Browsing by Subject "Food science"

Now showing 1 - 20 of 24
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    Characterization of key volatile compounds in red table wines produced from frontenac grapes (Vitis spp.)
    (2008-09) Mansfield, Anna Katharine
    Frontenac (Vitis spp. MN 1047) is a new, cold-hardy red wine grape that is currently the most-planted grape cultivar in much of the Upper Midwest. Though typically described as having notes of cherry, black currant and spice, the volatile characteristics of Frontenac wine have not been investigated, and no structured evaluation of common sensory characteristics has been performed. To develop a standard set of aroma descriptors that characterize red Frontenac table wines, descriptive analysis was performed on six products. Thirteen sensory descriptors were developed and defined with reference standards; correlation plots indicated that attributes were discrete and not redundant. All 13 attribute descriptors were useful for describing and/or distinguishing between red Frontenac table wines. In order to determine odor active compounds, eight Frontenac table wines were evaluated using stirbar sorptive extraction (SBSE) combined with concurrent gas chromatography-olfactometry/ mass spectrometry (GCO/MS). Twenty-four volatiles perceived by panelists were identified via mass spectra comparison, and included five alcohols, fourteen esters, one lactone, two acids and two volatile phenols. Twenty-four of these were confirmed with LRI comparisons in separate GC/MS analyses using a C6 to C16 carbon ladder, and 23 were quantified in runs using a known concentration of internal standard. Analyses of wines produced from V. riparia clone #89, a parent of Frontenac, identified 16 volatiles common to Frontenac wines. Tentative identification, via GC/MS, of Frontenac juice with two days of skin contact suggested that four volatiles found in the wine may originate in the fruit.
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    Cinnamon Hydrolysis Enzymatic and Acid Treatments for Viscosity Reduction
    (2017-11) Pederson, Pamela
    Cinnamon is a desirable spice in a variety of food products for flavor enhancement; however, it is a problematic ingredient in food processing because viscosity is increased due to large polysaccharides that give cinnamon its unique functionality. To help mitigate viscosity issues that arise during manufacturing food products, such as cereal, different treatment methods to hydrolyze the polysaccharides in cinnamon were conducted. Different treatment methods utilizing a variety of enzymes and acid resulted in viscosity reduction by rapid-visco analyzer (RVA) analysis followed by high pressure liquid chromatography size exclusion chromatography (HPLC-SEC), soluble and insoluble dietary fiber analysis and light microscopy verification methods. A cellulase, xylanase, pectinase in combination and a β-Glucanase were used in the study. Hydrochloric acid treatment resulted in 88% viscosity reduction, β-Glucanase resulted in a 50% viscosity reduction, cellulase, xylanase, and pectinase combined resulted in an 11% viscosity reduction.
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    Comparing astringency and sourness of whey protein beverages acidified with four different acids
    (2015-03) Dornbusch, Abby M.
    Increasing interest in whey protein beverages stems from the wide range of nutritional benefits whey proteins have to offer. A useful characteristic of whey proteins is their solubility over a wide pH range, however in order to ensure clarity of a ready-to-drink whey protein beverage, it needs to be manufactured at a pH of approximately 3.4. At an acidic pH of 3.4, the beverages become astringent and can lead to consumer acceptability issues. The main objective of this research was to determine which, if any, of four different acids (hydrochloric, malic, phosphoric, tartaric) achieved the lowest perceived astringency rating when used to acidify a 4% (w/v) whey protein isolate (WPI) solution to pH 3.4. A secondary objective was to identify the buffer capacities of each acid in both a water solution and WPI solution, in efforts to detect a relationship between buffer capacity and perceived astringency. Sourness ratings for each sample were also gathered. A 4% (w/v) WPI solution acidified with hydrochloric acid generated the lowest perceived astringency and sourness ratings. Conversely, the malic acid WPI sample produced the highest perceived astringency rating. Additionally, hydrochloric and phosphoric acid samples buffered the least within the pH range of interest (3.4-7.0). This research indicates a potential relationship between the perceived astringency of an acidified-WPI solution and the buffer capacity of the acidulant used.
