Browsing by Author "Santamaría, Brenda"

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    Effects of the Plasma-Activated Water on the Quality and Preservation of Fresh-Cut Lettuce.
    (2023) Chamorro, Juan Camilo; Denoya, Gabriela Inés; Santamaría, Brenda; Fina, Brenda; Ferreyra, Matías; Cejas, Ezequiel; Rodriguez, Anabel; Vaudagna, Sergio; Prevosto, Leandro
    — The effect of the application of plasma-activated water (PAW) on the quality and preservation of fresh-cut lettuce is reported in this article. PAW was produced by using a liquid cathode air discharge. The average (bulk) water temperature was kept at ∼22 ◦ C during the activation procedure and stored at 4 ◦ C for up to five days. The pH value, electrical conductivity, and concentrations of H2O2 and NO− in liquid at day 1 were 2.81, 1492µS/cm, and 77.8 and 223.4 mg/L, respectively, with slight variations over the whole storage time. No measurable amounts of NO− 10 2 were found. Twenty pieces of lettuce leaves were washed for 1 and 5 min in 1 L of PAW and stored for one and five days. PAW treatments were compared to tap water treatments. The lettuce samples were stored at 4 ◦ C and analyzed on days 1, 3, and 7. The chromatic parameter results suggest that PAW treatments significantly reduce the degradation of lettuce chlorophyll from day 3 of refrigerated storage. The lettuce firmness was not significantly modified. The microbiological results of aerobic mesophilic, enterobacteriaceae, and psychrotrophs populations have shown that lettuce treated with PAW after three days of storage exhibited the strongest inactivation efficiency. Psychrotrophs counts were maintained for up to seven days. Similar inactivation efficiencies were found regardless of the PAW storage time. PAW treatments also favored both the antioxidant capacity FRAP, ABTS, and DPPH, and the total phenolic.
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    Indigo Carmine Degradation in Water Induced by a Pulsed Positive Corona Discharge in Air: Discharge and Postdischarge Effects.
    (2022) Ferreyra, Matías; Fina, Brenda; Milardovich, Natalio; Chamorro, Juan Camilo; Santamaría, Brenda; Balestrasse, Karina; Prevosto, Leandro
    In recent years, one of the fastest growing technological applications in the field of nonthermal plasmas is the degradation of organic contaminants of water. In this work, the degradation of indigo carmine (IC) in water induced by a pulsed positive corona discharge operating in ambient air is reported. Degradation levels in different volumes of IC in solution with distilled water treated with different plasma exposure times immediately after discharge (0 h), and in the postdischarge up to 24 h were examined. To explain the IC discoloration in the postdischarge phase, a chemical model was developed. The stability of the reactive species in solution nitrate (NO3 −), nitrite (NO2 −) and hydrogen peroxide (H2O2 ), as well as the properties of the solution (electrical conductivity, pH) were also measured. The results suggest that the hydroxyl radical (OH˙) as well as ozone (O3 ) are the main oxidizing species during the discharge phase, being primarily formed in the gas phase through plasma-mediated reactions and then transferred to the liquid by diffusion, while the OH˙ production in the bulk liquid through the decomposition of peroxinitrous acid (O=NOOH) plays a major role in the IC degradation during the postdischarge. These results are associated with a noticeably increase in the energy-yield values observed at 24 h post-treatment.
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    Physicochemical Properties and Time Stability of Plasma Activated Water by a Liquid-Cathode Glow-Type Discharge in Air: The Effect of Air Confinement.
    (2023) Santamaría, Brenda; Ferreyra, Matías; Chamorro, Juan Camilo; Cejas, Ezequiel; Fina, Brenda; Prevosto, Leandro
    Nonthermal discharges in atmospheric pressure air in contact with water produce large amounts of reactive species in the gas phase that can enter into the water by diffusion, thus inducing the formation of secondary reactive species in the liquid phase, including those long-lived species such as NO2 NO3, and H2O2. Depending on the controllable parameters of the discharge, the plasma activated water (PAW) may acquire differ 8 ent physicochemical properties, resulting in various applications. Physicochemical measurements of PAW obtained by means of a water-cathode glow-type discharge in atmospheric pressure air operating in open and closed reactor conditions are reported. The discharge was operated in a millisecond pulsed-dc regime at an rms current value of 100 mA and a power of 100 W. A large volume of 1 L of distilled water was treated for 30 min. In both cases, low pH values of ∼2.5 and very high levels of NO3(up to 250 mg/L) in PAW were obtained; however, in the closed system, no H2O2 was found and high concentrations of nitrite (120 mg/L) were measured, while in the open system, large levels of H2O2 were observed (45 mg/L) and no NO 2 was found. Likewise, the electrical conductivity value for the closed reactor (≈2000 µS/cm) was significantly higher than for the open reactor (≈1000 µS/cm). The reasons for these different behaviors in terms of PAW chemistry are discussed. Also, the time stability of PAW was measured.