Browsing by Author "Dr. Brian Farkas, Committee Member"

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Aggregation of alpha-Lactalbumin at PH 3.5-6.0
(2006-12-28) Schneider, Paula Anne; Dr. John Cavanagh, Committee Member; Dr. Brian Farkas, Committee Member; Dr. E. Allen Foegeding, Committee Chair
Heat-induced protein aggregation is an important reaction in food processing because it causes undesirable appearance changes, which may lead the beverage to phase separate. Recently, there has been an increased demand for and growth in the area of sports beverages. Sports beverages can be categorized several different ways; although the category of current interest is that of beverages having a low pH (from 2.8 to 3.5) and representing a good source of protein. Generally these beverages derive a high proportion of their protein from bovine whey, since it is a source for branched chain amino acids which can benefit muscle building and maintenance. These low pH beverages can be astringent. Astringency is positively related to low pH where the degree⁄intensity of perceived astringency increases as the pH of the beverage decreases. One way to minimize astringency is to increase the pH; although aggregation readily increases the nearer the pH is to the protein's isoelectric point. The selection of a less heat sensitive protein source (ex. α-lactalbumin) and/or the use of molecular aggregation blockers can provide ways to control aggregation. The first objective of this research was to study the aggregation of α-lactalbumin over a pH range 3.5 to 6.0. Protein solubility and turbidity development were used to monitor aggregation. Turbidity was evaluated using a spectrophotometer set to monitor at 400 nanometers, and a turbiditimeter that measures scattering at a 90° angle from the incident light. Change in protein solubility in response to pH adjustment with 1M phosphoric acid and thermal (120 seconds in a 85°C water bath) treatment was determined by measuring dispersed protein after centrifugation at 11950 x g (18-24°C) for 60 to 90 minutes. As expected, the lowest protein solubility and highest degree of turbidity resulted near the isoelectric point of α-lactalbumin. The affect of calcium content was also evaluated. In the holo-form, α-lactalbumin was more stable to native aggregation; although no difference was seen in stability after heat treatment. Indirect determination of the mechanism for α-lactalbumin aggregation was facilitated through the use of various compounds that had previously demonstrated aggregation-blocking or reduction abilities in different systems (ex. protein, pH, heating conditions, etc.). Blocking agents included amyloid/β-sheet blockers (ex. thioflavin-T and quercetin), hydrophobic amino acid-interacting molecules (ex. Hydroxyl-propyl-β-cyclodextrin), and the use of proteins as blockers (ex. αs-casein) were evaluated. The amyloid/β-sheet blockers were not effective in suppressing turbidity development or maintaining/increasing protein solubility. Further investigations were made to determine if a specific type of aggregate was possible. Under the conditions tested, α-lactalbumin did not form the specific aggregates (spherulites), which helps explain why these blockers were ineffective in an α-lactalbumin protein system. The use of sodium dodecly sulfate (SDS) was used to control aggregation by binding to exposed hydrophobic patches on the protein's surface. SDS was not effective in controlling aggregation in β-lactalbumin systems, as monitored through turbidity development and protein solubility, but was effective in systems that contained β-lactoglobulin. The difference in response may be attributed to the structural differences between these proteins. Blocking of hydrophobic amino acid residues with hydroxyproply- β-cyclodextrin had the most potential for success in suppressing aggregation of α-lactalbumin. However, further work is needed to determine where they are binding, strength of binding, and the effect of polar components on the core cyclodextrin molecule.
