Processing of Fresh-Cut Potato Using Plasma-Activated Water Prepared by Decreasing Discharge Frequency

Abstract

As a novel non-thermal processing method, the concentration of active compounds in plasma-activated water (PAW) is usually adjusted by changing the voltage and preparation time. We recently adjusted the discharge frequency and found that the PAW properties were improved. In this study, fresh-cut potato was selected as a model, and PAW was prepared using a frequency of 200 Hz (200 Hz-PAW). Its efficacy was compared with that of PAW prepared using 10 kHz. The results showed that the ozone, hydrogen peroxide, nitrate, and nitrite concentrations in 200 Hz-PAW were 5.00-, 3.62-, 8.05-, and 1.48-fold higher than those of 10 kHz-PAW. PAW inactivated the browning-related enzymes polyphenol oxidase and peroxidase, lowering the browning index and inhibiting browning; 200 Hz-PAW exhibited the lowest of these parameters during storage. In addition, PAW induced PAL to promote phenolic synthesis and increase antioxidant activity to delay malondialdehyde accumulation; 200 Hz-PAW exhibited the highest of these parameters. Moreover, 200 Hz-PAW had the lowest weight loss and electrolyte leakage rates. Furthermore, microbial analysis showed that the lowest aerobic mesophilic, mold, and yeast counts during storage were observed in the 200 Hz-PAW group. These results suggest that frequency-controlled PAW has the potential to treat fresh-cut produce.

Pulsed-control plasma-activated water: An emerging technology to assist ultrasound for fresh-cut produce washing

“…The physical and chemical properties of PAW and PCPAW are listed in Table 1 . We observed increases in the output power, ORP, conductivity, and concentrations of ozone, H 2 O 2 , nitrate, and nitrite of 15 %, 10 %, 90 %, 144 %, 47 %, 217 %, and 41 %, respectively, while the frequency decreased from 10 kHz to 50 Hz, which is consistent with our previous report [17] . This was attributed to the increased output power, which led to a higher RONS concentration [17] .…”

“…6 E). PAW and US, as a solution containing ROS and a physical stimulus to fresh produce, respectively, can induce a stress response that promotes phenolic synthesis; however, the processing time is at least 2 min [17] , [35] . The processing time in this study was set to 1 min to meet the continuous processing line requirements [36] , [37] .…”

“…A modified dielectric barrier discharge (DBD) plasma system (CTP-2000 KP, Suman, Nanjing, China) containing a plasma generator (with a fixed discharge frequency of 10 kHz), pulsed wave generator (used for frequency control), DBD chamber, voltage booster, and digital oscilloscope was used for PAW preparation. Detailed information on the plasma system, PAW preparation procedure, plasma output power calculation, RONS concentration, and physical properties (pH, conductivity, and ORP) of PCPAW and PAW was obtained from our previous study [17] . Because the increased temperature was associated with plasma discharge, the resulting PCPAW and PAW was immediately transferred to a tube and placed in liquid nitrogen to decrease the temperature to 4 ± 1 °C within 30 s. Although the highest RONS concentration was observed at 200 Hz [17] , quality loss (browning spots) was observed in lettuce leaves after washing with 200 Hz PAW and was not observed when employing 50 Hz PAW.…”

“…Detailed information on the plasma system, PAW preparation procedure, plasma output power calculation, RONS concentration, and physical properties (pH, conductivity, and ORP) of PCPAW and PAW was obtained from our previous study [17] . Because the increased temperature was associated with plasma discharge, the resulting PCPAW and PAW was immediately transferred to a tube and placed in liquid nitrogen to decrease the temperature to 4 ± 1 °C within 30 s. Although the highest RONS concentration was observed at 200 Hz [17] , quality loss (browning spots) was observed in lettuce leaves after washing with 200 Hz PAW and was not observed when employing 50 Hz PAW. Thus, in this study, PAW and PCPAW were prepared at 10 kHz and 50 Hz, respectively.…”

“…Recently, a novel approach to PAW preparation, known as pulsed-control PAW (PCPAW), was introduced. The PCPAW involves adjusting the plasma discharge frequency to enhance the concentration of RONS [17] . Aihemaitijiang et al [17] observed that a discharge frequency of 200 Hz resulted in the highest concentrations of ozone, H 2 O 2 , nitrate, and nitrite (5.0-, 3.6-, 8.1-, and 1.5-fold, respectively) when compared to PAW prepared under the original plasma frequency of 10 kHz.…”