91E-5 |
Comparison of the physical stability of high-pressure and thermally processed Valencia orange juice |
T. TRUONG, Department of Food Science, The Ohio State University, 110 Parker FST, 2015 Fyffe Rd, Columbus, OH 43210 and T. H. Shellhammer. Pectinmethylesterase (PME) activity can degrade the quality of orange juice, and lead to cloud loss. Supercritical carbon dioxide has been proven to be effective at inactivating orange juice PME. High pressure processing (HPP) is effective at inactivating the thermal-labile PME isozymes, but has little effect on the thermo-stable isozymes. The implications of residual PME after processing is well understood in thermal processing literature, but still needs further investigation in high pressure research. The objective of this study was to compare the cloud stability and color changes of thermally processed juice, HPP juice, and HPP carbonated juice over time. Fresh Valencia orange juice was packed in nylon/EVOH pouches, quickly frozen, and stored at –40 °C until needed. Thermal pasteurization was accomplished by immersing pouches of thawed juice in hot water at 91°C for 110 sec (30 sec at temp). Non-carbonated juice was pressure treated at 600 MPa, 25°C, 346 sec, while carbonated juice was saturated with ~12 psig of CO2(g), and pressurized at 600 MPa, 25 °C, and for 130 sec. Processed juice was held at two temperatures, 4 °C and 30 °C, and periodically examined over 120 days for % transmission @ 650 nm and color score (Hunter Lab L, a, b values). Compared to the unprocessed control, percent residual PME activity was determined to be 0.8±0.32% in the pasteurized juice, 20.2± 2.7% in the HPP juice, and 27.4±1.47% in the carbonated, HPP juice. The cloud remained stable for all three treatments over 120 days at both temperatures, with <6.22 %T at 4 °C, and <2.73 %T at 30 °C. Samples stored at 30 °C had lower %T values, and lower L, a, b values over time. Combined CO2(g) and HPP technologies can stabilize orange juice cloud without a complete inactivation of the PME enzymes.
Session 91E, Nonthermal Processing: Nonthermal processing of foods
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