VTechWorks Repository :: Browsing by Author "Duncan, Susan E."

Browsing by Author "Duncan, Susan E."

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Acid and Volatiles of Commercially-Available Lambic Beers
Thompson Witrick, Katherine; Duncan, Susan E.; Hurley, E. Kenneth; O'Keefe, Sean F. (MDPI, 2017-10-26)
Lambic beer is the oldest style of beer still being produced in the Western world using spontaneous fermentation. Gueuze is a style of lambic beer prepared by mixing young (one year) and older (two to three years) beers. Little is known about the volatiles and semi-volatiles found in commercial samples of gueuze lambic beers. SPME was used to extract the volatiles from nine different brands of lambic beer. GC-MS was used for the separation and identification of the compounds extracted with SPME. The pH and color were measured using standard procedures. A total of 50 compounds were identified in the nine brands. Seventeen of the 50 compounds identified have been previously identified. The compounds identified included a number of different chemical groups such as acids, alcohols, phenols, ketones, aldehydes, and esters. Ethyl acetate, 4-ethylphenol, and 4-ethylguaiacol are known by-products of the yeast, Brettanomyces, which is normally a spoilage microorganism in beer and wine, but important for the flavor characteristics of lambic beer. There were no differences in pH, but there were differences in color between the beer samples.
Activity and mRNA abundance of enzymes for fatty acid synthesis and desaturation in mammary cell cultures
Jayan, Geetha C. Jr. (Virginia Tech, 1998-08-14)
The effect of exogenous unsaturated fatty acids on cellular fatty acid biosynthesis in mammary cells was examined. Under normal situations, even though the diet of a dairy cow contains considerable amounts of unsaturated fatty acids, viz. oleic acid (18:1) and linoleic acid (18:2), the major 18-carbon fatty acid that enters the circulation post-ruminally for delivery to the mammary gland is saturated fatty acid, viz. stearic acid (18:0). This is due to extensive ruminal biohydrogenation of unsaturated fatty acids. Studies have indicated that saturated fatty acids such as 18:0 are enhancers and that certain unsaturated fatty acids are inhibitors of de novo fatty acid synthesis in tissues such as the liver and adipose tissue. The present study investigated the effect of cis and trans isomers of 18:1 and 18:2 on de novo fatty acid synthesis and desaturation in mouse and bovine mammary epithelial cell cultures, and compared it with the effect caused by 18:0. In the first experiment 12.5, 25, 50 or 100 micromoles stearic acid (SA), oleic acid (OA), elaidic acid (EA), trans-vaccenic acid (TVA), linoleic acid (LA) or conjugated linoleic acid (CLA) were supplemented in the media of mouse mammary epithelial (MME) cells that were grown to confluence in Dulbecco's modified Eagle's medium (DMEM). As indicated by cellular palmitic acid (16:0) content and fatty acid synthetase (FAS) activity, when compared with SA all unsaturated fatty acid treatments inhibited de novo fatty acid synthesis in MME cells. In addition, OA at all concentrations and LA and CLA at 50 and 100 micromoles inhibited cellular stearoyl-CoA desaturase (SCD) activity and mRNA abundance. However, EA and TVA, when compared with SA, enhanced SCD activity and mRNA abundance at 12.5 and 25 micromoles. In the second experiment 25, 50 or 100 micromoles SA, OA, TVA, LA or CLA were supplemented in the media of bovine mammary epithelial cells that were grown to confluence in DMEM. As indicated by cellular 16:0 content, acetyl-CoA carboxylase (ACC) activity and FAS activity, treatment with the unsaturated fatty acids inhibited de novo fatty acid synthesis at all concentrations, when compared with SA. Unsaturated fatty acid treatments also reduced the abundance of ACC and FAS mRNA in the cells. When compared with SA at all treatment-concentrations, OA and LA inhibited whereas TVA and CLA enhanced cellular SCD activity and mRNA abundance in the bovine cells. In both cell types, CLA and TVA appeared to be the most potent inhibitors of saturated fatty acid biosynthesis.
Analysis of salivary fluid and chemosensory functions in patients treated for primary malignant brain tumors
Mirlohi, Susan; Duncan, Susan E.; Harmon, M.; Case, D.; Lesser, G.; Dietrich, Andrea M. (Springer, 2015-01-01)
Objectives The frequency and causes of chemosensory (taste and smell) disorders in cancer patients remain under-reported. This study examined the impact of cancer therapy on taste/ smell functions and salivary constituents in brain tumor patients. Materials and methods Twenty-two newly diagnosed patients with primary malignant gliomas underwent 6 weeks of combined modality treatment (CMD) with radiation and temozolomide followed by six monthly cycles of temozolomide. Chemosensory functions were assessed at 0, 3, 6, 10, 18, and 30 weeks with paired samples of saliva collected before and after an oral rinse with ferrous-spiked water. Iron (Fe)- induced oxidative stress was measured by salivary lipid oxidation (SLO); salivary proteins, electrolytes, and metals were determined. Parallel salivary analyses were performed on 22 healthy subjects. Results Chemosensory complaints of cancer patients increased significantly during treatment (p=0.04) except at 30 weeks. Fe-induced SLO increased at 10 and 18 weeks. When compared with healthy subjects, SLO, total protein, Na, K, Cu, P, S, and Mg levels, as averaged across all times, were significantly higher (p<0.05), whereas salivary Zn, Fe, and oral pH levels were significantly lower in cancer patients (p<0.05). Neither time nor treatment had a significant impact on these salivary parameters in cancer patients. Conclusions Impact of CMT treatment on chemosensory functions can range from minimal to moderate impairment. Analysis of SLO, metals, and total protein do not provide for reliable measures of chemosensory dysfunctions over time. Clinical relevance Taste and smell functions are relevant in health and diseases; study of salivary constituents may provide clues on the causes of their dysfunctions.
