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Title: THE EVALUATION OF THERMAL INACTIVATION OF COXIELLA BURNETII NINE MILE PHASE II IN SKIM MILK BY INTEGRATED CELL CULTURE-POLYMERASE CHAIN REACTION (ICC-PCR) ASSAY
Creator: Zheng, Jiaojie
Date: 2014, 2014-07
Description: Coxiella burnetii (C. burnetii) is an obligate intracellular bacterium and replicates exclusively in an acidified, lysosome-like vacuole which...
Show moreCoxiella burnetii (C. burnetii) is an obligate intracellular bacterium and replicates exclusively in an acidified, lysosome-like vacuole which means the analysis of C. burnetii is difficult than other bacterial which can growth on regular liquid medium. An Integrated Cell Culture-Polymerase Chain Reaction (ICC-PCR) assay has been developed as a potential alternative to animal bioassays for evaluating C. burnetii inactivation in milk. This thesis research is to demonstrate the usefulness of this assay for evaluating C. burnetii inactivation in skim milk and comparing the results found for whole milk which was completed by another researcher. Before the thermal studies, the thermal kinetics of heating skim milk in glass vials and the polymerase chain reaction (PCR) detection limit were determined. For thermal treatments, Ultra High Temperature (U.H.T.) skim milk containing C. burnetii at ~7.2 log10 genome equivalents/ml (ge/ml) was treated in submerged vials at 60 °C, 62 °C and 64 °C for various times. After serial dilution of milk to 10-6, triplicate Vero cell monolayers were infected at each level for 48 hours followed by 9 days incubation after inoculum removal and addition of fresh RPMI + 1% FBS media. Infected cells were freeze-thawed followed by deoxyribonucleic acid (DNA) extraction and real- time PCR (RT-PCR) for the C. burnetii IS1111a gene. C. burnetii in samples was considered as viability if the Day 9 post infection (p.i.) level increased by ≥0.5 log10 C. burnetii ge/ml over the most concentrated Day 0 p.i. sample. The numbers of positive wells from each dilution were used to calculate the remaining viable C. burnetii/ml by MPN method. The thermal kinetics profile for heating the skim milk showed that the come up and cool down time would not adversely affect the thermal x treatment at 60 °C and 62°C. The qPCR could detect the propagation of C. burnetii in skim milk containing as low as 120 C. burnetii ge/ml. The ICC-PCR assay demonstrated that the thermal inactivation of C. burnetii in skim milk was faster than in whole milk at 62 °C and 64 °C. For the 62 °C treatment, the infectious C. burnetii in skim milk was reduced by 1.3 log10 ge/ml at 10 minutes and was no longer infectious after 20 minutes, whereas C. burnetii in whole milk had no obvious reduction after 10 minutes, 3.7 log10 ge/ml after 20 minutes, and was no longer infectious after 26 minutes. After 6 minutes treatment at 64 °C, infectious C. burnetii was reduced by 6.2 log10 ge/ml for skim milk vs. 3.8 log10 ge/ml for whole milk with complete inactivation after 9 minutes for both milk types. This ICC-PCR assay is a specific and sensitive method to detect the inactivation of C. burnetii in skim milk and allows differentiation of the thermal inactivation kinetics of different types of milk, and may be useful for the evaluation of thermal and novel non-thermal processes for C. burnetii inactivation in milk.
M.S. in Food Safety and Technology, July 2014
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Title: A THERMAL RESISTANCE STUDY OF SHIGA TOXIN-PRODUCING ESCHERICHIA COLI (STEC) IN LOW MOISTURE FOOD WITH THE USE OF A DIFFERENTIAL SCANNING CALORIMETER (DSC)
Creator: Liu, Shi
Date: 2014, 2014-12
Description: According to CDC's Foodborne Disease Outbreak Surveillance System database, from the years 2007-2011, there were eight outbreaks associated...
Show moreAccording to CDC's Foodborne Disease Outbreak Surveillance System database, from the years 2007-2011, there were eight outbreaks associated with low-moisture food including nuts, cheese, cookie dough, and wheat snack food involving Shiga toxinproducing Escherichia coli O157:H7 (STEC), which led to over 318 cases of foodborne illnesses. Yet, insufficient data on STEC thermal inactivation has been obtained in lowmoisture food. In this study, a novel methodology using a Differential Scanning Calorimeter was used to measure STEC thermal inactivation kinetics in low moisture environments. The objective of this study was to use a Differential Scanning Calorimeter to measure D- and z-values, and therefore to determine the microbial thermal resistance, of select STEC strains. Five strains of outbreak related E. coli O157:H7 and one strain of E. coli K12 were individually grown on tryptic soy agar with 0.6% yeast extract (TSAYE). The cells were harvested and inoculated into sample matrices. Matrices included a moist buffered peptone water solution, a simple model low-moisture food matrix (corn syrup), and lowmoisture food (oat flour and peanut butter). Samples were individually heated using a Differential Scanning Calorimeter (DSC). The DSC was able to achieve a reproducible and accurate thermal environment. Following heat treatment, microbial survivors were enumerated via a traditional plate counting method. The six strains showed greater thermal resistance in corn syrup than in a buffered solution and in peanut butter and oat flour compared with both the corn syrup or buffer solution (p < 0.05). At the same processing condition linearly rising temperature at 5oC/min, in low moisture food matrices, approximately 90oC and 95oC was needed to reduce the outbreak strains of STEC in peanut butter and oat flour by 5-log CFU/g; whereas 85oC and 75oC were needed for corn syrup and buffer solution, respectively. D65 o C ranged from 0.26-0.92 min for all strains tested in buffer. Those same strains exhibited a 10-100 times increase in resistance in corn syrup (D65 o C = 2.6-108.6 min). The measurement that quantifies the increased heat resistance of STEC in low moisture food will improve science-based risk reduction by ensuring process lethality in these types of food.
M.S. in Food Safety and Technology, December 2014
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Title: EFFECT OF ABUSIVE STORAGE CONDITIONS ON THE SUBSEQUENT INACTIVATION OF SALMONELLA ON THE SURFACES OF BLACK PEPPERCORNS BY ATMOSPHERE PRESSURE PLASMA
Creator: Sun, Shengqian
Date: 2013-04-30, 2013-05
Description: Outbreaks of salmonellosis associated with low moisture foods have raised public concerns. Meanwhile, fulfillment of consumers’ demand for...
