Progress 01/01/24 to 12/31/24
Outputs
Target Audience:1. Research institutions and industries engaged in milk processing research 2. Ordinary citizens who are interested in the impact of nonthermal milk processing technologies 3. Nationally and internationally professional communities for promoting food processing and food safety Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project in this period has provided training and professional development for 1 PhD student, 1 postdoc, and 1 Master student. How have the results been disseminated to communities of interest?The results have been disseminated to the communities of interest through a conference presentation at the ASABE 117th Annual International Meeting,University of Idaho Institute for Health in the Human Ecosystem Annual Research Symposium,as well asseveral peer-reviewed journals. What do you plan to do during the next reporting period to accomplish the goals?The plan for next reporting period will be focused on milk quality examination and reservation, and mechanism of shelf life extension of milk.
Impacts
What was accomplished under these goals?
In this periodwe investigated the efficacy of continuous-flow liquid plasma discharge (CLPD) treatment against four different bacterial strains: Shiga toxin-producing Escherichia coli (STEC), Salmonella, Staphylococcus aureus (S. aureus), and Listeria monocytogenes. These strains were chosen because they are associated with foodborne illnesses and have varying degrees of resistance to antimicrobial treatments. The objective was to evaluate the extent of microbial inactivation achieved by CLPD under different experimental conditions for each strain. Results showed that CLPD treatment significantly reduced the bacterial load of all four strains; however, the extent of inactivation varied between strains, reflecting differences in their inherent resistance mechanisms. Listeria monocytogenes and S. aureus were the most susceptible to CLPD. These strains achieved a 6-log reduction under relatively mild treatment conditions, which included a balanced combination of system power and liquid flow rate. The ease with which these strains were inactivated suggests a low threshold for oxidative damage induced by reactive oxygen and nitrogen species (RONS) generated during CLPD. Salmonella species showed significant reductions, reaching 6-log reductions, but required slightly more aggressive experimental conditions compared to Listeria and Staphylococcus. Salmonella required higher power levels and longer exposure times, indicating that it was moderately resistant to CLPD, likely due to its ability to resist oxidative stress and maintain cellular integrity under harsh conditions. STEC showed the highest resistance to CLPD treatment. The most aggressive experimental conditions, including the highest system power and extended exposure times, were required to achieve a 6-log reduction of STEC. The enhanced resistance of STEC suggests that its strong cell wall structure and efficientDNA repair mechanisms protect against the damaging effects of RONS. To optimize the antibacterial efficacy of Continuous-Flow Liquid Phase Plasma Discharge (CLPD) treatment, the impact of varying liquid flow rates was systematically investigated. Three distinct flow rates were selected for this study: 30 mL/min, 50 mL/min, and 70 mL/min. These flow rates were chosen to explore how the residence time of milk within the plasma treatment zone influences the extent of bacterial inactivation. The results revealed a clear inverse relationship between the liquid flow rate and the bacterial log reduction achieved. As the flow rate decreased, allowing milk to remain longer within the plasma field, a more substantial reduction in bacterial load was observed. Specifically, the lowest flow rate of 30 mL/min resulted in the most significant bacterial reduction, achieving a 7.2-log CFU decrease. This suggests that longer exposure to plasma discharge enhances the interaction between reactive species generated by the plasma and the bacterial cells, leading to more effective inactivation.Several physicochemical properties and plasma diagnostics were measured, including electrical characteristics, optical emission spectroscopy (OES), and the concentration of reactive oxygen and nitrogen species (RONS). A typical oscillogram of the applied voltage and discharge current, obtained using a Plasma 250 power supply, is shown in Figure. The oscillogram reveals multiple pulses, with maximum voltage and current amplitudes ranging from 5.2 to 6.8 kV, corresponding to an input power range of 180 to 320 W. OES measurements were conducted across a wavelength range of 200 to 900 nm to identify the reactive species generated during CLPD treatment. The OES spectrum, depicted in Figure X, indicates the presence of various excited species. A significant emission peak at 777 nm corresponds to atomic oxygen (O), with additional peaks at 844 nm indicating further oxygen emissions. The spectrum also shows nitrogen emissions, with a prominent peak at 656 nm for hydrogen alpha (Ha) and multiple nitrogen-related vibrational bands, reflecting the strong presence of nitrogen species within the plasma. These peaks are consistent with the use of air as the working gas in the plasma discharge, contributing to the generation of both reactive nitrogen species (RNS) and reactive oxygen species (ROS). These findings provide crucial insights into the active species produced during CLPD treatment and their roles in the microbial inactivation processes observed in treated milk.
