Food Microbiology Commons^™

Effect Of Environmental Factors And Residual Sanitizers On Survival And Attachment Of Indicator Organism And Human Pathogens On Fresh Produce, Vijay Singh Chhetri

LSU Doctoral Dissertations

A comprehensive understanding of the behavior of microbial contaminants on produce surfaces in agricultural farms and during post-harvest activities is essential for the development of produce safety risk management strategies. Our studies investigated the survival and the attachment of E. coli on watermelon surfaces in agricultural settings with different levels of vegetation, and the effect of residual sanitizers on the survival and the attachment of E. coli O157: H7 and L. monocytogenes on spinach leaves. The attachment strength (S_R) of the E. coli cells on watermelon surfaces significantly increased (P<0.05) from 0.04 to 0.99 in the first 24 h, which was primarily due to the decrease in loosely attached population, given that the population of strongly attached cells was constant. The daily die-off rate of E. coli ranged from -0.12 …

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 …

Combined Effects Of Calcium Ascorbate Treatment And Modified Atmosphere Packaging To Improve Quality Retention Of Fresh-Cut Cantaloupes, Joongmin Shin, Kevin Mis Solval, Bob Xiang, Youn Suk Lee

Journal of Applied Packaging Research

The impact of passive modified atmosphere packaging technique (MP) and calcium ascorbate (CA) on the extension of freshness and shelf life in fresh-cut cantaloupe was studied at two storage temperatures (4 and 10°C). Fresh cantaloupes were cut into uniform size cubes (25.4 mm x 25.4mm x 25.4mm). Then, half of the fresh cut cubes was dipped into the treatment solution, and the others were not. Clamshell tray with snap-on lid (control) and micro-perforated sealable lid (MP) was used as the fresh cut fruits packaging. Fresh cut cantaloupes in CA and MP combination (CA-MP) observed the highest quality preservation among the …

Hydrodynamic Cavitation As In-Line Process To Control Common Dairy Sporeformers, Pratibha Chaudhary

Electronic Theses and Dissertations

Sporeforming bacteria and their endospores have the ability to survive thermal treatments and proliferate in the milk and dairy products to cause spoilages. We applied the effect of hydrodynamic cavitation in controlling these bacteria and their spores at pilot scale level. Our aim was to investigate a technology that would improve the microbial quality of milk and dairy products, and is capable of being scaled up to be adapted at industrial level. Cavitation damages the cell walls of the bacteria and their endospores (releasing dipicolinic acid, responsible for endospore resistance to extreme conditions), thereby making them susceptible to thermal treatments …

Metabolic And Morphological Evaluation Of Two Brewer’S Yeast Strains Throughout Serial Re-Pitching In Beer Fermentation, Anh Pham

All Graduate Theses, Dissertations, and Other Capstone Projects

Beer fermentation is the process of growing yeast anaerobically in a malt-based medium, ultimately resulting in alcohol and carbon dioxide production. In order to reduce the cost and waiting time, serial repitching has been practiced among microbrewers. The technique emphasizes transferring yeast from one batch of beer to the subsequent brewing cycles. It has been shown that aged yeast cultures have higher fermentation efficiency and shorter lag period, thereby resulting in shorter fermentation times, faster pH drop, and lower concentrations of unwanted products. Despite the advantages of serial repitching, one can only practice repitching for approximately 5-6 times with a …

Degradation Kinetics Of Cold Plasma-Treated Antibiotics And Their Antimicrobial Activity, Chaitanya Sarangapani, Dana Ziuzina, Patrice Behan, Daniela Boehm, Brendan F. Gilmore, Patrick J. Cullen, Paula Bourke

Articles

Antibiotics, such as ofloxacin (OFX) and ciprofloxacin (CFX), are often detected in considerable concentrations in both wastewater effluents and surface water. This poses a risk to non-target organisms and to human health. The aim of this work was to study atmospheric cold plasma (ACP) degradation of antibiotics in water and meat effluent and to explore any residual antimicrobial activity of samples submitted to the plasma process. The results revealed that ACP successfully degraded the studied antibiotics and that the reaction mechanism is principally related to attack by hydroxyl radicals and ozone. According to the disk diffusion assay, the activity of …

