Progress 12/01/13 to 11/30/18
Outputs
Target Audience:Environmental Scientists, Food Safety Scientists, Food Processing Industry, Food Regulatory Agencies, General Consumers Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project provided training for two doctoral students, one master student and three undergraduate students in conducting research. How have the results been disseminated to communities of interest?A total of 22 publications have been resulted from this project, which include 12 presentations at international conferences and research institutions, eight journal papers (including two in preparation to be submitted in the near future) and two theses. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Six specific research objectives were developed in order to achieve the overall goal: (1) Improve and develop analytical methods for measuring conventional and emerging DBPs in process water and produce; (2) Prioritize DBPs based on screening of their concentrations that can be formed after typical chlorine disinfection for produce; (3) Evaluate the formation of DBPs and impact on microbial inactivation efficacy due to different types of disinfectant, produce, oxidant dosage, contact time, pH, temperature and ionic composition; (4) Evaluate the stability and transfer of DBPs in and between water and produce; (5) Elucidate the mechanisms of DBP formation from organic precursors prevalent in produce; and (6) Develop effective disinfection strategies of high microbial inactivation efficacy and minimized DBP formation for fresh and fresh-cut produce. For Objective 1: Robust, sensitive and reliable analytical methods were successfully developed to measure a total of 45 different conventional and emerging DBPs in produce and produce wash water. The DBPs encompass many classes of compounds including trihalomethanes, haloacetic acids, nitrogenous DBPs, other carbonaceous DBPs, nitrosamines and aldehydes. The analytical methods were evaluated and validated by a variety of different produce samples. In total, according to the different chemical properties of the many DBPs, four analytical methods were developed for measuring DBPs in produce wash water, and four analytical methods were developed for measuring DBPs in produce samples. The details and performance of these analytical methods have been published in journal papers (Lee et al. 2018; Lee and Huang, 2019; Lee et al. 2019). For Objective 2: Many chlorine washing experiments were conducted with various fresh and fresh-cut produce samples including lettuce (iceberg and romaine), green cabbage, spinach, mushroom, strawberry and grape for the potential of DBPs formation in wash water and/or produce. Based on the results, some general trends of DBPs formation were observed, although the DBPs formation is highly variable depending on the type of produce and washing conditions. For the largest consumption produce lettuce, we found the general trend of DBPs formation after chlorine washing followed the rough order of haloacetic acids ≥ haloacetamides > haloacetonitries > carbonacerous DBPs > trihalomethanes > halonitromethanes > nitrosamines in decreasing abundance. Such formation abundance trends for the different DBPs were roughly similar in the wash water and in the produce, respectively, and these trends appear to hold not only for lettuce but for other produce samples we have investigated. These results have helped us prioritize the DBPs according to their abundances, which will be useful for future work in further evaluation and monitoring. These results are reflected in our publications (Lee et al. 2018; Lee and Huang, 2019; Lee et al. 2019). For Objective 3: We have evaluated the DBPs formation under different washing conditions and for different forms of produce (fresh produce, fresh-cut and produce liquid mixture from stomacher). Indeed, for the same type of produce, chlorine dosage, produce loading, washing time, temperature, and water pH all exhibited significant impacts on the DBPs formation potential, in terms of concentration as well as DBP compound type. The chlorine demands of fresh-cut produce were also evaluated for a variety of produce. Based on the results, robust modeling tools were developed to successfully predict the chlorine demands of fresh and fresh-cut produce, and these tool were further utilized to develop smarter chlorine dosing strategies (Chen and Hung, 2016, 2017 and 2018). For Objective 4: Our experimental results showed that a major proportion (>80%) of the total generated DBPs after chlorine washing of fresh-cut lettuce were in the wash water, indicating the hydrophilic nature of most of the DBPs due to their relatively low molecular weights. This trend is reported in our publication (Lee and Huang, 2019). Additional clean water (without sanitizer) washing could assist washing off DBPs from the produce surfaces, and the sorption tendency of DBPs from water to the produce was modest. For Objective 5: We have evaluated the DBPs formation potential of various produce organic matter after their were exposed to chlorine sanitizer. The bulk organic properties of the different crushed produce mixtures (including spinach, Romaine lettuce, Iceberg lettuce, tomato, strawberry and grape) were characterized extensively, revealing that different produce contain very different organic constituents. The produce organic mixtures also showed substantially different DBPs formation potentials and chlorine demands. It is evident that different organic content of produce significantly affected the types and concentrations of DBPs formation. However, no clear trend or correlations could be established between the amounts of DBPs formed versus the specific properties of the produce organic matter. The difficulty to obtain any generalization suggested the highly complicated DBP formation reactions. For Objectives 6: We have conducted studies to develop a chlorine dosing strategy to maintain microbial safety as well as minimize the DBPs formation potential. Prediction equations to estimate residual chlorine based on water quality parameters were developed and validated using fresh-cut iceberg lettuce and whole strawberries in an automated produce washer. Validation results show that equations successfully predicted the initial chlorine concentration needed to achieve residual chlorine at 10, 30, 60, and 90 mg/L for both lettuce and strawberry washing processes, with the root mean squared error (RMSE) at 4.45 mg/L. In addition, the populations of E. coli O157:H7 on inoculated lettuce and strawberries treated with solutions containing residual chlorine ranging from 10 to 90 mg/L was reduced by 0.6 log CFU/g. Our study demonstrated that 10 mg/L can be set as the targeted residual chlorine for the prediction equations. The chlorine dosing strategy based on equations can be used for produce industry to maintain microbial inactivation efficacy without using excess amount of chlorine (Chen and Hung, 2018). Overall, chlorine-containing disinfectants are widely used in the processing of fresh and fresh-cut produce; however, there had been significant knowledge gaps regarding the formation, identities and quantities of DBPs generated as food residues or in the processing water. Our work in this project has significantly addressed this knowledge gaps by investigating many conventional and emerging DBPs of concern for their mechanisms of formation and transfer into fresh and fresh-cut produce after chlorine disinfection methods. The results will be very useful for the produce industry to better understand the risks of food-borne DBPs and develop strategies to improve current chlorine sanitation processes. They will also contribute to the long-term sustainability of food production systems by providing safer products, reducing improper usage of hazardous chemical disinfectants, and reducing contamination in food processing water.