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    Control of pathogenic bacteria in Queso Fresco by using generally recognized as safe ingredients
    (2011-07) Gadotti, Camila
    Soft-style fresh Hispanic cheeses like “queso fresco” are generally prepared through minimal processing and recent outbreaks have shown that they can be a vehicle of transmission of L. monocytogenes, Salmonella, and E. coli O157:H7. Currently there are no available treatments to reduce post-pasteurization contamination. The goal of this research was to identify effective queso fresco antimicrobial treatments using available Generally Recognized as Safe (GRAS) ingredients. These antimicrobial agents included nisin (Nisaplin®), caprylic acid, trans-cinnamaldehyde, monolaurin, carvacrol, eugenol, levulinic acid, orange-terpenes, d-limonene, eucalyptol, thymol, and clove essential oils. Batches of queso fresco were inoculated with mixtures of approximately 104 CFU/g of different L. monocytogenes, Salmonella, or E. coli O157:H7 strains/serovars and treated with different combinations of antimicrobials. Twenty five strains of L. monocytogenes, 28 strains of S. enterica, and 24 strains of E. coli O157:H7 were tested. Inoculated queso fresco samples were stored at 4˚C or 8˚C for 3 weeks and the bacterial count was determined every other day by direct plating onto PALCAM, bismuth sulfate, or sorbitol MacConkey agar. All nisin and caprylic acid combinations were effective to decrease survival and growth of all L. monocytogenes and caused at least 4 log CFU/g reductions by the end of storage compared to controls. The levels of most strain mixtures were markedly reduced immediately after treatment and their numbers remained below 103 CFU/ g during the experiments. Combinations of nisin and caprylic acid were only effective to reduce at least 2 log CFU/g Salmonella and E. coli O157:H7 if the caprylic acid concentration was greater than 2 g/kg and 0.7 g/kg respectively. Treatments that included cinnamaldehyde (1 to 2 g/kg) reduced Salmonella and E. coli O157:H7 counts almost 3 and 5 log CFU/g respectively. The combination of nisin, caprylic acid, and cinnamaldehyde was the only antimicrobial treatment able to noticeably inhibit the growth of L. monocytogenes, Salmonella, and E. coli O157:H7 in queso fresco. This combination was also tested to evaluate the impact on the quality and sensory attributes of the cheese. For the quality and sensory analysis, treated cheese samples (sample A containing 0.5 g/kg nisin, 0.4 g/kg caprylic acid, and 0.3 g/kg cinnamaldehyde, sample B containing 0.5 g/kg nisin, 0.4 g/kg caprylic acid, and 0.6 g/kg cinnamaldehyde) were stored over a four week period and tested for lactic acid bacteria, aerobic plate count, and psychrotrophic plate counts. Treated queso fresco samples stored for 4 weeks had similar numbers of lactic acid bacteria, aerobic plate counts, and psychrotrophic plate counts to those of control samples. These results indicated that the treatments had no effect on the growth of potential background spoilage microorganisms. A consumer liking test was used to evaluate sensory aspects of treated samples. A total of 4 samples were tested including control, treated sample A (0.5 g/kg nisin, 0.4 g/kg caprylic acid, and 0.3 g/kg cinnamaldehyde), treated sample B (0.5 g/kg nisin, 0.4 g/kg caprylic acid, and 0.6 g/kg cinnamaldehyde), and a commercial sample. The cheese containing 0.6 g/kg of cinnamaldehyde was the least acceptable of all samples, including a commercial sample, and the control sample was rated highest for moderately liking. The panelists were able to note the presence of off-flavors in both treated samples without significant differences between them. All cheese samples, however, were rated between the levels of dislike slightly and like moderately, indicating a certain level of liking for all cheese samples. The combination of nisin, caprylic acid, and cinnamaldehyde was able to control L. monocytogenes, Salmonella, and E. coli O157:H7 in queso fresco with relatively little impact on quality and sensory characteristics of the cheese. This antimicrobial combination could eventually be used to manufacture safer queso fresco.
