(594k) Microbial Load Control by Intermittently Delivered Pulsed Electric Fields

Microbial load control
by intermittently delivered pulsed electric fields.

Alexander Golberg

Department
of Mechanical Engineering, Etcheverry
Hall 6124, University of California at Berkeley, Berkeley, CA 94720, USA.

Abstract: Microbial
contamination prevention by intermittent delivery of pulsed electric
field (IDPEF) is a new concept and method for turbid products storage. The
treatment may be delivered at time intervals that is prescribed by PEF
inactivation efficiency and microorganisms' growth kinetics, when known. This
approach facilitates sterile storage without the need for chemical
preservatives, additives, radiation or the complex infrastructure demanded by
constanct connection to the electrical grid, which is not available in many developing
countries. Unlike ultraviolet radiation, IDPEF can be used in turbid media. Furthermore,
our previous work showed that IDPEF microbial control is comparable with
refrigiration. Here, we first discuss the efficient IDPEF protocol desing
principals. Second, we present the preliminary, laboratory scale studies of
IDPEF application for milk storage. In this work we investigated the impact of
IDPEF on Lysteria monocytogines in milk. Using
the L.
monocytogines kinetics growth data, we designed an
IDPEF protocol that consists of 2 sequences
of 10 square wave pulses, 50 μs duration, 12.5 kV/cm electric field
strength, delivered at 0.5 Hz and 1 min pause between the sequences applied every 1.5
h.  In a demonstration, 12 hours experiment, at 32⁰C
storage temperature, L. monocytogines concentration of
untreated samples reached (9.1±0.6)∙10⁷CFU/ml
and (7.1±0.3)∙10⁸CFU/ml for initial contamination levels of (1.4±0.2)∙10³
CFU/ml and (3.1±0.3)∙10⁶ CFU/ml, respectively; while the final
concentration in the IDPEF treated samples was 120±44 CFU/ml and
(1.1±0.3)∙10⁵ CFU/ml. The IDPEF storage method is of
particular importance for parts of the world lacking continuous electricity
supply, where today's pasteurization technologies use biomass burning that
contributes to 4% of global CO₂ emissions. Prelimenary life-cycle
analyses reveals that an energy needed for IDPEF storage of milk in India can
be generated by a small scale 2kW solar energy system operating 5.5 hours per
day in combination with small scale energy storage systems.