Show moreOutbreaks of salmonellosis associated with low moisture foods have raised public concerns. Meanwhile, fulfillment of consumers’ demand for safety and wish quality on the fresh products has increased the interest of the food industry to adopt innovative processes for food decontamination and preservation. The FDA Food Code (2005) requires a 5-log bacterial reduction for a product to be labeled pasteurized. Compared to thermal processing, some emerging technologies rely on physical and chemical processes, such as high hydrostatic pressure, ionizing radiation, ultra-sound, pulsed electric fields, ultraviolet radiation and atmosphere pressure plasma (APP) have potential to decontaminate microorganisms at ambient temperature or sub-lethal temperature. APP of these treatments is one of the more desirable microbial inactivation technologies. The purpose of this research was to study the effect of abusive storage conditions on the subsequent inactivation of Salmonella on the surfaces of black peppercorns by APP. This was achieved by investigating the survival of Salmonella cocktails: Oranienburg, Tennessee, Anatum and Enteritidis under storage condition of 25°C, 33% RH; 25°C, 97% RH; and, 37°C, 33% RH for 10 days and additionally at 25°C, 33% RH for 1 and 30 days. Results showed that Salmonella populations decreased significantly (p<0.05) with respect to the treatment time. Approximately a 4.5 to 5.5 log reduction in population was achieved after 60 to 80 s treatment after storage at abusive condition. This study also determined that rate of destruction did not differ (p>0.05) with respect to the prior storage temperature and RH as well as storage time. The storage condition did not significantly (p>0.05) impacted the microbial inactivation by APP. xi xii Based on the previous work, the equipment was adding moisture to investigate the effect of the destruction of Salmonella cocktails that had been previously stored under the conditions of 25°C, 33% RH by APP with the second gas Air. The results showed that approximately a 2.5 to 3.5 log reduction in population was achieved after 60 to 80 s treatment. The reason might be that the moisture consumed energy to split H2O molecules into H2, O2 & O3 while plasma generated. These findings help advance our understanding of APP has the potential to decontaminate Salmonella on the surfaces of black peppercorns.
M.S. in Food Safety and Technology, May 2013
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Title: VIRUS INACTIVATION IN CONTAMINATED FRUIT PUREE AND JUICE VIA HYDROSTATIC PRESSURE PROCESS
Creator: Pan, Hao
Date: 2015, 2015-07
Description: The use of the high hydrostatic pressure process (HPP) of food allows for retention of many sensory qualities. However, it is not clear if the...
Show moreThe use of the high hydrostatic pressure process (HPP) of food allows for retention of many sensory qualities. However, it is not clear if the process is effective in inactivating viruses on contaminated produce. This study’s objective is to evaluate the factors that affect the survival of viral surrogates MS2 coliphage and murine norovirus MNV during HPP treatment of fresh fruit puree and juice. Fresh strawberries and frozen pomegranate arils were used to prepare separate puree or juice products which were inoculated with the viral surrogates for each trial. The inoculated juice or puree was prepared for treatment treated in an Avure QFP 24L-828-S HPP pilot system using process temperatures of 10 to 40⁰C, pressures ranging from 250 to 600 MPa, and holding times from 1.5 to 3 mins. After HPP treatments, MNV/MS2 inoculated sample matrices were eluted and quantified. Control samples were prepared in the same way, but did not receive HPP treatment. The recovery range in the control samples was 12 to 40% for MS2 or MNV from inoculated puree and juice. In treated samples, it was found that viruses (MNV or MS2) survived better in the semi-solid puree as compared to liquid matrices (juice or medium) regardless of pH. In general, higher pressures enhanced the virus inactivation with constant holding time and temperature. However, MS2 was found more resistant to HPP treatment than MNV, though the trend of their responses to HPP are consistent. The MS2 inactivation in strawberry puree was more efficient under the treatment with higher HPP temperature. Surprisingly, an opposite trend was observed for MNV inactivation. Among 11 HPP trials, the MNV inactivation in strawberry juice has no significant difference from that in pomegranate juice. Overall the results of this study provide valuable information on the effect of food matrix, holding temperature and pressure on virus survival during hydrostatic pressure process of fruit puree and juice. MS2 coliphage is somewhat resistant to HPP in fruit puree and juice, suggesting it could serve as an indicator for human enteric virus particularly hepatitis A virus in future studies.
M.S. in Food Safety and Technology, July 2015
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Title: THE FATE OF TOTAL ARSENIC CONTENT IN RICE FOR SEVERAL PROCESSING VARIABLES: RINSING AND HIGH VOLUME COOK WATER
Creator: Parvanehvar, Alireza
Date: 2015, 2015-07
Description: This project evaluated rinsing and cooking rice in a high volume of water for several brown and white rice’s, from the United States, India...
Show moreThis project evaluated rinsing and cooking rice in a high volume of water for several brown and white rice’s, from the United States, India and Iran. There has been more attention to the arsenic content in certain foods, such as apple juice, and regional rice in the U.S. has become an issue as well. The purpose of rinsing or using a high volume of water to cook rice was to reduce the total arsenic content. Previous work on long grain white rice showed a 25% to 46% reduction of arsenic in rice cooked in a high volume of water. This previous work showed no significant decrease in arsenic in rice rinsed in 2 parts of water to rice. This project optimized the procedure of rinsing and cooking rice in a high volume of water from previously presented work. Advances in sampling due to more efficient procedures in sample preparation with emphasis on chilling, grinding and drying prepared rice significantly reduced the relative standard deviation from >10% to 3-7%RSD. Arsenic was measured for total and species (As+3, As+5, monomethyl arsenite, dimethyl arsenate) and the two methods compared within 90% when analyzed by ICP-MS (total) and HPLC-ICP-MS (Species).Results from this project demonstrated an average 45.91% decrease in total arsenic for rice cooked in a high volume of water (1 part of rice to 7 parts of water) and a 50.28% in average decrease in inorganic arsenic for rice cooked using the same procedure. This data provides information on arsenic content in domestic and international rice and provides processing strategies to reduce the arsenic content.