Publications
- Type:
Journal Articles
Status:
Other
Year Published:
2019
Citation:
Huang, C.-H.; Lee, W.-N. 2019. Evaluation of formation potential and risk of DBPs in fresh-cut produce washing by chlorine sanitizer. (in preparation)
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Lee, W.-N; Huang, C.-H. Analytical Method Development and Improvement for Detection of Multi-Classes of Disinfection By-Products in Water and Produce, poster presentation at the SETAC North America 35th Annual Meeting, Vancouver, Canada, November 9-13, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Lee, W.-N; Huang, C.-H. Analytical method development and improvement for detection of multi-classes of disinfection by-products in water and produce, poster presentation at the SETAC North America 35th Annual Meeting, Vancouver, Canada, November 9-13, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Lee, W.-N; Huang, C.-H. Screening and prioritizing conventional and emerging disinfection by-products developed in fresh and fresh-cut produce during chlorine-based disinfection, oral presentation at the IAFP Annual Meeting, Portland, Oregon USA, July 25-28, 2015.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Hung,Y.-C. 2015. Ensuring produce safety through non-thermal treatments. The 8th UGA-SHOU-SAAS-NTOU Food Safety and Trade Initiative Mini Summit. Taipei, Taiwan. October 26-27, 2015.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Huang, C.-H.; Lee, W.-N. F-DBPs - Formation and control of disinfection byproducts in produce processing, Gordon Research Conference on Disinfection By-Products, South Hadley, MA, August 1, 2017.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Hung,Y.-C. and X. Chen. 2017. Predicting chlorine demand for produce washing. 10th Food Safety, Policy and Sustainability mini Summit. College Park, Maryland, USA. October 30-31, 2017.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Huang, C.-H. Disinfection By-Products from Food Processing. College of Public Health, National Taiwan University, Taipei, Taiwan, December 21, 2017.
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Chen, X.; Hung, Y.-C. 2016. Predicting chlorine demand of fresh and fresh-cut produce based on produce wash water properties. Postharvest Biology and Technology, 120, 10-15.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2016
Citation:
Mao, M. 2016. Critical Review of Disinfection By-Products (DBPs) in Fresh Produce and Process Water, M.S. thesis, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332.
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Chen, X.; Hung, Y.-C. 2017. Effects of organic load, sanitizer pH and initial chlorine concentration of chlorine-based sanitizers on chlorine demand of fresh produce wash waters. Food Control, 77:96-101.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2017
Citation:
Chen, X. 2017. Development of a chlorine-based sanitation strategy to ensure microbial safety for fresh produce. Ph.D. dissertation. Department of Food Sciences, University of Georgia, GA.
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Lee, W.-N.; Huang, C.-H.; Zhu, G. 2018. Analysis of 40 Conventional and emerging disinfection by-products in fresh-cut produce wash water by modified EPA methods. Food Chemistry, 256, 319-326.
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Chen, X.; Hung, Y.-C. 2018. Development of a chlorine dosing strategy for fresh produce washing process to maintain microbial food safety and minimize residual chlorine. J. Food Sci.83 (6), 1701-1706.
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
Lee, W.-N.; Huang, C.-H. 2019. Formation of disinfection byproducts in wash water and lettuce by washing with sodium hypochlorite and peracetic acid sanitizers, Food Chemistry X, vol. 1, open access.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Chen, X.; Hung, Y.-C. Predicting Chlorine Demand of Fresh and Fresh-cut Produce during Washing, oral presentation at the IAFP Annual Meeting, St. Louis, Missouri USA, July 31- August 3, 2016.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Huang, C.-H.; Lee, W.-N; Chen, X.; Hung, Y.-C. Factors Influencing the Development of Conventional and Emerging Disinfection By-Products during Fresh-Cut Produce Washing using Chlorine Sanitizer, oral presentation at the IAFP Annual Meeting, St. Louis, Missouri USA, July 31- August 3, 2016.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Chen, X.; Hung, Y.-C. Predicting the chlorine demand of various produce wash waters under different sanitizer pH, initial chlorine concentration and organic load. IFT Ann Mtg. Las Vegas, NV. June 25-28, 2017. Session P01-59.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Lee, W.-N.; Huang, C.-H. Formation of disinfection byproducts in wash water and lettuce by washing with sodium hypochlorite and peracetic acid sanitizers, poster presentation at the IAFP Annual Meeting, Tampa, Florida USA, July 8- July 12, 2017.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Lee, W.-N.; Huang, C.-H.; Luo, Y.; Morris, D. Comparison of flume wash and single-pass wash on the formation of disinfection by-products for produce processing, poster presentation at the IAFP Annual Meeting, Tampa, Florida USA, July 8- July 12, 2017.
- Type:
Journal Articles
Status:
Submitted
Year Published:
2019
Citation:
Lee, W.-N.; Huang, C.-H.; Zhu, G. 2019. Analysis of a wide range of conventional and emerging disinfection by-products in fresh-cut produce, revised manuscript submitted to Food Chemistry.
- Type:
Journal Articles
Status:
Other
Year Published:
2019
Citation:
Huang, C.-H.; Lee, W.-N.; Morris, D.; Luo, Y. 2019. Impacts of washing conditions on disinfection byproducts formation during produce processing. (in preparation)
|
Progress 12/01/16 to 11/30/17
Outputs
Target Audience:Environmental Scientists, Food Safety Scientists, Food Processing Industry, Food Regulatory Agencies, General Consumers Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project provided training for two doctoral students in conducting research. How have the results been disseminated to communities of interest?In this project period, the study results were disseminated by two journal papers and five conference presentations (see the list of publications). What do you plan to do during the next reporting period to accomplish the goals?For Objective 1, this part of project is completed. For Objective 2, this part of project is completed. For Objective 3, we will analyze the correlations between produce wash water properties and the DBP formation potential for various fresh produce wash water. For Objective 4, a few more different types of produce will be tested for the adsorption and desorption of DBPs. The cut produce will be soaked in the water with 100 μg/L DBPs standards. Both water and produce will be analyzed for the DBPs concentrations to determine the transfer between water and produce. From the experiments, a part of the produce will be washed by DI water, tap water and water containing baking soda assess how effectively the household washing processes may remove the DBPs residues in produce. The other part of the DBPs-soaked produce will be refrigerated for different time periods (e.g., 3, 7, 15, and 30 days) to assess the stability of DBPs residues in the produce. For Objective 5, new results to be obtained under the Objective 3 may provide insight on the important characteristics of produce organics that are high DBPs generators. Based on these results, we may conduct additional experiments to separate product organic matter into different fractions (e.g. by polarity or molecular weight) and then subject the fractions to chlorine for DBPs formation to probe additional insight on the key characteristics of produce's DBPs precursors. For Objective 6, this part of project is completed.
