EFFECT OF ULTRASONICATION ON MICROBIAL QUALITY, COLOUR, AND ASCORBIC ACID CONTENT OF PASSION-FRUIT JUICE DURING STORAGE

Passion fruit juice (PFJ) has a delicate fl avour, very susceptible to thermal degradation. This study pursued to test the effect of sonication as non-thermal preservation method on some quality parameters of PFJ. The effect of ultrasound (20 kHz, 263 W, 89.25 mu m) on the indigenous microfl ora, colour, pH, and ascorbic acid content of PFJ was studied. Firstly, the kinetic of microbial inactivation was determined for aerobic mesophilic bacteria and yeasts. Data was fi tted to Weibull model, and a treatment time of 8 min was selected for stability studies. To this, untreated and sonicated juice was stored at 4 and 10 degrees C up to 10 days and microbial quality, instrumental colour, pH, and ascorbic acid content were evaluated. In general, ultrasound kept juice microbiologically stable for up to 10 days at 4 degrees C without markedly affecting other parameters evaluated. Ultrasound seems suitable to stabilize PFJ microbiologically.