M.S. in Food Process Engineering, July 2015
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Title: ENRICHMENT OF COXIELLA BURNETII FROM BOVINE AND NON-BOVINE MILKS USING AN AXENIC LIQUID CULTURE MEDIUM
Creator: Shi, Manman
Date: 2016, 2016-07
Description: Non-bovine milks are becoming more popular as beverages and for making cheeses, however little are understood regarding how pathogens are...
Show moreNon-bovine milks are becoming more popular as beverages and for making cheeses, however little are understood regarding how pathogens are inactivated in these milks during pasteurization. Recently, a tissue culture-PCR method has been developed to quantify inactivation of Coxiella burnetii, the obligate intracellular bacterium which is the reference pathogen for milk pasteurization. Unfortunately, this method is time-consuming and quite laborious. A potential improvement over the ICC-PCR method may be the use of a new specialized liquid medium which has been shown to allow growth of pure cultures of C. burnetii outside of host cells. In this study, ACCM-2 was evaluated for its’ ability to enrich C. burnetii from bovine and non-bovine milks as a potential alternative to tissue culture enrichment for Most Probably Number (MPN) quantification of inactivation of C. burnetii in milks. C. burnetii in bovine whole milk and cream (as a surrogate for a high fat product), camel, water buffalo, and goat milk were grown in ACCM-2 media (1:10) in 10 mL volumes in T-25 flasks at 37 °C under 5% CO2 and 2.5% O2 with sampling over 14 days. C. burnetii levels were determined by quantitative PCR (qPCR) against a standard curve for the Coxiella-specific IS1111a gene. C. burnetii in all milks grew at least 3 logs over 10 days with the exception of the water buffalo milk which did not allow growth. Bovine milk allowed the least growth and additional studies determined that the detection limit for growth of C. burnetii from this milk is about 6 ge/mL. Additional studies showed that adjustment of the pH from ~5.0 to 4.75 results in much improved growth of C. burnetii from bovine milk. Adjustment of pH did not allow growth from water buffalo milk, however additional dilution of the milk did allow improved C. burnetii growth but the added dilution also decreases the detection limit of the proposed new MPN-PCR assay. Further studies were completed to determine how thermal injury affects recover and growth of Coxiella burnetii in ACCM-2 media after thermal processing at 64 °C for up to 8 minutes. Although injury did increase the lag phase period and reduce the log phase growth rate from these samples, recovery and growth of at least 0.5 log was possible from all samples indicating that this media should be useful as an alternative enrichment method for use in an MPN format for quantification of thermal inactivation of C. burnetii in both bovine and non-bovine milks.
M.S. in Food Safety and Technology, July 2016
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Title: COMPARATIVE ANALYSIS OF GROWTH KINETICS OF LISTERIA MONOCYTOGENES LINEAGES I AND II IN CHOPPED RED CABBAGE AND CUCUMBER USING PRIDICTIVE MODELING
Creator: Qi, Yan
Date: 2015, 2015-07
Description: Recently, outbreaks oflisteriosis assoc iated with cons umption of contaminated fresh produce by Listeria monocytogenes have increased....
Show moreRecently, outbreaks oflisteriosis assoc iated with cons umption of contaminated fresh produce by Listeria monocytogenes have increased. However, we know little about L. monocytogenes persistence and growth in fresh-cut produce items . The two main human foodbome outbreak lineages ofL. monocytogenes are LI and LB. Strains in LI (including serotypes 1/2b and 4b) are most likely to be isolated from human with listeriosis and Strains in LII (including serotypes 1/2a and 1/2c) are most likely to be isolated from food products and the natural environment. In order to determine the comparative survival and growth kinetics of these two lineages in chopped red cabbage and cucumber, samples of produce were chopped into 100 grams quantities and inoculated with 104 CFU/g of a cocktail of either LI (F2365, H7858, R2-502) or LII (LS814, JI-I 01, J1-067) antibiotic resistant strains. Samples were stored in deli-style containers at 5 or 10°C for 14 days, or 25°C for 7 days. At various intervals, samples were stomached and plated onto PCA with appropriate antibiotics. Data were modeled using DMFit from ComBase and statistical analyses were performed with GraphPad InStat. A p -value less than 0.05 was considered significant. The res ults for the grow th rates ((logIOCFU/g)/h) of the L. monocytogenes LI cocktail in red cabbage were significantly higher at 5°C (0.006±0.003), 10°C (0.017±0.004), and 25°C (0.051±0.017) than the LII cocktail ; and L. monocytogenes LI cocktail in cucumber were significantly lower at 25°C (0.098±0.00 84). Secondary models using the Ratkowsky equation presented r 2 values of 0.9866 for LI in red cabbage whereas presenting / values of 0.9998 and 0.9997 for LI and LII in cucumber, respectively. No significant difference between two lineages was seen in red cabbage and cucumber during ambient temperature display. Finally, the behavior of L. monocy togenes LI and LII on red cabbage and cucumber after potential consumer temperature abuse was determined. In red cabbage, LI grew steadily. However, the growth of L1I in red cabbage was more dynamic. In cucumber, there was no significant difference between LI and LII. The result s from this study will aid in comparing the growth and survival kinetics of Ll and L1l of L. monocytogenes and will provide guidance to both customers and the food industry.
M.S. in Food Safety and Technology, July 2015
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Title: COMPARISON OF RNA EXTRACTION KITS FOR THE DETECTION OF MS2 COLIPHAGE ON GREEN ONIONS VIA RT-PCR
Creator: Xu, Ruoyang
Date: 2013, 2013-07
Description: This thesis writing has become possible due to the constant contribution of certain individuals and they deserve a special mention. First and...
