OHMIC HEATING HAS POSITIVE IMPACT ON THE MICROBIAL SHELF LIFE IN PREBIOTIC VANILLA WHEY FLAVOURED BEVERAGE: A PREDICTIVE MICROBIOLOGY APPROACH

The microbial shelf life of prebiotic whey dairy beverage (70:30 % v/v pasteurized milk/sweet whey, 3.0 w/v % galactooligosaccharide) pasteurized using ohmic heating (0, 30V, 60B, 100, 200, 300 Hz, 72-75°C/15-20s) or conventional processing was evaluated using predictive microbiology model. Microbial quantifications of aerobic mesophilic, psychrotrophic bacteria, and lactic acid bacteria (MESO, PSYCHO, LAB) were carried out at times of 0, 1, 4, 7, 10, 14, 20, and 24 days in appropriate culture media. The data were adjusted to Baranyi's model, and log reductions (γ) were calculated. Higher voltage and frequency values in the ohmic heating proportionated positive reduction for all microbial groups, generating increased y values. The predictive model showed that higher microbial counts were observed in the conventional processing-treated sample compared to the others, although there was no difference between growth rates. However, verifying the absence of the lag phase in all cases and the existence of stability at the end of the storage period in some samples when evaluating MESO and LAB was possible. For PSYCHO, a more homogeneous pattern of microbial counts and growth rate values was observed. Ohmic heating delayed the microbial growth along the shelf life of the prebiotic beverages, and the use of predictive models confirmed this hypothesis. Therefore, ohmic heating presented increased performance compared to conventional processing for prebiotic whey dairy beverage.