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Graduate Thesis Abstracts


Sensory and Consumer Anaylsis of Indigenous Vegetables: Potential for Intergration into African Americans’ Diets for Cancer Prevention
 

By Keleish A Blake-Allie, 2013, Major Professor: A. Bovell-Benjamin
The overall objective of this research was to ultimately integrate indigenous African and Asian vegetables (Armaranth, Celosia, Gboma and Long bean) in the dietary system of African Americans to reduce cancer risk.  The specific aims were to: (i) determine the moisture, ash contents and color of four African and Asian indigenous vegetables; (ii) develop a descriptive language for the vegetables Amaranth, Celosia, Gboma and Long bean; (iii) determine consumer acceptance of the indigenous vegetables (Amaranth, Celosia, Gboma and Long bean.   Moisture, ash and color were analyzed in the indigenous vegetables Amaranth, Gboma and Long bean over the duration of the study. Descriptive and consumer tests were conducted to develop a language and to determine consumer acceptance of the indigenous vegetables.  Also, a Consumer Purchase Intention questionnaire was administered to determine consumers’ willingness to purchase Amatanth, Celosia, Gboma and Long bean.  Statistical analysis was performed using repeated measures analysis of variance (RM-ANOVA), Analysis of Variance (ANOVA), Fishers’ Least Significant Difference (LSD) and Kruskal-Wallis test at (P<0.05).  Mean moisture contents for Amaranth, Celosia, Gboma and Long bean were 84.0, 84.3, 90.0 and 90.1%, respectively. The overall mean ash contents for Amaranth, Celosia, Gboma, and Long bean ranged from 2.2±0.1 to 2.8±03%.  Mean L*, a*,b* color values for the indigenous vegetables Amaranth, Celosia, Gboma and Long bean ranged from 44.2 to 48.8, -0.3 to 2.1 and 1.3 to 6.5, respectively.  A highly trained panel consisting of 14 judges developed a descriptive language of six attributes, (color, blandness, aftertaste, bitterness, tenderness and coarseness) for the indigenous vegetables and rated the intensity of the six attributes.  Overall, the dark green color was equally intense for the poultry litter (8.0), NPK (8.0) and fish protein fertilizer-treatments (8.1) for Amaranth and Celosia.  The intensity of the bland favor was rated equally intense for all treatments and all plants. A similar trend was observed for the aftertaste, except for Gboma, which had significantly (P<0.05) stronger aftertaste than all the treatments.   The bitter attribute was significantly (P0.05; 8.0±1.4) more intense in Gboma as compared to the other vegetables.  The terms/attributes developed by the trained panel in the descriptive analysis were used in hedonic scale testing.  Overall, all vegetables were liked moderately by consumers with mean acceptability score ranging from 7.2 to 7.5.  Purchase intention revealed that the majority of respondents indicated that they would definitely buy the newly introduced vegetables: Amaranth, Celosia, Gboma and Long bean.  Respondents stated that they rarely or never buy organic foods and would prefer to eat non-organic foods over organic foods.

Quality Characteristics and Microflora of a Newly Developed Sweetpotato Beverage

By, Steven Tyree Moultrie, 2010, Major Professor: A. Bovell-Benjamin
The overall objective of this research was to investigate the chemical and nutritional characteristics and microflora of a novel sweetpotato beverage (SPB) after pasteurization and during refrigerated storage (4 degrees C). The specific objectives were to (i) determine the B-carotene, total phenolics, absorbic acid, titrable acidity, pH, °Brix, ash, polyphenol oxidase, peroxidase, radical scavenging activity, °Brix/Acid ratios, phenolic/peroxidase and β-carotene/peroxidase relationships of three SPBs; and (ii) determine the aerobic plate count (APC), isolate and characterize the bacteria from the three SPBs during storage. Statistical analysis was performed using repeated measures analysis of variance (RM-ANOVA) and Fishers’ Least Significant Difference. Pearsons correlations were used to determine the relationship between phenolics/peroxidase and B-carotene/peroxidase.  The mean β-carotene contents were 487±80 and 626±80 µg/100 mL for LSP, MSP and HSP respectively. The overall mean phenolic contents for LSP, MSP, and HSP was 225±14.26, 241±14.26 and 256±14.26 mg/ mL GAE, respectively. Mean vitamin C contents for LSP, MSP and HSP were 7.4±0.14, 4.8±0.14 and 4.4±0.14 mg/100mL, respectively. Mean pH values were 4.4±0.025, 4.5±0.025, and 4.6±0.025 for LSP, MSP and HSP, respectively. The sweetpotato beverages can compete with other fruit and/or vegetable beverages, in terms of attributes such as β-carotene, phenolics, vitamin C, °Brix and pH. The sweetpotato beverages had higher microbial counts than most pasteurized beverages that were reported and the most probable pathogens were absent based on this study.

