Pulsed ultra high pressure treatments for pasteurization of pineapple juice

Sinusoidal and step-pressure pulses were compared with static pressure treatments for the inactivation of Saccharomyces cerevisiae 2407-1a in pineapple juice. No inactivation was observed after 40-4,000 fast sinusoidal pulses (10 cycles/s) at 4-400 sec in the 235-270 MPa range. Static 270 MPa treatments at 40 and 400 sec resulted in 0.7 and 5.1 decimal reductions, respectively. Slower 0-270 MPa step pulses at 0.1 (10 pulses), 1 (100 pulses), and 2 (200 pulses) cycles/s with 100 sec total on-pressure time resulted in 3.3, 3.5, and 3.3 decimal reductions, respectively. A comparable static pressure treatment resulted in 2.5 decimal reductions. Changing the on-pressure/off-pressure time ratio (3: 1, 3:3 and 1:3) showed that treatments with longer on-pressure time, e.g,, 0.6 sec on-pressure and 0.2 sec off-pressure were significantly more effective showing nearly a 4 decimal reduction in 100 sec.