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    Determining the effect of gradual sugar reduction on liking of sweetened iced tea
    (2020-02) Inamdar, Loma
    Overconsumption of sugar has been of great concern because of its association with health risks like obesity, diabetes, and cardiovascular disease. Surveys conducted by the National Institute of Health show sugar-sweetened beverages as a primary contributor to increased sugar consumption. The objectives of this study were threefold: 1) To determine if and how sugar-sweetened iced tea liking would change over time for a gradual reduction of sugar group compared to a no reduction of sugar group, 2) To determine if the gradual reduction of sugar group's liking will change from the initial to the final taste test and 3) To determine if the gradual reduction of sugar affects the participant's lowest acceptable level, ideal level, and the highest acceptable level of sweetness in iced tea. Sixty-two participants who consumed sweetened tea at least three times per week were enrolled in this three-phase study: an initial taste test, a 12-week repeated consumption phase, and a final taste test. At the initial and final taste tests, participants were served teas differing in sugar content from 0% to 12% added sugar. Participants were divided into a no reduction or gradual reduction group for the 12-week repeated consumption phase based on their hedonic sensitivity to sweetness (the difference between overall liking of the 7.7% and 0% sweetened teas) and their motivation to decrease their dietary sugar intake. The no reduction group received a 7.7% sugar-sweetened tea for the duration of the 12 weeks. The gradual reduction group received a tea that was reduced in 10% sucrose increments each week from the initial 7.7% sugar-sweetened tea. Over time, liking decreased equally for the no reduction and gradual reduction groups. From the initial taste test to the final taste test, overall liking ratings decreased for both the no reduction and gradual reduction groups. The no reduction group's liking of the 3.1% and 6.1% added sugar teas significantly decreased from the initial to the final taste test compared to the gradual reduction group's liking of the 3.1% and 6.1% added sugar teas. From the initial taste test to the final taste test the, lowest acceptable, ideal level, and the highest acceptable level of sweetness did not differ between the no reduction and gradual reduction group. During the repeated consumption phase, the gradual reduction group's decrease in liking may have been related to monotony, as the decrease in liking was equal to the no reduction group.
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    Development of an high performance liquid chromatography-mass spectrometry.
    (2012-02) Jilek, Margaret L.
    Summary abstract not available.
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    Effect of cereal grains on the formation of heterocyclic aromatic amines in fried beef patties
    (2012-08) Kyllo, Rachel Renae
    The effect of incorporating flours representing different anatomical parts of the grain of corn, wild rice, and oat as well as corn bran extract into beef patties on the formation of heterocyclic aromatic amines (HAAs) during grilling was investigated. Beef burgers containing 5 or 10% dry cereal solids or cereal extract adsorbed to a cellulose carrier were grilled for 7 minutes per side on an electric grill. The HAA content of the cooked material was assessed using an optimized solid-phase extraction method, reversed-phase HPLC separation, and UV and fluorescence detection. 9H-Pyrido[3,4-b]indole (norharman), 1-methyl-9H-pyrido[3,4-b]indole (harman), 9H-pyrido[2,3-b]indol-2-amine (A-alpha-C), 1-methyl-6-phenyl-1H-imidazo[4,5-b]pyridin-2-amine (PhIP), and 3,8-dimethyl-3H-imidazo[4,5-f]quinoxalin-2-amine (MeIQx) were detected in all burgers. Norharman and harman formation were significantly increased in fried beef patties grilled with wild rice hulls, wild rice flour, and oat hulls. Other treatments also tended to increase beta-carboline (harman and norharman) and PhIP levels relative to plain beef patties. Due to the analytical set-up it was not possible to obtain a full set of reliable data about the effect of cereal materials on the formation of MeIQx, but some materials may be able to reduce the formation of this HAA. It is concluded that the addition of whole cereal materials in beef patties is not an effective way to reduce the formation of beta-carbolines and PhIP during grilling. Definite conclusions about the effect of cereal materials on the formation of MeIQx and structurally related HAAs cannot be drawn from this study.
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    The effect of temperature and heating time on the formation of alpha, beta unsaturated hydroxyaldehydes in various vegetable oils and fats
    (2014-08) Liu, Xiaoyu
    The formation of HNE, HHE, HOE and HDE was investigated in commercial corn, soybean, peanut, canola oils, lard and beef tallow which were heat treated at different temperatures (145, 165 and 185°C) for 1, 3 and 5 hours. The formation of these 4–hydroxyaldehydes was monitored as 2, 4–dinitrophenylhydrazone derivatives by HPLC. These oils and fats were selected based on their different fatty acid distributions. In general, the formation of these 4–hydroxyaldehydes increased with higher temperatures (145, 165 and 185°C), longer heating time (in the range of 0 to 5 hours) and higher unsaturation in the samples. It was found that the formation of HNE was dependent on temperature, heating time and the level of linoleic acid in the oils. Therefore, to minimize the formation of the toxic HNE in high linoleic acid containing oils, the lowest temperature and the shortest heating time should be used.
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    Effects of chemical, enzymatic and mechanical treatments on the phenolics and water holding capacity in wheat bran.