Antioxidant Activity of Ampelopsis Grossedentata Crude Extract and its Major Component Dihydromyricetin
Ye, Liyun (Virginia Tech, 2011-07-12)
Oxidation limits the shelf life of many food products. Adding antioxidants to foods is the most common way to solve this problem. Reports on safety issues of synthetic food additives have raised consumer interest in "all natural" foods, without added antioxidants or with synthetic replaced with natural antioxidants. The natural antioxidants now in use are much more expensive and less potent than the synthetic antioxidants. Thus, effective and economical natural antioxidants are of great interest to researchers. Teng Cha is a type of herbal tea found in China that has reported high levels of antioxidants. Antioxidant activity of Teng Cha extract and its major component dihydromyricetin has been reported, but no studies have provided clear evidence for the antioxidant effectiveness of Tech Cha extracts. The goal of this study was to measure the antioxidant activity of Teng Cha extract and dihydromyricetin (DHM), a major component of Tech Cha extract. The DPPH assay was conducted and antioxidant activities of the crude extract and dihydromyricetin were evaluated in soybean oil based on the peroxide value, anisidine value, Totox value, headspace volatiles and headspace oxygen. Antioxidant effectiveness was also evaluated in a cooked beef model system. DHM was more potent than BHA in preventing soybean oil oxidation. The crude extract was not as effective as BHA and DHM, possibly because it contained transition metals. In cooked beef, DHM and the crude extract showed lower activity than BHA, possibly due to their low solubility. Overall, Teng Cha extract and DHM are potential natural food antioxidants for future applications.
The Antioxidant Function of Lutein in Controlling Photo-Oxidation of a Colloidal Beverage System
Kline, Mark Alan (Virginia Tech, 2006-12-13)
The effect of light on a model colloidal beverage system under two different test conditions, refrigerated storage (14 d, 4°C) and accelerated storage at room temperature (12 hr, 25°C), was investigated. The addition of lutein to provide protection against photo-oxidation of susceptible compounds also was investigated. Fluorescent light-exposure (14 d, 4°C) of the control beverage system led to a decline in sensory quality based on triangle test results. Sensory quality also declined in the lutein-fortified beverage due to light-exposure. Sensory quality of light-exposed, lutein-fortified beverage compared to the light-protected control did not yield significant sensory differences for two out of three replications giving positive implications towards the use of lutein for photo-protection. Overall, panelists preferred beverages that were protected from light exposure with no specific preference towards control or lutein-fortified beverage, indicating lutein did not inhibit photo-chemical reactions leading to a decline in sensory quality. Chemical analysis showed limonene concentration was significantly higher in the lutein-fortified beverage compared to the control beverage after light exposure (14 d, 4°C). Hexanal concentration, however, was not closely correlated with sensory differences. Results of the accelerated storage (12 hr, 25°C) study showed that the most damaging wavelengths to lutein stability were UV (200-400 nm) and 463 nm wavelengths. Degradation of lutein at 463 nm was expected and can be attributed to lutein''s absorption of blue light at 450 nm. Hexanal formation was highest in the control beverage when exposed to full spectrum light and specifically UV (200-400 nm) wavelengths. Hexanal was also formed in the lutein-fortified beverage under full spectrum light and UV (200-400 nm) wavelength but to a significantly lesser degree. Limonene degraded significantly under all treatment conditions, with the most occurring during full spectrum light exposure. Lutein-fortification did not effectively protect limonene from degradation under these conditions.