Spent Coffee Waste As A Potential Media Component For Xylanase Production And Potential Application In Juice Enrichment, Rajeev Ravindran, Gwilym Williams, Amit Jaiswal

Articles

In this study, spent coffee waste (SCW) was used as the sole carbon source for xylanase production in solid state fermentation mode using Aspergillus niger. A Box–Behnken design was constructed using three parameters viz. temperature, initial moisture content, and log number of sporestodeterminetheoptimalfermentationcondition. Thebestfermentationconditionsforxylanase productionwerefound to beincubation at30◦Cwith aninitial moisture contentof 70%and usingan inoculum of 6.5×106 spores/g of dry SCW. Furthermore, the design of experiments revealed that maintaining a medium composition of 0.2 g of yeast extract, 0.04 g of K2HPO4, and 0.03 g of MgSO4 increased xylanase production. Under optimised solid-state fermentation conditions an enzyme activity of 6495.6 IU/g …

Antimicrobial Effects Of Microwave-Induced Plasma Torch (Minimip) Treatment On Candida Albicans Biofilms, Oliver Handorf, Uta Schnabel, André Bösel, Thomas Weihe, Sander Bekeschus, Alexander C. Graf, Jörg Ehlbeck

Articles

The susceptibility of Candida albicans biofilms to a non-thermal plasma treatment has been investigated in terms of growth, survival and cell viability by a series of in vitro experiments. For different time periods , the C. albicans strain SC5314 was treated with a microwave-induced plasma torch (MiniMIP). The MiniMIP treatment had a strong effect (reduction factor (RF) = 2.97 after 50 s treatment) at a distance of 3 cm between the nozzle and the superior regions of the biofilms. In addition, a viability reduction of 77% after a 20 s plasma treatment and a metabolism reduction of 90% after a …

The Evaluation Of Pathogen Survival In Dry Cured Charcuterie Style Sausages, Jennifer Michelle Mcneil

Theses and Dissertations--Animal and Food Sciences

The objective of this study was to evaluate the survival of non-O157:H7 STEC, Salmonella spp., and S. aureus in dry fermented sausages. Chorizo and Landjager sausages were inoculated with individual bacterial cocktails and stuffed into natural casings. Temperature, relative humidity, pH, and water activity were monitored through fermentation, drying, and storage. Bacterial counts were determined by serial dilution and plated in triplicates on selective media. Plates were incubated at 37°C for 24 hours and colony forming units per gram (CFU/g) were observed.

Results of the first study validate that contaminated raw materials contribute to pathogen survival and background bacteria outcompeted …

Development And Diagnostics Of Novel Non-Thermal Plasmatreatment Systems, Laurence Scally

Doctoral

Non-thermal plasma (NTP) has been a point of interest in many areas over the last few decades. Much research has been,and continues to beundertaken,to understand the fundamentals of plasma discharges. This is such a broad topic due to the very nature and variable dependencies that set the conditions for plasma discharge to occur. This can come in the form of electrode geometry and spacing, dielectric barrier thickness, humidity of environment, material selection for electrodes and dielectric barriers, the power supply used, and the operating gas(es) used. A lot of these influencing factors can be set and kept constant, but still …

Efficacy Of Cold Plasma Functionalised Water For Improving Microbiological Safety Of Fresh Produce And Wash Water Recycling, Apurva Patange, Peng Lu, Daniela Boehm, Patrick J. Cullen, Paula Bourke