    (2011-12) Guo, Mufan
    Epidemiological studies have demonstrated that consumption of whole grain products is beneficial for human health due to its high dietary fiber content, and the consumption of fruits and vegetables can prevent chronic disease due to their high antioxidant activity. However, whole grain is also a good source of antioxidant, which has been underestimated by literature because most antioxidants in grains exist in their bound form, which cannot be detected using previous analysis methods. With the development of new approach to analyze the bound phenolics, scientists find the bound phenolics can take up almost as high as 70-80% of the total phenolics. Wheat bran is a good source of dietary fiber and also phenolics. The phenolics in wheat bran are mainly ferulic acid, which is bound to arabinose, the side chain of arabinoxylans, through ester linkage. The bound phenolics reduce the bioactivity and bioaccesibility of wheat bran. Therefore, releasing them from the complex polysaccharides structure is beneficial for the functionality and bioactivity of wheat bran. This objective of this study is to optimize the conditions to improve the bioavailability of free phenolics from wheat bran using combined physical, chemical, thermal, and enzymatic treatments. The treatments include alkaline treatment, enzymatic treatment, high shear mixing, and high-pressure homogenization. In this study, the optimal conditions of enzymatic treatment and combined alkaline and enzymatic treatments were evaluated. The phenolics acids content, flavonoids content, ferulic acid content and the water holding capacity were determined in processed wheat bran. Results showed that alkaline treatment was the most efficient in releasing bound phenolics in wheat bran due to its strong hydrolysis capacity of cleaving the ester linkage. Enzymatic treatment was the most efficient in releasing flavonoids in wheat bran due to its effects on opening the polysaccharide structure. Mechanical treatments helped to reduce the particle size and opened the polysaccharide structure and improve the functionality and bioactivity of wheat bran as well.
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    Encapsulation and real-time release characteristics of spray dried l-menthol
    (2008-11) Mortenson, Michael Alan
    The objective of this research was to understand the effects of octenyl succinic anhydride (OSAn) substitution level of carbohydrate encapsulation materials on the capsule characteristics and real-time release of l-menthol from spray dried powder. Spray dried l-menthol powder was prepared from modified dextrin and gum acacia of varying levels of OSAn substitution. Physical properties of the microcapsules and encapsulation matrices were determined by: constructing moisture sorption isotherms, particle sizing, density measurement via pycnometry, and by total and surface menthol content of the finished powders. Real-time menthol release and moisture uptake profiles were accomplished by using dynamic vapor sorption (DVS) coupled with either Tenax trapping and gas chromatography (GC) or proton transfer reaction mass spectrometry (PTR-MS). It was found that as OSAn substitution of carbohydrates increases, total and surface menthol appeared to increase and decrease, respectively. The particle size of the finished spray dried powder was influenced by spray dryer infeed solids concentration with higher solids leading to larger particle size. Microcapsule density did not appear to be affected by OSAn substitution or carrier type. Menthol release profiles varied greatly with carrier material used. Increased OSAn substitution (up to 3% treatment level) of the carrier material resulted in a significantly greater, but not earlier burst of menthol release. For most samples, the characteristic burst of menthol was followed by a decrease in release which was attributed to an observed matrix collapse. Moisture uptake rates of the powders were related to corresponding menthol release rates. As OSAn substitution increased for gum acacia (Acacia seyal), a trend of increased moisture uptake rate with menthol release rate was evident. However, for the dextrins, the moisture uptake rate had no influence on the rate of menthol release. The degree of OSAn substitution did not affect moisture sorption characteristics for dextrin samples. For gum acacia, increased levels of OSAn substitution resulted in a decreased affinity for moisture in the range of 0.3 to 0.7 aw.
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    Enhancing the functionality of delactosed whey by enzymatic hydrolysis using Response Surface Methodology Approach (RSM)
    (2012-09) Folly, Edem-Elikplim E.
