22P075-P
Long Preservation and Sterilization of Fresh Plants
生鮮植物の長期保存法と殺菌法
C.M. Liu１, Y. Nishida1,2,3, K. Iwasaki4, and K. Ting１
劉 沖明、西田 靖、岩﨑憲一、丁 鯤
１College of Engineering, Lunghwa University of Science and Technology
300 Wan-Shou Rd., Gueishan, Taoyuan 33306, Taiwan
２
Plasma and Space Science Center, National Cheng Kung University.
1, Ta-Hsueh Road, Tainan 70101, Taiwan,
３
Research Center for Biomedical Devices, Taipei Medical University,
Taipei 110, Taiwan
4
Daikoh Shoji Corporation, Takaraki-cho, Utsunomiya, Tochigi 320-0075, Japan“High-field plasma” technique in an atmospheric pressure has been developed to control and keep theenvironmental atmosphere in clean state. Here the “high-field plasma” system has no apparent discharges
between electrodes and the electric field inside the plasma area is high as 3  4  10 6 V/m in theatmospheric pressure. It is demonstrated that fresh fruits are preserved for much longer duration without
apparent bacterial contamination compared with the conventional method. In order for this purpose special
refrigerator has been developed, equipped with high-field plasma system. In the present refrigerator, usageof harmful or poisonous materials such as ozone, OH radicals or UV light is suppressed.

1. Introduction
In the contemporary world, it is important
requirement to supply the fresh foods stably.
Therefore, it is necessary to develop thepreservation system of fresh plants including foods
for a long duration without consuming much energy.
The plasma phenomena are employed as one of thepossible tools for solving these problems and many
new techniques are under developing.
The corona or glow plasma is one of the usefulcandidate for the present purpose due to its easy operation
at atmospheric pressure, and this is applied to manyindustrial field such as electrostatic precipitation,
generation of ozone, sterilization of bacteria and manyothers [1]-[4]. In reforming or decomposing and/or
sterilization of gases by using electrical discharges
in atmospheric pressure, however, harmful ozone
was generated, and new serious problems weretaken place so far, such as change of color of crops,
poisonous for human body and so on. When UV
light is employed instead of discharge system, thesame problems were arisen. In addition, more
important thing is quite low energy conversion
efficiency from electricity to UV lights.
We have developed new technique [5]-[9],named “High-Filed Plasma” system. This meansthat the plasma has no apparent discharges, such as
corona or silent discharges, and the electric field
inside the plasma area is as high as 3  4  10 6 V/m inthe atmospheric pressure. From now on we wish touse the terminology of “high-field plasma” insteadof just “plasma” or “discharges”. The precise
mechanism on high-field plasma has been
explained in Ref.[9]. In the present system theozone generation and/or UV light related effects
were suppressed and no apparent effects appeared.
The plants are breathing to put off the ethylenegas. As ethylene gas has strong ripe effects on the
fresh plants, it is necessary to remove it from thepreservation spots in order to keep crops in fresh
state for a long duration. The purposes of thepresent study include carbon hydrate decomposition
by using high-field plasma system.
2. Experimental setup
The experimental apparatus have been shown inRef.[10]. In the refrigerator, the air circulating system withhigh field plasma is set under well controlled conditions intemperature and humidity. The temperature can beadjusted within 1C accuracy and the humidity is5 % to the set values.
2-1 The case of grape preservation test;
The grapes were kept in two refrigerators; one
with high-field plasma system and the other withoutit, both were kept under the temperature 2±1ºC andhumidity 90%±5 % through the experimentalduration.
2-2 The case of banana preservation test;
The bananas were kept in two refrigerators withclear glass windows. The measured parameters
were ethylene gas amounts, weight changes andapparent changes. All bananas were kept at 12±1ºC

and humidity at 85%±5%.
2-3 The case of peach preservation test;
In the case of peach preservation, one refrigerator
was employed without high field system; instead
activated carbon (charcoal) was installed within an
air flow duct for absorbing ethylene gas under thetemperature 2±1ºC and humidity 80%±5%.
3. Preservation results
In the present paper, only the results on banana
preservation results are shown only because of space
limitation. Figure 1 shows the result how the ethylene gas
exhausted from the bananas inside of the refrigerator wastreated by the high-field plasma system. In the case shownby the “blue” color, plasma system was turned off or on in
the way of the experiments. When the high-field plasma
was turned-off, ethylene gas amount increases, but once
the high-field system was turned-on, the gas concentration
quickly went done.