Impacts
What was accomplished under these goals?
Chlorine-containing disinfectants are widely used in the processing of fresh and fresh-cut produce. However, significant knowledge gaps still exist regarding the formation, identities and quantities of disinfection by-products (DBPs) generated as food residues or in the processing water. This project addresses this issue by investigating many conventional and emerging DBPs of concern for their mechanisms of formation and transfer into fresh and fresh-cut produce after chlorine-based disinfection methods (sodium hypochlorite, chlorine dioxide and electrolyzed oxidizing water), and for their impact on the efficacy in inactivating pathogens. For Objective 1: We have developed and improved the analytical methods for measuring a total of 43 conventional and emerging DBPs (including nine HAAs, 24 DBPs, nine nitrosamines and one halobenzoquinone) in process water and produce by adjusting different reaction time, temperature, and other parameters in the extraction procedures and analytical instrumentation. The method detection limits (MDLs) of the process water analytical methods were between 0.0003-1.51 μg/L and the calibration linearity were at R2 = 0.9967-0.9999. The recoveries of DBPs spiked (100 ng/L or 1 μg/L standards) in DI water were between 60-130%. The recoveries of the DBPs in process water with lettuce were between 42-147%, in process water with strawberries were between 32-132%, and in process water with cabbage were between 28-183%. For haloquinolones, good linearity (R2 = 0.9998) in 1-1000 μg/L was achieved in the standard calibration of DCBQ. The MDLs of the produce analytical methods were between 0.25-10.2 ng/g and the calibration linearity were at R2 = 0.9913-0.9999. The recoveries for spiking 42 DBPs (except DCBQ) in the homogenized lettuce were between 40-146%, in the homogenized strawberries were between 36-144%, and in the homogenized cabbage were between 31-137%, indicating that the similar method could be applied to other types of produce. For Objective 2: Further experiments were conducted to compare lettuce, strawberry and cabbage for the DBPs formation in both wash water and produce. Lettuce, strawberries and cabbage from the supermarket were cut into sizes similar to those in the previous method and washed by 100 mg/L (as Cl2) NaOCl solution at pH 6 controlled by phosphate buffer. For the results of washing lettuce, the top three DBPs that formed the most in the wash water were dichloroacetic acid, dichloroacetonitrile, and dichloroacetamide. In the washed lettuce, the top three DBPs that formed the most were chloroform, dichloroacetic acid, and dichloroacetamide. For the results of washing strawberries, the top three DBPs that formed the most in the wash water were trichloroacetic acid, dichloroacetic acid, and dichloroacetamide. In the washed strawberries, the DBPs that formed the most were trichloroacetic acid, dichloroacetic acid, and tribromoacetic acid. For the results of washing cabbage, the top three DBPs that formed the most in the wash water were trichloroacetamide, trichloroacetic acid, and dichloroacetamide. In the washed cabbage, dichloroacetamide, dichloroacetic acid, and trichloroacetic acid formed the most. The type of produce affected the DBPs formation significantly. The results also showed that dichloroacetic acid and dichloroacetamide have high potential to form in all the three types of lettuce and in both wash water and produce during NaOCl washing. For Objective 3: We have investigated the DBPs formation in different fresh produce wash water and correlated wash water properties with DBPs formation potential. Six fresh produce (Iceberg lettuce, Romaine lettuce, spinach, strawberry, grape and tomato) were selected to prepare produce wash water. Produce wash waters were diluted to COD at approximately 400 mg/L. Water properties including chlorine demand, pH, ORP, total protein, total phenolic, UV254, COD, turbidity and color difference of each produce wash water sample were measured in Dr. Hung's laboratory at UGA Griffin Campus. Portions of wash water samples were transported to Dr. Huang's laboratory at Georgia Tech to determine the DBPs formation. The results from two laboratories will be combined to evaluate wash water properties as relate to the DBP formation potential. For Objective 4: No new experiments were conducted for this part of project in the past year. A few additional experiments are planned for the remainder of this project. For Objective 5: The bulk organic properties of different crushed produce mixtures (including spinach, Romaine lettuce, Iceberg lettuce, tomato, strawberry and grape) were quite different, indicating different produce contain very different organic constituents. The produce organic mixtures also showed a wide range of DBPs formation potentials and chlorine demands. It is clear that different organic content of produce significantly affects the types and concentrations of DBPs formation. However, elucidating the specific precursors or formation mechanisms is difficult due to the high complexity of the product organic mixture and many reactions that are involved to yield the overall outcome of DBPs amounts. For Objectives 6: The antimicrobial efficacy of sodium hypochlorite (NaOCl) for fresh produce washing process could be compromised by its reaction with organic matter. Excess amounts of NaOCl can generate a large amount of hazardous disinfection by-products such as trihalomethanes and haloacetic acids, whereas deficiency of NaOCl may result in incompletely removing pathogens on produce. The purpose of this part of study was to develop a chlorine dosing strategy to maintain microbial safety as well as minimize the DBPs formation potential. Prediction equations to estimate residual chlorine based on water quality parameters were developed and validated using fresh-cut Iceberg lettuce and whole strawberries in an automated produce washer. Validation results show that equations successfully predicted the initial chlorine concentration needed to achieve residual chlorine at 10, 30, 60, and 90 mg/L for both lettuce and strawberry washing processes, with the root mean squared error (RMSE) at 4.45 mg/L. In addition, the populations of E. coli O157:H7 on inoculated lettuce and strawberries treated with solutions containing residual chlorine ranging from 10 to 90 mg/L was reduced by 0.6 log CFU/g. Our study demonstrates that 10 mg/L can be set as the targeted residual chlorine for the prediction equations. The chlorine dosing strategy based on equations can be used for produce industry to maintain microbial inactivation efficacy without using excess amount of chlorine.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Huang, C.-H.; Lee, W.-N. F-DBPs - Formation and control of disinfection byproducts in produce processing, Gordon Research Conference on Disinfection By-Products, South Hadley, MA, August 1, 2017.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Hung,Y.-C. and X. Chen. 2017. Predicting chlorine demand for produce washing. 10th Food Safety, Policy and Sustainability mini Summit. College Park, Maryland, USA. October 30-31, 2017.