Characterizing a Biomedical Hydrogel Device
(2005-07-26) Funke, Melissa Marie; Dr. Christopher R. Daubert, Committee Chair; Dr. Brian Farkas, Committee Member; Dr. Van-Den Truong, Committee Member
E-Matrix™, a hydrogel principally composed of gelatin and dextran, common food ingredients, is being manufactured with an amino acid formulation and considered as a new medical device. The compound purportedly accelerates the rate of healing once injected beneath a wound. The improved healing is believed to be caused by shifting the healing process from a slower healing adult inflammatory tissue stage to a quicker healing fetal regenerative tissue stage. In addition, gelatin and dextran are anticipated to interact within the medical device to form a stable hydrogel. The objectives of this study were to rheologically characterize E-Matrix™, develop quality control protocols for evaluation of E-Matrix™ and gelatin, investigate the nature of the proposed relationship between gelatin and dextran, and examine rheological properties of E-Matrix™ components. Rheological techniques using a StressTech Controlled Stress Rheometer (ReoLogica Instruments AB, Lund, Sweden) were used to characterize E-Matrix™, to establish physical properties, and to describe the material flow behavior. Differential scanning calorimetry (PerkinElmer DSC7) was used to determine melt points of E-Matrix™ and a 12% gelatin solution to compare thermal transition temperatures. Rheological protocols were developed for both E-Matrix™ and the principle ingredient in the material, a 12% gelatin solution. The protocols evaluate specific rheological properties to compare either gelatin lots or manufactured E-Matrix™ batches with established standards. Incorporation of the rheological protocols into a quality control procedure would be a valuable tool for accessing the acceptability of gelatin lots and newly manufactured E-Matrix™ batches. To further understand and characterize E-Matrix™, studies were performed to examine key physical components of the material. Specifically solutions of 12% gelatin, 17% gelatin, 5% dextran, 12% gelatin-5% dextran, and the gelatin-rich domain of E-Matrix™ were rheologically examined and compared to rheological properties of E-Matrix™. In addition the affect of ionic strength and salt valence was also examined through rheological analysis. To determine whether a protein-carbohydrate conjugation resulted from the Maillard reaction, a spectrophotometric technique was performed to determine the degree of covalent conjugation by measuring the change in free amino groups. E-Matrix™ was rheologically characterized at 37°C and 50°C as having pseudoplastic and Newtonian material flow behaviors, respectively. Differential scanning calorimetry determined the calorimetric melt point of E-Matrix™ (23.9°C) and a 12% gelatin solution (26.0°C) to occur sooner than those determined rheologically (33.7°C) and (32.7°C), respectively. Rheological protocols were developed for quality control evaluation of E-Matrix™ and gelatin. The protocols can be used as a quality control tool by the manufacturer of E-Matrix™, Encelle, Inc. of Greenville, North Carolina. Rheological properties were evaluated for different components of E-Matrix™; individual components, salt type, and ionic strength concentration. Individual E-Matrix™ components were found to differ significantly in regard to rheological properties. However salt type; monovalent versus divalent, using NaCl and CaCl₂ was not found to create significant differences for the properties examined in this study, but ionic strength concentration was found to produce rheological properties of significant difference. In addition, according to spectrophotometry, a hypothesized chemical interaction between gelatin and dextran was not likely occurring. By understanding the rheological properties of E-Matrix™, the nature of the protein and carbohydrate interaction, and the rheological properties of the E-Matrix™ components, the mechanisms behind the functionality of the wound healing accelerant can be more clearly understood and benefit the product producers through further formulation optimization.
Effects of High Hydrostatic Pressure and Thermal Processing on the Antioxidant and Sensory Characteristics of Blueberry Juice
(2007-12-08) Leavens, Je'Velle Bonique; Dr. Leon Boyd, Committee Chair; Dr. MaryAnne Drake, Committee Member; Dr. Brian Farkas, Committee Member
Blueberries are recognized for their potential health benefits and high antioxidant levels. Increased dietary consumption of blueberry products may reduce risk factors associated with cancer, heart disease, and other degenerative diseases. Blueberries are often processed into juices or wines. However during blueberry processing, the levels of antioxidants may be altered resulting in a change in antioxidant and sensory qualities. Due to the high antioxidant levels found in blueberries, blueberry processors are seeking effective processing techniques such as High Hydrostatic Pressure (HHP) to further optimize the amount of antioxidants retained in the final product. Therefore, the objectives of this study were to determine the effects of different processing techniques on the antioxidant properties of blueberry juice and consumer acceptability of blueberry