Determination of the process effects on koruk juice quality

Abstract

In this study, clarified koruk juice was manufactured by using Sultani Çekirdeksiz and Cabernet Sauvignon koruk grape samples, and the effects of process stages on physicochemical quality of koruk juice were investigated. The processing effects were searched by collecting samples from six different stages during koruk juice processing. In Sultani Çekirdeksiz and Cabernet Sauvignon samples, soluble solid values were 7.47-8.33 and 7.07-7.60 °Brix, pH values 2.67-2.77 and 2.75-2.93, titretable acidity 2.56-2.77 and 2.55-2.79 g 100 mL-1, dry matter 8.03-9.96 % and 8.11-16.38 %, respectively. The koruk juice turbidity decreased by depectinization, clarification and filtration treatments. The turbidity values were 1.33 and 1.51 NTU in Sultani Çekirdeksiz and Cabernet Sauvignon samples, respectively. The color properties improved and yellowness was increased depending on the process. Tartaric acid, malic acid and citric acid contents were 36-49 %, 43-58 % and 6-8 % of the total acidity of koruk juice samples, respectively. Total phenolic contents decreased about 71-88 % and 1-27 % according to koruk samples and the pressing samples while these decrease rate was 97 % and % 33-36 for total flavonoid contents, respectively. In addition, antioxidant capacities decreased by about 72-82 % and 89-93 % for ABTS and DPPH, respectively, in the juice samples according to koruk samples. The decrease of the total phenolic and flavonoid contents and antioxidant capacity was due to both pressing and separation processes of the grape skin and seeds as well as clarification treatments.