Food Microbiology Commons^™

High Pressure Processing Of Cashew Milk, Rachel Coggins

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Plant-based foods are becoming increasingly popular because of changing consumer preferences. Most plant-based milks are not a direct replacement for cow’s milk because they do not have the same nutritional value and physicochemical properties. However, these properties could be modified and enhanced through processing. For example, high pressure processing (HPP) can affect irreversibly protein structure and functionality and potentially enhance enzymatic hydrolysis. HPP is used widely in the beverage industry for cold pasteurization. In this study, the effects of HPP treatment on (a) the inactivation of Listeria innocua, a commonly used surrogate for Listeria monocytogenes in HPP research, in …

Evaluation Of Human Microbiota-Associated (Hma) Porcine Models To Study The Human Gastrointestinal Microbiome, Nirosh D. Aluthge

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Research conducted in the past couple of decades has showcased the importance of the gut microbiota in human health and well-being. While many studies have reported on the differences in community membership between a disease state and a healthy state, few have investigated the mechanisms through which an aberrant microbiota contributes to a disease phenotype. One of the primary reasons for this are the many technical and ethical barriers to conducting the necessary studies directly in human individuals. Human microbiota-associated (HMA) porcine models have the potential to become important research tools which can enable the testing of hypotheses regarding host-microbiota …

Evaluating The Microbial Quality And Use Of Antimicrobials In Raw Pet Foods, Leslie Pearl Cancio

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Raw meat-based diets (RMBDs) are emerging pet foods that pose food safety risks because of the potential presence of pathogens that could cause illness to humans. In this research, the microbial quality of select RMBD products sold by pet food companies online and the use of chemical antimicrobials to reduce the microbial load in chicken liver, a common RMBD ingredient, were evaluated.

Ground meat blends and livers from four animal species (beef, pork, chicken, turkey) were purchased from four online companies that delivers directly to consumers through parcel businesses. Products were procured at three different times during one year and …

Knowledge-Informed Data-Driven Modeling Of Microbial Inactivation In Food, Steve Zhang, Firnaaz Ahamed, Hyun-Seob Song

UNL Student Research Days Posters, Graduate

Prevention of the growth of harmful microorganisms in food products is an important requirement for ensuring food safety and quality. Mathematical models to predict the quantitative changes in microbial populations in food to the variations of environmental conditions are useful tools in this regard. Current approaches that use empirical formulation generate arbitrary forms of model equations, impeding systematic analysis towards identifying key factors governing microbial growth and inactivation in food. To address this challenge, we present a data-driven modeling pipeline that enables automatic discovery of model equations (through parsimonious selection of relevant terms in a pre-built library) without having to …

The Molecular Basis For Natural Competence In Acinetobacter, Yafan Yu

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Bacteria use Horizontal Gene Transfer (HGT) to acquire genetic material, leading to the development of novel traits, such as the spread and development of antibiotic resistance. Natural competence is one type of HGT accomplished by DNA uptake from the environment and incorporation into the genome. Bacteria from Acinetobacter are wildly distributed in the environment and are naturally competent. This propensity is a key factor to the steady increase in drug resistance in Acinetobacter, which is a cause for concern in human health as Acinetobacter is a major source of nosocomial infections. During natural competence, type IV pili (T4P) and related …

Risk Based Simulations Of Sporeformers Population Throughout The Dairy Production And Processing Chain: Evaluating On-Farm Interventions In Nebraska Dairy Farms, Rhaisa A. Crespo Ramírez

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Sporeformer bacteria are ubiquitous in the farm environment. These bacteria produce enzymes that negatively affect the quality of dairy products representing a problem for the dairy industry. Two major issues associated with high levels of sporeformers in raw milk are shelf-life reduction of fluid milk and market limitations for milk powder. Specific attention has been given to the contamination of milk powders with sporeformers due to their ability to survive pasteurization and milk powder processing conditions. Hence, the control of sporeformers is crucial to benefit the whole dairy industry. Researchers have suggested that certain management practices could decrease sporeformers in …

Synthesizing Inactivation Efficacy Of Treatments Against Bacillus Cereus Through Systematic Review And Meta-Analysis And Evaluating Inactivation Efficacy Of Commercial Cleaning Products Against B. Cereus Biofilms And Spores Using Standardized Methods, Minho Kim

