Title: Nonthermal processing of orange juice using a pilot-plant scale supercritical carbon dioxide system with a gas-liquid metal contactor Authors
Submitted to: Journal of Food Processing and Preservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 7, 2012
Publication Date: October 22, 2012
Citation: Yuk, H., Sampedro, F., Fan, X., Geveke, D.J. 2012. Nonthermal processing of orange juice using a pilot-plant scale supercritical carbon dioxide system with a gas-liquid metal contactor. Journal of Food Processing and Preservation. DOI:10.1111/jfpp.12013. Interpretive Summary: Small scale supercritical carbon dioxide (SCCO2) systems to kill harmful bacteria in juice products without heating have been studied. However, there is no comparable study using a pilot-plant scale system. This study evaluated the effect of a pilot-plant scale SCCO2 system on safety and quality of orange juice (OJ). SCCO2 processed OJ was compared with fresh OJ and heat processed OJ regarding quality. Results showed that the killing effect of SCCO2 were similar with heat processing. SCCO2 and heat treatments did not affect pH, brix, titratible acidity, and ascorbic acid contents in OJ, indicating no difference between fresh and treated OJ. The color of SCCO2 treated OJ was slightly different from fresh OJ but better than heat treated OJ. SCCO2 treatment reduced about 46.5% of pectin methylesterase(PME) activity, whereas heat treatment inactivated 86.4% of total activity. The cloud value was greatly improved by SCCO2 treatment compared with fresh OJ and heat treated OJ. This pilot-plant study indicates that SCCO2 can be commercially used for OJ processing at low temperature without any quality change.
Technical Abstract: To evaluate the effect of pilot-plant scale, non-thermal supercritical carbon dioxide (SCCO2) processing on the safety and the quality of orange juice (OJ), SCCO2 processed juice was compared with untreated fresh juice and equivalently thermal processed juice in terms of lethality. SCCO2 processing was carried out with CO2 concentration of about 8.5 wt% at 42 deg C for 20 min and thermal processing was at 70 deg C for 2.0 s. After processing, aerobic bacteria and yeast & mold counts were determined to evaluate microbial inactivation. For quality analysis, changes in pH, brix, titratable acidity, ascorbic acid content, and color were measured. The degree of pectin methylesterase (PME) inactivation and cloud stability were also analyzed. The number of naturally occurring bacteria and yeast & mold were decreased approximately from 2.0 – 3.0 x 103 to 18–28 CFU/mL after both SCCO2 and thermal processing, indicating no significant difference (P > 0.05) between processing methods. No noticeable changes in pH, brix, titratible acidity, and ascorbic acid content were observed among fresh, SCCO2 processed and thermal processed OJ. The color of SCCO2 processed OJ was slightly altered compared to the untreated fresh juice but less than the thermal processed juice. SCCO2 processing inactivated 46.5% of PME, whereas thermal processing inactivated 86.4%. However, the cloud stability of the SCCO2 processed juice was greatly enhanced compared with fresh and thermal processed juices, despite of difference in PME inactivation. This study demonstrates that pilot-plant scale SCCO2 processing can enhance the safety of OJ without quality deterioration, suggesting the potential for commercialization.