Show moreThis thesis writing has become possible due to the constant contribution of certain individuals and they deserve a special mention. First and foremost, I would like to express my sincerest gratitude to my research advisor, Diane Stewart, who provided me the great opportunity to work on this unique research project. Her supervision, valuable guidance, advice, love and incessant support from the initial to the final level helped me develop a strong foundation on this subject. I am gratefully thankful to Dr. Carol Sheih for suggesting novel ideas to perform this research and for her overall contribution. I would also like to extend a deep thank to Christina Megalis for her guidance and high quality time in giving me training on this project. I am indebted to the thesis committee, Dr. Wei Zhang and Dr. Andrew J. Howard for accepting my request to be on the thesis defense committee. Their productive comments on this research work were very valuable. My special thanks go to Renee Mc Brien and David Griesemer for their constant encouragement during the time I spent at Institute for Food Safety and Health. I would like to show my gratitude to my friends, Xueyan Wang, Jingbo Wang and Yan Sun for their direct or indirect support in this research. Last but not the least; I would like to deeply acknowledge my parents and all my family members, for their moral, financial and emotional support. They are the constant source of inspiration for me and without their support; I would have never reached to this level in my life.
M.S. in Food Safety and Technology, July 2013
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Title: HIGH PRESSURE PROCESSING CONDITIONS FOR INACTIVATION OF HUMAN NOROVIRUS SURROGATE IN OYSTERS
Creator: Agarwal, Sagar
Date: 2015, 2015-07
Description: Noroviruses are the leading cause of acute nonbacterial gastroenteritis in humans. Bivalve mollusks bio-accumulate norovirus as they feed....
Show moreNoroviruses are the leading cause of acute nonbacterial gastroenteritis in humans. Bivalve mollusks bio-accumulate norovirus as they feed. High pressure processing (HPP), a non-thermal processing technology, can inactivate microorganisms in foods while preserving flavor, appearance, nutritional value, and extending shelf-life. In the present study, we have systematically investigated the effect of parameters such as temperature, salinity and product composition on the efficacy of HPP for inactivation of human norovirus surrogate. For temperature analysis MNV-1 suspended in aqueous media, oyster homogenate, and bio-accumulated in whole oysters were treated with pressures varying from 200-500 MPa at 4, 10, and 20oC with a hold time of 1 minute. In media, a 4-log10 reduction was observed upon treatment at 300 MPa for 1 minute at 4oC, whereas pressures of 400 and 500 MPa were required for a comparable reduction at initial processing temperatures of 10 and 20oC. Colder temperature promoted higher reduction in virus titer at a given pressure. Addition of 1, 2 and 3% (w/v) sea salt to aqueous media provided significant baroprotective effect at colder temperatures. While pressure of 300 MPa for 1 min at 4oC was sufficient to achieve 3-log10 reduction for MNV-1 suspended in 1% (w/v) sea salt media, the same conditions resulted in only 1.4-log10 reduction for MNV-1 suspended in 3% (w/v) sea salt media. However increasing processing temperature the minimized the baroprotective effects. Similar results were observed for the effect of food matrix on virus survival, with significant baroprotective effect at colder temperatures and a minimal impact of matrix on increasing processing temperature. For initial processing temperature of 4oC a 300 MPa treatment with a hold time of 1 min resulted in a 4-log10 reduction for MNV-1 suspended in aqueous media, 3.35-log10 reduction in oyster homogenate, and <1-log10 reduction in whole oysters. Whereas at higher initial processing temperatures of 10 and 20oC the difference in reduction between matrices was insignificant. A comparison of temperature v/s salinity and temperature v/s composition revealed that effects of temperature far outweighed the impact of product properties (salinity and composition).Whole oysters seeded with MNV-1 treated at 350 MPa for 1 min at 4oC was found to have a 4-log10 reduction, while MNV-1 suspended in aqueous media at 20oC on similar treatment had a 0.5-log10 reduction. Similarly MNV-1 suspended in aqueous media with 3% salt when treated with 400 MPa for 1 min at 4oC resulted in a 5-log10 reduction, whereas MNV-1 suspended in aqueous media at 20oC on similar treatment had a 1.9-log10 reduction. Oyster processors should use refrigerated temperature to achieve higher reduction in virus titer at lower pressures.
M.S. in Food Safety and Technology, July 2015
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Title: IMPROVED METHODS FOR DETECTING PARTIALLY HYDROLYZED GLUTEN IN FOOD
Creator: Cao, Wanying
Date: 2016, 2016-07
Description: Celiac disease is an autoimmune disorder in susceptible individuals caused by the consumption of gluten, a class of storage proteins present...
Show moreCeliac disease is an autoimmune disorder in susceptible individuals caused by the consumption of gluten, a class of storage proteins present in wheat, barley and rye. There is no cure for celiac disease, and the only effective treatment is strict adherence to a gluten-free diet. Manufacturers who label their products as “gluten-free” must ensure that these products contain < 20 ppm gluten. Analytical methods currently exist for detecting and quantifying gluten in foods. However, quantifying gluten in fermented or hydrolyzed foods presents an analytical challenge. In order to develop reliable and accurate gluten analytical methods, a better understanding is needed with respect to gluten hydrolysis reactions that occur in fermented and hydrolyzed foods. In addition, research is needed to determine ways to control gluten in food production facilities that produce gluten-containing and gluten-free products on the same processing line. The objectives of this project were to: 1) evaluate the effectiveness of different cleaning procedures on removing gluten from a pilot-scale beer brewing line, 2) assess gluten cross-contact from a shared beer brewing line, 3) track the changes in gluten detection in traditionally brewed soy sauce at different stages of production using five commercial gluten ELISA kits and 4) evaluate the effects of an enzyme (a prolyl endopeptidase- Brewers Clarex®) on detecting gluten in beer brewed with barley malt as an ingredient. A pilot-plant scale beer brewing line located at the University of Wisconsin-Madison (UW-Madison) was used to produce sorghum beer (gluten-free beer), barley malt-containing beer and Clarex®-treated barley malt beer. Three cleaning methods (a push-through cleaning treatment, a hot water rinse, and a full cleaning procedure involving the use of an alkaline detergent) were evaluated for effectiveness at removing gluten residue from the pilot-scale brewing line at UW-Madison. Cleaning study results indicated that a hot water rinse and a push-through cleaning treatment with sorghum beer were less effective in removing gluten from equipment in the brewing line than a full cleaning procedure that included use of an alkaline detergent solution followed by a final hot water rinse. Gluten-free sorghum beer samples used to evaluate cross-contact from an inadequately cleaned brewing line were analyzed, and up to 105.1± 9.3 ppm (μg/mL) gluten was detected using the RIDA Competitive ELISA test kit which is designed to detect hydrolyzed gluten. Model soy sauce products were produced in a pilot-plant at Kikkoman R&D Center in Japan, and samples were obtained at different stages of production. Studies that traced gluten in soy sauce products found that high levels of gluten could be detected at the early stages of production prior to fermentation. However, gluten concentrations in soy sauces after fermentation were below the limit of quantitation (LOQ) for all of the gluten ELISA kits evaluated in the study. Use of Clarex® during the production of barley malt beer resulted in substantial reductions in the amount of gluten (intact and partially hydrolyzed) detected in beer compared to the control treatment without added enzyme. Although, gluten was detected at levels >20 ppm in some Clarex®-treated beer samples, filtration treatment further reduced gluten concentrations in these beer samples below 20 ppm gluten. Results of this project indicate that use of adequate cleaning procedures is needed to control gluten in food production facilities that have shared processing lines. Some fermentation and hydrolysis reactions that occur in food result in substantial reductions in gluten content as measured by ELISA. However, more work is needed to determine if celiac-reactive peptides still remain in these products.