Characteristics of Anthocyanins and Phenolic Compounds in Organic and Conventional Blueberries in Selected Cultivars

By Qi You, 2010, Major Professor: B. Wang and R. Pace
Fruit and vegetables are sources of natural antioxidants. The important antioxidants in plant foods are anthocyanins, flavonoids, and other phenolic compounds. Although organic fruits and vegetables are popular among health-conscious consumers, the level of antioxidant content in organic fruit and vegetables has not been well studied. To compare the antioxidant content and determine the characteristics of anthocyanins and phenolic compounds in organically and conventionally grown blueberries, this study measured the antioxidant capacity, total phenol and total anthocyanin content, and identified and quantified the phenolic compounds and anthocyanins in blue berries with the use of High Performance Liquid Chromatography-Mass spectrometry (HPLC-MS). Four Rabbit eye blueberry cultivars were studied: Powder blue, Climax, Tifblue and Woodward. Based on the results of this study, blue berries have high total phenol and total anthocyanin contents. The antioxidant activity was also high. However, organically grown blueberries did not show significantly higher antioxidant capacity, total phenol and total anthocyanins were identified without hydrolysis. After hydrolysis, seven individual phenolic compounds were identified from nineteen HPLC-MS peaks. Further study should focus on finding better ways, other than hydrolysis, to purify the phenolic compounds in samples, so peaks can be more clearly identified and the complete profile of phenolic compounds can be delineated.

Evalution of the Metabolic Responses of Adult Zucker Fatty Rats to a Sweetpotato Starch Syrup for Diabetes Management

By Tulani R. Murphy, 2009, Major Professor: A. Bovell-Benajmin
Diabetes mellitus is a major public health problem in the United States.  One useful tool in the management of diabetes is referred to as the glycemic index (GI).Although there is growing interest in the sweetpotato [Ipomoea batas (L.) Lam] as low GI food, its impact has not been clearly established. The objectives of this research were: i) to measure glucose tolerance, weight gain, high density lipoproteins, low density lipoprotein, total cholesterol and triglyceride levels in Zucker fatty (fa/fa) rats fed a sweetpotato starch syrup for five weeks; and ii) to analyze the effects of the morphogenesis of rats’ liver, heart and kidneys. The sweetpotato starch and sweetpotato starch syrup were produced in the Food Processing and Product Development laboratory at Tuskegee University. Fifty 4-week-old adult male Zucker fatty rats were housed individually in handeling cages with free access to a standard diet and water and acclimated for 7 days.  After acclimation period, the rats were divided into six groups, distributing weights evenly throughout each group. Following an overnight fast, rats were weighed and blood samples (~0.7mL) collected from the tail vein the determine baseline blood glucose levels. Oral glucose tolerance tests were performed on rats using one of four diet tretaments: i) a 50% aqueous glucose standard; ii) maple; iii) corn; or iv) sweetpotato syrup via a 20-22 gauge oral gavage needle.

The Phytosterol Content and Fatty Acid Profile of Three Cultivars of Sweetpotato Leaves