    Delactosed whey (DLW), which has ~24% protein, is a by-product of lactose production and is mostly used as animal feed. DLW applications can be expanded to include food products, and its economic value improved by amplifying its protein functionality. Moderate enzymatic hydrolysis can significantly enhance protein functionality. It is, therefore, hypothesized that subjecting DLW to enzymatic proteolysis will lead to enhanced functionality. To amplify and improve the functionality of DLW via enzymatic hydrolysis, hydrolysis conditions need to be optimized. The infinite number of possible combinations of factors and their levels to be tested makes the task quite challenging. Using response surface methodology (RSM), the number of experimental units necessary to find the optimal point can be tailored depending on the time and resource constraints of the experimenter. The first objective was, therefore, to amplify the functional properties of the protein component of DLW by enzymatic hydrolysis using response surface methodology (RSM). The second objective was to monitor the functional properties and sensory quality of beef patties fortified with selected DLW hydrolysates as compared to those fortified with whey protein isolate (WPI) and whey protein concentrate 34% (WPC 34). In order to determine the optimal hydrolysis conditions, a Box-Behnken design with 4 independent variables at 3 levels was generated and implemented. The variables chosen, temperature (x1), enzyme-to-substrate (e/s) ratio (x2), time (x3) and pH (x4), are known to have the most significant influence on the degree of hydrolysis (DH) and protein functionality. The design had 27 experimental units that included 3 center points to assess the pure error. Each experimental unit was run in triplicate and the means of DH and measured functional properties were recorded as the y responses. The behavior of each response was explained by a quadratic equation. The effect of the independent variables on each response was evaluated and tridimensional response plots were generated. The conditions at which the responses were maximal/optimal were then determined. To validate the model, experimental data was obtained using the predicted optimized levels. iii In triplicate, ground beef patties were formulated using selected DLW hydrolysates, with optimized functionality, non-hydrolyzed DLW, WPC34 or WPI. A control sample was formulated without the addition of any whey protein ingredient. Cook loss due to losses in water and fat was assessed. Texture analysis of the cooked patties was done using a TA-XT2 texture analyzer. Sensory analysis was conducted to determine differences in various attributes among the different beef patties. Several response surface models were compared to determine the best fit for the RSM data collected. The point within the range of experimentation with the highest fitted value was determined. Using the model with the best fit (high R2 and P ≤ 0.05) for each response, prediction equations were generated and used to determine optimal hydrolysis conditions. Within the range tested, the emulsification capacity and activity of the DLW hydrolysates, produced under optimal conditions, were comparable to, if not greater, than that of WPI, which is known for its exceptional functionality attributes. The RSM approach provided an understanding of the effect of each hydrolysis parameter on the DH and on the assessed emulsification properties. Results highlighted that the extent of hydrolysis had a significant effect on the final functionality. While emulsification properties were enhanced significantly, hydrolysis of DLW was detrimental to the gelation property. Beef patties formulated with hydrolyzed DLW, with optimal emulsification properties, lost about half as much moisture as the control. The fat loss in the beef patties formulated with hydrolyzed DLW was about 5 times less than that of the control. The beef patty formulated with Alcalase hydrolyzed DLW had significantly (P < 0.05) higher compression force than the control. The functional performance of DLW hydrolysates in the formulated beef patties was comparable to that of WPI. While instrumental measurements indicated functional differences, the formulation with hydrolyzed DLW did not affect the sensory quality of the beef patties. Results of this work showed, for the first time, that the functionality of the protein component of DLW can be amplified upon limited and controlled hydrolysis. The tested DLW hydrolysates can be incorporated into meat products to amplify the functional properties without jeopardizing the overall sensory quality. Therefore, functionally iv enhanced DLW have a great potential to reduce processing cost by replacing WPI, while maintaining acceptable quality.
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    Enzyme treatment of wheat bran to release antioxidants and combination processing to further enhance this release
    (2012-12) Hohn, Allison Carlquist
    Whole grains have long been associated with good health due to the complex carbohydrates, vitamins, and other nutrients such as antioxidants, found within them. It is this last class that has the most untapped nutritional power when looking at whole grain products. This is because a majority of the antioxidants found are in the insoluble bound form and are not bioavailable to the consumer. Treating whole grains with multiple processes, including physical, chemical, and biological, can release some of these nutrients into a free or soluble bound form that is much more bioavailable, making the whole grain products much more beneficial to health. Treating wheat bran with different individual and combinations of enzymes over varying lengths of time and at different concentrations was done in a 3x4 factorial to show which combination led to the highest release of the indicator phenolic compound- ferulic acid. The information from enzyme optimization was then combined with multiple pre-processing steps including a NaOH soaking period, high shear mixing, and high pressure homogenization to provide the greatest increase in ferulic acid release, as well as the largest increase in viscosity, which is a positive driver for functionality in whole grain products. Results of the enzyme optimization study showed the highest release was almost always found at the highest concentration and time combination- 1.0% and 48 hours. Three individual enzymes showed high release- Xylanase BX-AN, S and Pentopan. The testing done on combinations of enzymes did not show a significantly larger release than any individual enzyme and so a synergistic effect among enzymes was not found. When testing the enzyme with the pre-processing steps there was a significant increase in the release of ferulic acid. The NaOH soaking treatment proved extremely effective in aiding in release of ferulic acid. The high pressure homogenization treatment provided a dramatic increase in viscosity. Overall, the combination of treatments gave the highest release of ferulic acid and the largest increase in viscosity. A preliminary animal study was done that showed the use of treated wheat bran gave an increase in intestinal contents viscosity, which leads to cholesterol lowering. A longer 12 week study by another graduate student is planned to confirm these findings.