Antioxidant Protection of an Omega-3 Fatty Acid Fortified Dairy-Based Beverage
Moore, Robert Lee (Virginia Tech, 2009-12-08)
Skim, butter-derived aqueous phase, anhydrous milk fat, and fish oil were used to formulate ultra high temperature (UHT) processed extended shelf-life omega-3 fatty acid fortified dairy-based beverages with fat contents mimicking whole milk (3.25%). Oxidation of the lipids in the formulated beverages was investigated during storage for 35 days at 4 °C using GC/MS analysis, conjugated diene analysis, and headspace solid phase micro-extraction GC/MS (SPME-GC/MS) analysis of headspace. Omega-3 fatty acid fortified dairy-based beverages were produced that mimicked the physical properties of 3.25% fat whole milk. Oxidation resulted in only small changes in omega-3 lipid content and sensory analysis by an untrained panel indicated that the overall aroma was no different than that of commercially available UHT processed milk. An omega-3 fatty acid fortified dairy-based beverage was produced that delivered 440mg of omega-3 fatty acid per 8oz serving. When consumed daily, the beverage could provide the equivalent amount of omega-3 fatty acids recommended by the American Heart Association, and the equivalent amount of omega-3 fatty acids found in two fatty fish meals over the period of one week. Antioxidants were added to the lipid phase, immediately prior to processing, of additionally produced formulations to determine if a reduction in omega-3 lipid oxidation was observed. No overall reduction in oxidation was observed, as indicated by GC/MS and SPME-GC/MS analysis. Sensory analysis indicated that oxidative aromas increased during storage for the antioxidant and omega-3 fatty acid fortified dairy-based beverage. Ascorbyl palmitate was determined to have a pro-oxidative effect on the formulated omega-3 fortified dairy-based beverages. Antioxidants present in the commercial grade fish oil used for fortification were effective in controlling oxidation in the formulated omega-3 fatty acid fortified dairy-based beverages.
Application of Automated Facial Expression Analysis and Facial Action Coding System to Assess Affective Response to Consumer Products
Clark, Elizabeth A. (Virginia Tech, 2020-03-17)
Sensory and consumer sciences seek to comprehend the influences of sensory perception on consumer behaviors such as product liking and purchase. The food industry assesses product liking through hedonic testing but often does not capture affectual response as it pertains to product-generated (PG) and product-associated (PA) emotions. This research sought to assess the application of PA and PG emotion methodology to better understand consumer experiences. A systematic review of the existing literature was performed that focused on the Facial Action Coding System (FACS) and its use to investigate consumer affect and characterize human emotional response to product-based stimuli, which revealed inconsistencies in how FACS is carried out as well as how emotional response is inferred from Action Unit (AU) activation. Automatic Facial Expression Analysis (AFEA), which automates FACS and translates the facial muscular positioning into the basic universal emotions, was then used in a two-part study. In the first study (n=50 participants), AFEA, a Check-All-That-Apply (CATA) emotions questionnaire, and a Single-Target Implicit Association Test (ST-IAT) were used to characterize the relationship between PA as well as PG emotions and consumer behavior (acceptability, purchase intent) towards milk in various types of packaging (k=6). The ST-IAT did not yield significant PA emotions for packaged milk (p>0.05), but correspondence analysis of CATA data produced PA emotion insights including term selection based on arousal and underlying approach/withdrawal motivation related to packaging pigmentation. Time series statistical analysis of AFEA data provided increased insights on significant emotion expression, but the lack of difference (p>0.05) between certain expressed emotions that maintain no related AUs, such as happy and disgust, indicates that AFEA software may not be identifying AUs and determining emotion-based inferences in agreement with FACS. In the second study, AFEA data from the sensory evaluation (n=48 participants) of light-exposed milk stimuli (k=4) stored in packaging with various light-blocking properties) underwent time series statistical analysis to determine if the sensory-engaging nature of control stimuli could impact time series statistical analysis of AFEA data. When compared against the limited sensory engaging (blank screen) control, contempt, happy, and angry were expressed more intensely (p<0.025) and with greater incidence for the light-exposed milk stimuli; neutral was expressed exclusively in the same manner for the blank screen. Comparatively, intense neutral expression (p<0.025) was brief, fragmented, and often accompanied by intense (albeit fleeting) expressions of happy, sad, or contempt for the sensory engaging control (water); emotions such as surprised, scared, and sad were expressed similarly for the light-exposed milk stimuli. As such, it was determined that care should be taken while comparing the control and experimental stimuli in time series analysis as facial activation of muscles/AUs related to sensory perception (e.g., chewing, smelling) can impact the resulting interpretation. Collectively, the use of PA and PG emotion methodology provided additional insights on consumer-product related behaviors. However, it is hard to conclude whether AFEA is yielding emotional interpretations based on true facial expression of emotion or facial actions related to sensory perception for consumer products such as foods and beverages.
