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Kali Kniel - University of Delaware. Newark, DE, US

Kali Kniel

Professor, Microbial Food Safety | University of Delaware


Prof. Kniel’s laboratory explores issues of food safety and public health that involve transmission of viruses and pathogenic bacteria.




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UD food science students keep fresh fruits and vegetables safe CPS Minute with Kali Kniel of the University of Delaware Kali Kniel, One Health. FAFP Webinar




Dr. Kniel’s laboratory explores issues of food safety and public health that involve transmission of viruses, protozoa, and pathogenic bacteria. Few laboratories work with this extent of different microorganisms. Specific projects may address survival or transmission routes through various complex food systems. In light of needs related to the FDA FSMA Produce Safety Rule, research includes assessing risks associated with pre-harvest contamination of raw agricultural commodities through water and soil amendments. Research projects focus on survival and persistence in water and poultry litter and subsequent transfer onto the edible portion of the crop. Investigations into novel detection methods as well as biocontrol are also ongoing. Efforts are made to correlate behaviors of different microorganisms, including viral surrogates, with climate or other environmental metadata in our assessments. We also work with nearby government agencies and connect our research to the needs of policy makers. We have contributed data critical to addressing contemporary food safety questions; specifically, prevalence of pathogens in manure and time needed between application of manure and time to harvest. Students on all levels assist with this research.

Exploratory studies surrounding issues of food safety education is part of Dr. Kniel’s passion for research. Issues of food microbiology and food safety can be integrated across the K-16 curriculum in a novel way of connecting science to other topics. One Health is a holistic way of thinking about how the health of our environment is intertwined with human health and animal health. Food Safety is an outstanding example of a topic with a One Health focus. More information and examples are available on the Foodborne Illness Outbreak Investigation website.

Industry Expertise (2)



Areas of Expertise (5)

Food Systems

Pathogenic Bacteria

Food Safety

Public Health


Media Appearances (7)

The internet is freaking out about reheated rice. Should you be worried?

Mashable  online


"Heat-resistant endospores of this bacteria are more likely to survive cooking and start growing again (germinate) when the food is cooled gradually over an extended period of time," Kalmia Kniel, professor of animal and food sciences, told Mashable.

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Never eat these 4 popular foods, safety experts warn: ‘Just not worth the risk’

New York Post  online


Food safety experts have revealed the four things sold at the grocery store that they would never eat — and some of them may surprise you.

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6 Dangerous Multicooker Mistakes, According To Food Safety Experts

HuffPost  online


Professor Kniel tells HuffPo that eating undercooked meat is the most dangerous mistake that can occur when you prepare food with a slow cooker,

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UD’s CEWER takes on analyzing wastewater to track COVID-19

Delaware Public Media  online


New Castle County started analyzing its sewer water for COVID-19 last spring. Late last year, it moved that analysis to the University of Delaware’s Center for Environmental and Wastewater-based Epidemiological Research (CEWER). Delaware Public Media’s Sophia Schmidt talks with CEWER director Kali Kniel about this work.

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Leaping Listeria

University of Delaware UDaily  online


Opportunistic bacteria — salmonella, listeria and E.coli, for example — often piggyback on raw vegetables, poultry, beef and other foods to gain entry into a human host, causing millions of foodborne illnesses each year. But University of Delaware researchers Harsh Bais and Kali Kniel and their collaborators now have found that wild strains of salmonella can circumvent a plant’s immune defense system, getting into the leaves of lettuce by opening up the plant’s tiny breathing pores called stomates.

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One Health

University of Delaware UDaily  online


Many experts come from a variety of professions that historically do not consistently interact — public health professionals, food scientists, economists, educators, engineers, entomologists, epidemiologists, hydrologists, microbiologists, nutritionists, physicians, molecular biologists and veterinarians. UD has strong expertise in the great majority of these areas, so Arsenault and Kali Kniel are leading the charge to bring a critical mass of UD researchers together around the topic.

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Fighting foodborne illness with bacteria

Delaware Online  online


“Large distribution chains do allow for more chances of contamination, but we have to balance that with feeding the world,” said Kali Kniel, an animal and food science professor at the University of Delaware. “Unfortunately, it’s a complex problem with no easy answers.”

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Articles (5)

Deep ultraviolet fluorescence sensing with multispectral imaging to detect and monitor food-borne pathogens on the leafy green phyllosphere

Journal of Food Safety

2023 Demand for sustainable and safe raw agricultural commodities is growing rapidly worldwide. Reducing the risk of foodborne illnesses associated with fresh produce is a task which the industry and academic researchers have been struggling with for many years. There is an immediate need to devise a non-invasive optical detection system to monitor the food-borne pathogens on the leaf surface.

