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FIZIKA A 19 (2010) 2 , 83-92
 
DIRECT AND INDIRECT PLASMA YEAST STERILIZATION
NASSER N. MORGANa, ASEM METAWAa and ABDOU A. GARAMONb
aPhysics Department, Faculty of Science (male), Al-Azhar University, Nasr city, Cairo, Egypt
bCenter of Plasma Technology, Al-Azhar University, Nasr city, Cairo, Egypt
Received 23 November 2009; Revised manuscript received 21 March 2010
Accepted 2 June 2010 Online 12 July 2010
Atmospheric-pressure parallel-plate dielectric barrier discharge has been
designed for sterilization of Saccharomyces Cerevisiae and Candida yeasts.
Oxygen has been used as the input working gas. The output gas after discharge
operation was a mixture of both ozone and oxygen, with concentration that
depends on the applied voltage between the electrodes, gap space and gas flow
rate. Sterilization process has been done in two ways, by direct exposure to
oxygen plasma inside the discharge cell and by indirect exposure to the plasma.
Survivor curves, and scanning and transmission electron microscope were used to
study the inactivation kinetics and morphology of the yeast surface before and
after sterilization. It has been found that the indirect sterilization causes
yeast inactivation in a short time, less than three minutes, while the direct
sterilization took place in a longer time, more than ten minutes.
PACS numbers: 52.80.Dy, 52.75.Rx
UDC 537.523, 533.924, 535.682
Keywords: atmospheric pressure discharge in oxygen, sterilization of yeast,
exposure inside the discharge cell, indirect exposure, survivor curves,
inactivation kinetics
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