Effects of Adding Inulin and Tagatose on the Physicochemical and Sensory Properties of Functional Grape Juice

Fortification of fruit juices with new functional ingredients including prebiotics is one of the recent progresses in the juice field. So the objective of this study was to evaluate the effect of addition of some prebiotics on the physicochemical and sensory properties of grape juice at 4 and 25°C. Prebiotic compounds (inulin and tagatose) and sucrose with specific proportions were added to the samples. After pasteurization, the samples were placed at 4°C (refrigerator temperature) and 25±2°C (room temperature) for 3 months. Then their Brix, pH, acidity, total sugar and sensory properties were evaluated with the time intervals of one month. pH, brix and acidity of all treatments did not show statistical significant differences during 90 days of storage at 4 and 25°C (P>0.05). While total sugar content of all treatments decreased significantly during this time (P<0.05) the greatest decrease was seen in the treatment with 6% of inulin at room temperature with 53% loss (decrease from 21.5 to 10.1 g/100g), while the lowest increase of transparency (65%) reported for this treatment. The results further showed that the most desirable sense of taste with 8.1 score in zero time storage period and 7.9 in the third month of storage at 4°C belonged to the control sample, and it was observed addition of prebiotics reduced the sensory acceptability from the perspective of sensory evaluators. Fortification of juices such as grape juice with new functional ingredients including inulin and tagatose with or without sucrose (short chain inulin 3%/sucrose 3% and tagatose 3%/ sucrose 3%) with respect to the sugar replacement is possible.