juices developed from selective processing techniques (i.e. cold processing versus hot processing). Individually quick frozen Croatan blueberries were treated with enzyme (Rapidase TM) and pressed at 22oC, 43oC and 75oC, followed by further pasteurization of the initial cold press and hot pressed (43oC) juices at 75oC. In addition, trial studies were conducted using HHP processing at 400 MPa for 10 min, 20 min, and 30 min holding times. Antioxidant levels were measured by changes in total anthocyanins, total phenols, and Oxygen Radical Absorbance Capacity (ORAC) values. Results indicated the hot-pressed juice (75oC) was significantly higher in antioxidant activity compared to the hot-pressed juice (43oC) followed by the cold-pressed juice (22oC). Addition of heat to the cold and hot-pressed juices caused an increase in the overall antioxidant activity. However, juice samples pressed at 75oC resulted in the greatest levels of total anthocyanins, phenols, and antioxidant capacity. There was a substantial amount of anthocyanins and phenolics recovered in the blueberry juice processed using HHP. The HHP30min resulted in a higher antioxidant activity than the HHP20min with the HHP10min exhibiting the lowest antioxidant activity. In comparison to thermal processing, there were no significant differences between the hot pressed juice (43oC) and the pressurized treatments at 20 min and 30 min holding times. Overall, equivalent antioxidant activity was achieved between the HHP20min and the hot pressed juiced (43oC), with a similar ORAC value for the HHP30min. These results suggest that selective processing can be used to improve the antioxidant yield in blueberry juice. Though the addition of heat to the juices resulted in the highest levels of antioxidant activity, the application of greater levels of HHP may be an effective non-thermal processing technique to maximize antioxidant activity while minimizing sensory loss during blueberry juice processing. Evaluation of heat treated blueberry juices by consumers (n=79) was based on the following attributes: overall acceptability, blueberry flavor intensity, blueberry flavor liking, sweetness intensity, sweetness liking, overall flavor liking, overall acceptability and overall appearance liking. Results from the consumer acceptability test indicated the juice extracted at 75oC and 43oC was more readily accepted by consumers than the cold- pressed juice with mean hedonic ratings of 6.33, 6.05, and 4.78, respectively. Overall, the thermally processed blueberry juices yielded a product with relatively high levels of antioxidants with a deep rich blue-purplish color that was appealing to consumers.
Influence of Moisture Content on Quality and Shelf-life of Oil Roasted Virginia-type Peanuts
(2010-08-02) DeBruce, Miniayah Tyasia; Dr. Lisa Dean, Committee Co-Chair; Dr. MaryAnne Drake, Committee Member; Dr. Brian Farkas, Committee Member; Dr. Leon Boyd, Committee Member; Dr. Timothy Sanders, Committee Chair
ABSTRACT DEBRUCE, MINIAYAH. Influence of Moisture Content on Quality and Shelf-life of Oil Roasted Virginia-type Peanuts (Under the direction of Dr. Timothy H. Sanders and Dr. Lisa Dean). Consumer studies have shown that oil roasted peanuts are by many consumers the preferred; however, oil roasting of food products may increase oil content. There are numerous factors that can affect roasting oil uptake and one notable factor is moisture content. Moisture content is measured and monitored throughout processing in the peanut industry and it is a important factor in overrall peanut quality during processing. The moisture content of shelled peanuts used for processing, may range from 5.5% â€“ 8.5%. The purpose of this experiment was to determine if pre-roast moisture content has an effect on the amount of oil uptake or exchange that occurs during oil roasting of virginia market type peanuts and also to determine the effect of pre-roast moisture content on the physical characteristics, sensory attributes and storage quality of oil roasted peanuts. Peanuts of final dry weight moisture of 4.2%, 4.5%, 5.8% and 6.6%. Peanuts used to further examine oil uptake were roasted in a peanut oil/coconut oil mixture in which the coconut oil served as a marker compound. Peanuts used to study the relationship of moisture content and oxidation were roasted in peanut oil and placed in storage for 48 weeks. Increasing moisture content resulted in decreased oil content and oil uptake The presence of C12 fatty acids found in coconut oil in the roasted peanuts indicated uptake did take place. More oil was present at the surface; however, fatty acid profiles indicated less C12 at the surface than inside the peanut. Scanning electron microscopy images revealed that more structural damage was prevalent on peanuts with high moisture content than those with low moisutre content. Results indicated that pre-roast moisture content did not have a significant effect on of free fatty acids and peroxide values; however, increases in these compounds did indicate that some lipid cxidation occurred. Low moisture content had high roast peanutty flavor throughout storage; however, storage did have a significant affects to flavor causing a slight decrease in flavor and a slight increase in off flavors related to lipid oxidation.
