99E-22 |
|
E. MEJÍA-MEZA, Biological Systems Engineering, Washington State Univ., Pullman, WA 99164-6120, K. Versteeg, Food Science Australia, 671 Sneydes Road, Werribee, Vic, 3030, Australia, and G. V. Barbosa-Cánovas, Dept. of Biological Systems Engineering, Washington State Univ., 220 L.J. Smith Hall, PO Box 646120, Pullman, WA 99164-6120. Ultrasound technology is a new non-thermal technology based on the transmission of ultrasonic waves through a liquid at high frequency (20 to 40 kHz). The microbial inactivation effect ultrasonic waves in combination with temperature depends on the type of microorganism (G (+) or G (-)), the liquid and the action of the ultrasonic waves penetration by the acoustic cavitation phenomenon. The objective of this work was to study the inactivation effect of ultrasonic waves in combination with moderate temperature circulating water on ,Escherichia coli (ATCC 11775) in apple cider. A UP 400s Ultrasonic processor system with mechanical oscillation of 24 kHz was used. Continuous flow cell was selected and provided with a recirculation system. Apple cider samples were treated using ultrasonic waves of 400 W, and a flow rate of 65.8 mL/min. The flow cell jacket was kept at moderate temperature of 30, 40, 50 or 60° C. Pour plating in Eosin Methylene Blue (EMB) agar was used to asses total microbial count. DUS values obtained from plotting log (Nt/No) vs. time were 4.09 (R2>0.98), 1.60 (R2>0.98) and 1.46 (R2>0.98) min at 30, 40 and 50°C, respectively. Maximum log reduction of 4.97, 4.62 and 5.44 were also observed at 30, 40 and 50°C, respectively, after 10 min of treatment. Increasing temperature to 60° C resulted in a reduction of 2.13 log cycles after 4 min of treatment. No survivors were observed in apple cider samples treated with ultrasonic waves at 60° C and processing times above 6 min. Ultrasound technology in combination with moderate temperature circulating water exhibited potential to inactivate E. coli in liquid foods. Therefore, this technology may be a useful alternative to maintain quality and safety aspects related to processing of liquid foods such as juices usually processed by conventional treatments.
Session 99E, Nonthermal Processing: General II
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |