Uses of supercritical (SC) fluids in citrus processing in conventional applications such as citrus oil fractionation, lemon oil extraction, and orange juice debittering are reviewed. In a non-conventional application, single strength orange juice was treated with SC CO2. Effect of pressure (7–34 MPa), temperature (35–60°C), and time (15–180 min) on pectinesterase (PE) activity, cloud stability, microorganisms, and sensory attributes were investigated. SC CO2 inactivated PE below thermal inactivation temperatures. (Activation energy at 31 MPa = 97.4 KJ/mole; at atmospheric pressure = 166.6 KJ/mole.) SC treatment did not change pH and °Brix; but stabilized and enhanced cloud and color. Ascorbic acid was better preserved. Sensory evaluations of color and cloudiness of treated juice were better. Flavor, aroma and overall acceptability were not different. Aerobic total plate counts showed that D value of treated juice decreased as pressure increased. D values at 35, 45 and 60°C of SC treated juice at 33.1 MPa were 28, 22.6 and 12.7 min, respectively.
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