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    Isolation and Characterization of Bacteriophages for Bicontrol of Salmonella and Shiga Toxin-Producing Escherichia coli in Food Applications
    (2021-08) Hansen, Eleanore
    Salmonella poses a significant risk to public health, with tens of thousands of cases occurring each year. Food is the primary vehicle for Salmonella outbreaks, and several diverse foods are frequently attributed to outbreaks. Traditional methods of pathogen control in the food industry are often indiscriminate, killing microbes that may be beneficial alongside the pathogens. In addition, these methods can alter the organoleptic properties of foods and may not be usable for raw and ready-to-eat foods such as raw poultry or fresh produce. Use of chemical antimicrobials is also growing out of favor in some settings as concerns rise over antimicrobial resistance in foodborne pathogens. Interest is growing in using phage cocktails as an alternative method to combat Salmonella and other foodborne pathogens.Bacteriophages, or phages, are viruses that infect bacteria. They are highly host specific, safe to consume, relatively inexpensive, and do not alter the organoleptic properties of food, making them ideal as a biocontrol agent in a variety of food applications. Using several phages combined in a cocktail can increase their success in killing pathogens and lower the chance of resistance to the phages developing. Phages are the most abundant biological entity on the planet, and most remain undiscovered. A few commercial phage cocktails exist that may be used in the food industry, but identifying novel cocktails of unique phages increases the diversity of the tools available to handle troublesome pathogens that arise. In this study, phages were isolated from local Minnesota wastewater samples. The newly isolated phages were tested for their ability to lyse and kill several serotypes of Salmonella and a few serotypes of Shiga-toxin producing E. coli. Six promising phages were picked for a putative novel cocktail. This putative cocktail was assessed for its ability to reduce Salmonella levels in a raw chicken breast model. The cocktail shows promise as a tool to manage both Salmonella and Shiga-toxin producing E. coli in food and food processing environments.
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    Patulin degradation by yeast protein extract
    (2014-05) Folger, Brian Charles
    The mycotoxin patulin, produced by a number of fungi, most prominently Penicillium expansum, has proven problematic for the apple industry due to contamination of apple juice and apple cider. Presently, techniques to control patulin accumulation have proven increasingly ineffective due to the presence of antifungal resistant strains of mold, stability of patulin during thermal processing, and conflicting data on the efficacy of other treatments. However, fermented apple products such as hard ciders and apple cider vinegars are devoid of patulin. Fermentation with yeast resulted in complete degradation of patulin, possibly due to enzymatic degradation by yeast enzymes. Patulin has also been shown to be susceptible to adduct formation with free thiol containing molecules such as glutathione, which is naturally present in yeast cells. Limited studies have also looked at patulin adsorptivity onto the call walls of yeast. Degradation of patulin is, therefore, hypothesized to be caused by multiple mechanisms mainly caused by yeast proteins/enzymes.To assess the loss of patulin by protein extracted from yeast (Rhodosporidium kratochvilovae strain 62-121), patulin extraction methods were compared to determine the optimal method for patulin extraction from protein rich environments. The effect of boiling to halt any possible enzymatic degradation on total patulin loss was assessed by comparing patulin recovery to that of samples placed on ice after the assay. Yeast growth was optimized for the production of patulin-degrading protein extracts by surveying days of growth and subsequent storage at 4°C. Additionally, free thiol group reactivity with patulin was assessed upon incubation with protein extract, cysteine, and glutathione. Liquid chromatography and mass spectrometry (LC/MS) was used to detect patulin degradation products. Potential enzymatic activity was assessed by comparing the degradation activity of different protein extracts from yeast. Finally, patulin loss due to adsorption to inactivated yeast cell walls was determined. The use of acid and salt to precipitate the protein before patulin extraction resulted in the best patulin recovery from protein rich media, and an additional extraction following a modified AOAC method allowed for removal of excess salt without sacrificing patulin recovery. The use of boiling to denature the protein after the assay resulted in 10% higher patulin loss than when the samples were placed on ice, presumably due to adduct formation with thiol groups. Growing yeast for 6 days at room temperature was deemed adequate to obtain optimal patulin degradation; and subsequent incubation of the yeast at 4°C did not impair the patulin degradation activity. Yeast protein extracts were found to be inconsistent with respect to patulin degradation activity, nevertheless patulin degradation activity (up to 100% patulin) was observed in several batches. Patulin incubated with cysteine showed signs of free thiol blockage in both samples of protein extract and pure cysteine. Patulin incubated with glutathione was degraded at both pH 7 and 3.7, and one patulin-glutathione adduct (462 m/z) was identified via LC/MS. Lyophilized yeast cells demonstrated patulin adsorption capabilities after incubation at 30°C for 20 min. Observed results confirm that patulin can be degraded by the protein extract from yeast. The exact mechanism of patulin degradation by protein extracts remains unclear, yet it appears to be either enzymatic or chemical through thiol adduct formation. Our results indicated that the mechanism is a combination of the two. This research offers insight into possible patulin degradation mechanisms, and can give direction in applying this new method of patulin control in an industrial setting.