Microstructure and Functionality of Processed Cheese: The Role of Milk Fat
(2007-12-20) Price, Kristin Michelle; Dr. Orlin Velev, Committee Member; Dr. Brian Farkas, Committee Member; Dr. Christopher Daubert, Committee Chair
Cooling, the final stage in processed cheese manufacturing, plays a significant role in determining the texture and firmness of the final product. To interpret cooling mechanisms of processed cheese, model processed cheese analogues were formulated including rennet casein powder, anhydrous milk fat, and emulsifying salts. Small amplitude oscillatory shear (SAOS) and large deformation compression tests analyzed rheological properties and trends exhibited in processed cheese analogues when cooled with different cooling schedules. Two cooling rates, 0.5 oC⁄min and 0.05 oC⁄min, were selected, and based on protein network formation and fat crystallization, two significant cooling phases were identified: 80-40oC and 40-5oC. In all, four cooling schedules were developed from a two-by-two matrix of cooling rates and cooling phases. After the cheese analogues were cooled with the desired cooling schedules, SAOS rheology measured the complex shear modulus (G*) of cheese analogues through a frequency sweep range of 0.01-10 Hz. Utilizing the same cooling schedules, the normal, compressive strength of cheese analogue cylinders was measured and converted into shear modulus (G) values. Rheological analysis revealed that a slower cooling rate through the first phase of coolig (80-40oC) created a firmer cheese product (larger G* and G values) when compared with a faster rate of cooling through the same temperature range. The cooling rate through the second phase of cooling, during fat crystallization, did not impact final cheese storage modulus. Small and large deformation rheological analyses found that the final cheese texture was governed by the cooling rate through the first phase of cooling (80o-40oC), formation of the protein network. Confocal laser scanning microscopy (CLSM) was used to investigate the effects of cooling rate on the microstructure of processed cheese analogues. Micrographs of cheese analogues stained with Rhodamine B and Nile Red fluorescent probes revealed a protein ring surrounding fat droplets that formed during cooling from 80-5oC. The protein ring thickness was not influenced by cooling cheese analogues at two different rates, 1 oC⁄min and 10 oC⁄min. However, the presence of the protein ring surrounding fat droplets in processed cheese analogues lays the framework for future study on the effects of very slow cooling rates on the thickness of the protein ring. With a better understanding of cheese rheology and cheese microstructure during cooling, cheese manufacturers can control cooling schedules to help optimize quality attributes in processed cheese.
Monitoring of Fishery Product Quality Using an Electronic Nose and Visible/Near-Infrared Spectroscopy
(2007-03-23) Dodd, Thomas Herman; Dr. John Classen, Committee Member; Dr. Brian Farkas, Committee Member; Dr. Gary Roberson, Committee Member; Dr. Andy Hale, Committee Chair
In order to evaluate new technologies that could improve quality determination of fishery products, this research investigated the application of electronic noses (e-nose) and Visible⁄Near Infrared (VIS⁄NIR) spectroscopy as possible sensing technologies. The quality of fishery products has always been hard to define, and is typically based on the general perception of the consumer evaluating the product. Expiration dates serve as a guide, but the sensory appeal of a fishery product is generally the deciding factor as to whether a product is deemed good or "spoiled", defined as unfit for consumption. Various chemical and sensory methods to determine fish freshness are available to the food industry, but most are expensive, time consuming or destructive. A rapid, non-destructive method to ascertain fish quality would be of great benefit to both the industry that is eager to provide its consumers with a fresh, safe product and the consumer who is increasingly looking for a better guarantee of food quality. The multivariate analysis (MVA) techniques used by both e-nose and VIS⁄NIR technologies are similar, but widespread use of these techniques has only become possible with the increased computing power of the past few years. E-nose technology is a slightly newer technology than VIS⁄NIR. Due to its more recent introduction, a rapid decay study was first performed to evaluate the feasibility of this method to sense decay time in a readily available fishery product of tilapia. Linear discriminate analysis (LDA) was used as a feature extraction method. This allows for the class of a given sample to be taken into account when features are extracted to yield a much better model. Separating the samples