ABSTRACT
Prospects of pulsed electric field technology application on acid whey concentrate pretreatment were analyzed. Stationary and flow pre-treatment systems were combined with different treatment parameters: electric field strength (Eâ¯=â¯39â¯kV/cm, 95â¯kV/cm, 92â¯kV/cm), pulse duration (τâ¯=â¯60â¯ns, 90â¯ns, 1000â¯ns) and pulse number (pnâ¯=â¯up to 100 pulses). Isolates of Saccharomyces sp. and Lactobacillus sp. were predominant in concentrate. Significant non-thermal inactivation effect was achieved after PEF treatment. Exposure to short pulses selectively inactivated yeast cells, as a result PEF technology can be applied for low-energy acid whey processing.
Subject(s)
Electricity , Food Contamination/prevention & control , Food Microbiology , Lactobacillus , Saccharomyces/physiology , Whey/microbiology , Electroporation , Food Preservation , Microbial ViabilityABSTRACT
Saccharomyces cerevisiae yeast cells were used as a model organism to investigate the effects of various pulsed electric fields on the programed death of such cells. These were exposed to electric field pulses with field strengths (E) of up to 220kV/cm. The effects of square shaped pulses having different durations (τ=10-90ns) and different pulse numbers (pn=1-5) were then analysed. The obtained results show that nanosecond pulses can induce the death of such cells, which in turn is dependent on the electric field pulse parameters and increase with the rise in E, τ and pn. The decrease of the cells' viability was accompanied by an increase in the active form of intracellular yeast metacaspases. It was thus shown that nanosecond electric field pulses induced the caspase-dependent yeast cell death.