Application of Automated Facial Expression Analysis and Qualitative Analysis to Assess Consumer Perception and Acceptability of Beverages and Water
Crist, Courtney Alissa (Virginia Tech, 2016-04-27)
Sensory and consumer sciences aim to understand the influences of product acceptability and purchase decisions. The food industry measures product acceptability through hedonic testing but often does not assess implicit or qualitative response. Incorporation of qualitative research and automated facial expression analysis (AFEA) may supplement hedonic acceptability testing to provide product insights. The purpose of this research was to assess the application of AFEA and qualitative analysis to understand consumer experience and response. In two studies, AFEA was applied to elucidate consumers emotional response to dairy (n=42) and water (n=46) beverages. For dairy, unflavored milk (x=6.6±1.8) and vanilla syrup flavored milk (x=5.9±2.2) (p>0.05) were acceptably rated (1=dislike extremely; 9=like extremely) while salty flavored milk (x=2.3±1.3) was least acceptable (p<0.05). Vanilla syrup flavored milk generated emotions with surprised intermittently present over time (10 sec) (p<0.025) compared to unflavored milk. Salty flavored milk created an intense disgust response among other emotions compared to unflavored milk (p<0.025). Using a bitter solutions model in water, an inverse relationship existed with acceptability as bitter intensity increased (rs=-0.90; p<0.0001). Facial expressions characterized as disgust and happy emotion increased in duration as bitter intensity increased while neutral remained similar across bitter intensities compared to the control (p<0.025). In a mixed methods analysis to enumerate microbial populations, assess water quality, and qualitatively gain consumer insights regarding water fountains and water filling stations, results inferred that water quality differences did not exist between water fountains and water filling stations (metals, pH, chlorine, and microbial) (p>0.05). However, the exterior of water fountains were microbially (8.8 CFU/cm^2) and visually cleaner than filling stations (10.4x10^3 CFU/cm^2) (p<0.05). Qualitative analysis contradicted quantitative findings as participants preferred water filling stations because they felt they were cleaner and delivered higher quality water. Lastly, The Theory of Planned Behavior was able to assist in understanding undergraduates' reusable water bottle behavior and revealed 11 categories (attitudes n=6; subjective norms n=2; perceived behavioral control n=2; intentions n=1). Collectively, the use of AFEA and qualitative analysis provided additional insight to consumer-product interaction and acceptability; however, additional research should include improving the sensitivity of AFEA to consumer product evaluation.
Application of Bacteriophage in Food Manufacturing Facilities for the Control of Listeria monocytogenes and Listeria sp
Reinhard, Robert Gordon (Virginia Tech, 2020-02-05)
The purpose of this research was to determine if bacteriophage (phage) could be used to treat and reduce the incidence of Listeria in food manufacturing facilities, and thereby reduce the risk of food products being cross-contaminated with Listeria monocytogenes. Listeria incidence in food manufacturing ready-to-eat environments was surveyed at 31 ready-to-eat (RTE) food plants. A total 4,829 samples were collected from all locations. Nine (29%) facilities had zero samples positive for Listeria spp., whereas 22 (71%) had one or more samples positive. The total incidence of Listeria spp. in all RTE food plants was 4.5%. The effectiveness of phage against Listeria was determined when applied to stainless steel, polyurethane thermoplastic, and epoxy. Each material was inoculated with a cocktail containing L. monocytogenes and L. innocua (4 to 5-log10 CFU/cm2) and treated with two different concentrations of phage (2x10^7 and 1x10^8 PFU/cm2). Treated samples were held at 4 or 20°C for 1 and 3h. After treatment with phage, Listeria reductions ranged from 1.27–3.33 log10 CFU/cm2 on stainless steel, 1.17–2.76 log10 CFU/cm2 on polyurethane thermoplastic, and 1.19–1.76 log10 CFU/cm2 on epoxy. Listeria reduction occurred on all materials tested, under all conditions. Higher phage concentration, longer time, and higher environmental temperatures led to significantly (P<0.05) greater reduction of Listeria on stainless-steel and polyurethane thermoplastic. The effectiveness of a phage against Listeria spp. was evaluated in two food manufacturing facilities, operating at either 4°C or 20°C. First, a moderate application of a 2x10^7 PFU/mL phage was applied once per day over three days and samples were collected and analyzed for Listeria at 0, 24, 48 and 72 h. This phage treatment led to a decrease in the incidence of Listeria by 67%. A second application method was studied with phage being applied in the food manufacturing environment in an intensified manner (3 times in 18 hours) at a higher concentration of phage (1x10^8 pfu/mL). This intensified application led to a 32% overall reduction in the incidence of Listeria in the production environment. Applications of Listeria specific phage can be an additional intervention strategy for controlling pathogenic Listeria organisms in food production facilities.
Application of Edible Coatings in Maintaining Crispness of Breaded Fried Foods
Ballard, Tameshia Shaunt'a (Virginia Tech, 2003-09-17)
Crispness is one of the most desirable textural characteristics of breaded fried foods. Consumers often judge the quality of breaded fried foods based on the perceived crispness of the product. Furthermore, today's consumers are showing increasing concern over fat intake. As a result, there is great interest in being able to enhance the crispness and reduce the fat uptake in breaded fried foods without sacrificing other quality attributes. To achieve these goals, modifications to both frying equipment and product formulation have been explored in this study. In this study, two edible film coatings, methylcellulose (MC) and whey protein isolate (WPI) were incorporated into the batter and pre-dust to determine their effect on the crispness of breaded fried chicken nuggets held under a heat lamp for varying time intervals. Crispness was evaluated by both objective (ultrasonic non-destructive evaluation system) and subjective methods. An untrained sensory panel was used to obtain subjective measurements of product crispness. Panelists rated product attributes such as crispness, juiciness, oiliness and flavor on a simple intensity scale. Additionally, panelists rated the liking of the products on a nine-point hedonic scale (1=dislike extremely, 9=like extremely). Two pressure sources (nitrogen gas and steam naturally released from the food material) were used to determine their effects on product crispness, texture, pressed juice, moisture content, fat content and color. Products fried with nitrogen gas as the pressurizing medium produced samples that were comparable to or exceeding the quality of products generated by frying with steam, as it relates to product crispness, texture, pressed juice, moisture content, fat content and color. As related to objective crispness, chicken nuggets fried with nitrogen were significantly crispier (p<0.05) than those fried with steam. Coating type and application also had a significant effect on product crispness. Samples coated with MC in the pre-dust were crispier than samples coated with WPI. However, no significant differences were found in product crispness, juiciness, oiliness or flavor, and overall liking among samples tested by the sensory panel. The results of this study demonstrated that applying an edible film coating to the pre-dust and using nitrogen gas as the pressurizing medium can enhance and maintain the crispness of breaded fried foods.