into 6 hour classes, a classification rate of 97.8% was achieved. Once the e-nose had shown promise in quantifying fish decay, a more continuous model was chosen to more accurately model the continuous decay of fish products. It was also decided to perform the testing at actual storage conditions and choose a product that has a higher commercial value than tilapia, so that results would be more useful to the market. As such, blue crab meat was chosen for the study. In order to compare the two technologies to a standard quality measurement, blue crab claw meat was sampled over its commercial storage period of 14 days on ice. Total Volatile Base Nitrogen (TVB-N) was used a baseline for measured meat quality and models were generated using data collect from both e-nose and VIS⁄NIR technologies. E-nose was found to be able to predict the TVB-N level in the meat with an accuracy of less than 5.0 mg TVB-N ⁄ 100 mg. Using visible spectroscopy TVB-N levels were predicted to an accuracy of 4.8 mg TVB-N ⁄ 100 mg. These values were found to be in the same range as that of the ion-specific electrode TVB-N measurements suggesting that these two technologies have the potential to be more accurate with better measurement of the calibration variable. Since most research has shown a steady decrease in product quality with time, storage time was used a calibration variable. While this does not tie to a specific chemical indicator, time has the advantage of taking into account many different changes that might be missed by any specific indicator. This study investigated both blue crab lump meat and claw meat. E-nose and VIS⁄NIR readings were taken throughout the storage time of 14 days. These measurements were then used to create a model that could predict total storage time of a meat sample under specific storage conditions. With e-nose technology a standard error of prediction (SEP) was achieved of 2.48 days for claw meat and 2.77 days for lump meat. VIS⁄NIR spectroscopy yielded significantly better results with 1.31 and 1.11 days for claw and lump meat respectively. This research shows that both e-nose and VIS⁄NIR spectroscopy can be used to generate an estimate of fish quality. By being able to model both time and specific indicators, these two technologies show the robust nature that is normally seen in sensory panels. While maintaining these advantages, both technologies yield a repeatable and nondestructive testing method that has not been available in the past
Process control parameters for Skipjack tuna (Katsuwonas pelamis) precooking
(2003-11-20) Webb, Elizabeth Lynn; Dr. Kevin Keener, Committee Member; Dr. James Young, Committee Member; Dr. S. Andrew Hale, Committee Chair; Dr. Brian Farkas, Committee Member
The purpose of this research was to define the critical process control parameters that influence texture and yield for the precook unit operation in the commercial canning of Skipjack tuna. To accomplish this goal, the impact of precook temperature and time combinations on the Instrumental Texture Profile Analysis (ITPA) texture parameters, protein state, weight loss, and moisture content of hydrothermally treated tuna loin meat was investigated. It was found that temperature was the primary influence for all ITPA parameters, however time influenced texture when samples were held at 55˚C. Auto proteolysis was suspected at this temperature, as some ITPA parameters declined with increased time. Data from small steamed and small hydrothermally treated samples were compared with data from whole steamed fish to ascertain whether small sample results could be extrapolated to data from whole precooked fish. Weight loss, moisture content, and ITPA values reacted similarly, regardless of experiment method. For all treatments, weight loss and moisture content decreased with increased temperature, and hardness, instantaneous springiness, and retarded springiness increased with increased temperature. Cohesiveness did not vary with temperature. Linear conversion equations were written to predict texture, weight loss, and moisture content results of whole precooked fish from small steamed and small hydrothermal samples. Process inputs which are available from a commercial precooking unit operation were used to model effects of precooking Skipjack tuna. Fuzzy logic, neural network, and multiple linear regression models were written to predict precook time, weight loss, friability, and edible weight of precooked fish from final backbone temperature, frozen weight, and storage time inputs. Both fuzzy logic and neural net models perform better than traditional multiple linear regression models in predicting cook time and weight loss. Friability and edible weight were difficult to quantify with all models, and more data was needed to better quantify these variables.