Publications
- Type:
Peer Reviewed Journal Articles
Status:
Published
Year Published:
2023
Citation:
Sheng, H., S. Wu, Y. Xue, W. Zhao, A. B. Caplan, C. J. Hovde. S. A. Minnich. 2023. Engineering conjugative CRISPR-Cas9 systems for the targeted control of enteric pathogens and antibiotic resistance. PLoS ONE, 18(9): e0291520. https://doi. org/10.1371/journal.pone.0291520.
- Type:
Peer Reviewed Journal Articles
Status:
Published
Year Published:
2024
Citation:
3. #Sheng, H., #R. Ndeddy Aka, *S. Wu. 2024. Lipopolysaccharide Core Truncation in Invasive Escherichia coli O157:H7 ATCC 43895 Impairs Flagella and Curli Biosynthesis and Reduces Cell Invasion Ability. International Journal of Molecular Sciences, 25:9224. https://doi.org/ 10.3390/ijms25179224.
- Type:
Peer Reviewed Journal Articles
Status:
Published
Year Published:
2024
Citation:
Mukhtar, A., S. Saqib, D. Mohotti, R.J. Ndeddy Aka, M.M. Hossain, E. Agyekum-Oduro, *S. Wu. 2024. Non-thermal plasma-catalytic processes for CO2 conversion toward circular economy: fundamentals, current status, and future challenges. Environmental Science and Pollution Research, https://doi.org/10.1007/s11356-024-34751-3.
- Type:
Peer Reviewed Journal Articles
Status:
Published
Year Published:
2024
Citation:
Hossain, MM., D. Mohotti, A. Mukhtar, S. Saqib, B. Miller, J. Zhu, *S. Wu. 2024. Investigating iron removal from wastewater and simultaneous iron oxide catalyst synthesis by dielectric barrier discharge. Journal of Water Process Engineering, 65:105893.
- Type:
Peer Reviewed Journal Articles
Status:
Published
Year Published:
2023
Citation:
8. #Hossain, MM., #R. Ndeddy Aka, YS. Mok, *S. Wu. 2023. Investigation of silver nanoparticle synthesis with various nonthermal plasma reactor configurations. Arabian Journal of Chemistry, 16(10):105174. https://doi.org/10.1016/j.arabjc.2023.105174.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Yuan, Y., H. Sheng, S. Deng, D. Mohotti, T. Booker, A. Mukhtar, S. Wu. 2024. Continuous Inactivating Shiga-toxin Producing E. coli in Milk By a Liquid-phase Plasma Process. ASABE 117th Annual International Meeting. Paper#: 2401484. Anaheim, CA. July 28-31, 2024.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
S. Wu, Y. Yuan, H. Sheng, MM. Hossain. NIFA Project Directors Annual Meeting for Joint Project Directors Meeting for Food Safety and Defense (A1332) and Mitigating Antimicrobial Resistance Across the Food Chain (A1366). Long Beach, CA, July 13-14, 2024.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2024
Citation:
Y. Yuan, H. Sheng, T. Booker, D. Mohotti, S. Wu. Nonthermal and Continuous Milk Processing Using a Novel Liquid-Phase Plasma Discharge Technology. University of Idaho Institute for Health in the Human Ecosystem Annual Research Symposium, April 8, 2024.
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Progress 01/01/23 to 12/31/23
Outputs
Target Audience:1. Research institutions and industries engaged in milk processing research 2. Ordinary citizens who are interested in the impact of nonthermal milk processing technologies 3. Nationally and internationally professional communities for promoting food processing and health Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project in this period has provided training and professional development for 1 PhD student, 1 postdoc, and 1 undergraduate researcher. How have the results been disseminated to communities of interest?The results have been disseminated to the communities of interest through a conference presentation at the ASABE 116th Annual International Meeting and submitting a journal manuscript to Frontiers in Microbiology. What do you plan to do during the next reporting period to accomplish the goals?In the next period, wewill continue to test the inactivation of 4 food pathogens-supplemented milk to find operational conditions that can result in at least 5-6 logs of inactivation for each pathogen in milk. We will also be working onidentifying operating conditions of the CLPD process that optimally preserve the physicochemical and nutritional properties of milk within conditions that achieve satisfying microbial inactivation with the lowest energy consumption.
Impacts
What was accomplished under these goals?
