30G-18 |
The inhibitory effect of oxalic acid on browning of banana slices |
R. YORUK1, M. O. Balaban1, M. R. Marshall1, and S. Yoruk2. (1) Food Science and Human Nutrition Department, University of Florida, S.W. 23rd Drive, P.0. Box 110720, Gainesville, FL 32611, (2) Department of Industrial & Systems Engineering, University of Florida, Gainesville, FL Browning of banana slices significantly affects their acceptance by consumers. Oxalic acid has been shown to suppress apple browning. Machine vision can quantify changes in non-uniform color samples. Our objectives were to analyze the effect of oxalic acid on the darkening of banana slices and on its PPO (EC 1.10.3.1) activity. Color changes were quantified by machine vision. Peeled banana slices (1 cm thick) were dipped in different concentrations of oxalic acid solutions (0, 0.1, 0.3, 0.5, 0.8 and 1%) for 1, 5 and 15 min at room temperature, excess surface liquid removed by paper towels, and video images of the samples were captured at 0, 15, 30, 45, 60, 90, and, 120 min time intervals. Average L, a, b values of the samples were calculated using Color Analysis software. Inhibition by oxalic acid on PPO activity was studied spectrophotometrically in a PPO-catechol model system, after the treated tissues were extracted in a pH 7 phosphate buffer containing 1% Triton X-100. Color analysis quantified the formation of darker colors and the disappearance of light colors as correlated to dipping time, storage time and oxalic acid concentration. PPO activity in banana slices treated with 0.3 and 1% oxalic acid solutions for 15 min decreased by 8 and 19%, respectively. However, when slices were cut in half to increase surface area and treated with oxalic acid solutions, inhibition increased to 36 and 51% for oxalic acid concentrations of 0.3 to 1%, respectively. Treatments of the slices under vacuum did not increase the anti-browning effectiveness of oxalic acid. Oxalic acid was previously shown as a potential anti-browning agent for apple PPO. Differences in its effectiveness to inhibit PPO activity in banana might be attributed to its absorption differences into these two tissues.
Session 30G, Fruit & Vegetable Product: Processed Fruits and Vegetables
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