INACTIVATION OF ESCHERICHIA COLI IN SKIM MILK BY HIGH INTENSITY PULSED ELECTRIC FIELDS

Abstract

The inactivation of microorganisms is the most important function in the processing of milk and dairy products. Traditionally, this purpose is realized by thermal treatment, but heat produces alterations to flavor and taste in addition to nutrient loss. The high intensity pulsed electric field (PEF) treatment should be a good alternative to heat because demonstrations have shown PEF can reduce the Escherichia coli survival fraction in aqueous solutions and model foods. In this study, PEF treatment was found to inactivate E. coli in skim milk (inoculum 109 CFU/mL) at 15C. The microorganism inactivation satisfied Hülsheger's model following a first order kinetic for both the electric field intensity and number of pulses when skim milk inoculated with E. coli was treated in a static or continuous flow chamber. PEF treatment in a continuous system when the critical electric field (Ec) and minimum number of pulses (nmin) were 12.34 kV/cm and 2.7 at 30 kV/cm and 30 pulses (0.7–1.8 μs pulse width) inactivated more microorganisms than in a static system. It has also been proven that increasing the pulse duration increases the E. coli inactivation. The inactivation of E. coli using PEF is more limited in skim milk than in a buffer solution when exposed to similar treatment conditions of field intensity and number of pulses due to the complex composition of skim milk, its lower electrical resistivity and the presence of proteins.

Comparative analyses of prediction models for inactivation of Escherichia coli in carrot juice by means of pulsed electric fields

“…The critical field intensities which are evaluated for Hülsheger and Peleg models, ranged from 6.5712-1.4743 to 8.993-1.663 kV/cm respectively. The evaluated critical field intensity is different from the other reported studies (Hülsheger et al 1981;Martín et al 1997;Zhong et al 2005). The cause of disagreement can be the environmental conditions and treatment setup used in these studies.…”

Moderate and high intensity pulsed electric fields : Effect on microbial inactivation, shelf life and quality of fruit juices

“…Most of the earlier studies with PEF treatment were using small static treatment chambers held between parallel plates (Grahl & Märkl, 1996;Hülsheger & Niemann, 1980;. Qin et al (1995a) showed a greater treatment uniformity in continuous flow systems than in static systems, which was confirmed in a study by Martín et al (1997) who found more inactivation within a continuous flow system with parallel plate chamber than in a static parallel system. Thereafter, especially in translation of the process to pilot and commercial scales, the preference has been to conduct kinetic studies in continuous flow mode (Sastry, 2016).…”

Pulsed Electric Fields for Food Processing Technology

“…These factors most likely influence the recovery of injured microbial cells and their subsequent growth following PEF exposure, since the presence of food components, such as fats and proteins , has reportedly had a preventive effect on microorganisms against PEF treatment (Ho et aI., 1995;Grahl and Markl, 1996;Martin et al, 1997).…”