During this period, amatrix of more than 20 unique operating conditions of CLPD processthat varied in voltage at discharge, input power, gas, and milk flow rates were used for nonthermal processing of commercially unpasteurized raw milk purchased from a local food coop. The design/operating parameters that achieved complete inactivation of total bacteria in the preliminary experiments included applied voltage at discharge: 780 V; input power: 250 W; air (carrier gas) flow rate: 0.2 standard liter per minute (SLPM); milk flow rate: 50 ml/min passing throughthe reactor system. For reactor design,the thickness of the quartz dielectric plate, δ = 3.2 mm; the dielectric plate opening, ? = 1.0 mm; and the internal diameter of the reactor, D = 12.7 mm was used. Continuous and stable plasma discharges were observed at both discharge points (at dielectric plate orifices) of the 2nd CLPD reactor as the milk flowed through. The raw milk was subjected to one single pass through the CLPD process, during which the effective contact time for milk with the plasma channel was estimated to be 6 milliseconds. At the end of treatment, the bulk milk temperature was 41.5°C. As compared to LTLT pasteurization which heats the same raw milk to 63°C for 30 minutes and HTST (72°C for 15 seconds), the CLPD exposure time is substantially shorter in the continuous-flow mode at a much lower processing temperature. In-series connection of two reactors will be studied for each one and combined inactivation efficiency. Results showed thatCLPD-treated raw milk had the highest values of true protein and solids-not-fat (lactose, caseins, whey, minerals, ash). Percentages of lactose, other solids (total solids minus fat and protein), milk urea nitrogen (a correlate of milk fat globule membrane or MFGM damage), and fatty acid components of CLPD-treated raw milk showed ignorable difference as compared to those in untreated raw milk and pasteurized milk samples. The slight increase in pH of CLPD-treated milk could be attributed to the stripping of dissolved CO2 in milk, but not to the production of unwanted inorganic ions which would reduce the pH. Although these data were derived from a single combination of operating conditions, all measured fatty acidsand physicochemical parameters were consistently unchanged from those of untreated raw milk and pasteurized milk.In addition, the forced passing of milk through two small orifices and the simplified one-pass continuous operation for bulk volumes will likely eliminate the need for homogenization and reduce scale-up costs for commercialization. Five typical pathogens in milk have been selected and collected to supplement pasteurized milk for CLPD treatment, including 1.Listeria monocytogenes, 2.Shiga-toxin producing E. coli (STEC), 3.Salmonella, 4.S. aureus, and 5.Bacillus cereus. Using the optimal condition identified with raw milk and E. coli (50 ml/min and 250 W), the log reduction for these five species is between 1-3 logs, signaling that the pathogens are more resistant to CLPD treatment and oxidation potential.In-series connection of two CLPD reactors have been studied and it was found that the trend for E. coli inactivation followed the addition relationship for log reduction. For example, at 100 ml/min flow rate, one reactor achieved 1.2 logs, while two achieved a little more than double at 2.9 logs of reduction for E. coli in milk. Further work in process design and optimizationis needed to improve pathogen inactivation efficiency.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Yuan, Y., H. Sheng, S. Deng, D. Mohotti, S. Wu. 2023. Nonthermal milk processing and quality preservation by continuous liquid plasma discharge process. ASABE 116th Annual International Meeting. Paper#: 2301501. Omaha, NE. July 9-12, 2023.
- Type:
Journal Articles
Status:
Submitted
Year Published:
2024
Citation:
Yuan Yuan, Shaobo Deng, Haiqing Sheng, MD Mokter Hossain, Robinson Junior Ndeddy Aka, Continuous inactivation of E. coli by air-activated liquid-phase plasma discharge. Submitted to Frontiers in Microbiology.
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Progress 01/01/22 to 12/31/22
Outputs
Target Audience: 1. Research institutions and industries engaged in milk processing research 2. Ordinary citizens who are interested in the impact of nonthermal milk processing technologies 3. Nationally and internationally professional communities for promoting food processing and health Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project in this period has provided training and professional development for 1 Master's student, 1 postdoc, and 2 undergraduate researchers. How have the results been disseminated to communities of interest?The results have been disseminated to the communities of interest through conference presentations at the University of Idaho Institute for Health in the Human Ecosystem Annual Research Symposium, University of Idaho Undergraduate Research Symposium, Idaho INBRE Statewide Research Conference, and the ASABE 115th Annual International Meeting. What do you plan to do during the next reporting period to accomplish the goals?In the next year, the novelCLPD processing system will be evaluatedfor microbial inactivation using raw milk and pasteurized milk supplemented with defined individual and community pathogenic bacteria.
