Optimization of Formulation of NFC Nanguo Pear and Okra Compound Juice and Effects of Different Sterilization Treatments on the Quality of Juices

Nanguo pear and okra were used as the main raw materials to produce NFC. The sensory quality were used as evaluation indicators, the formulation of juice was optimized by single factor experiments and orthogonal test. The three different sterilization methods, pasteurization, microwave sterilization and ultra high pressure sterilization were compared, and the changes of microbial, physicochemical properties and flavour was researched. The results showed that, the optimum formulation of juice was as that: The content of Nanguo pear and okra in juice was 93.98%, the mass ratio of Nanguo pear juice to okra was 15:1, the amount of sugar was 6%, and citric acid was 0.02%, and the sensory score was the highest 89.4. After sterilizated, the juice were commercial sterility. Compared with the unsterilized juice, the total acid and free radical scavenging rate by pasteurization and microwave sterilization were significantly decreased(P<0.05), the value of pH, non-enzymatic browning index, the bitterness and astringency were significantly increased, and the soluble solid content of juice by microwave and ultra high pressure terilized increased(P<0.05), the total acid and the bitterness and astringency by ultra high pressure terilized significantly decreased (P<0.05). Compared with the other methods, the ∆E of the juice by ultra high pressure treatment had minimum change was 4.26±0.12, and the scavenging rates of DPPH and ·OH were 78.79%±0.37% and 68.84%±0.42%, respectively, which was higher than the other methods significantly. Taken together, ultra high pressure sterilization could maintain the color and antioxidant properties of Nanguo pear and okra juices.