College of Agriculture & Natural Resources
Permanent URI for this communityhttp://hdl.handle.net/1903/1598
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Chemical Compositions of the Selected Cold-pressed Seed Flours and Their Free Radical Scavenging and Anti-proliferative Capacities(2019) Song, Zhangyi; Yu, Liangli (Lucy); Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The cold-pressed blackberry, broccoli, carrot, cucumber, and milk thistle seed flours were extracted with 100% ethanol and examined for their phytochemical compositions, total phenolic contents, ABTS•+ and relative DPPH• scavenging capacities, and anti-proliferative activities in HCT116 and SW480 colon cancer cells. Eleven, eight, ten, and thirteen compounds were tentatively identified in the blackberry, broccoli, carrot, and milk thistle seed flour extracts, with ellagic acid, glucoraphanin, kaempferol-3-O-rutinoside, and silychristin isomers being the primary components in each, respectively. Milk thistle seed flour extract had the greatest total phenolic content. Blackberry seed flour extract possessed the strongest free radical scavenging capacities against both DPPH• and ABTS•+. Milk thistle seed flour extract was the only extract capable of significantly suppressing the growth of SW480 colon cancer cells, but not HCT116 cells.Item The Development of a Qualitative Risk Assessment and Targeted Storage Decline Kinetics Data as Critical Components for Developing a Full Quantitative Risk Assessment of Salmonella Contamination in Milk Chocolate(2019) Oni, Ruth Adeola; Buchanan, Robert L; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Salmonella enterica infections and outbreaks have been associated with chocolate consumption over the last four decades. The source of contamination for these occasional salmonellosis outbreaks are often unidentified, and typically the level of contamination is only a few salmonellae per serving. The main goals of this dissertation were to collate relevant scientific information regarding microbial safety of milk chocolate, conduct a qualitative assessment of risk factors for Salmonella contamination encountered during the complex processes of cocoa bean cultivation and the subsequent process of milk chocolate manufacturing, and to generate targeted data and survival models for kinetics of Salmonella stored in milk chocolate crumb; all components critical to the development of a stochastic quantitative microbial risk assessment. The farm-to-packaging qualitative assessment provided categorizations of risk for relevant activities and ingredients, identified critical data gaps and “risk spots” and culminated in an Excel-based risk rating tool used to illustrate the usability of the qualitative assessment. Results indicate an overall low residual risk of Salmonella contamination of a packaged milk chocolate product for a base model, provided dictates of process control measures are rigorously adhered to, and the risk rating tool enables the assessment of what-if scenarios for deviations from optimal practices. One of the data gaps identified in the qualitative risk assessment led to investigation into the use of milk chocolate crumb, an intermediate product during milk chocolate processing, and its potential association with Salmonella risk. Evaluation of the survival kinetics of S. enterica in milk crumb showed a significant (p<0.05) dependence of survival on storage temperature, strain and crumb type. Due to the manner in which crumb is generally utilized during milk chocolate processing, findings from this study are the first to link the use of crumb and Salmonella risk, and presents promising opportunities for risk reduction which can be explored through further research into optimization of crumb storage parameters. This study serves as a valuable resource to food safety stakeholders in the chocolate industry as it builds the foundation and provides much-needed data for a quantitative microbial risk assessment model that can be used to optimize food safety control programs.Item Enhancement of Thermal Inactivation of Foodborne Pathogenic Bacteria at Mild Heating Temperatures with Inclusion of Butyl Paraben and the Application on Foods(2019) Gao, Zhujun; Buchanan, Robert L.; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Thermal processing is widely used in food industry to ensure the microbial safety, however, there is increasing demand on reducing the processing temperature and duration. This study specifically focused on mild heating temperatures (<60 °C) with inclusion of low level (≤ 125 ppm) of the approved preservative butyl-parahydroxy-benzoate (BPB). In a BHI model matrix, four pathogens were studied with submerged coil apparatus: Cronobacter sakazakii 607, Salmonella enterica serotype Typhimurium, attenuated Escherichia coli O157:H7 and Listeria monocytogenes. The results indicated that low concentrations of BPB combined with temperatures < 60 °C achieved 5 – 6 log reductions in less than 15 minutes with tested gram-negative microorganisms, whereas reductions without BPB were only 1 – 2 logs. We further extended the study to food applications: powdered infant formula, non-fat dry milk, and apple juice. The results indicate BPB will be inhibited by proteins, but apple juice is a suitable application.Item SALMONELLA ENTERICA STRATEGIES FOR PERSISTENCE ON TOMATO (SOLANUM LYCOPERSICUM) AND SEROVAR DYNAMICS IN SURFACE AND RECLAIMED WATER(2019) Ferelli, Angela Marie Cecelia; Micallef, Shirley A.