Polifenolni sastav i antioksidacijska svojstva komercijalnih voćnih čajeva: utjecaj dodatka askorbinske kiseline i meda

master's thesis

• Title (english): Polyphenolic composition and antioxidant properties of commercial fruit tea infusions
• Author: Nikolina Bukovac
• Mentor: Karin Kovačević Ganić (mentor)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Food Engineering); Zagreb
• Defense date and country: 2008-05-19, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Food Technology

Abstract

Vino, kava, sokovi i čajevi spadaju u svakodnevne namirnice s dokazanim antioksidacijskim svojstvima. Premda su zeleni, crni i bijeli čajevi do sada već bili predmeti raznih istraživanja, malo je pažnje posvećeno voćnim čajevima i njihovom antioksidacijskom potencijalu. Stoga je cilj ovog rada bio odrediti ukupne fenole, fenolni sastav te antioksidacijska aktivnost deset komercijalnih voćnih čajeva prisutnih na tržištu sa i bez dodatka askorbinske kiseline i meda. Koncentracija ukupnih fenola određena je reakcijom s Folin- Ciocalteau reagensom, a antioksidacijska aktivnost reakcijama s željezo(III)-tripiridiltriazin (FRAP), te radikalima 2,2'-azino-bis(3-etilbenzotiazolin-6-sulfonskom kiselinom) (ABTS) i 1,1-difenil-2-pikrilhidrazil (DPPH). Spektrofotometrijski je određen i intenzitet obojenja, ABS450. Rezultati spektrofotometrijskih metoda ukazuju na veliku gradaciju u vrijednostima; tako se po sadržaju ukupnih fenola i antioksidacijskoj aktivnosti najviše ističu čajevi Šipak, i Vanilija i jagoda, dok se najslabijim pokazao Pink grejp. Identifikacija pojedinačnih fenolnih spojeva provedena je primjenom tekućinske kromatografije visoke djelotvornosti (HPLC). Dva najzastupljenija fenolna spoja u analiziranim uzorcima su klorogenska kiselina i epigalokatehin-galat. Dodatkom askorbinske kiseline u čajeve zabilježen je prosječni porast vrijednosti ukupnih fenola (2,56 puta), kao i antioksidacijske aktivnosti (do 56%, ovisno o metodi) dok je dodatkom meda u čajeve s askorbinskom kiselinoma došlo do prosječnog pada vrijednosti ukupnih fenola (28%) i značajnog pada antioksidacijske aktivnosti ali samo u slučaju DPPH metode (22%). Visoki stupanj korelacija između sadržaja ukupnih fenola i antioksidacijske aktivnosti ukazuje na činjenicu da su upravo fenolni spojevi odgovorni za antioksidacijsku aktivnost čajeva.

Abstract (english)

Wine, coffee, juices and teas are daily consumed drinks that have been proven to have antioxidant properties. Although green, black and white teas have been till now the subjects of versatile studies, less attention has been paid to fruit teas and their antioxidant potential. Therefore the aim of this study was to determine the total phenol content, phenolic composition and antioxidant activity of ten different comercial fruit teas available on market with or without ascorbic acid and honey addition. Total phenol concentration was determined by reaction with Folin-Ciocalteau reagent and the antioxidant activity was determined with three different reactions, reaction with ferric-tripyridyltriazine (FRAP) and with radicals, 2,2′-azinobis-(3- ethylbenzothiazoline-6-sulfonic acid (ABTS) i 2,2-diphenyl-1-picrylhydrazyl (DPPH). Spectrophotometric determination was as well used to determine color intensity, ABS450. The results of spectrophotometric metods show the great gradation of values and the best results in total phenol content and antioxidant activity are obtained in Rose hip tea and Strawberry and vanilla tea, while Pink grapefruit tea has shown to have weak antioxidant activity. Identification of particular phenol compound was performed using high preasure liquid chromatography (HPLC). The two most abundant phenol compounds in analysed samples were chlorogenic acid and epigallocatechin-gallate. With addition of ascorbic acid increase of total phenol content (2,56x) and antioxidant activity (56%, depending on used method) while addition of honey in teas with ascorbic acid results in decrease of total phenol content and (28%) and significant decrease of antioxidant activity when DPPH method was uses (22%). High correlation rates between total phenol content and antioxidant activity indicates that phenols posses an antioxidant activity.

• Keywords: antioksidacijska aktivnost; fenoli; HPLC; voćni čajevi
• Keywords (english): antioxidant activity; fruit teas; HPLC; phenols
• Language: croatian
• URN:NBN: urn:nbn:hr:159:705722
• 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: 2017-09-05 08:18:55