Effect of ultrasonication on microbial quality, colour and ascorbic acid of passion-fruit juice during storage

Abstract

Passion fruit juice (PFJ) has a delicate flavour 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 µm) on the indigenous microflora, colour and ascorbic acid content of PFJ was studied. Firstly, the kinetic of microbial inactivation was determined for aerobic mesophilic counts and yeasts counts. Data was fitted 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 ºC 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 ºC without markedly affecting other parameters evaluated. Ultrasound seems suitable to stabilize microbiologically PFJ.