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Chen, X.; Hung, Y.-C. 2017. Effects of organic load, sanitizer pH and initial chlorine concentration of chlorine-based sanitizers on chlorine demand of fresh produce wash waters. Food Control, 77:96-101.
- Type:
Journal Articles
Status:
Submitted
Year Published:
2017
Citation:
Lee, W.-N.; Huang, C.-H.; Zhu, G. Analysis of 40 Conventional and emerging disinfection by-products in fresh-cut produce wash water by modified EPA methods. Food Chemistry (submitted).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Chen, X.; Hung, Y.-C. 2017. Predicting the chlorine demand of various produce wash waters under different sanitizer pH, initial chlorine concentration and organic load. IFT Ann Mtg. Las Vegas, NV. June 25-28, 2017. Session P01-59.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Lee, W.-N.; Huang, C.-H. Formation of disinfection byproducts in wash water and lettuce by washing with sodium hypochlorite and peracetic acid sanitizers, poster presentation at the IAFP Annual Meeting, Tampa, Florida USA, July 8- July 12, 2017.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Lee, W.-N.; Huang, C.-H.; Luo, Y.; Morris, D. Comparison of flume wash and single-pass wash on the formation of disinfection by-products for produce processing, poster presentation at the IAFP Annual Meeting, Tampa, Florida USA, July 8- July 12, 2017.
|
Progress 12/01/15 to 11/30/16
Outputs
Target Audience:Environmental Scientists, Food Safety Scientists, Food Processing Industry, Food Regulatory Agencies, General Consumers Changes/Problems:Nothing to report. What opportunities for training and professional development has the project provided?This project provided training for two doctoral students, one master student and two undergraduate students in conducting research. How have the results been disseminated to communities of interest?In this project period, the study results were disseminated by one journal paper, two conference presentations, and one MS thesis (see the listed publications). What do you plan to do during the next reporting period to accomplish the goals?The Objective 1 has been completed. For Objective 2, we will continue the screening tests for other three fresh vegetables (spinach, mushrooms and sprouts) and three fresh fruits (grapes, melon and pineapple). We will also test and compare three different disinfectants (sodium hypochlorite, chlorine dioxide and electrolyzed oxidizing water) in their effects on DBPs formation from different produces and at different pH values. For Objective 3, at Georgia Tech Dr. Huang's lab, the impact of different conditions of washing process (e.g., different oxidants, oxidant dose, contact time, pH and temperature) on the DBPs formation from select produce will continue to be conducted to build a wider range of knowledge base. Simultaneous to DBPs analysis, the water quality parameters of various fresh produce wash solutions will be determined. At UGA Dr. Hung's lab, efforts will be made to analyze the correlations between produce wash water properties and the DBP formation potential for various fresh produce wash water. For Objective 4, different produce will be soaked in the water with 100 μg/L DBPs standards. Both water and produce will be analyzed the DBPs concentration to determine the transfer mechanism between water and produce. Also, the soaked produce will be refrigerated for 3, 7, 15, and 30 days to determine the stability of DBPs in the produce. For Objective 5, different DBPs standards and precursor surrogates will be spike in DI water to understand the formation/degradation mechanism of DBPs in wash water and produce. The reaction will be performed under at certain pH controlled by phosphate buffer. The reaction time will be 0, 5, 10 and 30 min to determine the reaction mechanisms and kinetics of target DBPs from different organic precursors. For Objective 6, efforts will be made to determine the optimal chlorine dosing strategy with high microbial inactivation efficacy and minimized free chlorine residual for fresh and fresh-cut produce at food processing conditions. A total of 200 g of fresh-cut iceberg or romaine lettuce inoculated with E. coli O157:H7 and stored overnight at 4 °C will be washed in 4 L chilled NaOCl solution at pH 6.0 in an automated produce washer for 5 min. The initial chlorine concentration of NaOCl solution will be determined using following equations to ensure the chlorine residual after washing to be approximately 10, 30, 60 and 90 mg/L. If Phenolics/(Protein/ΔE) < 0.6, C = (R + 48.97 - 30 P + 330.74 U + 5.14 P2 - 435.8 U2 - 0.28 P3)/0.82 If Phenolics/(Protein/ΔE) < 0.6, C = (R + 43.76 - 30 P + 139.64 U + 5.14 P2 - 71.72 U2 - 0.28 P3)/0.82 where Phenolics is the total phenolics content (mg/L gallic acid equivalents), Protein is the total protein content (mg/L bovine serum albumen equivalents), ΔE is the CIEL*a*b* color difference between produce wash water and deionized H2O, C as the initial chlorine concentration (mg/L), R is targeted chlorine residual (mg/L), P is the sanitizer pH and U is UV254. Microbial reduction on lettuce and actual chlorine residual in NaOCl solution after washing will be measured and combined to determine the optimal initial chlorine concentration with high microbial inactivation efficacy and minimized free chlorine residual. DBPs levels will also be monitored in some of the above studies selectively to be discussed together with the microbial inactivation efficiency.
Impacts
What was accomplished under these goals?
