Abstract:
Cloudiness in tangerine juice was resulted from degradation of pectin structure during processing of tangerine juice. However, precipitation of degradated pectin was accerelated by PME which caused the unacceptable appearance. Therefore, this study was aimed to stabilize the cloudiness of tangerine juice by using low heat treatment together with adding stabilizers. Firstly, physicochemical property of tangerine juice was analyzed. The results showed that 9.00 ± 0.82 °Brix, pH 4.00 ± 0.25, 0.57 ± 0.04 g/100ml of citric acid, 26.69 ± 0.99 mg/ml of ascorbic acid, 0.37 ± 0.004 µg/ml, of total carotenoid, 0.25 ± 0.01 g/100ml of pectin, 2.25 ± 0.2 units/ml of PME enzyme, 1.92 ± 0.07 cPs of viscosity, 0.22 ± 0.01 of cloud content, The color of L, a, b were 39.37 ± 0.63, -01.48 ± 0.07, 12.15 ± 1.18 respectively. The selected product prototype was further improved by varying total soluble solid were 12, 14 , 16 °Brix by sucrose and varying salt were 0.05, 0.10, 0.15% (w/v). The results showed that the 14 °Brix and 0.1% salt was the best formulation because it has score near ideal score in Ratio Profile Test (RPT). Then the heating condition was 70, 80, 90 °C and 30, 60, 90 seconds were studies. The selected condition was 80 °C, 90 seconds, with this condition, the sample had a cloud stability, PME activity and microbial quality not differ 90 °C 30, 60, 90 seconds (p ≤ 0.05). However, this sample separated, ascorbic acid and carotenoid lost and darker by storage time (p ≤ 0.05). After that, some property of stabilizer : pectin (p), glucomannan (GM), guargum (GG), and xantam gum (XG) were studied. It was found viscosity of GM, GG and XG solution increase when concentration higher pectin and low viscosity and independent by concentration. Later, studied effect of pH, sugar and salt at 0.3% (w/v) solution. It was found that pH, sugar and salt not effect to viscosity of pectin solution. But sugar and pH had effect to another stabilizer solution. Then, add each of stabilizer at 0, 0.1, 0.3 and 0.5% (w/v) to tangerine juice. It was found that every concentration of pectin sample had cloud less than control (p ≤ 0.05). For another stabilizer, every concentration had turbidity and vitamin C higher than control. Optimum value was 0.3% (w/v) because sensory test founded the control that used stabilizer 0.5% had too high to acceptable. Then, the next step was vary GM and XG, GM and GG, GG and XG for concentration of solution 0.3% (w/v). The portion of mixture was 25 : 75, 50 : 50 and 75 : 25, respectively, added in tangerine juice. The results found that every portion of GG and XG had preserved stability of tangerine juice more than 4 week.