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Bacillus cereus is ubiquitous and can be easily carried in food processing facilities. It is problematic because it can survive various treatments such as heat, radiation, and chemical cleaning by forming spores and biofilms. Some review papers have discussed inactivation efficacies of different treatments against B. cereus, but they are narrative without quantitative summaries. This study first aimed to find effective and food industry-applicable treatment candidates against B. cereus spores and biofilms by synthesizing and comparing the efficacy of treatments using systematic review and meta-analysis. After screening, 17 studies were included, but only nine studies were used for meta-analysis …

Pre-Milling Interventions For Improving The Microbiological Quality Of Wheat, Shpresa Musa

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Development of pre-milling intervention strategies to improve the microbial quality of wheat and wheat-based products is an emerging concern for the food industry. When steam tempering conditions for hard and soft wheat were applied, the microbial population associated with the grain was significantly reduced compared to controls. Further reductions were observed when acid was applied as part of the intervention which is an added benefit since the addition of a tempering solution is required for both wheat classes since the desired milling moisture cannot be reached by applying steam alone. On average, the highest reductions for hard wheat were achieved …

Understanding The Roles Of Nutrient-Niche Dynamics In Clostridioides Difficile Colonization In Human Microbiome Colonized Minibioreactors, Xiaoyun Huang

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Clostridioides difficile is a Gram-positive pathogen that is one of the most common causes of health care-associated infections in the U.S. Because of its importance to human health, researchers are trying to understand risk factors for infection and identify new therapies to treat disease. A “healthy” gut microbiome has the ability to protect the host against colonization of C. difficile or other pathogens by providing colonization resistance. One proposed mechanism for colonization resistance is through competition for nutrients with pathogens by the members of the healthy microbiome. We tested whether competition for nutrients was important for colonization resistance in human …

Investigating The Prevalence And Control Of Listeria Monocytogenes In Food Facilities, Cyril Nsom Ayuk Etaka

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Small and very small food facilities in the ready-to-eat food industry face difficulties complying with the Food Safety Modernization Act-Preventive Controls for Human Food rule (FSMA-PCHF). This regulation highlights the need for sanitation to control environmental pathogens like Listeria monocytogenes. The main goal of this project was to investigate the prevalence and control of Listeria monocytogenes in food facilities. This study provides technical assistance to facilities to comply with the PCHF rule and addresses sanitation alternatives for food contact surfaces like aqueous ozone.

First, the prevalence of Listeria spp and L. monocytogenes in small and very small food manufacturing …

Gut Community Response To Wheat Bran And Pinto Bean, Shuen Leow

Department of Food Science and Technology: Dissertations, Theses, and Student Research

There is general consensus among the scientific community that dietary fibers reduce the risk of Western diseases through their fermentation by beneficial microbial communities in the human gut. However, dietary fibers in wheat bran (WB) and pinto bean (PB) are incompletely fermented by the gut microbiota. Therefore, there is a critical need to identify gut microbial communities that can increase fermentation of dietary fibers from these foods to maximize their disease-preventing properties. The goal of this study was to identify such communities with increased capacity to ferment the dietary fibers in WB and PB. To accomplish these goals, a stepwise …

Food Sensitivity In Individuals With Altered And Unaltered Digestive Tracts, Walker Carson

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Immunoglobulin G (IgG) against food proteins has become the subject of much discussion with regards to its role in adverse food reactions. An estimated 20% of the population suffers from some type of food intolerance. Food sensitivity can present with a vast range of symptoms and severities. Diet can have a substantial impact on the wellbeing of individuals with diseases of the gastrointestinal tract, such as Crohn’s disease or ulcerative colitis. Incidentally, these diseases have been associated with elevated levels of food-specific IgG as well an increased likelihood of food sensitivity. The presence of food-specific IgG and food sensitivity in …

Process Interventions For Improving The Microbiological Safety Of Low Moisture Food Ingredients, Tushar Verma

Department of Food Science and Technology: Dissertations, Theses, and Student Research