Chlorine-containing disinfectants are widely used in the processing of fresh and fresh-cut produce. However, significant knowledge gaps still exist regarding the formation, identities and quantities of disinfection by-products (DBPs) generated as food residues or in the processing water. This project addresses this issue by investigating many conventional and emerging DBPs of concern for their mechanisms of formation and transfer into fresh and fresh-cut produce after chlorine-based disinfection methods (sodium hypochlorite, chlorine dioxide and electrolyzed oxidizing water), and for their impact on the efficacy in inactivating pathogens. For Objective 1: We have developed and improved the analytical methods for measuring a total of 42 conventional and emerging DBPs (include nine HAAs, twenty-three DBPs, nine nitrosamines and one halobenzoquinone) in process water by adjusting different reaction time, temperature, and other parameters in extraction procedures and analytical instrumentation. The method detection limits (MDLs) of the analytical methods were between 0.01-0.1 μg/L and the calibration linearity were at R2 = 0.9924-0.9998. The recoveries of DBPs spiked (0.5 or 1 μg/L standards) in DI water were between 62-150%. The recoveries of the DBPs in process water with lettuce were between 33-134%, and in process water with strawberries were between 32-132%. For haloquinolones, good linearity (R2 = 0.9998) in 1-1000 μg/L was achieved in the standard calibration of DCBQ. The recoveries for spiking 41 DBPs (except DCBQ) in the homogenized strawberries were between 14-144%, and in the homogenized lettuce were between 20-131%, indicating that the similar method could be applied to other types of produce. For Objective 2: Lettuce and strawberries from the supermarket were washed by DI water and NaOCl (200 mg/L as Cl2) solution, respectively, and the process water was scanned for the presence of 32 target DBPs (include nine HAAs and twenty-three DBPs). For the results of washing by DI water, three target DBPs (chloroacetic acid, bromochloroacetic acid, bromoform) were detected at more than 0.1 μg/L in the wash water from lettuce, and seven DBPs (chloroacetic acid, bromoacetic acid, trichloroacetic acid, bromochloroacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid, bromoform, dibromoacetonitrile, carbon tetrachloride) were found at more than 0.1 μg/L in the wash water from strawberries. When the produce was washed with 200 mg/L NaOCl solution, most of the target DBPs increased significantly in the process water. For lettuce, dichloroacetic acid, dichloroacetonitrile and chloral hydrate were over 200 μg/L; for strawberries, dichloroacetic acid, trichloroacetic acid, bromochloroacetic acid, chloroform, dichloroacetonitrile, trichloroacetonitrile, chloral hydrate, 1,1,3,3-tetrachloro-2-propanone and 1,1,1,3,3-pentachloro-2-propanone were over 200 μg/L. After 30 min of contact time, the residual chlorine was 2.33±2.85 mg/L and 1.07±0.08 mg/L for lettuce and strawberries, respectively. The results show that dichloroacetic acid, dichloroacetonitrile and chloral hydrate have high potential to form during NaOCl washing, and more DBPs were formed from strawberries than from lettuce. For Objective 3: Experiments were conducted to evaluate the effect of sanitizer pH and initial chlorine concentration on chlorine demand of romaine lettuce wash water with different organic load. Fresh-cut romaine lettuce was homogenized with deionized water and further diluted to three different organic load. After that, 1 mL of lettuce wash water reacted with 9 mL of NaOCl solution with different initial chlorine concentration (50, 75 and 100 mg/L free chlorine residual) and pH (2.5, 4.0, 6.0, 8.0 and 9.5) for 5 min. Chlorine demand of each sample was measured using the DPD-FAS titrimetric method. The results showed that the chlorine demand of lettuce wash water significantly increased (P ≤ 0.05) with increasing organic load and initial chlorine concentration. Increasing the pH of NaOCl from 2.5 to 9.5 led to decrease in the chlorine demand except slight increase in the chlorine demand from 6.0 to 8.0. Based on collected data and our previous work (Chen and Hung, 2016), equations to predict chlorine demand of various produce wash waters for different organic load, sanitizer pH and initial chlorine concentration were developed. Prediction accuracy of developed equations was verified using four types of fresh produce (romaine lettuce, iceberg lettuce, strawberry and grape) at two different organic load reacting with NaOCl solution and electrolyzed water at different pH (2.5, 6.0 and 8.0). Another research activity was conducted to investigate the DBPs formation in different fresh produce wash water and correlate wash water properties with DBPs formation potential. Six fresh produce (iceberg lettuce, romaine lettuce, spinach, strawberry, grape and tomato) were selected to prepare produce wash water. Produce wash waters were diluted to COD at approximately 400 mg/L. Water properties including chlorine demand, pH, ORP, total protein, total phenolic, UV254, COD, turbidity and color difference of each produce wash water sample were measured in Dr. Hung's laboratory at UGA Griffin Campus. Portions of wash water samples were transported to Dr. Huang's laboratory at Georgia Tech to determine the DBPs formation. The results from two laboratories will be combined to evaluate wash water properties as relate to the DBP formation potential. For Objective 4: Preliminary experiments were conducted by spiking 10 μg/L DBPs standards (the 21 EPA Method 551.1 DBPs) in 400 mL DI water and then this water was use to wash/soak 100 g of strawberries for 30 minutes. At the end of the experiments, DBPs in the wash water and in strawberries, respectively, were analyzed. The results showed that most DBPs tended to remain in the wash water, with only a modest fraction of the DBPs transferred/sorbed to strawberries (at 1-22% depending on different DBPs). From the results, haloacetamides have a higher tendency (14-22%) to sorb to strawberries compared to other groups of DBPs. The preliminary results demonstrated that when the DBPs are formed in wash water, these by-products were more likely to stay in the water. For Objective 5: Six produce were selected (spinach, romaine lettuce, tomato, iceberg lettuce, strawberry and grape) by their different chlorine demand (from spinach to grape: 95.9, 89.4, 48.9, 48.5, 21.5, 11.1 mg/L) under 400 mg/L COD. The total of 32 DBPs (nine HAAs and twenty-three DBPs) were analyzed in this part of study. The results indicated that romaine lettuce formed the highest total DBPs concentration (,2024 μg/L), followed by strawberry (1,404 μg/L), iceberg lettuce (890 μg/L), spinach (843 μg/L), tomato (264 μg/L) and grape (70 μg/L). HAAs and nitrogenous DBPs formed the most in all of the produce. No apparent specific correlation could be found yet between the chlorine demand and DBPs formation. However, EEM (excitation-emission scanning) results of the produce organic mixture demonstrated that different organic constituents were found in the different produce, indicating that the formation of DBPs was likely related to the types of produce and organic constituents. For Objectives 6: Experiments are currently on-going to develop equations to predict the initial chlorine concentration needed to maintain targeted chlorine residual after washing fresh produce. The next step will be to examine the effect of free chlorine residual on the antimicrobial efficacy of NaOCl against E. coli O157:H7 on fresh-cut iceberg and romaine lettuce in an automated washer at food processing conditions. Eventually, the optimal initial chlorine concentration of high microbial inactivation efficacy and minimized free chlorine residual will be determined.