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    The relationships of dietary fat and blood lipids with brain MRI measures
    (2014-11) David, Preethi
    Objectives: This study examined the relation of dietary fat intake and blood lipid levels in a young African American and white population with subclinical MRI measures taken at a later age. Methods: Dietary intake was assessed 3 times over 20 years and fasting blood lipids measured x times over 25 years among CARDIA participants who were 18-30 years old at baseline (n=5111). Brain MRI measures were taken at year 25 in a sub-sample (n=690). Spearman partial correlations were used to evaluate relations of dietary intake and blood lipid levels with MRI measurements; analyses were stratified by gender and adjusted for age, race, education, smoking, energy and alcohol intakes, BMI, and intracranial volume. Results: Intakes of energy, alcohol and % kcal from total fat and saturated fat were greater in men than women. Total fat intake was not related to any brain MRI measures. However, both grams and % kcal from saturated fat were inversely related to white matter fractional anisotropy (FA) in men only (r = -0.12; p=0.03 and r=-0.14; p=0.01, respectively). Further, grams and % kcal from saturated fat were positively related to abnormal white matter tissue volume in women only (r=0.13; p=0.01 and r= 0.13; p=0.02, respectively). Omega3 fatty acids were inversely correlated to abnormal white matter (men: r=-0.11; p=0.05, women: r=-0.14; p=0.01). Additionally, omega3 fatty acids were inversely correlated with total ventricle volume in men (r=-0.11; p=0.05), but not in women. In men there were significant inverse correlations between total cholesterol and total brain volume (r=0.12, p=0.03) . Furthermore, there were significant positive correlations between both total (r=0.11, p=0.05) and LDL-cholesterol (r=0.12, p=0.04) and total ventricle volume in men. In women there was a significant inverse correlation between triglycerides and total brain volume (r=-0.12, p=0.03) and normal gray matter (r=-0.15, p<0.01). In addition, there was also a significant inverse relationship between total cholesterol and total brain volume (r=-0.11, p=0.05) in women. Conclusions: Given these study findings, we conclude that omega3 fatty acid intake and saturated fat may be associated with brain MRI measures in a beneficial and detrimental manner, respectively. Our studies further reveal interesting inverse relations between total and normal gray brain volumes with blood lipids in men and women. Additionally total ventricle volume was positively associated with blood lipids in men. Further research is needed to elucidate the relations of dietary fat intake and blood lipids with brain MRI measures.
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    Repressions of the toxic α, β-hydroxyaldehyde homologues, HHE, HOE, HNE and HDE formations by synthetic and natural antioxidants in commercial corn oil at frying temperature
    (2015-04) Jin, Wei
    Commercial corn oil, which contains high level of linoleic acid (~60%) is widely available and is often used for frying food products. The α, β-unsaturated-4-hydroxyaldehydes, the toxic degradation products of lipid peroxidation is forming due to heat treatment at frying temperature in high PUFA vegetable oils containing high level of linoleic acid. The objective of present experiment was to find the suppressing effects of α, β-unsaturated-4-hydroxyaldehydes in the presence of synthetic and natural antioxidants.In the present experiments corn oil was heated for 0, 1, 2, 4, and 6 hours at 185°C in the presence and absence of synthetic and natural antioxidants to measure the formation of the four α, β-unsaturated-4-hydroxyaldehydes, especially the 4-hydroxy-2-trans-nonenal (HNE) which is known to be the most toxic product of the unsaturated fatty acids peroxidation process. In addition to HNE, 4-hydroxy-2-trans-hexenal (HHE), 4-hydroxy-2-trans-octenal (HOE) and 4-hydroxy-2-trans-decenal (HDE) were also existed in commercial heat treated corn oil at 185°C. The formation of HHE, HOE, HNE and HDE increased with the length of heating time. The combinations of 200ppm TBHQ+50ppm citric acid (CA)+100ppm ascorbyl palmitate (AP) and 50ppm or 100ppm rosemary extracts (RE) were selected to study the repressing effects on the oxidation retarding the α, β-unsaturated-4-hydroxyaldehydes formation in heat treated corn oil at 185°C.It was found that the oxidation process and the formation of HHE, HOE, HNE and HDE in corn oil were suppressed by the addition of synthetic antioxidants and also by a natural antioxidant at frying temperature of 185°C. 200ppm TBHQ+50ppm CA+100ppm AP suppressed the oxidation of corn oil at 185°C after 6 hours by 27% for HNE, 88% for HHE, 70% for HOE and 96% for HDE formation. 50ppm or 100ppm Rosemary extracts (RE) suppressed 29% HNE, 40% HHE, 48% HOE and 74% HDE formation in corn oil.