The recurrence of Salmonella in low moisture foods and the implementation of the FSMA rule requires a need to validate legacy and novel processing technologies. In this dissertation, a legacy thermal (extrusion), a novel thermal (radiofrequency (RF) heating), and a non-thermal (chlorine dioxide) technology, were evaluated as intervention technologies for Salmonella in low moisture foods. The twin-screw extruder was performed at different levels of screw speeds, temperatures, moisture contents, and fat contents to understand the impact of processing conditions on Salmonella inactivation in oat flour. At temperature >65°C, the Salmonella population was below the detection limit. At 55°C, Salmonella reduction …

Microbial Challenge Studies Of Radio Frequency Heating For Dairy Powders And Gaseous Technologies For Spices, Xinyao Wei

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Persistence, thermal resistance, and survival of Salmonella in low moisture foods (LMF) have resulted in several foodborne illness outbreaks. Both existing and novel pasteurization technologies need to be validated for microbial safety of LMF. In this dissertation, a framework for using radio frequency (RF) heating to enhance microbial safety of milk powders and egg white powder was established. Thermal inactivation kinetics of Salmonella in milk powders were determined to guide the dairy industry for identifying thermal processing conditions for pasteurization. Storage time showed no effect on the thermal resistance of Salmonella, which can simplify the process validation study in …

Evaluation Of Listeria Innocua Transfer From Personal Protective Equipment (Ppe) To The Plant Environment And Effective Sanitation Procedures To Control It In Dairy Processing Facilities, Karen Nieto

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Listeria monocytogenes can survive and grow under wet environmental conditions encountered in dairy facilities. Pasteurization of milk kills L. monocytogenes; however, recent listeriosis outbreaks have linked post-pasteurization contamination from the food environment to the final product. One of the sources of microbial contamination may include employees and their personal protective equipment (PPE), which often become in contact with equipment and food contact surfaces. To understand this issue, this study evaluates Listeria innocua, as a surrogate for Listeria monocytogenes, transfer from PPE to food products and surfaces encountered in dairy plants. Gloves, aprons, and boots were inoculated with L. …

Assessment Of Grain Safety In Developing Nations, Jose R. Mendoza

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Grains are the most widely consumed foods worldwide, with maize (Zea mays) being frequently consumed in developing countries where it feeds approximately 900 million people under the poverty line of 2 USD per day. While grain handling practices are acceptable in most developed nations, many developing nations still face challenges such as inadequate field management, drying, and storage. Faulty grain handling along with unavoidably humid climates result in recurrent fungal growth and spoilage, which compromises both the end-quality and safety of the harvest. This becomes particularly problematic where there is little awareness about health risks associated with poor …

Improving Microbiological Safety Of Low Moisture Food Products Using Radio Frequency And Ethylene Oxide, Long Chen

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

Recent foodborne illness outbreaks in US associated with consumption of low-moisture foods (LMF) have heightened concerns of their microbial safety. Salmonella is a pathogen of major concern in LMF due to its ability to persist in low water activity (a_w) environments. The disadvantages of existing decontamination technologies for LMF call for novel and efficient intervention technologies. Radio frequency (RF) and ethylene oxide (EtO) were evaluated in this dissertation for improving microbial food safety and quality of LMF. Cumin seeds and inshell hazelnuts were selected as model foods.

It took < 2 min of stationary RF heating to achieve > 5 log reductions of Salmonella in cumin seeds without …

Do Lactic Acid Bacteria In Fermented Foods Persist In The Gastrointestinal Tract: An In Vitro Investigation, Chloe M. Christensen, Car Reen Kok, Robert W. Hutkins

UCARE: Research Products

It is now well established that the composition of the gastrointestinal (GI) microbiota has a profound influence on intestinal and overall health. Many contemporary diseases such as type two diabetes, IBS and obesity are associated with a dysbiotic microbiota. Therefore, researchers are interested in how diet and specific dietary components can modulate the gastrointestinal microbiota and possibly repair a dysbiotic state. One approach to improve gastrointestinal health is by consuming probiotics and prebiotics or a diet rich in fermented foods containing live microbes. Fermented foods are popular because of their enhanced preservation, safety, organoleptic, functionality, and nutritional properties. These fermented …

