Invited Paper PB+BI+PC+PS-WeA1
Pulsed Power Applications for Farming and Food Processing

Wednesday, October 24, 2018, 2:20 pm, Room 104A

High-voltage and plasma are useful in several stages in agriculture, fishery and food processing including contribution to the food safety. Pulsed high-voltage produces intense high-electric field which can cause some biological effects such as stress response (stimulation) and electroporation. Types of pulsed power that also have biological effects are caused with gas discharges and water discharges which include reactive species such as ROS and RNS. We developed repetitively operated compact pulsed power generators with a moderate peak power for the agricultural applications.

The pulsed repetitive discharge were used for promoting growth of the vegetables and fruits. The growth rate of the vegetables and sugar content in the strawberry harvested after the cultivation increased by the plasma irradiation to the hydroponic solution [1] . The plasma was irradiated in the drainage water for 10 and 20 minutes each day. The leaf size of the plants increased with plasma treatment time. Number of colony forming units (CFU) of R. solanacearum in the liquid fertilizer decreased from 10⁷ to 10² CFU/mL using the discharge plasma treatment [2]. Seedlings with discharge plasma treatment were relatively healthy; in contrast, all seedlings in the positive control wilted and died from infection of R. solanacearum after 12 days. The yielding rate of Shiitake mushroom (L. edodes) was also improved with the high-voltage stimulation in fruit-body formation phase [3] .

Electrostatics effect were used for keeping freshness of not only agricultural products [4, 5], but also marine products [6] . In postharvest phase of agriculture, keeping freshness in storage house and in transportation container is important. The electrostatic effects can contribute to remove airborne bacteria and fungi spore from the storage house and container [4] . This removal contributes to reduce the infection risk with fungi and bacteria. Some kinds of fruit and vegetable emit the ethylene gas which accelerate a degradation of other kind fruits and vegetables. The plasma can contribute the ethylene removal via oxidization reaction [5] . The AC electric field induces a conformational change of protein. This technologies can contribute to extend the freshness of marine products [6] .

References:

1. J. Takahata et al., Jpn. J. Appl. Phys., 54 (2015) 01AG07.

2. T. Okumura et al., Plasma Medicine, 6 (2017) 247.

3. K. Takaki et al., Microorganisms, 2 (2014) 58.

4. S. Koide et al., J. Electrostatics, 71 (2013) 734.

5. K. Takahashi et al., J. Jpn. Appl. Phys., 57 (2018) AG04.

6. T. Okumura et al., Jpn. J. Appl. Phys., 55 (2016) 07LG07.