Browsing by Author "Dr. Leon Boyd, Committee Chair"
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- Antioxidant Properties of Muscadine Grape Products(2003-04-10) Vaughan, Trivette Lashum; Dr. Leon Boyd, Committee ChairPhenolic compounds present in grapes and wines may play a positive role in human nutrition, related to their positive protective action towards reducing the risks associated with heart disease and the scavenging properties toward free radicals associated with degenerative diseases. Noble and carlos grapes were either cold pressed at room temperature or hot pressed at 43 C followed by collection of their free run juices and fermentation to wines. Resulting pomaces were dried at 37 C, 49 C, and 60 C by convection and vacuum ovens. Juices, wines and pomaces were tested for total phenol content and antioxidant capacity via the oxygen radical absorbance capacity assay (ORAC). Carlos grape skin, seed and delipidized seed extracts were analyzed to determine their antioxidant activity in a safflower oil model system. Carlos grape skin and seed were dried at 60 C and extracted using ethyl acetate and water. The antioxidant activity of carlos grape extracts were compared to tert-butyl hydroquinone (TBHQ) and propyl gallate (PG). Three levels (60, 180 and 300 milliequivalents of gallic acid) of extract were tested in an oil model system using the oxidative stability instrument (OSI) and conjugated diene, to measure levels of antioxidant activity. The objective of this research was to study the effects of processing on muscadine juices, wines and pomaces and to study the antioxidant properties of muscadine extracts in a lipid model system. Results of processing effects indicated that noble hot pressed juice and noble wine showed a significantly higher level of total phenols and total antioxidant capacity than for carlos samples. Total phenols indicated that all noble pomaces were significantly higher than carlos pomaces. Antioxidant capacity indicated no significant difference between noble and carlos dried samples. Analysis by OSI showed that ethyl acetate seed extracts at a level of 300 milliequilvalents of gallic acid was significantly higher than TBHQ and PG. Oxidative index values for water extracts were not significantly different from TBHQ and PG. Addition of both extracts into the oil model system using OSI index indicated increasing antioxidant activity with increasing concentration of extracts added.
- 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 MemberBlueberries 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.
- Evaluation of the Antioxidant and Biological Properties of Muscadine Grape Seed Extracts(2007-12-14) Dansby, Montreka; Dr. Leon Boyd, Committee ChairThe objectives of this research were i) to optimize extraction of phenolic compounds from muscadine grape seeds using food grade solvents, ii) to characterize and quantify the phenolic compounds present in Carlos muscadine grape seed extracts, iii) to assess the oxidative stability of the grape seed extract, iv) to evaluate the antimicrobial activity of the optimal muscadine grape seed extract, and v) to evaluate the effect of muscadine grape seed extract on MCF-10A breast cells. Carlos muscadine grape seeds were manually removed from the skin and pulp, then freeze-dried or oven-dried. Phenolic compounds were extracted from muscadine grape seeds using a Dionex Accelerated Solvent Extractor 200 following a two factor composite design. The two factors were solvent and temperature. Ethanol in combination with water and ethyl acetate in combination with water were evaluated in this research. Solvent percentages ranged from 35% to 95% and temperature ranged from 75C to 150C. Optimal extraction conditions were determined using the Folin-Ciocalteu and oxygen radical absorbance capacity assays. Identification and quantification of the phenolic compounds were determined by high performance liquid chromatography with mass spectroscopy. The optimal extraction conditions for the highest recovery of phenolic compounds consisted of the freeze-dried seeds extracted with 65% ethanol and 35% water at 150°C, with total phenolic and oxygen radical absorbance capacity values of 5.87 mg GAE⁄g and 60.32 M-TE⁄g of seeds, respectively. The four major phenolic compounds quantified in the muscadine grape seed extract were epicatechin, catechin, gallic acid and ellagic acid. Oxidative stability index of the muscadine grape seed extract resulted in an induction period of 4.6 hours. In the antimicrobial study, both muscadine grape seed extract and ellagic acid inhibited the growth of E. coli 0157:H7, Listeria monocytogenes, and Salmonella typhimurium at 104 cfu⁄ml. These research findings show that muscadine grape seed extracts contain phytochemicals with antioxidant and antimicrobial properties that can be used in applications including food ingredients, food supplements and other nutraceutical applications.
- Processing Effects on the Antioxidant Activities of Blueberry Juices(2003-07-17) Carlson, Joshua Steven; Dr. Leon Boyd, Committee Chair; Dr. Jonathan Allen, Committee Member; Dr. Daniel Carroll, Committee MemberThe inverse relationship between antioxidant intake and many disease states has been seen repeatedly. The importance of antioxidants has led blueberry processors and other food processors to look for ways to modify processing techniques to optimize the antioxidant levels in the final product. With the availability of new processing methods such as microwaving, it is important to determine the effects emerging process technologies have on antioxidant retention and product quality. The goal of this research was to determine the best processing method available to produce blueberry juice with the highest antioxidant activity. One experiment examined the effect of cold (22°C) versus hot processing (43°C) of seven cultivars of blueberries using the oxygen radical absorbance capacity (ORAC) and total phenols assays. The results showed that hot processing yielded, on average, a product with 50% more total phenols and antioxidant capacity. A second experiment used ORAC and total phenols to evaluate the effect of cold (22°C), hot (47°C), and pasteurization (90°C) of blended blueberries heated in a steam-jacketed kettle versus microwave heated (85°C, 92.5°C, and 95°C) blended blueberries. The results showed that pasteurization had the highest total phenols and ORAC values, and that the hot processed and microwaved juices had similar values, with the cold processed blueberries having the lowest total phenol and ORAC values. The final study used ORAC, total phenols, and total anthocyanins to evaluate a one month refrigerated (3-5°C) time study on pasteurized (90°C) and microwaved blueberry juices (85°C, 92.5°C, and 95°C). The results again showed that pasteurization was equal to or better than the microwaved treatments. The results also showed that the pasteurized and microwaved samples had stable ORAC and total phenol values, as well as a slight increase in total anthocyanin levels. The implication of this research was that the addition of heat increased the levels of total phenols and ORAC of juices. Addition heat, without sustained boiling, resulted in even higher levels of total phenols and ORAC in blueberry juices.