Impacts
What was accomplished under these goals?
During this year, the work has been focused on the evaluation ofthe inactivation of E. coli (as a template microbe) by the novel established CLPD reactor to set the bottom line for the proposed second-generation CLPD processfor microbial/pathogen inactivation and the effluent quality of the liquid. First, a second-generationCLPD process was set up with a polycarbonate material reactor body with one high-voltage electrode and two ground electrodes, separated by two dielectric plates. These dielectric plates have a 1 mmopening in the center to concentrate the generated electrons during discharge so that the E. coli solution passing through the system is processed at least once and uniformly. Other parts in the CLPD treatment reactor system simplyinclude a peristaltic pump, a power supply, and a high-voltage AC transformer.To evaluate the process efficiency for E. coli inactivation and determine the significant process parameters that affect the disinfection ability of E. coli in water, a two-level partial factorial design is used. Four process parameters were selected according to preliminary experiments: conductivity (adjusted by adding NaCl to the initial E. coliinoculatedwater, 300-1000 μs/cm), applied power (determined by adjusting the variac transformer, 150-250 Watt), water flow rate (controlled by the peristaltic pump controller, 40-80 ml/min), and gas flow rate (controlled by a mass flow controller in standard liters per minute, 0.2-0.5 L/min). Asolution with a concentration of 2*107CFU/L E. coli water was used for each experimental run andpumped through the reactor in acontinuous passing mode based on the set liquid flow rate. At the end of each run, a 15 ml sample was taken, and the voltage, temperature, current, and power were recorded. The conductivity, pH, and concentration of CFU, nitrate ions (NO3- & NO2-), hydrogen peroxide (H2O2), and log reduction of three replicatesamples from each experimental run were measured and/or calculated. The resultsanalyzed with the Design-Expert softwaredetermine the statistical significance of each process parameter. Only applied plower and liquid flow rate out of the fourparameters were found to result ina p-value <0.05 which can be interpreted as the significantprocess parameters for E. coli inactivation by CLPD. At 250 watts, a liquid flow rate lower than 60 ml/min can achieve 6 or higher log reduction. On the other hand, at a 60 ml/min liquid flow rate, power higher than 250 watts can also achieve a 6-log reduction or higher. The pictures obtained by scanning electron microscope (SEM) revealed thatthe surface of the E. coli cells without plasma treatment is smooth, and the bacteria have a complete cell structure. After plasma treatment, the E. coli cell structure was severely damaged, the cell membrane was ruptured, and clumps were aggregated at the same time, the cell shape became smaller and irregular, and the permeability changed, indicating that the bacteria had died. Experimental results show that CLPD has a significant damaging effect on E. colicell structure. To optimize the two significant parameters, liquid flow rate and applied power, a central composite design (CCD) was used to find the optimal levels at a center between the five different levelsfor each of the individual variables, Surface response plots and quadratic equations for modeling the total bacterial inactivation rate and energy efficiency as the response variables were analyzed by the Design-Expert® software. Optimization shows that thehighest energy efficiency is achieved whenthe liquid flow rate is 52.3 mL/min and the system power of 250 watts. Taking the removal of 6 logs of Escherichia coli as the process standard, the lowest energy consumptionis 7.6 J/mL, which is among the lowest levels found in the literature. Overall, our findings have proved that CLPD is very promising in continuous E.coli and microbial inactivation with very short treatment time and not to cause significant change in water/liquid quality.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Yuan, Y., S. Deng, H. Sheng, R. Ndeddy Aka, L. Zhu, D. Mohotti, S. Wu. 2022. Nonthermal Milk Pasteurization by Continuous-Flow Liquid Phase Plasma Discharge. ASABE 115th Annual International Meeting. Paper#: 2200905. Houston, TX. July 17-20, 2022.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Stachofsky L., Y. Yuan, J. Johnson, S. Wu. Production of plasma activated water as a green disinfectant for E. coli inactivation. University of Idaho Institute for Health in the Human Ecosystem Annual Research Symposium, April 7, 2022.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Schoth, S., S. Wu, A. Nasir, Y. Yuan. 2022. Continuous inactivation of E. coli by liquid-phase plasma discharge. University of Idaho Undergraduate Research Symposium, April 25, 2022.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Stachofsky, L., Y. Yuan, S. Wu. Evaluation of plasma activated water as a green disinfectant for E. coli inactivation. 2022 Idaho INBRE Statewide Research Conference. Moscow, ID. August 1-3, 2022.
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