M.S. in Food Safety and Technology, July 2016
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Title: THE TRANSCRIPTIONAL RESPONSE OF ARTIFICIALLY-INOCULATED LISTERIA MONOCYTOGENES DURING THE MANUFACTURE OF UNPASTEURIZED GOUDA CHEESE
Creator: Carstens, Christina K.
Date: 2017, 2017-05
Description: Listeriosis outbreaks indicate that L. monocytogenes contamination is an issue for various food types, such as unpasteurized (raw) cheese....
Show moreListeriosis outbreaks indicate that L. monocytogenes contamination is an issue for various food types, such as unpasteurized (raw) cheese. Current regulation prevents the interstate sale and distribution of raw cheese and mandates a ≥60 day aging period at ≥2˚C to ensure product safety; yet studies demonstrate that pathogens can persist during aging. Environmental stress can alter the transcriptomic profiles of pathogens; however, these surveys are rarely conducted in food matrices. This study aimed to assess the transcriptomic profiles of L. monocytogenes strain F2365 during environmental stressors inherent throughout cheesemaking. First, quantitative polymerase chain reaction (qPCR) was used to monitor transcription levels of nine L. monocytogenes genes involved in virulence, stress response, energy transport, and metabolism during osmotic stress (11% NaCl) and varying temperature/time (5˚C 24 h, 25˚C 24 h, 38˚C 30 min) conditions in Brain Heart Infusion (BHI) broth, raw milk, and pasteurized milk. Generally, the genes prfA, lmo1381, lmo0963, and lmo1875 were down-regulated, whereas the genes lmo1864, lmo0914, lmo0348, lmo1428, and lmo1264 were up-regulated. Virulence gene, prfA, was most down-regulated when L. monocytogenes was grown in raw milk with salt at 25˚C (4774.72±838.14 fold; relative to 24 h growth at 37˚C). The stress response gene lmo0914, encoding σB, was most up-regulated when L. monocytogenes was grown in BHI at 25˚C with salt (14.61±7.72 fold). Additionally, transcription levels of the nine genes were assessed at points during the laboratory-scale manufacture of Gouda cheese made with raw milk artificially-inoculated with L. monocytogenes via qPCR. Similar differential regulation for both prfA and lmo0914 in L. monocytogenes was observed during cheesemaking. The gene lmo1864, encoding a putative pore-forming hemolysin, was up-regulated throughout the cheesemaking process, but was most up-regulated after stirring the curd (449.81±432.53 fold). Ultimately, these results indicate that the lmo1864 gene may play a role in L. monocytogenes survival during cheesemaking. Methods developed in this study can be used to assess the risk of L. monocytogenes, not only during cheesemaking, but during the ≥60-day aging process. Overall, these results contribute to the understanding of L. monocytogenes survival mechanisms during the cheesemaking process.
M.S. in Food Safety and Technology, May 2017
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Title: THE IMPACT OF ORGANIC LOAD ON THE MINIMAL LEVEL OF CHLORINE NEEDED TO PREVENT E. COLI O157:H7 CROSS-CONTAMINATION DURING WASHING OF FRESH-CUT LETTUCE
Creator: Zhou, Chao
Date: 2015, 2015-05
Description: Fresh-cut vegetables are no longer considered low risk due to their association with an increasing number of E. coli O157:H7 outbreaks. E....
Show moreFresh-cut vegetables are no longer considered low risk due to their association with an increasing number of E. coli O157:H7 outbreaks. E. coli O157:H7 contamination in fresh produce originated on farm can spread during postharvest washing. Industry and government guidelines have suggested the use of chemical disinfectants such as sodium hypochlorite in wash water to prevent microbial cross-contamination and have recommended that wash water disinfectants be monitored. However, specific standards regarding the levels of chlorine needed have yet to be established. The goal of this study was to determine the minimal effective level of chlorine needed to prevent E.coli O157:H7 cross-contamination during post-harvest washing of fresh-cut lettuce with wash water containing different levels of organic load and to evaluate the way to monitor the organic load in wash water by correlating measurements of Total Organic Carbon (TOC) with turbidity measurements. Eight grams of cut romaine lettuce inoculated with 8 log cfu/g of E. coli O157:H7 were washed with 800 g of uninoculated lettuce in 40 L of sterile tap water at 3℃ for 2 min. Washing trials were performed in water with different levels of organic load (with the addition of 0, 3, 6, 12, or 30 g of lettuce juice powder) and at different levels of chlorine treatment (0 - 40 ppm of sodium hypochlorite). The degree of cross-contamination was determined by measuring the presence of E. coli O157:H7 in the wash water and uninoculated lettuce after washing. Wash water samples were also analyzed for total/free chlorine, turbidity, and TOC. In the absence of chlorine, E. coli O157:H7 transfer occurred at all levels of organic load and resulted in the contamination of wash water and uninoculated lettuce at levels of 3.61 ± 0.13 log cfu/ml and 3.34 ± 0.23 log cfu/g, respectively. Without the addition of lettuce juice powder, cross-contamination was prevented in wash water containing 5 ppm of sodium hypochlorite. With the addition of 3 g of lettuce juice powder, transfer of E. coli O157:H7 was observed when the washing run was conducted with 5 ppm of sodium hypochlorite but was prevented when the level of sodium hypochlorite was raised to 10 ppm. With the addition of 30 g of lettuce powder, 40 ppm of sodium hypochlorite was needed to prevent cross-contamination. It was difficult to have an accurate determination of the residual free chlorine level as it continued to decrease during the washing run. Measurements of the organic load of wash water are needed to determine the effective level of sanitizer required to prevent microbial cross-contamination during postharvest washing of fresh-cut produce. TOC is a good indicator of organic load in wash water, but it took hours to get results. Turbidity measurement only takes minutes and it correlated well with TOC, indicating that turbidity has the potential to indicate the organic load in wash water.