Research Tools And Their Uses For Determining The Thermal Inactivation Kinetics Of Salmonella In Low-Moisture Foods, Soon Kiat Lau

Department of Food Science and Technology: Dissertations, Theses, and Student Research

The reputation of low-moisture foods as safe foods has been crumbling over the past decade due to repeated involvement in foodborne illness outbreaks. Although various pasteurization technologies exist, a majority are thermal processes and have not been well-characterized for pasteurizing low-moisture foods. In addition, the nature of a low-moisture food matrix introduces various experimental complications that are not encountered in high-moisture foods. In this dissertation, the development, building instructions, and characterization of various open source tools for studying the inactivation kinetics of microorganisms in low-moisture foods are described. The first tool is the TDT Sandwich, a dry heating device for …

Edible Films Made Of Corn Zein Protein And Cellulose Derivatives, Gloria Dukuzeyesu, Changmou Xu, Zhang Yue

UCARE: Research Products

A composite edible film made of corn zein protein (Z) and cellulose derivatives (C) was successfully fabricated. Edible films are coatings used to wrap food products to protect them against microbial deterioration, loss of moisture, and to extend the shelf life of the product. These edible films are consumed together with the product . The mechanical properties, water vapor permeability, application on fruits, and shelf life of the composite film were studied. Zein demonstrated excellent packing characteristics; due to its high no polar contents and hydrophobic nature, zein film served as a moisture barrier. Hydroproxy methylcellulose (HPM) is tasteless, odorless …

Growing Torula Yeast (Candida Utilis) For Food Grade Fatty Acids, Zachary Christman

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The focus of this article is the cultivation of a food grade yeast for the production of fatty acids without the restrictions of climate or growing season. Torula yeast (Candida utilis) was selected since it can grow on a wide variety of culture media and has over 60 years of use in the food industry. The fatty acid composition of C. utilis grown on two different media are presented in this article; the first example using completely synthetic media and another using distiller’s vinasse. Also, the effect of different culturing conditions on the percentage of various fatty …

A Review Of Technologies For Malt Flour And Sourdough From Brewery Spent Grain, Zachary Christman

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The utilization of brewer's spent grain for the production of malt flour is the focus of this article. The reader is presented with superheated steam and extrusion as technologies to reduce mycotoxin contamination and improve shelf life. Another option is the fermentation of brewer's spent grain with a cereal grade lactic acid bacteria for the production of sourdough bread. Milling of the brewer's spent grain for the production of bread is also covered.

Effect Of Processing On Microbiota Accessible Carbohydrates In Whole Grains, Caroline Smith

Department of Food Science and Technology: Dissertations, Theses, and Student Research

There is potential to increase microbiota accessible carbohydrates (MAC) in whole grains through food processing. Therefore, different processing conditions for boiling and extrusion of whole wheat flour were studied for their effect on MAC. Processing conditions had a minimal effect on fermentation response using 2 fecal samples of disparate composition. However, the processing method had an impact on the fermentation of non-digestible carbohydrates and subsequent short chain fatty acids production, but only for a microbiome with high diversity and a predominance of microbes associated with dietary fiber intake. Subsequently, five processing methods: boiling, extrusion, unleavened bread, yeast bread, and sourdough …

Sustainability Assessment Of U.S. Beef Processing And Its Antimicrobial Systems, Shaobin Li

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

With the increasing meat demand and awareness of sustainability, concerns have been raised regarding the sustainability of beef production and processing. However, scarce data and inadequate sustainability assessment frameworks for the U.S. beef processing industry limit the ability to develop new technologies and policies comprehensively without shifting sustainability burdens. To fill those gaps, various assessments of the U.S. beef processing industry were conducted from multiple perspectives regarding the environmental, economic, microbial effectiveness of its antimicrobial systems, and human health impacts from foodborne illness, occupational hazards, and environmental pollution.

