COMPARISON OF STATIC AND STEP-PULSED ULTRA-HIGH PRESSURE ON THE MICROBIAL STABILITY OF FRESH CUT PINEAPPLE

Fresh cut pineapple cubes inoculated with 10(4-5) CFU g(-1) Saccharomy ces cerevisiae were packed in heat-sealed polyethylene pouches and sub jected at ambient temperature to static and step-pulsed ultra-high pre ssure (UHP) treatments. Static treatments included 100 and 9000 s at 2 70 MPa and 9000 s at 340 MPa. Step-pulsed pressure treatments included 100, 300 and 600 s at 0-270 MPa using 0.5-s and 10-s pulses. Inoculat ed treated and untreated samples were held at 4 degrees C for 60 days. Bacteria and yeast counts were determined using plate count agar and yeast extract peptone dextrose agar, respectively. Static treatment at 270 and 340 MPa for 9000 s resulted in <240 CFU g(-1) yeast and bacte ria counts for up to 60 days. Step-pulsed pressure treatments for 100 s at 0-270 MPa using 0.5-s (200 pulses) and 10-s pulses (10 pulses) we re more effective than a 100-s static 270-MPa treatment. Step-pulsed p ressure treatments (300 and 600 s) using 0.5-s pulses (600 and 1200 pu lses) and 10-s pulses (30 and 60 pulses) were as effective as 9000-s s tatic pressure treatments at 270 and 340 MPa. This storage study confi rmed the superiority of step-pulsed over static pressure treatments. ( C) 1998 SCI.