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    Soy protein hydrolysate; solubility, thermal stability, bioactivity, and sensory acceptability in a tea beverage.
    (2011-08) Lee, Jookyeong
    Protein solubility affects the quality of many food products, especially high-protein beverages (>4.2% protein). Beverages formulated with soy protein at >4.2% protein content are currently unavailable in the market due to thermal challenges affecting the protein solubility and also due to flavor challenges. Enzyme hydrolysis of soy protein may lead to enhanced solubility and thermal stability. However, bitter taste caused by hydrolyzing soy protein is a limiting factor to using SPH in food applications. Therefore, controlled and limited hydrolysis of 2-8% is required to minimize the production of bitter peptides. Another advantage of controlled hydrolysis of soy protein is the release of bioactive peptides. Among the many physiological benefits of bioactive peptides, antihypertensive activity has gained much attention. Therefore the objectives of this work were 1) to optimize hydrolysis conditions of soy protein for enhanced solubility, thermal stability and bioactivity, while maintaining low degree of hydrolysis (DH); and 2) to determine the sensory acceptability of lemon flavored iced tea beverages formulated with soy protein hydrolysate at various concentrations. Soy protein isolate (SPI) was hydrolyzed by papain, bromelain, trypsin, and alcalase at various enzyme levels while keeping other hydrolysis conditions constant. Enzymatic activities were optimized based on DH measurements. Degree of hydrolysis (DH) was measured using O-phthaldialdehyde method. Samples were subjected to SDS-PAGE analysis to monitor enzyme selectivity. ACE inhibitory activity was measured using a standardized assay. For determination of solubility and thermal stability, solutions (5% w/v) of hydrolysates and SPI were subjected to heat treatment at 95°C for 60 min followed by centrifugation and determination of protein content in the supernatant using a nitrogen analyzer. Solubility and thermal stability at different protein concentrations (1%, 2.5%, 5%, and 7%) in a black tea beverage were also measured. Alcalase-hydrolyzed SPI was chosen for the sensory study as it had the highest solubility, thermal stability, and antihypertensive activity among the hydrolysates. Nine formulations were prepared, including a control which was a tea with no added protein and the four different protein concentrations containing either SPI or alcalase-hydrolyzed SPI. One-hundred-one subjects rated overall liking, flavor, aroma, appearance, and mouthfeel on an 11-point hedonic scale and rated intensity of bitterness and off flavor on a line scale. Hydrolysates produced using 2.654 GDU of bromelain, 0.012 AU-A of alcalase, 19,680 USP units of papain, and 235,000 U of trypsin had DH of 3.98%, 3.57%, 6.77%, and 2.60%, respectively, thus were selected for further experiments. Use of different enzymes resulted in distinctive differences in hydrolysis patterns. Among the four produced hydrolysates, alcalase-hydrolyzed SPI was highly soluble (75.25%) at relatively high protein concentrations, thermally stable, and possessed the most pronounced antihypertensive activity (IC50=0.263 mg protein/ mL). Lemon flavored iced tea beverages fortified with alcalase-hydrolyzed SPI at various protein concentrations (1 up to 7 % protein) were found to be acceptable. The beverages formulated with the hydrolysate at 1%, 2.5%, and 5% protein content were liked as much as those without added protein. Beverages formulated with up to 5% hydrolysate also had significantly less bitter taste and off flavors than SPI beverages. These findings can be utilized in the development of high protein fortified beverages, which is acceptable with relatively low bitter taste and noted physiological benefits.