M.S. in Food Safety and Technology, May 2015
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Title: INACTIVATION OF SALMONELLA ENTERIDITIS PT 30 ON ALMONDS WITH A FLUIDIZED BED ATMOSPHERIC PRESSURE PLASMA
Creator: Narayanan, Kalyani
Date: 2012-11-27, 2012-12
Description: Low-moisture products, including almonds, have been associated with outbreaks of salmonellosis. The U.S. FDA reported 168 cases of S....
Show moreLow-moisture products, including almonds, have been associated with outbreaks of salmonellosis. The U.S. FDA reported 168 cases of S. Enteriditis PT 30 associated with almonds in the U.S. and Canada in 2001 and another 47 cases in the U.S. in 2004. Current pasteurization methods use either heat or propylene oxide, which have the disadvantage of long treatment times and quality loss. This study investigated the use of fluidized bed atmospheric pressure plasma (APP) as a possible pasteurization method for the treatment of Salmonella Enteriidis PT 30 on almonds. Each almond sample was spot inoculated with 10 μL of inoculum. Almonds were placed in a fluidized bed APP treatment chamber fixed to an Enercon Dyne-A-Mite Variable Chemistry Plasma discharge that uses a mixture of clean, dry air at 90 L/min and an inert secondary gas such as Helium at 4 to 20 L/min. The gas mixture was energized using a high voltage (4.4 kV) power supply to generate electrons, gaseous ions, ozone and ultraviolet light. Treatment variables explored in this study were secondary gas type, Argon and Helium, flow rate, 4 and 14 L/min, and the time of treatment (0 to 60 s). Each trial was completed in triplicate. A 4 log reduction was achieved on average after a treatment time of 60 s and microbial destruction appeared to be linear in nature. Temperature measurement of almonds during plasma treatment and predicted lethality of Salmonella determined that heat alone was not a contributing factor to microbial reductions. These results highlight the potential of a fluidized bed APP to reduce treatment time and increase efficacy thus improving the predictability of destruction as compared to earlier research aimed at pasteurizing almonds with plasma.
M.S. in Food Process Engineering, December 2012
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Title: IMPROVED METHODS FOR DETECTING PARTIALLY HYDROLYZED SOY IN FOOD
Creator: Kande, Parnavi
Date: 2016, 2016-12
Description: Methods are needed to detect soy allergens in hydrolyzed and fermented food. Project objectives included utilizing soy-specific ELISA kits and...
Show moreMethods are needed to detect soy allergens in hydrolyzed and fermented food. Project objectives included utilizing soy-specific ELISA kits and Western blot analysis to a) measure soy protein content of commercial soy sauce products; b) trace soy proteins in model soy sauces during a traditional brewing process, and c) investigate detection of soy proteins in soy protein isolate (SPI) hydrolyzed with trypsin. Twelve different soy sauce products were purchased locally. Traditionally brewed soy sauce formulated with soybeans and wheat was produced by Kikkoman in their pilot plant in Japan. Samples were obtained at the ingredient stage, after the soybeans were cooked, at the koji and moromi mash stages, and during six months of fermentation. Partially hydrolyzed SPI was prepared by treating SPI with trypsin for up to 8 h at 38 ºC. Samples were analyzed in triplicate using six soy-specific ELISA kits: 1) Neogen Veratox for Soy; 2) Ridascreen Fast Soya; 3) Elution Technologies Soy Protein; 4) Morinaga Soya; 5) AgraQuant Soy and 6) ELISA Systems Soy Protein. Western blot analysis was performed using Morinaga Soy ELISA kit antibodies. Of the 12 commercial soy sauce products, soy protein was detected in seven products at concentrations of 7.0 (1.7% CV) - 10.5 (1.8% CV) μg/g using the Elution Technologies kit, and in five samples at concentrations of 0.31 (0.6% CV) - 1.5 (0.3% CV) μg/g with the Morinaga kit. Qualitative Western blot analysis suggested the presence of beta-conglycinin in five commercial brands. Tracking soy proteins in model soy sauce by ELISA resulted >90% decrease in detection after cooking. After addition of koji culture and brine to form the moromi mash, soy protein levels were further reduced. The measured level of soy protein after one month of fermentation was 0.67 μg/g (1.1% CV) and decreased below the limit of quantitation (LOQ, 0.31 μg/g) for samples aged 2-6 months using the Morinaga assay, while other kits resulted in soy protein concentrations below the LOQ. Western blot results showed light bands of proteins for samples after 1-2 months of fermentation suggesting the presence of beta-conglycinin. Trypsin hydrolysis of SPI resulted in a gradual decrease in soy protein bands in SDS-PAGE analysis, while some ELISA kits indicated no changes in detectability of soy proteins after 10 min of hydrolysis. Overall, the results of this study indicate that heating, hydrolysis and fermentation processes can have substantial effects on the detection of soy proteins in food.
M.S. in Food Safety and Technology, December 2016
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Title: SYSTEMATIC CONSTRUCTION OF SALMONELLA ENTERITIDIS-SPECIFIC GENE DELETION MUTATIONS
Creator: Li, Ye
Date: 2013, 2013-12
Description: Salmonella enterica serovar Enteritidis infection is one of the major foodborne illnesses associated with egg, cattle and poultry products....
Show moreSalmonella enterica serovar Enteritidis infection is one of the major foodborne illnesses associated with egg, cattle and poultry products. Genes which are specific to S. Enteritidis may play an important functional role in the pathogens’ ability to survive and persist in these food products, and thus cause human foodborne outbreaks. Acquiring more knowledge on how this bacterium is capable of survival will aid in developing strategies to minimize its existence in the Nation’s food supply. In this study, we constructed S. Enteritidis-specific gene deletion mutants for use in subsequent functional studies. Out of more than 200 S. Enteritidis specific genes, 46 genes were selected for deletion in S. Enteritidis PT4. These 46 genes were selected because they are absent in both S. Typhimurium and S. Typhi based on percent identity scores retrieved from standalone BLAST software analysis. The deletion mutants were constructed using the lambda red recombinase method and a PCR product containing unique barcodes. This library of uniquely barcoded mutants will be useful in determining survival and persistence of this organism both in nature and in vivo.
M.S. in Food Safety and Technology, December 2013
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Title: INACTIVATION OF MURINE NOROVIRUS ON STRAWBERRIES USING PULSED LIGHT
Creator: Chen, Dongjie
Date: 2016, 2016-12
Description: Norovirus have become the predominant viral causes of foodborne illnesses worldwide, the foodborne happened mainly in schools and childcare...
Show moreNorovirus have become the predominant viral causes of foodborne illnesses worldwide, the foodborne happened mainly in schools and childcare facilities, strawberries were identified as the most likely vehicle according to the analytical epidemiological studies. So this study evaluated the efficacy of pulsed light (PL) treatments to inactivate murine norovirus (MNV-1), a human norovirus surrogate, inoculated onto strawberries. Two different PL treatments were evaluated - 3 Hz and 100 Hz PL treatments. PL treatments inactivated 1.5-3 log PFU/g MNV-1 on strawberry in a time-dependent manner of 30-120 s at both 3 and 100 Hz. The inactivation efficacy of PL is dependent on the pulsed frequency received with both PL treatment parameters. It can achieve 1.7 log PFU/g reduction after 120 s 3 Hz PL treatment at the distance of 8.3 cm from the quartz window, on the other hand, MNV-1 was inactivated by 3.2 log PFU/g after 120 s exposure to 100 Hz PL treatment at the distance of 8.3 cm from the quartz window. These results demonstrated that higher inactivation effect of MNV-1 on strawberry was associated with higher frequency of PL treatment. Therefore, this technology could be used to improve the microbial safety of fresh strawberries.
M.S. in Food Process Engineering, December 2016
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Title: INCORPORATION OF INORGANIC AND ORGANIC ADDITIVES INTO MODEL PACKAGING POLYMERS
Creator: Bajaj, Akhil
Date: 2016, 2016-12
Description: Nowadays, various commercial polymers such as low density poly(ethylene) (LDPE), poly(propylene) (PP), and Nylon, may contain or are...
Show moreNowadays, various commercial polymers such as low density poly(ethylene) (LDPE), poly(propylene) (PP), and Nylon, may contain or are fabricated with molecular and/or nano-sized inorganic filler elements. These fillers elements often modify, enhance or bring desired changes to the native properties of these polymers. However, these additives also have the potential to interact with the physical environment. For any new additive, it is important to assess and evaluate the potential consumer exposure under intended conditions of use. This thesis reports on the preparation of model polymer samples fabricated with various molecular and nano-sized filler elements (exfoliated clays, quantum dots, and organic colorants) to help evaluate factors affecting the rate of migration and the potential consumer exposure associated with these materials. One of the main aims of this project is the development of methods to incorporate organic and inorganic additives into polymers relevant to food packaging and medical devices using a laboratory scale twin-screw micro-compounder. Some of the samples prepared via optimized methods include (1) 1, 3, 5, and 7 wt.% Montmorillonite in LDPE; (2) quantum dots (QDs) spanning a size range of 3-8 nm into LDPE; and (3) 1-2 wt.% colorant-loaded polymer films, where the colorants include phthalocyanine blue, phthalocyanine green, quinizarin blue, manganese (II) phthalocyanine and titanium (IV) oxide, and the host polymers include poly(propylene), poly(carbonate), Nylon 12, and PEBAX (poly(ether-block-amide)). In addition to optimizing methods for composite fabrication, the properties of these materials were analyzed using many techniques, including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and Fourier transform-infrared (FT-IR) spectroscopy. Migration experiments were carried out to evaluate the interaction of samples with model food and environmental systems. This research was instrumental to support efforts to understand the mechanisms of potential exposure to polymer additives.
M.S. in Food Safety and Technology, December 2016
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Title: CHEMICAL INACTIVATION OF RICIN ON FOOD CONTACT SURFACES
Creator: Aluri, Bharat
Date: 2011-08, 2011-07
Description: Ricin is a glycoprotein which can be easily extracted from the seeds of the castor bean plant. Ricin has potential for being used as a...
Show moreRicin is a glycoprotein which can be easily extracted from the seeds of the castor bean plant. Ricin has potential for being used as a biological weapon since it is highly toxic, relatively easy to isolate and purify and can be disseminated as a food contaminant. Thus in the case deliberate contamination event with ricin in a food processing facility, remediation of the food-contact surfaces must be done safely and effectively. The objectives of this project were to 1) identify cleaning/sanitizing treatments that result in inactivation of ricin on food contact surfaces in the absence and presence of different classes of food matrices (high fat and high starch), and 2) evaluate glucose oxidase as a surrogate for ricin in chemical inactivation studies. Ricin dissolved in PBS or mixed with a slurry of peanut butter or pancake mix was treated with different classes of detergents (phosphoric acid-based, chlorinated alkaline-based) and a sanitizer (peroxy acid-based) used to clean and sanitize food-contact surfaces. A commercially available ELISA kit was used to detect ricin after chemical treatments. Of the cleaning solutions evaluated, the phosphoric acid-based detergent was the least effective at reducing ricin detection after exposure to the cleaning chemical. In contrast, chlorinated alkaline detergent was the most effective cleaning solution for chemically inactivating ricin. The half-lives for inactivation of ricin on coupons (without food matrices) exposed to 0.5, 2 and 5% chlorinated alkaline detergent were 2.38 ± 0.25, 0.48 ± 0.05 and <0.1 min, respectively, and half-live values for inactivation of ricin in solution were 3.05 ± 0.33, 0.36 ± 0.04 and <0.1 min, respectively. The half-lives for inactivation of ricin on coupons (without food matrices) treated with 0.1, 0.5 and 1% peroxyacid-based sanitizer were 4.28 ± 0.44, 0.45 ix ± 0.05 and 0.13 ± 0.01 min, respectively, and half-live values for inactivation of ricin in solution were 6.09 ± 0.70, 0.34 ± 0.03 and 0.12 ± 0.01 min, respectively. Although no significant difference was found for ricin stability in solution vs. on coupons, in the presence of food matrices, ricin on coupons was significantly more stable than ricin in the absence of food residue. Overall, the results from this study indicated that significantly (p<0.05) higher cleaning solution concentrations were needed to inactivate the toxin in the presence of food matrices. Initial studies aimed at the evaluation of glucose oxidase as a surrogate for ricin in chemical inactivation studies indicated that the enzyme demonstrates similar susceptibility to inactivation in the presence of chemical sanitizers (sodium hypochlorite, peroxy acetic acid) as ricin. More work is needed to validate the results found in this lab-scale study with experiments conducted in a pilot-scale operation and to determine if loss of ricin activity after chemical inactivation studies also corresponds to loss in biological activity of toxin.
M.S. in Food Safety and Technology, July 2011
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Title: LISTERIA MONOCYTOGENES SURVIVAL AND GROWTH IN FLAVORED MILKSHAKES MADE FROM NATURALLY-AND ARTIFICIALLY-CONTAMINATED ICE CREAM
Creator: Bathija, Vriddi Mahesh
Date: 2016, 2016-12
Description: Listeria monocytogenes is the causative agent of the disease listeriosis and was implicated in a multistate foodborne outbreak associated with...
Show moreListeria monocytogenes is the causative agent of the disease listeriosis and was implicated in a multistate foodborne outbreak associated with ice cream spread over four years from 2010 to 2014 in Kansas, Oklahoma, Texas and Arizona. Ten illnesses were reported during the course of this outbreak, resulting in 100% hospitalization and a mortality rate of 33%; the individuals who died in the outbreak had consumed milkshakes made with the contaminated ice cream. The ice cream was found to be contaminated uniformly at 10 MPN/g. This study assessed the growth kinetics of L. monocytogenes in milkshakes made with naturally- and artificially-contaminated ice cream, and with or without flavoring agents. Artificial-contamination of ice cream samples included inoculation with a cocktail of rifampicin-resistant L. monocytogenes into the middle of the product using a wide-orifice pipet tip. Milkshake were prepared with or without strawberry, chocolate, or mint flavoring, using the recipe associated with the healthcare facility where the illnesses occurred. Milkshakes were stored in sterile plastic cups at 10ºC and an asymmetric (3 tubes of 100ml, 5 tubes of 10 ml, 8 tubes of 1ml and 8 tubes of 0.1ml sampling scheme) most probable number (MPN) enumeration was conducted after 0, 12, 24, 48, 72, 96 and 144 h. The Baranyi model was used to model L. monocytogenes growth rates, maximum populations, and lag phases. Compared to milkshakes made with no flavoring agents, the milkshakes with flavoring resulted in decreased growth rates for L. monocytogenes for both contamination states; the lowest growth rate of the pathogen was observed in strawberry flavored milkshakes made from artificially-contaminated ice cream (0.029 log CFU/ml per hour). Chocolate and mint flavorings resulted in significantly (P < 0.05) longer lag phases for both natural (68.2 and 83.0 h) and artificial-contamination (47.7 and 54.2 h, respectively). The highest maximum population (5.79 log CFU/ml) was achieved by L. monocytogenes in naturallycontaminated milkshakes without any flavoring agent. Since challenge studies often depend on the artificial contamination of a food product, this study evaluated the differences between artificial and natural contamination of L. monocytogenes in milkshakes. The data obtained can be used for risk assessment purposes.
M.S. in Food Safety and Technology, December 2016
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Title: EFFICACY OF AQUEOUS INOCULATION IN LOW-WATER ACTIVITY MATRIX ON SALMONELLA ENTERICA SEROTYPE AGONA THERMAL RESISTANCE AND STABILITY DURING STORAGE
Creator: Liao, Li
Date: 2016, 2016-07
Description: Methods used to inoculate foods may impact the results of Salmonella survival and thermal resistance studies. Currently, there is little...
Show moreMethods used to inoculate foods may impact the results of Salmonella survival and thermal resistance studies. Currently, there is little information as to the most effective means to inoculate Salmonella into low-moisture food products for use in process validation studies. The objective of this study is to assess the resulting 42 d storage stability and thermal resistance of Salmonella inoculated by liquid addition in food and inert carrier matrices. Salmonella enterica serovar Agona 447967 was inoculated into ground pepper, oat flour, and sand at approximately 9-10 log CFU/g using a hand mixing procedure and stored at 25°C, 32% relative humidity (RH). After a 2 d equilibration, the samples were tested for inoculation homogeneity. Distribution of Salmonella populations proved uniform in black pepper and sand but not in oat flour. Subsequent testing for stability by enumeration with both tryptic soy agar with 0.6% yeast extract (TSAYE) and xylose lysine desoxycholate (XLD) agars was performed weekly with black pepper and sand only. Thermal resistance was determined periodically during storage using aluminum test cells for pepper and glass vial for sand as sample holders. Over 42 d, the average starting Salmonella populations in pepper and sand were 7.88 ± 0.13 and 7.69 ± 0.11 log CFU/g, respectively, and final populations were 6.14 ± 0.06 and 6.52 ± 0.07 log CFU/g, respectively. Population changes were significantly different (P < 0.05). For pepper the thermal resistance did not change significantly during storage (P > 0.05) and were similar to values reported by other researchers using alternative inoculation techniques. However, thermal resistance measured in sand (D90ᵒC = 3.39 ± 0.41 min) was substantially higher than that measured in black pepper (D75ᵒC-value = 4.99 ± 0.21 min) or other literature values. Overall a liquid inoculation protocol proved efficacious for small particles such as ground black pepper or sand but was unable to provide a uniform distribution of cell populations in a powder such as oat flour.
M.S. in Food Safety and Technology, July 2016
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