Publications
- Type:
Theses/Dissertations
Status:
Submitted
Year Published:
2016
Citation:
Mao, M. (2016) Critical Review of Disinfection By-Products (DBPs) in Fresh Produce and Process Water, M.S. thesis, School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Chen, X.; Hung, Y.-C. Predicting Chlorine Demand of Fresh and Fresh-cut Produce during Washing, oral presentation at the IAFP Annual Meeting, St. Louis, Missouri USA, July 31- August 3, 2016.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Huang, C.-H.; Lee, W.-N; Chen, X.; Hung, Y.-C. Factors Influencing the Development of Conventional and Emerging Disinfection By-Products during Fresh-Cut Produce Washing using Chlorine Sanitizer, oral presentation at the IAFP Annual Meeting, St. Louis, Missouri USA, July 31- August 3, 2016.
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Chen, X.; Hung, Y.-C. (2016). Predicting chlorine demand of fresh and fresh-cut produce based on produce wash water properties. Postharvest Biology and Technology, 120, 10-15.
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Progress 12/01/14 to 11/30/15
Outputs
Target Audience:Environmental Scientists, Food Safety Scientists, Food Processing Industry, Food Regulatory Agencies, General Consumers Changes/Problems:Nothing to report. What opportunities for training and professional development has the project provided?This project provided training for two doctoral students, one master student and one undergraduate student in conducting research. How have the results been disseminated to communities of interest?Thus far, the study results were disseminated by three conference presentations (see the listed publication). What do you plan to do during the next reporting period to accomplish the goals?For Objective 1, we will complete the analytical method development for haloquinones and for DBPs residues in produce. For Objective 2, we will continue the screening tests for other three fresh vegetables (spinach, mushrooms and sprouts) and three fresh fruits (grapes, melon and pineapple). We will also test and compare three different disinfectants (sodium hypochlorite, chlorine dioxide and electrolyzed oxidizing water) in their effects on DBPs formation from different produces and at different pH values. For Objective 3, the first activity will be to develop models to predict the effect of organic load, initial chlorine concentration, sanitizer pH on chlorine demand of different produce wash water for various chlorine-based sanitizers. Firstly, lettuce wash water with different organic load will be prepared and react with NaOCl at different pH (2.5, 6 and 9.5) and free chlorine concentration (50, 75 and 100 mg/L) for 5 min. The chlorine demand of wash water at each condition will be determined and used to develop linear regression models. After that, models will be combined with equations developed previously (the UV254 model) to extend their feasibility to various sanitizers at various pHs and concentrations. In addition, chlorine demand of electrolyzed oxidizing water and ClO2 at various washing conditions will be determined. Based on the results, equations will be further modified to include other sanitizers. Finally, models will be validated using various fresh produce and sanitizers at different washing conditions. Another research activity for the Objective 3 is to investigate the DBPs formation in different fresh produce wash water and correlate wash water properties with DBPs formation potential. Six fresh produce (iceberg lettuce, romaine lettuce, spinach, strawberry, grape and tomato) with different chlorine demand at approximately 400 mg/L COD will be selected to prepare produce wash water. Water properties including chlorine demand, pH, ORP, total protein, total phenolic, UV254, COD, turbidity and color difference of each produce wash water sample will be measured in Dr. Hung's laboratory at UGA Griffin Campus. Same wash water samples will be transported to Dr. Huang's laboratory at Georgia Tech to determine the DBPs formation. The results from two laboratories will be combined to evaluate wash water properties as relate to the DBP formation potential. At Georgia Tech Dr. Huang's lab, the impact of different conditions of washing process (e.g., different oxidants, oxidant dose, contact time, pH and temperature) on the DBPs formation from select produce will continue to be conducted to build a wider range of knowledge base. Simultaneous to DBPs analysis, the water quality parameters of various fresh produce wash solutions will be determined. For Objective 4, different produce will be soaked in the water with 100 μg/L DBPs standards. Both water and produce will be analyzed the DBPs concentration to determine the transfer mechanism between water and produce. Also, the soaked produce will be refrigerated for 3, 7, 15, and 30 days to determine the stability of DBPs in the produce.
Impacts
What was accomplished under these goals?
For Objective 1: We developed and improved the analytical methods for measuring a total of 41 conventional and emerging DBPs (include nine HAAs, twenty-three DBPs and nine nitrosamines) in process water by adjusting different reaction time, temperature, and other parameters in extraction procedures and analytical instrumentation. The method detection limits (MDLs) of the analytical methods were between 0.01-0.1 μg/L and the calibration linearity were at R2 = 0.9924 - 0.9998. The recoveries of DBPs spiked (0.5 or 1 μg/L standards) in DI water were between 62-150%. The recoveries of the DBPs in process water with lettuce were between 33-134%, and in process water with strawberries were between 32-132%. The lower recoveries of some DBPs in the presence of produce compared to those in DI water were likely due to the target DBPs adsorbing onto the produce. On the other hand, some of the DBPs were already present in the blank wash and might cause the higher recoveries observed in the presence of produce compared to those in DI water. For haloquinolones, good linearity (R2 = 0.9998) in 1-1000 μg/L was achieved in the standard calibration of DCBQ. The recoveries for spiking 21 DBPs in the homogenized strawberries were between 14 - 144%, indicating that the similar method could be applied to other types of produce. For Objective 2: Lettuce and strawberries from the supermarket were washed by DI water and NaOCl (200 mg/L as Cl2) solution, respectively, and the process water was scanned for the presence of 30 target DBPs (include nine HAAs and twenty-one DBPs). For the results of washing by DI water, three target DBPs (chloroacetic acid, bromochloroacetic acid, bromoform) was detected at more than 0.1 μg/L in the wash water from lettuce, and seven DBPs (chloroacetic acid, bromoacetic acid, trichloroacetic acid, bromochloroacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid, bromoform, dibromoacetonitrile, carbon tetrachloride) were found at more than 0.1 μg/L in the wash water from strawberries. When the produce was washed with 200 mg/L NaOCl solution, most of the target DBPs increased significantly in the process water. For lettuce, dichloroacetic acid, dichloroacetonitrile and chloral hydrate were over 200 μg/L; for strawberries, dichloroacetic acid, trichloroacetic acid, bromochloroacetic acid, chloroform, dichloroacetonitrile, trichloroacetonitrile and chloral hydrate were over 200 μg/L. After 30 min of contact time, the residual chlorine was 2.33±2.85 mg/L and 1.07±0.08 mg/L for lettuce and strawberries, respectively. The results show that dichloroacetic acid, dichloroacetonitrile and chloral hydrate have high potential to form during NaOCl washing, and more DBPs were formed from strawberries than from lettuce. By adding phosphate buffer in the 200 mg/L NaOCl wash water to fix pH at around 8 for both produce, the formation concentration of some DBPs changed. For bromochloroacetic acid, it decreased significantly in lettuce but increased in strawberries; for trichloronitromethane, the formation concentration increased significantly in both produce. Thus, the reactions of NaOCl with produce to form the various DBPs are pH dependent. For Objective 3: Cut lettuce and strawberries were washed by 0.5-200 mg/L chlorine dose for 30 minutes. The results showed that the DBPs formation was increased when chlorine dose was