Assessing Consumer Preferences and Intentions to Buy Edamame Produced in the US
Carneiro, Renata C. V.; Drape, Tiffany A.; Neill, Clinton L.; Zhang, Bo; O'Keefe, Sean F.; Duncan, Susan E. (Frontiers, 2022-01-18)
Due to the growing consumer demand for edamame (vegetable soybean) in the U.S., the domestic production of this specialty crop has been promoted in several Mid-Atlantic and Southeast states as an economically attractive alternative to replace the decreasing tobacco production. For the edamame agrobusiness to be successful in the U.S., consumer studies are as needed as new commercial cultivars that are developed for the U.S. environment. Thus, in this exploratory study, we investigated consumers' preferences and intentions to buy edamame products in the U.S., especially domestic products. Data was collected through a web-based survey distributed through Qualtrics(XM) and a convenience sampling method was chosen. Volunteers who completed the survey (N = 309) were 82% female, 57% residents of the South Atlantic area, and 79% daily consumers of vegetables. Survey respondents had a positive attitude toward domestically produced vegetables and valued supporting U.S. producers. Overall, domestically grown, in-shell edamame products were preferred compared to shelled edamame or imported products. Regarding future purchasing, respondents exhibited higher intention to buy fresh edamame relative to frozen edamame. Additionally, respondents considered price, availability, and familiarity with the vegetable brand, respectively, as the most important factors in their decision-making process to buy edamame products. Our study confirmed there is a market potential for domestically produced edamame and it also provides valuable information to support future studies, production decisions, and the growth of the edamame agrobusiness in the U.S.
Assessing the Role of Cyberbiosecurity in Agriculture: A Case Study
Drape, Tiffany A.; Magerkorth, Noah; Sen, Anuradha; Simpson, Joseph; Seibel, Megan M.; Murch, Randall Steven; Duncan, Susan E. (Frontiers, 2021-08-19)
Agriculture has adopted the use of smart technology to help meet growing food demands. This increased automation and associated connectivity increases the risk of farms being targeted by cyber-attacks. Increasing frequency of cybersecurity breaches in many industries illustrates the need for securing our food supply chain. The uniqueness of biological data, the complexity of integration across the food and agricultural system, and the importance of this system to the U.S. bioeconomy and public welfare suggests an urgency as well as unique challenges that are not common across all industries. To identify and address the gaps in awareness and knowledge as well as encourage collaborations, Virginia Tech hosted a virtual workshop consisting of professionals from agriculture, cybersecurity, government, and academia. During the workshop, thought leaders and influencers discussed 1) common food and agricultural system challenges, scenarios, outcomes and risks to various sectors of the system; 2) cyberbiosecurity strategies for the system, gaps in workforce and training, and research and policy needs. The meeting sessions were transcribed and analyzed using qualitative methodology. The most common themes that emerged were challenges, solutions, viewpoints, common vocabulary. From the results of the analysis, it is evident that none of the participating groups had available cybersecurity training and resources. Participants were uncertain about future pathways for training, implementation, and outreach related to cyberbiosecurity. Recommendations include creating training and education, continued interdisciplinary collaboration, and recruiting government involvement to speed up better security practices related to cyberbiosecurity.
Assessment of Current Guidelines for Culinary Preparation Methods of Fish and Shellfish
Kostal, Jeri Elizabeth (Virginia Tech, 2012-12-17)
Consumers regularly decide to consume fish and shellfish raw or undercooked, which can cause foodborne illness due to product contamination or unsafe handling by the consumer. In order to be considered safe for consumption, intact fish and shellfish should be prepared to an internal temperature of 63"C, according to the 2009 FDA Food Code, with Salmonella spp. as the target organism. Focus groups (5 groups, 32 participants) were conducted to determine consumer beliefs and concerns regarding fish and shellfish safety and preparation. Transcripts of focus groups where coded for themes, which were then grouped into categories. Nine categories emerged including: experience, trust, confidence, quality of product, motivation, concerns, cooking procedures, cooking instructions, and knowledge. Emerging themes were used to help develop educational materials to increase consumer ability to properly prepare fish and shellfish. In a separate experiment, participants (n=6) cooked salmon (baked, broiled), tilapia (baked, broiled), and shrimp (broiled, boiled) according to cookbook-based directions. Internal temperatures of products were recorded, with 33.3% of products cooked to a temperature less than 63"C. A group training session was held, during which participants received additional visual and non-oral cues to determine when products were prepared to 63"C and safe food handling practices. After training, participants prepared the same products. Participants demonstrated improved food safety behaviors and were more successful at cooking products to temperatures "63"C (94.4% of products). Improved cooking instruction and educational materials may reduce the risk of foodborne illness from undercooked fish and shellfish.
