master's thesis
Comparison of the Antioxidant Activity of Dry Leaves of Green, Yellow and Black Tea and Their Extracts

Maja Tadić (2013)
Josip Juraj Strossmayer University of Osijek
FACULTY OF FOOD TECHNOLOGY
Department of Food Technologies
Sub-department of Fruits and Vegetables Technology
Metadata
TitleUsporedba antioksidativne aktivnosti suhih listića zelenog, žutog i crnog čaja i njihovih ekstrakata
AuthorMaja Tadić
Mentor(s)Mirela Kopjar (thesis advisor)
Abstract
U ovom radu ispitivan je utjecaj veličine čestica zelenog, žutog i crnog čaja (listići čaja i usitnjeni čaj) i ekstrakcijskog otapala na udio fenola, flavonoida, kondenziranih tanina, boju i antioksidativnu aktivnost. Najveći udio fenola (3,823, 4,226 i 6,829 g/kg za zeleni, crni i žuti čaj) određen je ekstraktima dobivenim zakiseljenim metanola usitnjenih listića čajeva. Primjenom metanola kao ekstrakcijskog otapala udio fenola se smanjivao redom žuti > zeleni > crni čaj, a primjenom zakiseljenog metanola udio fenola se smanjivao redom žuti > crni > zeleni čaj, bez obzira na veličinu čestica čajeva za ekstrakciju. Udio flavonoida i kondenziranih tanina pratio je tendenciju udjela fenola. Najveće vrijednosti antioksidativne aktivnosti su određene u ekstraktima dobivenim ekstrakcijom sa zakiseljenim metanolom usitnjenih uzoraka, bez obzira na metodu određivanja (DPPH i ABTS). U radu je korištena za određivanje antioksidativne aktivnosti i „QUENCHER“ metoda kod koje se direktno suhi uzorak hrane tretira slobodnim radikalima (DPPH i ABTS). Rezultati antioksidativne aktivnosti „QUENCHER“ metode su uspoređeni s rezultatima dobivenim nakon ekstrakcije sa zakiseljenim metanolom. Veće vrijednosti antioksidativne aktivnosti određene su u zelenom i žutom čaju primjenom „QUENCHER“ metode, za razliku od crnog čaja gdje je veća antioksidativna aktivnost određena u ekstraktu.
Keywordstea tea extracts phenols antioxidant activity color
Parallel title (English)Comparison of the Antioxidant Activity of Dry Leaves of Green, Yellow and Black Tea and Their Extracts
Committee MembersVlasta Piližota (committee chairperson)
Mirela Kopjar (committee member)
Anita Pichler (committee member)
Nela Nedić Tiban (committee member)
GranterJosip Juraj Strossmayer University of Osijek
FACULTY OF FOOD TECHNOLOGY
Lower level organizational unitsDepartment of Food Technologies
Sub-department of Fruits and Vegetables Technology
PlaceOsijek
StateCroatia
Scientific field, discipline, subdisciplineBIOTECHNICAL SCIENCES
Food Technology
Food Chemistry
Study programme typeuniversity
Study levelgraduate
Study programmeFood Engineering
Academic title abbreviationmag. ing. techn. aliment.
Genremaster's thesis
Language Croatian
Defense date2013-04-16
Parallel abstract (English)
In this study influence of particle size of green, yellow and black tea (leaves and powdered leaves) and solvent on content of phenols, flavonoids and tannins, colour and antioxidant activity was investigated. Extracts obtained by extraction of powdered tea leaves with acidified methanol had the highest phenol content (3.823, 4.226 and 6.829 g/kg for green, black and yellow tea). In methanol extracts phenol content decreased in order yellow > green > black tea, and in acidified methanol extracts yellow > black > green tea, regardless of particle size. Flavonoid and tannins content followed the same tendency as phenol content. The highest antioxidant content had acidified methanol extracts of powdered tea leaves, regardless of used method (DPPH and ABTS). Also, in this study, for determination of antioxidant activity „QUENCHER“ method was used which is based on direct treatment of dry sample with free radicals (DPPH and ABTS). Results of antioxidant activity obtained with „QUENCHER“ method were compared with results of acidified methanol extracts. Green and yellow tea had higher antioxidant activity when „QUENCHER“ method was used in contrast to black tea where higher antioxidant activity was determined in extract.
Parallel keywords (Croatian)čaj ekstrakt čaja fenoli antioksidacijska aktivnost boja
Resource typetext
Access conditionAccess restricted to students and staff of home institution
Terms of usehttp://rightsstatements.org/vocab/InC/1.0/
URN:NBNhttps://urn.nsk.hr/urn:nbn:hr:109:726534
CommitterIvana Šuvak