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)While select aspects of Salmonella enterica subspecies enterica persistence in agricultural matrices have been illustrated, serovar specific survival strategies in surface water, transmission, and persistence on plants are multifaceted and remain only partially examined. In the present work, we utilized an interdisciplinary approach to illustrate novel mechanisms by which S. enterica may adapt to plants as an alternative host. Furthermore, we leveraged the wealth of diversity in S. enterica serovars to investigate specific dynamics and drivers of persistence in water and transfer onto produce crops. Through biochemical, gene expression, and plant challenge assays of both tomato (Solanum lycopersicum) vegetative and fruit organs, we found that plant-derived NO was generated in response to S. Newport recognition. Furthermore, bacterial gene expression on both leaves and fruit was indicative of adaptation to a novel environment including upregulation in NO detoxification machinery, indicating plant-derived NO as a novel bacterial stress. NO tolerance of various S. enterica was then evaluated to investigate drivers of “produce associated’ S. enterica adaptation to the plant niche. We identified that plant derived NO can negatively affect titers of all S. enterica serovars tested and that serovar specific tolerance to NO in vitro was apparent in a concentration and exposure time dependent manner. Finally, the survival of various S. enterica in surface and reclaimed water was investigated while evaluating the potential for transition to viable but non-culturable (VBNC) organisms. Furthermore, surface water used for irrigation, a common water environment for S. enterica, was investigated as a priming reservoir for various S. enterica serovars for enhanced transmission onto tomato crops. Persistence in water included VBNC subpopulations and was driven by water type. Transfer success onto tomato was driven by serovar, and prolonged incubation in water increased the transfer ability of serovars that initially transferred poorly onto tomato. Finally, attachment to polystyrene and water oxidation-reduction potential were identified as possible indicators of foodborne pathogen transfer success onto tomato. Moving forward, a greater understanding of the environmental queues used by S. enterica subspecies enterica responding to the agricultural environment will aid researchers in developing S. enterica targeted on-farm management techniques to ensure safe yet sustainable fresh produce cultivation practices.Item EVALUATION OF PUBLIC HEALTH RISK FOR ESCHERICHIA COLI O157:H7 IN CILANTRO(2019) Horr, Taryn; Pradhan, Albani; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The supply chain of cilantro was modeled for growth and die-off of Escherichia coli (E. coli) O157:H7 from infield and harvesting, transportation and storage and ultimately consumption at home. Using Visual Basic for Applications (VBA) macros and @RISK software, a simulation model was developed for exposure and estimation of illnesses. Test scenarios were modeled to determine the relative importance of different factors on the risk of illness. The developed model was simulated using Monte Carlo technique and Latin Hypercube sampling for 100,000 iterations. Results showed an increase in the mean E. coli O157:H7 concentration along the supply chain for cilantro grown in both winter and summer weather conditions. In the winter, the mean pathogen concentration increased from 5.6×10-5 CFU/g to 24.7 CFU/g from after harvest to after home storage, respectively. In summer conditions, the mean pathogen concentration increased from 3.2×10-4 CFU/g to 5.2×10-2 CFU/g. The inner quartile ranges (IQRs) for the same model conditions showed a decrease in E. coli O157:H7 concentration along the supply chain for cilantro grown in both winter and summer weather conditions. This indicates a majority of situations result in a decrease in E. coli O157:H7 concentration along the supply chain however rare situations can occur where the concentration will increase greatly. With a prevalence of 0.1% E. coli O157:H7 contamination for cilantro post-harvest used for illustration, the model predicted the mean number of illnesses per year due to the consumption of E. coli O157:H7 contaminated cilantro in the United States as 86 and 164 for cilantro grown during winter and summer conditions, respectively. Sensitivity analysis results indicated that transportation temperatures and quality of irrigation water had the largest impact on the number of illnesses per year. Scenario testing results for different risk factors demonstrated the importance of limiting