increased. The total DBPs formation in strawberry wash water was higher than that in lettuce wash water, and the difference was mainly in the magnitude of THMs formation. Similar trend was observed with wash water's chlorine demand - strawberry wash water consumed a greater amount of chlorine and more rapidly than lettuce wash water. The average concentrations of THMs in lettuce wash water were 0.11, 6.25, 15.9, 34.9 and 77.0 μg/L under the chlorine doses of 0.5, 25, 50, 100 and 200 mg/L, respectively. In comparison, the THMs concentrations in strawberry wash water were 0.87, 58.8, 137, 253 and 536 μg/L, which were 7-8 times higher than those in lettuce wash water. Also noted is that the dominant DBPs in wash water did not change much when the chlorine dose was changed. Based on the results, further study was conducted to evaluate the effect of washing time using 50 mg/L NaOCl as Cl2 as the initial concentration. The DBPs formed rather quickly in strawberry wash water, while a more obvious increase of DBPs over time was seen in lettuce wash water for the period of 30 minutes of reaction time. By monitoring the residual chlorine in wash water, it showed that all free chlorine was consumed by strawberry wash water by 10 minutes. The results of COD, TOC and UV254 also indicated that strawberry wash water had a much higher organic loading than lettuce wash water, and thus could explain the greater DBPs formation in strawberry wash water. Experiments were conducted to determine the correlations between chlorine demand and properties of various fresh produce wash water. Ten fresh and fresh-cut fruit and vegetable (iceberg lettuce, romaine lettuce, spinach, celery, mushroom, broccoli, strawberry, grape, cantaloupe, and tomato) simulated wash waters at different chemical oxygen demand (COD) were prepared. The chlorine demand and wash water quality parameters including pH, ORP, UV254, COD, turbidity, total protein content, total phenolic content and color difference between water and tested samples (ΔE) were measured. The correlations between variables were determined. The results showed that UV254 had the highest correlation coefficient with chlorine demand of various fresh produce (R2 = 0.77). Further analysis of chlorine demand and UV254 data showed two clusters exist: clusters for produce with high phenolic content and low phenolic content. The phenolic-to-protein/ΔE ratio (PPC) was created to identify which cluster each produce wash water belongs. Empirical models for predicting chlorine demand were developed as: chlorine demand = 295.23 UV254 + 6.97, if PPC < 0.6; or chlorine demand = 119.77 UV254 + 2.41, if PPC ≥ 0.6. The validation results showed that models can predict chlorine demand for the same produce tested at different COD as well as other produce that were not used for model development, with prediction error of 11.3 and 8.16 mg/L, respectively. The next step was to evaluate the effect of environmental factors (such as sanitizer pH and initial chlorine concentration) on chlorine demand of produce wash water. The preliminary results showed that for each produce the chlorine demand increased with decreasing pH of NaOCl solution and increasing initial chlorine concentration. Therefore, a full factorial experiment was designed and research is currently on-going. Based on the results, linear regression equations to predict the chlorine demand of produce wash water at different concentration and pH will be developed and validated. For Objective 4: Preliminary experiments were conducted by spiking 10 μg/L DBPs standards (the 21 EPA Method 551.1 DBPs) in 400 mL DI water and then this water was use to wash/soak 100 g of strawberries for 30 minutes. At the end of the experiments, DBPs in the wash water and in strawberries, respectively, were analyzed. The results showed that most DBPs tended to remain in the wash water, with only a modest fraction of the DBPs transferred/sorbed to strawberries (at 1-22% depending on different DBPs). From the results, haloacetamides have a higher tendency (14-22%) to sorb to strawberries compared to other groups of DBPs. The preliminary results demonstrated that when the DBPs are formed in wash water, these by-products were more likely to stay in the water. For Objectives 5-6: No activities during the second year.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Lee, W.-N; Huang, C.-H. Screening and prioritizing conventional and emerging disinfection by-products developed in fresh and fresh-cut produce during chlorine-based disinfection, oral presentation at the IAFP Annual Meeting, Portland, Oregon USA, July 25-28, 2015.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Hung,Y.-C. 2015. Ensuring produce safety through non-thermal treatments. The 8th UGA-SHOU-SAAS-NTOU Food Safety and Trade Initiative Mini Summit. Taipei, Taiwan. October 26-27, 2015.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
1) Lee, W.-N; Huang, C.-H. Analytical method development and improvement for detection of multi-classes of disinfection by-products in water and produce, poster presentation at the SETAC North America 35th Annual Meeting, Vancouver, Canada, November 9-13, 2014
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Progress 12/01/13 to 11/30/14
Outputs
Target Audience: Environmental Scientists, Food Safety Scientists, Food Processing Industry, Food Regulatory Agencies, General Consumers. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? This project provided training for two doctoral students and one master student in conducting research. How have the results been disseminated to communities of interest? Thus far, the study results were disseminated by a poster presentation at the 2014 Society of Environmental Toxicology and Chemistry (SETAC) North America National Meeting (see the listed publication). What do you plan to do during the next reporting period to accomplish the goals? For Objective 1, we will finish the method development for nitrosamine and DCBQ DBPs in process water, and also establish the methods to analyze target DBPs in the produce. For Objective 2, we will continue the screening tests to other three fresh vegetables (spinach, mushrooms and sprouts) and three fresh fruits (grapes, melon and pineapple). We will also test and compare three different disinfectants (sodium hypochlorite, chlorine dioxide and electrolyzed oxidizing water) in their effects on DBPs formation from different produces and at different pH values. For Objective 3, the first activity will be to complete the activity from Year 1 to identify parameters and properties of fresh produce wash solution and its reaction with chlorine-based sanitizers. Water quality parameters of various fresh produce wash solutions at different soaking time, such as iceberg lettuce, spinach, mushroom, bean sprout, grape, strawberry, apple and cantaloupe will be determined. Chlorine reduction when these produce wash solution react with 50 mg/L chlorine-based sanitizer for 5 min will be determined. A model to predict chlorine loss at 50 mg/L (Cl50) as a function of wash solution properties and soaking time will be developed. The second activity will be to determine chlorine loss for each sanitizer with various produce wash solution at different contact time and chlorine concentration. Results will be used to develop a model to predict chlorine loss as a function of washing time, chlorine concentration, and Cl50. After that, two models will be combined, and a model to predict chlorine loss during produce washing as a function of washing time, chlorine concentration, and produce wash solution property will be developed. Finally, this model will be verified using different fruit and vegetable wash water samples which are not included for the model development. The chlorine loss will be compared with the DBPs formation results. The second activity will be to evaluate the antimicrobial efficacy of sodium hypochlorite, chlorine dioxide and electrolyzed oxidizing water on E.coli O157:H7 in different produce wash solutions. A model for predicting microbial inactivation at different initial chlorine concentration, washing time, and produce wash solution property will be developed following a similar process as the first activity. The microbial inactivation will be compared with the DBPs formation results.