Articles

Atmospheric cold plasma (ACP) is an effective method for microbiological decontamination. This study evaluated an alternative water-based decontamination approach for inactivation of bacterial population from fresh produce and in the wash water generated from fresh produce washing. The study characterised ACP inactivation of attached Listeria innocua and Pseudomonas fluorescens inoculated on lettuce in comparison to chlorine treatment. P. fluorescens was sensitive to ACP treatment and was reduced below detection limit within 3 min of treatment. L. innocua population was reduced by ∼2.4 Log10 CFU/g after 5 min of treatment; showing similar inactivation efficacy to chlorine treatment. The microbial load in …

High Voltage Atmospheric Cold Air Plasma Control Of Bacterial Biofilms On Fresh Produce, Apurva Patange, D. Boehm, Dana Ziuzina, Patrick J. Cullen, Brendan Gilmore, Paula Bourke

Articles

Atmospheric cold plasma (ACP) offers great potential for decontamination of food borne pathogens. This study examined the antimicrobial efficacy of ACP against a range of pathogens of concern to fresh produce comparing planktonic cultures, monoculture biofilms (Escherichia coli, Salmonella enterica, Listeria monocytogenes, Pseudomonas fluorescens) and mixed culture biofilms (Listeria monocytogenes and Pseudomonas fluorescens). Biotic and abiotic surfaces commonly occurring in the fresh food industry were investigated. Microorganisms showed varying susceptibility to ACP treatment depending on target and process factors. Bacterial biofilm populations treated with high voltage (80 kV) ACP were reduced significantly (p <  0.05) in both mono- and mixed species biofilms after 60 s of treatment and yielded non-detectable levels after extending treatment time to 120 s. However, an extended time was required to reduce the challenge mixed culture biofilm of L. monocytogenes and P. fluorescens inoculated on lettuce, which was dependent on biofilm formation conditions and substrate. Contained treatment for 120 s reduced L. monocytogenes and P. fluorescens inoculated as mixed cultures on lettuce (p <  0.05) by 2.2 and 4.2 Log10 CFU/ml respectively. When biofilms were grown at 4 °C on lettuce, there was an increased resistance to ACP treatment by comparison with biofilm grown at temperature abuse conditions of 15 °C. Similarly, L. monocytogenes and P. fluorescens exposed to cold stress (4 °C) for 1 h demonstrated increased tolerance to ACP treatment compared to non-stressed cells. These finding demonstrates that bacterial form, mono versus mixed challenges as well as environmental stress conditions play an important role in ACP inactivation efficacy.

Effect Of Cold Plasma On The Techno-Functional Properties Of Animal Protein Food Ingredients, Juan M. Pérez-Andrés, Carlos Álvarez, Patrick J. Cullen, Brijesh K. Tiwari

Articles

Proteins, as food ingredients, are employed in the food industry, not only for their high nutritional value, but also because of their techno-functional properties. Modifications of their native structure due to the action of external factors such as pH, temperature or processing by emerging technologies, can lead to changes in their functionality; and consequently, their applicability. The present study investigates the effects of cold atmospheric air plasma on the techno-functional properties of two common food ingredients (haemoglobin and gelatine from pork), and a novel source of functional proteins extracted from a meat co-product (bovine lung protein). Significant effects were found …

Assessment Of Salmonella Enterica Biofilms And Expression Differences Among Serovars, Zhaohao Shi

Graduate Theses and Dissertations

Biofilms are communities of microorganisms associated by a matrix of extracellular polymers. In this state, microorganisms occupy an ecological niche distinct from their free-floating, planktonic counterparts. Also, biofilm bacteria become biologically unique as they form communities and lose motility. The acquisition of these physiological attributes enables the biofilm to persist through harsh environmental conditions, including antimicrobial induced stress and to resist sanitization efforts. Because of these features, biofilms can rapidly disseminate across numerous surfaces and as they establish, become challenging to remove. This is a particular issue for the food industry as processing plants offer favorable conditions for biofilm formation …

Efficacy Of Natural Compounds With Novel Carrier Systems For Controlling Campylobacter Jejuni In Post-Harvest Poultry, Sandip Shrestha