and reducing cross contamination along the production chain, especially at higher initial prevalence levels and preventing temperature abuse during transportation from farm to retail, when reducing overall risk of illness. The developed risk model can be used to estimate the microbiological risks associated with E. coli O157:H7 in cilantro and determine areas along the supply chain with the most effect on the final concentration per serving for future mitigation strategies.Item Effect of the kashering process on the safety and quality of meat(2019) Sherman-Wood, Robert Michael; Tikekar, Rohan V; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The process of making meat kosher, or “kashering,” involves soaking the meat, covering it in salt for at least one hour, and several rinses after. This study evaluates the effect this process has on the survivability and thermal resistance of Escherichia coli O157:H7 and Salmonella enterica serovar Newport on fresh chicken and beef, as well as the effect on quality and acceptability of both meats. The process yielded a minor reduction of both pathogens at ~1 log CFU/g. Surviving Salmonella from kashered chicken displayed an increase in thermal resistance (p<0.05). A sensory analysis panel rated salted chicken and beef higher quality and saltier than not kosher meat (p<0.05). The kashering process did change the color of both meats (p<0.05), attributable to the significant increase in salt content of the meats (p<0.05), but did not affect the texture of the meat (p>0.05).Item Novel Antimicrobial Treatments Based on the Interaction of Gallic Acid and UV Light: Characterization, Investigation of Antimicrobial Mechanism, and Application on Fresh Produce(2018) Wang, Qingyang; Tikekar, Rohan V; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Produce safety continues to be a challenge because produce undergoes minimal processing prior to consumption and existing sanitizers are not effective in inactivating pathogens. Novel decontamination technologies for produce are required as alternatives to traditional methods. In this project, two non-thermal process techniques were developed based on the interaction of UV light and gallic acid (GA) to enhance the safety of fresh produce. The first technique is the simultaneous application of UV-A light and GA (UVA+GA). UVA+GA treatment was effective against E. coli O157:H7, and the mechanism behind the synergistic antimicrobial effect was associated with the cellular uptake of GA, generation of reactive oxidative species (ROS), inactivation of enzymes superoxide dismutase, and damage to the bacterial membrane. In the second technique, the antimicrobial activity of GA was enhanced by its prior UV-C exposure (UVC-GA) against E. coli O157:H7 and was persistent for at least 4 weeks. The antimicrobial activity was affected by solution pH and the wavelength of UV-C exposure. The generation of ROS during UV light exposure and photo-oxidized compounds of GA such as quinone contributed to the antimicrobial activity of the UVC-GA solution. Both UVA+GA and UVC-GA treatments can enhance the inactivation of inoculated E. coli O157:H7 on produce such as spinach leaves and tomatoes without affecting the color and firmness. Common environmental stresses could confer complex cross-stress response in E. coli O157:H7 towards UVA+GA and UVC-GA treatments in that both resistance and sensitization can be induced depending on the stress applied and the technology studied. Repeated exposure to moderate UVA+GA or UVC-GA treatment can also select for sub-population that demonstrates higher resistance towards these treatments as well as cross-resistance to other lethal stress such as heat and acid. ROS scavenging enzymes and alternative sigma factor RpoS are highly likely to be associated with the adaptive response process. In conclusion, both UVA+GA and UVC-GA treatments are promising novel non-thermal techniques that are potential alternative methods for fresh produce disinfection. For future work, a better understanding of the inactivation mechanisms, optimizing of processing parameters, and the development of adaptive response associated with the two treatments need to be explored.Item Chemical profile and adulteration detection of olive oils(2018) Luo, Yinghua; Yu, Liangli Lucy; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A combination of ultra-performance convergence chromatography (UPC2) combined with quadrupole time-of-flight mass spectrometry (Q-TOF MS) analyses was utilized to determine the triacylglycerols (TAGs) composition and sn-positions of olive, corn, soybean and sunflower oils, for better understanding of their nutritional value and shelf stability. Ten commercial olive oil samples were analyzed, and a total of 23 TAGs were detected, of which O-O-O was the most abundant TAG in the olive oil samples, followed by P-O-O, O-O-S and O-O-L. The TAGs composition of olive oils were compared to that of the local commercial soybean, corn and sunflower oils. Comparing soybean, corn and sunflower oils with olive oils, L-L-L, P-L-L, B-L-L and M-L-L could be