Impacts
What was accomplished under these goals?
Chlorine-containing disinfectants are widely used in the processing of fresh and fresh-cut produce. However, significant knowledge gaps still exist regarding the formation, identities and quantities of disinfection by-products (DBPs) generated as food residues or in the processing water. This project addresses this issue by investigating many conventional and emerging DBPs of concern for their mechanisms of formation and transfer into fresh and fresh-cut produce after chlorine-based disinfection methods (sodium hypochlorite, chlorine dioxide and electrolyzed oxidizing water), and for their impact on the efficacy in inactivating pathogens. For Objective 1: We developed and improved the analytical methods for measuring 27 conventional and emerging DBPs (include nine HAAs and eighteen DBPs) in process water by adjusting different reaction time, temperature, and other parameters in extraction procedures and analytical instrumentation. The method detection limits (MDLs) of the analytical methods were between 0.01-0.1 μg/L. The recoveries of target compounds spiked in DI water were between 62-150%. The recoveries of the DBPs in process water with lettuce were between 5-192%, and in process water with strawberries were between 9-175%. The lower recoveries of some DBPs in the presence of produce compared to those in DI water were likely due to the target DBPs adsorbing onto the produce. On the other hand, some of the DBPs were already present in the blank wash and might cause the higher recoveries observed in the presence of produce compared to those in DI water. For haloquinolones, good linearity (r2 = 0.9998) in 1-1000 μg/L was achieved in the standard calibration of DCBQ. For Objective 2: Lettuce and strawberries from the supermarket were washed by DI water and NaOCl (200 mg/L as Cl2) solution, respectively, and the process water was scanned for the presence of 27 target DBPs. For the results of washing by DI water, three target DBPs (chloroacetic acid, bromochloroacetic acid, bromoform) was detected at more than 0.1 μg/L in the wash water from lettuce, and seven DBPs (chloroacetic acid, bromoacetic acid, trichloroacetic acid, bromochloroacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid, bromoform, dibromoacetonitrile, carbon tetrachloride) were found at more than 0.1 μg/L in the wash water from strawberries. Concurrently, it was found that there was measurable residual chlorine at 0.24±0.2 mg/L and 0.94±0.2 mg/L in the washed water from lettuce and strawberries, respectively. The results indicate that the produce was treated with chlorine sanitizer and some residual chlorine remained in the produce and could be transferred into the wash water. The chlorine treatment also likely led to formation of DBPs in the produce, and the DBPs could leach into the produce wash water. When the produce was washed with 200 mg/L NaOCl solution, most of the target DBPs increased significantly in the process water. For lettuce, dichloroacetic acid, dichloroacetonitrile and chloral hydrate were over 200 μg/L; for strawberries, dichloroacetic acid, trichloroacetic acid, bromochloroacetic acid, chloroform, dichloroacetonitrile, trichloroacetonitrile and chloral hydrate were over 200 μg/L. After 30 min of contact time, the residual chlorine was 2.33±2.85 mg/L and 1.07±0.08 mg/L for lettuce and strawberries, respectively. The results show that dichloroacetic acid, dichloroacetonitrile and chloral hydrate have high potential to form during NaOCl washing, and more DBPs were formed from strawberries than from lettuce. By adding phosphate buffer in the 200 mg/L NaOCl wash water to fix pH at around 8 for both produce, the formation concentration of some DBPs changed. For bromochloroacetic acid, it decreased significantly in lettuce but increased in strawberries; for trichloronitromethane, the formation concentration increased significantly in both produce. Thus, the reactions of NaOCl with produce to form the various DBPs are pH dependent. For Objective 3: The first activity of this Objective was to identify parameters and properties of fresh produce during washing that would react with chlorine-based sanitizers in the wash solution. Preliminary study to evaluate the impact of fresh produce soaking time on free chlorine loss of electrolyzed oxidizing water (EO water) was conducted. We measured the residual free chlorine of EO water solution after reacting with fresh-cut romaine lettuce wash water prepared at different soaking time (1, 5, 10, 15 and 30 min). The result was shown that there was a negative relationship between residual free chlorine and soaking time at the first 10 min. No further chlorine reduction was found by produce wash solution prepared for longer soaking time (≥ 10 min). Hence, for further studies, the maximal soaking time for fresh-cut romaine lettuce is set at 10 min. The next step is to test the water quality parameters and properties of wash solution at different soaking time. In addition, the impact of all the other fresh/fresh-cut produce wash solutions on other chlorine based sanitizers as well as the properties of each produce wash solution will be determined following the similar protocol as romaine lettuce. For Objectives 4-6: No activities during the first year.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
1) Lee, W.-N; Huang, C.-H. Analytical Method Development and Improvement for Detection of Multi-Classes of Disinfection By-Products in Water and Produce, poster presentation at the SETAC North America 35th Annual Meeting, Vancouver, Canada, November 9-13, 2014.
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