Graduate Theses and Dissertations

Campylobacter jejuni, a leading cause of bacterial gastroenteritis worldwide, is strongly associated with the consumption and/or mishandling of raw contaminated poultry products. Thus, interventions aiming to reduce C. jejuni counts on poultry products could greatly reduce the incidence of human campylobacteriosis. In the first study, the efficacy of a generally recongnized as safe (GRAS) compound, carvacrol (CR; derived from oregano oil), as an antimicrobial wash treatment to reduce C. jejuni on chicken skin was evaluated. Three delivery systems of CR: suspension, emulsion and nanoemulsion were used. C. jejuni counts were reduced up to 4 log10 cfu/sample by 2% dose of …

Aqueous Ozone Inactivation Of Viruses And Bacteria On Biotic And Abiotic Surfaces, Cailin Dawley

Graduate Theses and Dissertations

Produce is susceptible to contamination by foodborne pathogens. Food service establishments utilize sanitizing agents to reduce microbes on produce surfaces. The research objectives were to evaluate the efficacy of aqueous ozone 1) on the inactivation of viruses and bacteria on produce; 2) on the inactivation of viruses on stainless steel; and 3) against viruses in association with bacteria on produce surfaces. For objective 1, Boston bibb lettuce and cherry tomatoes were spot inoculated with a cocktail of viruses (murine norovirus (MNV) and MS2 bacteriophage) or bacteria (Enterobacter cloacae and Bacillus cereus) and washed for 40 min with samples taken every …

Efficacy Of Antimicrobial Mitigation On Escherichia Coli Cfu And Growth And Development Of Hydroponic Leafy Greens, Nathan J. Eylands

Graduate Theses and Dissertations

The Food and Drug Administration (FDA) have set new standards that apply to agriculturalists producing crops eaten fresh and/or raw by consumers. This new produce safety rule, known as the Food Safety Modernization Act (FSMA), has established science-based standards for all areas of production in agriculture with regards to microbial contamination. Escherichia coli (E. coli) O157:H7 is a particular bacterium of concern under FSMA guidelines. Grower compliance is mandatory and therefore vital to the continuation of any farm. Greenhouse hydroponic growers have shown advantages in efficiency when compared to conventional farming methodology. Those, however, with recirculating hydroponic systems face unique …

Microbiota Metabolic Product Deoxycholic Acid Prevents Campylobacter Jejuni Chicken Colonization Through Modulating Ceca Anaerobes, Bilal Ali Alrubaye

Graduate Theses and Dissertations

Campylobacter jejuni is a prevalent infectious enteritis mainly foodborne from chickens. Despite of reducing C. jejuni food contamination dramatically decreases campylobacteriosis, few effective approaches are available for the bacterial reduction in chickens. The aim of this study was to use microbial metabolic product deoxycholic acid (DCA) to reduce C. jejuni chicken colonization. Broiler chicks were fed 0 or 1.5 g/kg DCA, lithocholic acid (LCA), or urodeoxycholic acid (UDCA) in diets or orally gavaged with cholic acid (CA, 1.5g/kg body weight). Birds were also transplanted with DCA modulated anaerobes (DCA-Anearo) or aerobes (DCA-Aero). Birds were infected with 109 CFU/bird human clinical …

With-In Host Dynamics Of L. Monocytogenes And Thresholds For Distinct Infection Scenarios, Ashrafur Rahman, Daniel Munther, Aamir Fazil, Ben Smith, Jianhong Wu

Mathematics and Statistics Faculty Publications

The case fatality and illness rates associated with L. monocytogenes continue to pose a serious public health burden despite the significant efforts and control protocol administered by private and public sectors. Due to the advance in surveillance and improvement in detection methodology, the knowledge of sources, transmission routes, growth potential in food process units and storage, effect of pH and temperature are well understood. However, the with-in host growth and transmission mechanisms of L. monocytogenes, particularly within the human host, remain unclear, largely due to the limited access to scientific experimentation on the human population. In order to provide insight …

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 …