Capture filtration for concentration and detection of selected microorganisms in milk
Byrne, Robert Duane (Virginia Tech, 1994-05-04)
The effectiveness of an adsorption filter in retaining bacteria present in milk was examined. Skim milk and whole milk (100ml) were separately filtered through a 47mm adsorption filter. No significant change in total solids, total fat, and solids-not-fat percentages of skim and whole milk permeates was observed after filtration. Adsorption of Pseudomonas fluorescens at target concentrations of 103 , 102 , and 101 cells/ml was determined in 100ml of dairy standard methods buffer, nutrient broth, whole milk, and skim milk. The average percentage bacterial retentions were 95 ± 5.5%, 95 ± 2.6%, 28 ± 22.1%, and 62 ± 15.5%, respectively. A treatment was developed for milk to increase the bacterial retention of ~ fluorescens after filtration. The preferred treatment for 100ml of skim milk involved the following final concentrations (v/v): 0.80% disodium ethylenediamine-tetraacetic acid, 0.02% sodium dodecyl sulfate, pH to 7.5 with 1N sodium hydroxide. The average bacterial retention of ~ fluorescens using the treatment was 91 ± 7.1%. Enumeration of bacteria adsorbed to the filter was then conducted using impedance microbiology. When milk was inoculated with ~ fluorescens at target concentrations of 103 , 102 , and 101 cells/ml, an average log bacterial increase of 1.4 ± 0.1 (25x) was obtained. This method will allow for rapid detection of microorganisms in milk by increasing microbial load in the tested sample and eliminating the need for pre-enrichment.
Carbohydrate Mediation of Aqueous Polymerizations: Cyclodextrin Mediation of Aqueous Polymerizations of Methacrylates
Madison, Phillip Holland IV (Virginia Tech, 2001-06-14)
Cyclodextrin mediation offers a unique mechanism with the potential for interesting control of reaction parameters. Cyclodextrin mediation of hydrophobic monomers may offer desirable kinetics over conventional free radical polymerizations, and it has been shown in this work that cyclodextrin mediation facilitates polymerization of hydrophobic monomers in aqueous solution and in ethylene glycol. It also may be a facile method for controlling relative reactivity of comonomer mixtures. In addition, complexation of cyclodextrin with guest molecules has been utilized in selective synthesis where the host cyclodextrin has been utilized to sterically hinder the attack of certain reactive sites contained within the host cavity. This aspect of inclusion complexation could also be utilized in free radical polymerizations of monomers with multiple reactive double bonds to preferentially reduce the reactivity of the hindered reactive sites. This thesis involves the use of methylated(1.8)-beta-cyclodextrin (MeCD) as a mediator for polymerizations in solvents that would not facilitate polymerization of the pure monomer in the absence of cyclodextrin. This study focuses on the carbohydrate mediation of a series of methacrylic monomers. t-Butyl methacrylate, n-butyl methacrylate, cyclohexyl methacrylate, and 2-ethylhexyl methacrylate were complexed with methylated(1.8)-beta-cyclodextrin and subsequently dissolved in either water or ethylene glycol. The complexes were studied by 1H and 13C NMR spectroscopy, thin layer chromatography, CPK modeling, and thermogravimetric analysis, and were found to have molar ratios of cyclodextrin to monomer as high as 1.0 to 0.72. These complexes were then free radically polymerized in either water or ethylene glycol and resulted in high molecular weight polymers that precipitated out of solution, allowing for facile polymer isolation through filtration. Isolated yields were found to be as high as 86 %. The majority of the cyclodextrin remained in solution after polymerization. It was also recovered and found to be recyclable. Heterogeneous polymerizations were also performed with 2-ethylhexyl methacrylate in which linear dextrin and methylated (1.8)-beta-cyclodextrin were used in emulsifier quantities. It was found that linear dextrin, at concentrations of 3.0 wt% produced a stable latex product with high molecular weight and an isolated yield of >90%. MeCD on the other hand failed to produce a stable emulsion at concentrations between 0.9-3.0 wt%, but remarkably MeCD at 3.0 wt% gave high molecular weight coagulated polymer with a yield of >90%. It is proposed that a heterogeneous mechanism inconsistent with the four major types discussed by Arshady is taking place. Unlike typical suspension or emulsion polymerizations, the cyclodextrin mediated polymerizations are completely homogeneous at the onset, making them more like a dispersion or precipitation polymerization. However, in dispersion and precipitation polymerizations the pure monomer is soluble in the reaction media. In the absence of cyclodextrin, the monomers utilized in this study possessed no appreciable solubility in the reaction media. Therefore, it is proposed that cyclodextrin acts as a phase transfer agent, effectively solublizing the hydrophobic monomer and allowing for the aqueous dispersion or precipitation type polymerization to occur, depending on the relative solubility of the components. Bulk polymerizations of t-butyl methacrylate, cyclohexyl methacrylate, and 2-ethylhexyl methacrylate and their subsequent use in the preparation of carbohydrate/poly(alkyl methacrylate) blends was also performed in this project. Bulk polymers were utilized as references for physical properties for the polymers produced through polymerization of the MeCD/monomer complexes in either aqueous solution or in ethylene glycol. 1H NMR analysis of the polymers from both the cyclodextrin mediation and bulk polymerizations indicated that the tacticity of the polymers produced in both cases were identical. The bulk polymers were also used in the preparation of carbohydrate/methacrylic blends with potential applications in the areas of selective barriers, biodegradable films. Inclusion of drug molecules or antioxidants into these cyclodextrin containing films also may have potential in drug delivery, or food packaging applications. In addition, the side chain liquid crystalline monomer, 6-(4-hexyloxy-biphenyl-4-yloxy)hexyl methacrylate was synthesized in high purity via a three-step procedure and confirmed by a combination of mass spectrometry, thin layer chromatography, and 1H and 13C NMR. This hydrophobic liquid crystalline monomer was subsequently complexed with 1.0-3.0 equivalents of methylated(1.8)-beta-cyclodextrin in an attempt to alter the water solubility of the monomer. Complexes of this side-chain liquid crystalline monomer have not been studied previously and it is proposed that complexation with cyclodextrin will lead not only to novel polymerizations routes for this monomer, but also to novel smectic phases for this thermotropic liquid crystalline polymer.
