| Abstract | Žuti čaj se dobiva obradom lišća biljke Camellia sinensis i proizvodi se samo u Kini. U Kini je tradicija ispijanja žutog čaja jako duga, dok se zapadno tržište sa njime tek upoznaje. Kao i svim ostalim vrstama čaja, zahvaljujući bogatom sastavu bioaktivnih sastojaka, pripisuju mu se mnogi pozitivni učinci na zdravlje ljudi. Cilj ovog istraživanja bio je odrediti udjel ukupnih fenola, flavonoida i neflavonoida u čaju, u rinfuzi i filter vrećici, ovisno o uvjetima ekstrakcije (temperatura vode, duljina trajanja ekstrakcije, ponovljene ekstrakcije, ultrazvuk, dodatak limuna i mlijeka) kao i promjenu udjela navedenih spojeva u čaju tijekom jednodnevnog stajanja napitka. Takoñer je odreñena i antioksidacijska aktivnost svih uzoraka čaja primjenom tri spektrofotometrijske metode: reakcija s Fe3+-2,4,6-tripiridil-S-triazin kompleksom (FRAP), 1,1-difenil-2-pikrilhidrazil radikalom (DPPH˙) i 2,2'-azino-bis(3-etilbenzotiazolin-6-sulfonskom kiselinom) radikalom (ABTS˙). Rezultati istraživanja pokazali su važnost uvjeta ekstrakcije (temperatura vode, trajanje ekstrakcije, ponovljene ekstrakcije, dodatak limuna i mlijeka) na udjel polifenolnih sastojaka i antioksidacijsku aktovnost čaja. Primjena ultrazvuka u kombinaciji sa vodom sobne temperature rezultirala je povećanjem udjela polifenola i antioksidacijske aktivnosti žutog čaja. |
| Abstract (english) | Yellow tea is manufactured from leaves of a tea plant Camellia sinensis and it is produced only in China. Although drinking yellow tea has a very long tradition in China, it is still pretty new in Western World. Like all the others sorts of tea, owing to their numerous bioactive compounds, it is believed that yellow tea has healing powers on human health. The goal of this research was to determinate yellow teas, which were prepared from a loosed and bagged form, total phenols, flavonoids and nonflavonodis concentrations depending on extraction conditions (water temperature, extraction duration, repeated extractions, ultrasound, addition of lemon and milk), as well as variation of set forth compounds concentrations during one-day down time. Antioxidant capacity of all tea samples was also determined. Antioxidant capacity was determined using spectrophotometric methods: FRAP assay (Fe3+-2,4,6-tripyridyl-S-triazine complex), DPPH assay (1,1-diphenyl-2-picrylhydrazyl radical) and ABTS assay (2,2'-azino-bis(3-ethylbenzothiazoline-6- sulfonic acid) diammonium salt). Study results showed that extraction conditions (water temperature, extraction duration, repeated extractions, ultrasound, and addition of lemon and milk) are very important for the concentrations of total phenols, flavonoids and nonflavonoids, and as well for the antioxidant capacity in yellow tea. Ultrasound extraction in a combination with room temperature water resulted in increased concentrations of polyphenols and antioxidant capacity of yellow tea. |