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Temporal Stability of Salmonella enterica and Listeria monocytogenes in Surface Waters Used for Irrigation in the Mid-Atlantic United States

Journal of Food Protection

2023 Enteric bacterial pathogen levels can influence the suitability of irrigation water sources for fruits and vegetables. We hypothesize that stable spatial patterns of Salmonella enterica and Listeria monocytogenes levels may exist across surface water sources in the Mid-Atlantic U.S. Water samples were collected at four streams and two pond sites in the mid-Atlantic U.S. over 2 years, biweekly during the fruit and vegetable growing seasons, and once a month during nongrowing seasons.

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Human Norovirus Surrogates Persist in Nontraditional Sources of Irrigation Water in Excess of 100 Days

Journal of Food Protection

2023 Human norovirus (HuNoV) has been implicated as the leading cause of foodborne illness worldwide. The ability of HuNoV to persist in water can significantly impact food safety as agriculture and processing water could serve as vehicles of virus transmission. This study focused on the persistence and infectivity of the HuNoV surrogate viruses, murine norovirus (MNV), and Tulane virus (TV), after prolonged storage in diverse environmental water types currently used for agricultural irrigation.

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Variations in Bacterial Communities and Antibiotic Resistance Genes Across Diverse Recycled and Surface Water Irrigation Sources in the Mid-Atlantic and Southwest United States

Environmental Science & Technology

2022 Reduced availability of agricultural water has spurred increased interest in using recycled irrigation water for U.S. food crop production. However, there are significant knowledge gaps concerning the microbiological quality of these water sources. To address these gaps, we used 16S rRNA gene and metagenomic sequencing to characterize taxonomic and functional variations (e.g., antimicrobial resistance) in bacterial communities across diverse recycled and surface water irrigation sources. We collected 1 L water samples (n = 410) between 2016 and 2018 from the Mid-Atlantic (12 sites) and Southwest (10 sites) U.S. Samples were filtered, and DNA was extracted.

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Ranking Produce Safety Priorities of Fresh Produce Industry Stakeholders in the United States

IAFP 2022

2022 A comprehensive understanding of stakeholder food safety priorities around fresh produce does not currently exist. Such information is essential to improve food safety knowledge and practices effectively and efficiently throughout the fresh produce industry.

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Research Grants (3)

Inactivation of viruses by pressure in ready to eat food products

USDA-CSREES-Integrated Food Safety Program $450,205


Fate of viral and bacterial pathogens during the growth of leafy greens

ISEQ and ABC Graduate Fellowship $40,000


Survival of enteric viruses on salad greens, green onions and strawberries after treatment with ultraviolet light

CANR Seed Grant $16, 538


Accomplishments (3)

Excellence in Research Award (professional)

2020 University of Delaware College of Agriculture and Natural Resources

2018 John N. Sofos Most-cited JFP Research Publication Award (professional)

2018 for paper entitled, “Comparing Human Norovirus Surrogates: Murine Norovirus and Tulane Virus” by K.A. Hirneisen and K.E. Kniel

Outstanding Advisor Certificate of Appreciation (professional)

2017 Department of Animal and Food Sciences

Education (4)

United States Agricultural Research Service, Animal Parasitic Diseases Laboratory: Postdoctoral, Microbiologist

Virginia Polytechnic Institute and State University: PhD, Food Science 2002

Virginia Polytechnic Institute and State University: MS, Molecular Cell Biology 1998

Virginia Polytechnic Institute and State University: BS, Biology 1996

Affiliations (4)

  • International Association for Food Protection (IAFP) : Current Past President (2020-2021), President (2019-2020), Executive Board Member (2016-2021), and Member
  • Capital Area Association for Food Protection : Member
  • Institute of Food Technologists : Member
  • American Society for Microbiology : Member

Event Appearances (3)

Evaluation of Zero-valent Iron Filtration in the Removal and Persistence of Escherichia coli in Non-traditional Irrigation Water Sources: A Conserve Study

International Association of Food Protection, A Virtual Annual Meeting  Virtual

Role of Edaphic Soil Factors and Climatic Conditions in Pathogen Survival on the Farm

International Association of Food Protection, A Virtual Annual Meeting  Virtual

Web-based Game Engages Post-secondary Students in Food Safety and Shifts Perceptions

International Association of Food Protection, A Virtual Annual Meeting  Virtual