Changes in Aromatic Chemistry and Sensory Quality of Milk Due to Light Wavelength
Webster, Janet B. (Virginia Tech, 2006-11-09)
Gas chromatography (GC) and gas chromatography olfactometry (GCO) was used to determine the effect of specific light wavelengths on light oxidation in milk. The most damaging wavelengths to milk quality appear to be the UV (200-400 and 395 nm) and short visible (463 nm) wavelengths. However, exposure to 610 nm also appears to be damaging. GC and GCO were also used to look at the efficacy of film over-wraps made from iridescent films. Single-layer over-wraps were not as effective in reducing light oxidation as multi-layer film over-wraps. Single-layer over-wrap treatments had higher numbers of odor-active compounds than multi-layer over-wrap treatments with a number of odor-active compounds detected consistently in single-layer over-wrap treatments but not in the multi-layer over-wrap treatments. Concentrations of volatile compounds were slightly lower in the multilayer treatments. Multi-layer film over-wrap treatments were tested for light oxidation flavor intensity with a balanced incomplete block multi-sample difference test using a ranking system and a trained panel. Packaging over-wraps limited the production of light oxidation flavor in milk over time but not to the same degree as the complete light block. Blocking all visible riboflavin excitation wavelengths was better at reducing light oxidation flavor than blocking only a single visible excitation wavelength. A method to determine light oxidation in oil using Fourier Transform Infrared (FTIR) spectroscopy was established and preliminary data is presented.
Changes in flavor volatile composition of oolong tea after panning during tea processing
Sheibani, E.; Duncan, Susan E.; Kuhn, D. D.; Dietrich, Andrea M.; Newkirk, J. J.; O'Keefe, Sean F. (2016-05)
Panning is a processing step used in manufacturing of some varieties of oolong tea. There is limited information available on effects of panning on oolong tea flavors. The goal of this study was to determine effects of panning on flavor volatile compositions of oolong using Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography-Olfactometry (GC-O). SDE and SPME techniques were applied for extraction of volatiles in panned and unpanned teas. A total of 190 volatiles were identified from SDE and SPME extractions using GC-MS and GC-O. There were no significant differences (P > 0.05) in aldehyde or terpene contents of unpanned and panned tea. However, alcohols, ketones, acids and esters contents were significantly reduced by panning. Among 12 major volatiles previously used for identification and quality assessment of oolong tea, trans nerolidol, 2- hexenal, benzaldehyde, indole, gernaiol, and benzenacetaldehyde contents were significantly decreased (P < 0.05) by panning. Panning increased (P < 0.05) contents of linalool oxide, cis jasmone, and methyl salicylate. The GC-O study also showed an increase of aroma active compounds with sweet descriptions and decrease of aroma active compounds with fruity and smoky descriptions after panning. Panning significantly changes the volatile compositions of the tea and created new aroma active compounds. Results from this study can be used in quality assessment of panned oolong tea.
Characterization of A-type Proanthocyanidins in Peanut Skins Using MALDI-TOF MS
Ye, LiYun (Virginia Tech, 2015-02-27)
Peanut skin, a low-value agriculture waste product, has drawn lots of research interest in recent years, due to its high content of A-type proanthocyanidins. A-type proanthocyanidins have been believed to contribute to cranberries' anti-UTI (urinary tract infection) effect. In this study, we compared the A-type proanthocyanidins in cranberry and peanut skin crude extracts using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Many similarities were found in the proanthocyanidin composition of cranberries and peanut skins. New oligomeric and polymeric proanthocyanidins in peanut skins, including heteroproanthocyanidins and proanthocyanidins with sugar moieties or galloyl esters, were tentatively identified. Solid phase extraction (SPE) and HPLC fractionation largely improved MALDI-TOF's ability to detect proanthocyanidins with high degrees of polymerization (DP). By analyzing the identified compounds in each fraction, we were also able to find some interesting elution pattern of the proanthocyanidins on the SPE cartridges and on the HPLC column. For example, the elution order on both the SPE cartridges and the diol phase column generally followed the DP. A-type proanthocyanidins tended to elute earlier than the B-type. Prodelphinidins retained much longer than other proanthocyanidins with the same DP. These findings may help researcher to identify future research directions and develop new separation methods to facilitate the identification of bioactive components in proanthocyanidin-rich plant extracts.
