99E-25

 

There is a growing interest by the consumers for mixed fruit juice and milk beverages. Non-thermal technologies, such as Pulsed Electric Fields (PEF) can produce microbiologically safe foods preserving that added value.

                  

The objective of this study was to evaluate the effects of PEF on the inactivation of E. coli inoculated in a mixed beverage of flash pasteurized orange juice with milk.

 

The samples were PEF processed using a bench-scale equipment (OSU-4D, Ohio State University). Six co-field treatment chambers connected in series were used to treat the samples which never remained at temperatures higher than 55ºC. Flow rate was set at 60 ml/min. Square-wave bipolar pulse duration of 2.5 ms was selected. Treatment times ranged from 40 to 700 ms, and electric field strengths from 15 to 40 kV/cm. Samples were collected after each treatment, serially diluted in sterile 0.1% buffered peptone water, plated in NB Agar, and incubated for 24 hours at 37ºC. The inactivation data were adjusted to the Bigelow and Hülsheger models and the Weibull frequency distribution function.

 

Up to 3.8 decimal reductions were achieved under the conditions (15kV/cm, 700µs) of this study. The Weibull  frequency distribution function gave better fittings for the inactivation by PEF.

 

The PEF is shown as appropriate to reduce the pathogens contamination in a mixed fruit juice and milk beverage.