By Aneesha A. Daniels, 2006, Major Professor: B. Wang
Cardiovascular disease, the major cause of death in the developed world, is considered to have atherosclerosis as the major underlying cause. Atherosclerosis develops slowly after many years, causing fatty plaques and stenosis that impedes proper blood flow. Hypercholesterolemia has been identified as the key factor in the etiology of atherosclerosis. Essential ω-3 and ω-6 fatty acids, found in many leafy vegetables, are responsible for many cardiovascular physiological responses including lowering blood pressure, blood platelet aggregation and smooth muscle concentration.  Phytosterols occur naturally in plants and are structurally similar to cholesterol yet have the ability to interfere with the absorption of cholesterol, thus reducing the risk of coronary heart disease.  The basic mechanism of action of phytosterols is that they can become efficiently incorporated into intestinal micelles in the lumen, displacing and reducing cholesterol absorption. The overall objective of this experiment was to determine the total lipid, phytosterol and fatty acid content in raw sweetpotato leaves of three cultivars, J6-66, W308, and N31 at three different harvest dates.Sweetpotato cultivars (J6-66, N-31 and W-308) were grown and the leaves were harvested at 78, 108 and 140 days. The 27 samples were grown at the George Washington Carver Agricultural Experiment Station in Norfolk loamy-sand soil (fine-loamy, siliceous, thermic, typic paleudult), watered twice per week, and kept free of chemicals and pesticides.  At the various collection dates, the leaves and petioles were collected, labeled, washed, freeze-dried and ground into powder to be analyzed for the phytosterol, fatty acid and total lipid content.Results showed significant differences (P<0.05) in total lipids among cultivar.  W-308 had significantly higher level of total lipid than other cultivars. Total lipid contents for all cultivars at collection date two were higher than the other collection dates.  For linolenic acid, there were significant differences between W-308 and N-31 cultivars. Additionally, there were significant differences in linolenic acid per collection date or cultivar.  Palmitic acid contents differed significantly amongst collection date, but not cultivar. The amount of β-sitosterol found in the sweetpotato leaf samples ranged between 0.30 and 3.20 mg/g.  Significantly higher β-sitosterol contents were found at collection date three for all cultivars.  There were no significant differences between W-308 and N-31 cultivars.  W-308 and J6-66, however, were significantly higher in β-sitosterol than N-31. Some results were different from previous findings on the nutrient content of sweetpotato leaves.  Differences were probably due to variations in harvesting times, parts of leaf sampled, agronomic practices, environmental conditions and season of the year. Since sweetpotato research mainly focuses on storage root production, the chemical composition of sweetpotato leaves and petioles should be further researched to determine their nutritional value.
 
The use of HPLC/MS to Identify and Quantify Phenolic Compounds of Selected Muscadine Grapes

By Paul A. Williams, 2007, Major Professor: B. Wang
An extensive research has been done with muscadine grapes in order to identify and quantify their phenolic compounds and anthocyanins. The purpose of this research was to use High Pressure Liquid Chromatography-Mass Spectrometry (HPLC/MS) to identify and quantify these phenolic compounds. Four grapes were studied in this research: 2 bronze, Higgin and Carlos, and two purple, Cowart and Jumbo. The purple samples contained more anthocyanins than the bronze samples. Among the five anthocyanins ( delphinindin, cyanidin, pelagonidin, and malvidin), three anthocyanins (delphinindin, cyanidin and malvidin) were present in high qualities. Petunidin was identified but no pelargonidin was found in the samples. The total anthocyanin content ranged from 9.44 to 14.10 mg/g for the Cowart and Jumbo samples, respectively. For the four individual anthocyanins identified, the content ranged from 9.04 to 0.88 mg/g for the cowart sample and from 7.86 to 1.29 mg/g for the jumbo sample.  Although there were many peeks from the chromatogram of phenolic analysis, none of the peaks matched with the reference compounds in retention time. However, the mass numbers of the sample did match with some of the reference compounds, but these compounds could not be confirmed. Further research may need to be conducted to identify the compounds under different conditions.

Quantification and Characterization of Residual Volatiles from a Model Sweetpotato Bread

