University of Guelph

Ruanduff Electrical Limited

James D Cross

Gauri S Mittal

Mansel W Griffiths

Shirley Yuet Ho

A method and apparatus for electrically treating foodstuffs flowing through a treatment chamber with low energy, high voltage electrical pulses for non-thermal pasteurization and/or sterilization. Instant-charge-reversal electrical pulses are applied to a foodstuff located between two electrodes in a treatment chamber, each electrical pulse having a pulse width in a range from about 1 to 5 .mu.s with vertically rising voltage to a peak followed immediately with a decreasing voltage through zero volts and continuing to a voltage peak of opposite polarity and rising vertically back to zero volts. The electrical pulses are very low energy (0.1-25 Joules/pulse) and the field strengths are in the range 15 kVolts/cm to 120 kVolts/cm. This instant-charge-reversal electrical pulse is shown to have a much greater microbial killing power compared to other pulse waveforms used to treat foodstuff. The apparatus uses an electrode arrangement including a cylindrical inner electrode and an annular disc with the cylindrical electrode inserted through the hole in the disc.

Method and apparatus for electrically treating foodstuffs for

A power supply for producing a high voltage DC output. The power supply comprises a primary winding and a series of secondary stages each having secondary windings coupled to the primary winding through a magnetic circuit. Each secondary stage comprises a printed circuit board with the secondary windings formed as a series of independent coils or turns on the board substrate. The magnetic circuit comprises a series of segments which are separated by an insulating film to maintain each segment at the same potential as the associated printed circuit board. Each coil includes a rectifier element for converting the induced AC voltage into a DC voltage. The rectifier elements are connected in series and the printed circuit boards are coupled to produce a high level DC voltage output signal, for example, a minimum 200 kV output. To compensate for Magneto Motive Force (MMF) losses through the insulating film, the rectifier elements include a compensation capacitor.

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Waterloo, Canada

James D Cross