detected in the soybean, corn and sunflower oils but not in the olive oils. Po-O-Po, O-Po-O and G-O-O could be detected only in olive oil and O-O-O was much greater in olive oils. Using UPC2-Q-TOF MS, pure soybean, corn, and sunflower oils could be differentiated from pure olive oil samples based on their triacylglycerol compositions. However, UPC2-Q-TOF MS analysis could not detect olive oils adulterated with small amount of soybean, corn or sunflower oils. UPC2-Q-TOF MS system combined with multivariate data analysis was tested for potential utilization in detecting of olive oil adulterated by soybean, corn or sunflower oils. A combined UPC2-Q-TOF MS and multivariate data analysis approach was developed to potentially detect the olive oil adulterated with other vegetable oils at 0.5% (v/v) level. In addition, 10 representative marker ions of TAGs were selected to create a model using PCA, which could be used to differentiate pure olive oil from the olive oils adulterated with small amounts of soybean, corn and sunflower oils. The UPC2 system coupled with Q-TOF-MS approach can examine TAG sn-position compositions of olive oils with improved resolution of TAGs and reduced use of organic solvent. UPC2-Q-TOF MS may also be a more environmentally friendly approach for the rapid and accurate analysis of TAGs composition in edible oils and fats, as well as biologically lipids. UPC2-Q-TOF MS system combined with multivariate data analyses may be a possible approach for edible oil adulteration detection.Item INFLAMMATION AND PROSTATE CANCER DEVELOPMENT: THE ROLE OF CHEMOKINE (CXC MOTIF) LIGAND 12 AND ITS RECEPTORS CXCR4 AND CXCR7, TUMOR ENVIRONMENTS AND MODULATION BY DIET-DERIVED COMPOUND PHENETHYL ISOTHIOCYANATE(2018) Yu, Lu; Yu, Liangli; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Prostate cancer is the most prevalent and the third leading cause of cancer death in men in the United States and effective cure remain elusive. In the etiology of prostate cancer, the mediators and cellular effectors of inflammation are important constituents associated with the regulation of prostate cancer progression but detail mechanisms remain unclear. It would be important to further elucidate the mechanisms to allow for development of effective preventive/therapeutic strategy for prostate cancer. C-X-C motif ligand 12 (CXCL12) is a constitutive and inflammatory chemokine that modulates autoimmune inflammation and homeostasis in the immune system. It is also a pleiotropic chemokine that is expressed in malignant prostate tumors and regulates prostate cancer migration and invasion via interaction with its two receptors CXCR4 and CXCR7. However, regulations of CXCL12 and its receptors in the immune system and prostate cancer are poorly understood. In addition, phenethyl isothiocyanate (PEITC) is a dietary compound from Cruciferae family with an inhibitory effect on prostate cancer progression. The mechanisms that underlie the anti-cancer effects of PEITC on prostate cancer are not well studied. This dissertation elucidated 1) the role of CXCL12 and its receptors in the immune system, specifically during monocyte-macrophage differentiation; 2) the transcriptome alterations in androgen-responsive human prostate cancer LNCaP cells and its xenograft; 3) roles of prostate cancer microenvironment in prostate cancer progression; 4) molecular effects of diet-derived cancer-preventive compound phenethyl isothiocyanate (PEITC) on monocytes. The accomplishment of this dissertation will 1) provide critical mechanistic information of the interaction between inflammation and prostate cancer development and 2) validate the role of CXCL12/CXCR4/CXCR7 chemokine axis and PEITC in the regulation of prostate cancer development and immune response. Ultimately, the study of the mechanisms mentioned above could help identify new strategies for the prevention/treatment of prostate cancer.Item Photoirradiated Caffeic Acid as an Antimicrobial Treatment for Fresh Produce(2017) Gilbert, Andrea Rochelle; Tikekar, Rohan V; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The antimicrobial efficacy of 400 nm photoirradiated caffeic acid (CA, 5 mM) was evaluated against Escherichia coli O157:H7 and Listeria innocua. A stronger antimicrobial effect was observed on E. coli than on L. innocua where the combined treatment resulted in 4 and 1 log CFU/mL reductions, respectively. The treatment’s effects on metabolism (resazurin assay), uptake of CA (fluorescence technique) and membrane damage (prodpidium iodide assay) were studied in both species. CA uptake increased in both species, but membrane damage was only observed in E. coli. The treatment had minimal impact on metabolic activity in both species. The treatment applied to the surface of spinach leaves was found to be effective against E. coli. A combined treatment of 400 nm light and plant extracts known to contain CA was also evaluated for antimicrobial activity against E. coli and found to be effective. The novel treatment proposed in this study has the potential to improve the microbial food safety of fresh produce.