EFFECT OF DENSE PHASE CARBON DIOXIDE PROCESS ON PHYSICOCHEMICAL PROPERTIES AND FLAVOR COMPOUNDS OF ORANGE JUICE

Orange juice samples were treated in DPCD process under 40 Mpa at 55C within duration ranging from 10 to 60 min. Physicochemical characteristics and flavor compounds of DPCD-treated samples were detected and compared with those of orange juices freshly squeezed and thermally processed at 90C for 60 s. Particle size, consistency coefficient and a* value tended to become smaller as the DPCD treatment was prolonged. The proportion of the small particles increased greatly after DPCD treatment, indicating that the increase in cloud and stability of orange juice treated by DPCD should be primarily ascribed to the effect of homogenization by DPCD. The relative contents of ethyl butyrate and trans-2-hexenol decreased linearly after 10-60 min of DPCD treatment, their mathematical models with higher correlation coefficients (R-2 = 0.968 and 0.804) and confidence interval (P < 0.05) indicating a good prediction for DPCD process, whereas the relative content of nonanal and citronellol after DPCD treatment increased, higher than that after thermal treatment or even higher than that in fresh juice. The Herschel-Bulkley model was best fit to the juice flow behavior. The consistency coefficient, K, and the flow behavior index, n, could be considered constants and time-independent properties within the first 30 min and the second 30 min, respectively, and the consistency coefficient in the second period was about 28% lower than that in the first period, which is significant for energy saving in commercial application of the juice DPCD process.