Abstract

Effect of different clarifying agents on the physico-chemical properties of grape juice concentrate

Author(s): Masoome Hatamikia, Ali Mohamadi Sani, Shahin Zomorodi

Grape juice concentrate is a traditional product of grape-harvesting areas of Iran which is generally produced from the year-end harvest of poor quality. In order to examine the effect of different clarifying materials on the quality of grape juice concentrate, a plan was executed using factorial statistical method with completely randomized design. The first factor was type of clarifiers in six levels, comprising grape juice concentrate soil (GJCS), bentonit, silicasol, gelatin-bentonit, gelatin-silicasol, gelatinbentonit- silicasol; and the second factor was the quantity of clarifiers at three levels with three replicate. Results of statistical analysis showed that an increase in the quantity of GJCS decreased acidity of grape juice concentrate and leaded to increasing pH, while an increase in other clarifiers concentration (bentonit, silicasol and gelatin) did not influence the acidity and pH significantly. Bentonit and silicasol compared to GJCS, significantly increased transparency and decreased turbidity of grape juice concentrate. Adding gelatin to bentonit and silicasol, compared to the sole application of bentonit and silicasol, decreased the turbidity and increased the transparency. Treatment with gelatin-bentonit-silicasol compound leaded to a product with highest level of transparency (89.47%) and lowest level of turbidity (8.48%). In grape juice concentrate produced via this treatment, no crucial decrease in important quality criteria; such as pH, acidity, protein, sugar, ash, brix and total dry material; was observed. Finally, treatment of grape juice concentrate using a complex clarifying agent containing 2% gelatin, 4% bentonit and 7% silicasol, is prescribed in order to produce a clear and transparent product.