First, process-level water and energy usage at a typical large-size beef processing …

Characterization And Evaluation Of The Probiotic Properties Of The Sporeforming Bacteria, Bacillus Coagulans Unique Is-2, Amy Garrison

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Probiotics are live organisms, that when consumed in adequate amounts, confer a health benefit to the host. To achieve probiotic status, each potential strain’s functional properties and their safety to the consumer must be comprehensively evaluated. Probiotic effects have been observed to be strain specific, therefore each new strain of interest must be characterized according to their phenotypic and genetic characteristics. There is a list of characteristics that potential probiotic strains should have to be considered as a probiotic. Potential probiotic strains should be evaluated for their acid and bile salt resistance, antimicrobial activity and adherence and colonization to intestinal …

A Comparative Analysis Of The Fermentation Capabilities Of Various Bifidobacterium Strains, Ella Oney

Honors Program: Senior Projects (Public)

Bifidobacterium is a genus of anaerobic bacteria that are commonly found to inhabit the gastrointestinal tract of many members of the animal kingdom. These microorganisms are adapted to obtain their carbon from the breakdown of complex carbohydrates. Marmosets, a mammal whose gut microbiome is inhabited by high levels of Bifidobacteria, consume gum Arabic as a major part of their diet. The purpose of this experiment is to determine whether Bifidobacterium strains isolated from the guts of marmosets are able to degrade and ferment this complex carbohydrate or one of its main constituents, arabinose. This was accomplished by inoculating isolates of …

A Risk-Based Approach To Evaluate The Impact Of Interventions At Reducing The Risk Of Foodborne Illness Associated With Wheat-Based Products, Luis Sabillon

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Pathogens are emerging on previously unrecognized food vehicles, such as wheat flour, which is a widely consumed commodity. Despite its low water activity, wheat-based ingredients and products have been implicated in several foodborne outbreaks over the last few years, resulting not only in the recall of food products but also in consumer illnesses. As a raw agricultural commodity, wheat is exposed to naturally occurring microbiological contamination that may compromise the overall safety of flour and other derived products. To address the increased concern regarding the safety of wheat-based foods, the objectives of the present research study were designed to develop …

Experimental Evaluation Of The Importance Of Colonization History In Early-Life Gut Microbiota Assembly, Inés Martínez, Maria X. Maldonado-Gomez, João Carlos Gomes-Neto, Hatem Kittana, Hua Ding, Robert J. Schmaltz, Payal Joglekar, Roberto Jiménez Cardona, Nathan L Marsteller, Steven W. Kembel, Andrew K. Benson, Daniel A. Peterson, Amanda Ramer-Tait, Jens C. Walter

Department of Food Science and Technology: Faculty Publications

The factors that govern assembly of the gut microbiota are insufficiently understood. Here, we test the hypothesis that inter-individual microbiota variation can arise solely from differences in the order and timing by which the gut is colonized early in life. Experiments in which mice were inoculated in sequence either with two complex seed communities or a cocktail of four bacterial strains and a seed community revealed that colonization order influenced both the outcome of community assembly and the ecological success of individual colonizers. Historical contingency and priority effects also occurred in Rag1^-/- mice, suggesting that the adaptive immune system …

Thermal Inactivation Kinetics Of Salmonella Enterica And Enterococcus Faecium In Ground Black Pepper, Sabrina Vasquez

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Food safety concerns of low-a_wfoods have boosted, given the increased number of foodborne illnesses related to these products. Black pepper, among other spices, has been implicated in several outbreaks and recalls in recent years.Salmonella entericahas been identified as the causing agent of outbreaks of contaminated spices. Therefore, increased efforts should be conducted to ensure food safety of spices, including black pepper. Food Safety Modernization Act (FSMA) demands all food processing facilities to conduct proper validations of the decontamination technologies applied to food products. Complete thermal process validations require a deep understanding of the thermal inactivation kinetics …

Implementation Of Iso/Iec Practices In Small And Academic Laboratories, Eric Layne Oliver

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Food Manufacturers are facing challenging times due to regulations such as the Food Safety Modernization Act (FSMA) requiring them to provide evidence they are producing safe foods. Food testing laboratories aid in the mitigation of food safety issues providing evidence that a manufacturers food safety system is acceptable. To perform these activities laboratories are required to adhere to certain standards such as ISO/IEC 17025 General Requirements for the Competence of Testing and Calibration Laboratories. However, implementation of ISO/IEC 17025 practices is challenging, especially for small and academic laboratories, due to lack of available guidance. A long-term goal of the University …