54F-16

Y. Yagiz¹, S. LIM², and M. O. Balaban¹. (1) Dept. of Food Science and Human Nutrition, Univ. of Florida, 359 FSHN Bldg., Newell Dr., PO Box 110370, Gainesville, FL 32611-0370, (2) Dept. of Food and Bioengineering, Cheju National Univ., 1 Ara 1-dong, Jeju-si, Jeju-do, 690-756, South Korea

Mandarin cultivar 'Murcott' is harvested from January to March and has an excellent eating-quality. However, processing of juice with heat treatment causes undesirable changes in quality including off-flavor. Continuous high pressure CO₂ pasteurization is an alternative method without altering the original quality of fresh juice. The objective was to investigate the effects of temperature, pressure, residence time, and ratio of CO₂ to juice on pasteurization of microorganisms, inactivation of pectinesterase (PE), and quality of juice. Frozen mandarin juice was thawed and ripened at room temperature for 36 hr. Response surface methodology was used to investigate the effects of the processing parameters such as temperature (25, 35, 45^o C), pressure (13.8, 27.6, 41.4 MPa), residence time (5, 7, 9 min) and ratio of CO₂ to juice (2, 7, 12%). Total aerobic count (TAC), activity of PE, cloud, Brix, pH and titratable acidity (TA) of the juices before and after treatment were analyzed. Experimental data were correlated well with the processing parameters (p<0.05), and there was a statistically significant multiple regression relationship for pasteurization of juice, inactivation of PE, cloud change, and color change. Maximum log reduction (3.47) of TAC was observed at 35^o C, 41.1 MPa, 7% CO₂ and retention time of 9 min. PE was inactivated by 7~51% after treatment. Cloud increased by 38% with the increase of process temperature. Lightness and yellowness increased, and redness decreased after treatment. The processing temperature and ratio of CO₂ to juice significantly affected to high pressure CO₂ processing of mandarin juice. The Brix, pH and TA before and after treatment were the same. The above results shows that continuous high pressure CO₂ processing offers a prominent alternative to conventional processing technology in mandarin juice processing industry. This process can apply for especially heat-labile fruit and vegetable juices.

Session 54F, Nonthermal Processing: General I
2:00 PM - 5:30 PM, Monday PM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana