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Title: FABRICATION, CHARACTERIZATION AND RELEASE STUDIES OF LOW DENSITY POLYETHYLENE/CLAY NANOCOMPOSITES
Creator: Zhao, Ziqian
Date: 2015, 2015-07
Description: Nanocomposites exhibit enhanced physical properties including mechanical strength, thermal stability, and gas barrier properties. The...
Show moreNanocomposites exhibit enhanced physical properties including mechanical strength, thermal stability, and gas barrier properties. The development of nanocomposites has led to applications in food industry, mostly in food packaging. The application of nanocomposites in food packaging may extend the shelf life of a food, thus increasing the market value for manufactures. However, there is limited data and research to assess the risk of exposure of nanomaterials to consumers. This project aims at evaluating the factors that can influence the release of nanomateirals in low density polyethylene/clay nanocomposites films. Nanocomposites based on low density polyethylene (LDPE), containing 1, 3, 5 and 7 wt.% of Cloisite 20A and maleic anhydride-grafted polyethylene (MAPE) as a compatibilizer were prepared by melt compounding and characterized in this thesis project. Cloisite 20A is mostly composed of montmorillonite (MMT), which is commonly used as a nanoscale size filler. LDPE/Clay nanocomposite films containing MMT and three mass equivalents of MAPE were successfully extruded into thin films with good optical clarity. The materials were characterized by using transmission electron microscope (TEM), thermogravimetric analysis (TGA), oxygen permeation analysis and a material testing machine. Important properties such as tensile modulus, oxygen transmission rate, thermal resistance and glass transition temperature were measured. Nanocomposite films were immersed in three kinds of food simulants (absolute ethanol, 3% acetic acid and deionized water). Storage time, storage temperature and percent fill of clay were evaluated as the factors that can influence the release of nanomaterials. The content of released of Al, Mg, and Si was quantified using inductively coupled plasma mass spectrometry (ICP-MS). Mg, Al and Si were continuously released from nanocomposite films in duration of 30 days. Fastest releasing speed was found in 3% aqueous acid at 75 °C, and lower temperature can largely decrease the release of nanoparticles. This project is an initial attempt to assess the risks from the use of nanocomposites as food packaging.
M.S. in Food Safety and Technology, July 2015
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Title: SALMONELLA SURVIVAL DURING INOCULATION AND STORAGE OF DRIED SPICES CONTAINING ANTIMICROBIAL COMPONENTS
Creator: Hu, Chuxuan
Date: 2016, 2016-05
Description: To provide an adequate initial microbial level for spices containing antimicrobial compounds for use in stability testing of foodborne...
Show moreTo provide an adequate initial microbial level for spices containing antimicrobial compounds for use in stability testing of foodborne pathogens, a dry-transfer inoculation was designed and compared with a traditional aqueous inoculation protocol. A five serovar cocktail of Salmonella spp. was prepared at different concentrations (~11 log CFU/mL, ~8 log CFU/mL and ~4 log CFU/mL). It was inoculated onto 1g silica beads and four types of dried ground spices (clove, oregano, ginger, and black pepper). Both spices and beads were dried for 24h at ambient conditions (~22°C). Silica beads were then used as a carrier to inoculate the same four types of spices. The results suggest that dry-transfer of Salmonella via inoculated silica beads provided a greater starting inoculum than aqueous transfer alone and are a viable alternative to aqueous inoculation when spices contain antimicrobial components. This dry-transfer inoculated ground clove with 8.4 log CFU/g and 3.9 log CFU/g initial populations was then used to determine the survival of Salmonella on spices containing antimicrobial components. Salmonella spp. survival on silica beads with 9.2 log CFU/g and 5.9 log CFU/g initial populations and subsequent transfer to ground clove was also examined. Samples were enumerated at selected time point up to 210 d. Results of this study indicate that Salmonella transfer and recovery from beads and in ground clove was not affect by storage and that Salmonella may persist for an extended period of time. The calculation of recovery was, however, affected by detection limits in clove. To improve detection limits an oil extraction was used and compared to the BAM method (detection limit 3.7 log CFU/g). After oil extraction the clove samples were soaked for 1 h (or 24 h for low inoculum concentration) in TSB at 37ᵒC and subsequently enumerated on tryptic soy agar with 0.6% yeast extract and xylose lysine deoxycholate agars. The result demonstrates that the oil extraction detection method holds promise as an alternative method to detect Salmonella in dry spices containing antimicrobial components and can provide a lower detection limit (1.7 log CFU/g).
M.S. in Food Process Engineering, May 2016
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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: Video Object Detection using CenterNet
Creator: Mondal, Madhusree
Date: 2021
Description: This thesis investigates the options of video object detection with key-point-based approaches. The problem of recognizing, locating, and...
Show moreThis thesis investigates the options of video object detection with key-point-based approaches. The problem of recognizing, locating, and tracking objects in videos has been a challenging task in the computer vision area. There are few applications on key-point-based object detectors like CornerNet and CenterNet. At the first stage, this work involves the use of the previously proposed CenterNet module as a baseline detector on each frame of the Imagenet Video dataset. Then we apply an RNN module to exploit the temporal information from the past frames for better results.There are challenges in video object detection compared to still image-based object detection. It is not efficient to apply a still-image-based detector on each frame independently because we cannot exploit the temporal contextual information in videos since neighboring frames in a video are highly correlated. Object detection from videos suffers from motion blur, video focus, rare poses, etc. To overcome these issues one way of improving CenterNet for video object detection is to propagate the previous reliable detection results to boost the detection performance.
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