High-voltage technologies for agriculture and food processing

Abstract

High-voltage technologies, including plasma, are used in agriculture and food processing applications. Repetitively operated, compact high-voltage power supplies with moderate peak power have been developed for controlling discharge plasmas and electric field distribution for agricultural and food processing applications. These applications are mainly based on the biological effects of a spatially distributed electric field and the chemically active species produced by the plasma. The intense pulse electric fields (PEFs) that have biological effects are caused by applying pulse voltage between the electrodes. When the applied voltage exceeds the corona discharge criterion, discharge plasmas that produce free radicals, UV radiation, an intense electric field and shock waves are generated by the accelerated electrons within the intense electric field in a gas or liquid medium. Different high voltages and plasmas may have different biological effects on substrates via the electric field and reactive species. For instance, intense electric fields form pores on the cell membrane (i.e. electroporation) or influence the nucleus. The agricultural applications of plasma are categorized as seed germination promotion, plant growth acceleration, the inactivation of bacteria in soil and liquid hydroponic media, and the promotion of fruit-body formation such as in mushrooms and fruits in the pre-harvest phase. In the postharvest phase, maintaining the freshness of agricultural products is important for a sustainable food supply chain. High-voltage and plasma technologies can contribute to maintaining freshness by decontaminating the air and liquid in agricultural products storage containers. In the food processing phase, an intense PEF can be used to extract juice, nutritional agents and antioxidant metabolites such as vitamin, carotenoids and polyphenols from fruits and vegetables. Some foods and liquors are made by fermenting a food substance. Fermentation is a metabolic process enabled by yeast and bacteria, the activity of which can be controlled by an intense electric field.