Characterization of antioxidant activities of soybeans and assessment of their bioaccessibility after in vitro digestion
Chung, Hyun (Virginia Tech, 2009-11-05)
Nine Virginia soybeans grown in a single location were compared for their antioxidant properties and isoflavone profiles. The extracts were evaluated for their total phenolic contents (TPC), Oxygen Radical Absorbance Capacity (ORAC), and DPPH™ radical scavenging activities. In order to evaluate efficient preparation methods for soybean antioxidants, three Virginia-grown soybeans were extracted using different extraction strategies. The extraction techniques included soxhlet extraction, conventional solvent extraction, and ultrasonic-assisted extraction (UAE) with 5 different common solvent systems including 50% and 80% aqueous acetone, 50 and 70% aqueous ethanol, and 80% aqueous methanol. The TPC in the soybean extracts and isoflavone compositions were significantly different among cultivars. Malonylgenistin was the major isoflavone in all soybean seeds, accounting for 75-83% of the total measured isoflavones. The V01-4937 variety had the highest total isoflavone and malonylgenistin contents, followed by V03-5794. The antioxidant activities of the soybean extracts were also significantly different. Overall, the V01-4937 soybean was the variety that stood out from the other tested Virginia soybeans because it had the highest TPC, ORAC value, and isoflavone contents as well as the second highest DPPH™ scavenging activity. Ultrasonic treatment improved the extraction of soybean phenolics by more than 50% compared to solvent alone. The UAE with 50% aqueous acetone was the most efficient for extraction of phenolic compounds in the soybean seeds. The conventional and UAE with 70% aqueous ethanol extracts had the highest ORAC values, while the soxhlet methanol extracts had the highest DPPH™ radical scavenging activities. Our results suggest that different extraction technologies have a remarkable effect on soybean antioxidant estimation and the UAE is more appropriate for soybean phenolic extraction because it is less time and solvent consuming than the conventional solvent and soxhlet extractions. The V01-4937 soybean with the highest TPC was evaluated for its antioxidant activity and isoflavone contents in an in vitro digestive system. After gastrointestinal digestion, soybean extracts contained higher TPC and ORAC values than cooked soybean (before digestion) but they were relatively low in DPPH™ radical scavenging capacity. The glucosides, daidzin, genistin, and malonylgenistin showed stability during simulated digestion with 83.3 %, 59.4 %, and 10.7 % recovery, respectively. Aglycones, including daidzein and genistein, were recovered at 37 % and 73.7 %, respectively, after in vitro digestion. In this study, daidzin was the most stable and bioaccessible isoflavone determined using the in vitro digestive system. Among the aglycones, genistein was more stable and bioaccessible than daidzein after digestion. In conclusion, soybean antioxidant activities were different among cultivars and efficient extraction for TPC was found using UAE with 50% aqueous acetone. Furthermore, antioxidant activities were stable during digestion and genistein, within aglycones tested, was the most stable and bioaccessible compound following in vitro digestion. This information may provide manufacturers or researchers information required to develop food or nutraceutical products processed for better bioaccessibility of soybean bioactive components.
Characterization of aroma and flavor compounds present in lambic (gueuze) beer
Witrick, Katherine Amy Thompson (Virginia Tech, 2012-12-10)
Lambic beer is one of the oldest beer styles still being brewed in the western world today and the only beer that is still brewed through spontaneous fermentation. Lambic beers are only produced within a 500 km radius of Brussels because of the natural microflora found within the air in that region. Little is known about the chemical composition of lambic beers. The objective of this research were (1) to compare SPME and SAFE for the isolation of flavor and aroma compounds, (2) determine the volatile composition and acids of commercially available lambic gueuze using SPME/GC-MS and HPLC, and (3) determine the major aroma compounds of aging lambic beer using GC-O. Comparing the two extraction methods, both SPME and SAFE were able to identify a similar number of chemical compounds, however SAFE identified a greater number of acid compounds. A total of 50 compounds were identified within nine commercial brands of lambic beer. HPLC was used in the identification and quantification of acetic and lactic acids. The concentration of acetic acid in the commercial products ranged from 723 mg/L â " 1624 mg/L and lactic acid ranged from 995 â " 2557 mg/L. GC-O was used in the analysis of aged (3-28 months) lambic beer samples. As the samples increased in age, the number of aroma compounds detected by the panelists also increased. Panelists were detected nine aroma compounds in the 3 month old sample, while 17 compounds were detected in the 28 month old sample. The research conduct increased the number of volatile and semi-volatile compounds identified in lambic beer from 27 to 50.

Browsing by Author "Duncan, Susan E."

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