Polyphenols and Antioxidant Activity of Gels Based on Caboxymethyl Cellulose and Blackberry Juice

Hidrogelovi na bazi soka kupine pripremljeni su dodatkom soka kupine, karboksimetilceluloze, pululana i proteina mlijeka. Količina karboksimetilceluloze u svim uzorcima iznosila je 2%, pululana 0,1% ili 0,2%, te proteina mlijeka 1%. Uzorcima su određeni različiti parametri nakon pripreme i nakon 6 mjeseci skladištenja: ukupni fenoli, proantocijanidini, antocijani, polimerna boja, indeks posmeđivanja, antioksidacijska aktivnost primjenom FRAP, CUPRAC, DPPH te ABTS metoda te parametri boje. Kontrolni uzorak bio je hidrogel pripremljen sa sokom kupine i karboksimetilcelulozom. Dobiveni rezultati ukazuju na to da dodatak pululana i proteina mlijeka utječe na ispitivane parametre. Najveću koncentraciju polifenola (određeno HPLC-om) imali su hidrogelovi pripremljeni uz dodatak pululana i proteina mlijeka. Ujedno su isti uzorci imali i najveći udio antocijana. Tijekom skladištenja došlo je do gubitka ukupnih fenola, proantocijanidina i antocijana, te do povećanja indeksa posmeđivanje i polimerne boje.Blackberry juice-based hydrogels are prepared by adding blackberry juice, carboxymethylcellulose, pullulan and milk protein. The amount of carboxymethylcellulose was 2%, pullulan was added in amount of 0.1% or 0.2%, and milk protein in amount of 1%. Different parameters were determined after preparation and after 6 months of storage: total phenols, proanthocyanidins, anthocyanins polymer color, browning index, antioxidant activity using FRAP, CUPRAC, DPPH and ABTS methods, and color parameters. The control sample was hydrogel prepared with carboxymethylcellulose. The results indicate that the amount of additives affected the mentioned parameters. The highest concentration of total phenols (determined by HPLC) was determined in hydrogels with the addition of pullulan and milk proteins. Additionally, the same samples had the highest concentration of anthocyanins. During storage, decrease of total phenols, proanthocyanidins and anthocyanins, and an increase of browning index and polymer color was observed