abstract

Čaj je jedan od popularnijih napitaka koji se konzumira u svijetu. Pozitivni učinci čaja na zdravlje vezani su uz polifenolne spojeve koji pokazuju veliku antioksidacijsku aktivnost, te antimutageni, antikancerogeni, antialergijski učinak. U ovom radu spektrofotometrijski su praćene promjene udjela ukupnih fenola i flavonoida te antioksidacijska aktivnost prvog, drugog i trećeg ekstrakta žutog čaja u rinfuzi, kuglici te filter vrećici, kao i tijekom jednodnevnog stajanja prvog ekstrakta na sobnoj temperaturi. Čajevi u rinfuzi, kuglici te filter vrećici ekstrahirani su klasičnom ekstrakcijom vodom i otopinama etanola različitih koncentracija (10%, 25%, 50%, 75%, 100%). Ispitan je i utjecaj ultrazvuka na ekstrakciju polifenola i antioksidacijsku aktivnost čaja u rinfuzi. Antioksidacijska aktivnost određena je primjenom tri metode: DPPH (reakcija s 1, 1- difenil- 2- pikrilhidrazil), ABTS (reakcija s 2, 2'- azinobis(3- etilbenzotiazolin- 6- sulfonska kiselinom)), te FRAP (reakcija sa željezo(III)-tripiridiltriazinom) metodom. Najveći udio fenola određen je u čaju u kuglici ekstrahiranom 75%- tnim etanolom, a najmanji u čaju u filter vrećici ekstrahiranom 100%- tnim etanolom. Najveća antioksidacijska aktivnost je dobivena u 75%- tnom etanolnom ekstraktu čaja u filter vrećici, a najmanja u 100%- tnim etanolnim ekstraktima. Određeni su visoki koeficijenti korelacije između udjela ukupnih fenola i flavonoida te udjela ukupnih fenola i antioksidacijske aktivnosti.

Abstract (english)

Tea is one of the most popular beverages consumed worldwide. Polyphenols in tea contribute its health benefits possessing great antioxidant, as well as antimutagenic, antitcarcinogenic and antiallergic activity. Total polyphenol, flavonoid content and antioxidant activity were determined spectrophotometrically for tea in loose leaf form, filter bag and tea ball after particular time (hours) and multiple extractions. Furthermore, tea in loose leaf form prepared by ultrasound extraction was also analyzed. DPPH (reduction of (1, 1-diphenyl-2-picrylhydrazyl), ABTS (reaction of 2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) and FRAP (reaction with iron(III)tripyridyiltriazine) assay were applied in order to determine antioxidant activity of tea. Ethanol extract (75%) of tea in tea ball has shown the highest phenol content, and tea in filter bag extracted by absolute ethanol has shown the lowest phenol content. The highest antioxidant activity has shown ethanol extract (75%) of tea in filter bag, but the lowest activity has been determined in teas extracted by absolute ethanol. Statistical linear correlation was confirmed between total phenol and flavonoid content, as well as between total phenol content and antioxidant activity.

• Keywords: antioksidacijska aktivnost; Camellia sinensis; polifenoli; flavonoidi; žuti čaj
• Keywords (english): antioxidant activity; Camellia sinensis; phenols; flavonoids; yellow tea
• Language: croatian
• URN:NBN: urn:nbn:hr:159:096465
• Study programme: Title: Food Technology; specializations in: Food Engineering; Course: Food Engineering; Study programme type: university; Study level: graduate; Academic / professional title: diplomirani inženjer prehrambene tehnologije; smjer prehrambeno inženjerstvo (diplomirani inženjer prehrambene tehnologije; smjer prehrambeno inženjerstvo)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2017-08-31 07:33:46