Enhancing drying efficiency and nutritional quality of oat grass using high-voltage discharge plasma drying

Oat grass is a premium forage with exceptionally high nutritional value and quality. Freshly harvested oat grass requires rapid drying to extend its shelf life. Currently, the primary methods employed for drying oat grass are natural air drying (AD) and hot air drying (HAD); however, prolonged drying times or elevated temperatures can lead to degradation in hay quality. In response to this issue, this study explores the use of a novel non-thermal drying technology—high-voltage discharge plasma drying (HVDPD) treatment—for oat grass dehydration. We comparatively investigate the effects of high-voltage discharge plasma drying (HVDPD), hot air drying (HAD), and natural air drying (AD) on the physicochemical properties as well as quality characteristics of oat grass. Oat grass was dried by maintaining a constant voltage at 35 kV while varying the gradient needle spacing. At the same time, a series of studies are conducted on the characteristics of electric fields, including the voltage and current waveforms of needle–plate electrodes, the energy consumption for high-voltage discharge plasma drying (HVDPD), and ICCD emission spectroscopy. The results indicate that reducing needle spacing during HVDPD treatment leads to significant improvements in rehydration performance, microstructural integrity, forage quality, and energy consumption of the oat grass. Specifically, compared to the natural air drying (AD) treatment, the improvements in the performance of oat grass after HVDPD treatment are primarily reflected in the following aspects: (1) the average drying rate increased by 2.36 times. (2) Relative feed value (RFV) and relative forage quality (RFQ) improved by 1.14 times and 1.18 times, respectively. (3) Although specific energy consumption (SEC) was generated, it amounted to only 0.06 times that of hot air drying (HAD) treatment. In summary, HVDPD represents an effective dehydrating technique capable of considerably enhancing both the nutritional quality and inherent characteristics of oat grass. This research offers innovative methodologies for storage and preservation concerning oat grasses' quality.