Figure 1. Exhausted ethylene gas amount vs. time. Here,high-field plasma system was turned-on or off whilerunning the system (blue colored case).

The preservation results are shown in Fig.2 bysample photographs, where the photos of bananas
with starting days and week later are shown. As
clearly seen the bananas stored in the refrigerator
with high-field plasma system shows much smaller
damage (color change) than the case withouthigh-field system. This is resulted from the fact thatthe high-field system decomposes ethylene gas andripe effects on bananas from ethylene gas wereweak.
4Discussions
In the present system, no corona or silent
discharges occurs at all, rather high electric-field isbuilt between electrodes. For the present purposethe electric field between electrodes should bestrong enough to accelerate electrons in the ambient
atmospheric air. The field strength is uniform overmost of the electrode area with 0 . 6  3  10 6 ,(V/m) depending on the applied voltages.

Figure 2. Sample photos of experimental results.

The bonding energy of O-H is about 4.74 eV, thatof H-H is 4.44 eV, and that of C-H is 4.22 eV [11].
Therefore, electrons with energy more than 5 eV
could decompose these bonding, and as a result
oxygen, hydrogen and carbon could be produced as
final products.
These processes can decompose many kinds ofchemical bonding including the origin of polluted
materials in the air, bacteria, and drying action of
the air. This technique is extended to apply for thecontaminated gas cleaning system or forsterilization devices of contaminated air withbacteria [10].
References[1] J.S. Chang, P. A. Lawless, and T. Yamamoto, IEEE
Trans. Plasma Sci. 19, 1152 (1991).
[2] M. Sato, N. Ishida, Miho Neide, A.T. Sugiarto, T.
Ohshima, and H. Taniguchi, IEEE Trans. Ind. Appl.,
37(6), 1646 (2001).
[3] T. Ohshima, T. Ono, and M. Sato, J. Electrostatics,46(2/3), 163 (1999).
[4] L. Zhou, B. Xue, U. Kogelschatz and B. Ellassson,
Energy Fuels, 12, 1191 (1998).
[5] T. Nagasawa, Y. Nishida, and T. Miyazaki, T. IEE ofJapan, 119-A, pp. 1429-1435 (1999) (in Japanese).
[6] T. Nagasawa, Y. Nishida, Y. Uda, and T. Kawatsu, T. IEE of Japan, 121-D, pp. 526-527 (2001) (in Japanese).
[7] Y. Nishida and K. Iwasak, Proc. of The 5th
Asia-Pacific Int. Symp. on the Basic and Appl. ofPlasma Tech. pp.-151-152, Dec.10-12, (2007),Kaohsiung, Taiwan.
[8] Nihon Hosen System Co, Apr. 20, 1993 (jp 2733470)(Japanese patent). , Jul. 17, 1991 (jp 12047013)(Japanese patent). T. Nagasawa , Y. Nishida and K.
Iwasaki., Nov. 22, 2001 (jp 3650932) (Japanesepatent)[9] C.M. Liu, Y. Nishida, K. Iwasaki, and K. Ting:, IEEE
Trans. Plasma Sci. 39, 717 (2011).
[10] Y.Nishida and K.Iwasaki,(JP2009-165183) (Appliedfor the Japanese patent).
[11] Table 9.123 and others, Chemical Handbook vol.3,2 (June, 1984). The chemical Society of Japan,Maruzen (in Japanese).