By Jessica E. Mason, 2005, Major Professor: A. Bovell-Benjamin
The sweet potato [Ipomoea batatas (L.) Lam] is a very versatile crop that can be grown in tropical areas. It contains several nutrients such as vitamin C, protein, and carbohydrates. Because of these advantages, the sweet potato was selected by the National Aeronautics and Space Administration (NASA) Advanced Life Support (ALS) program as a candidate crop to be grown on long-term space missions. Crew health and safety is the overriding criterion when establishing standards for exposure to volatiles during space flight. In an effort to reduce the occurrence of health hazards during these missions, NASA has established exposure limits and monitoring protocols for controlling organic constituents such as volatile organic compounds (VOCs). These limits have been published and are available as Spacecraft Maximum Allowable Concentrations (SMACs). SMACs give a quantitative understanding of exposure limits to compounds emitted from natural and anthropogenic sources. However, volatile emission from the processing of sweet potato products have not yet been characterized and quantified. The objective of this research is to characterize and quantify the residual volatile constituents from model sweet potato bread. This was done by using a combination of several techniques such as Thermo gravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), Solid Phase Microextraction (SPME), Gas Chromatography Mass Spectrometry (GC-MS), and scanning electron microscopy (SEM).Twelve sweet potato breads prepared from three cultivars of sweet potato field grown, two preparations methods, and two storages times were formulated. TGA-FTIR data identified the presence of four volatiles which were carbon dioxide, carbon monoxide, methanol, and water. Results from each technique indicated that samples stored at one month and prepared with enhancers and stored at two months. SEM data revealed that the samples prepared with enhancers and stored for one month had smoother and more spherical starch granules indicating that larger surface areas increase volatile emissions. The data collected from this research could be helpful in assessing the health risk associated with exposure to violate compounds emitted during the bread making process aboard space shuttles during long-term space missions as well as provided indications for risk to humans on earth.

Influence of pH, Concentration Time, and a-Amylase on the Physical Properties and Acceptability of a Sweetpotato Syrup

By Samia Yousif Ibrahim, 2004, Major Professor: A. Bovell-Benjamin
The sweet potato [Ipomoea batatas (L.) Lam] is a feasible option for conversion into glucose syrup because of its high starch content. The overall objective of the study was to optimize previously developed sweet potato syrup. Specifically, the study determined the effect of varying pH and time at the liquefaction and concentration stages, respectively, on the moisture, refractive index, color, and yield of the sweet potato syrup. Sweet potato starch was used to produce three syrups in which the protocol remained constant, except for the pH and concentration times. At the liquefaction stage, the pH was adjusted to 6.4, 7.0 and 8.0 for Syrup A (SPSA), Syrup B (SPSB) and Syrup C (SPSC), respectively. At the concentration stage the, syrups were exposed to 35, 40 and 43 minutes of heat. The moisture contents of the syrups concentrated for 35 minutes were significantly (P<0.05) different, with SPSC having the highest moisture content. Similarly, the moisture content for SPSC was the highest when heated for 40 minutes, but lowest when heated for > 43 minutes. The mean refractive index values were similar for the syrups, ranging from 1.4 to 1.5. As the concentration time increased, the L* value decreased for the syrups, with SPSA being lightest in color at all concentration times. At all concentration times, the total syrup yield from 30 g sweet potato starch were highest for SPSC. The syrup with pH 8.0 and 40 minutes heating time, at liquefaction and concentration stages, respectively, had the most desirable RI, color and overall yield.  Secondly, the study determined the effect of the varying levels of a-amylase at the liquefaction stage on moisture, refractive index, color, Brix, and yield of the syrup. At the liquefaction stage, two volume levels of a-amylase, the total syrup yield of sweet potato starch was significantly higher (p<0.0001) than for the 3mL a-amylase level. The moisture content was highest for the 4.5 mL level of a-amylase for syrup A than syrup B. The L* values ranged from 97 to 98, and the a* value was -0.03; no significant differences were (p>0.05) were observed. The b* value, refractive index, and the Brix were significantly higher (p<0.0001) for syrup A than syrup B.   A storage study was conducted to evaluate the effect of the temperature on storage of sweet potato starch syrup. The result indicated that except for moisture there were significant differences (p<0.001) for syrup A than for syrup B.   A Storage study was conducted to evaluate the effect of the temperature on storage of sweet potato starch syrup. The results indicated that except for moisture there were significant differences (p<0.0001) between the physical properties of the syrup stored for 5.2 months at room temperature and when refrigerated at 4°C.  Thirdly, consumer test was conducted on the sweet potato Starch Syrup (SPSS) with 112 students from Drake Middle School, Auburn, Alabama, using a nine-point hedonic scale. The results indicated that there were no significant differences in liking between the sweet potato starch syrup and two commercial syrups.

Development and Characterization of Peanut Cookies 

By Aisha S. Quadeem, 2004, Major Professor: B. Wang      
To develop food products for NASA Advanced Life Support program, the present study prepared partially defatted peanut flour from field-grown and hydroponic peanut seeds and analyzed the crude protein, crude fat, moisture, and color of the peanut flour.  The cookies had reduced fat and sucrose in their formula.  The color texture, and sensory attributes of the cookies were evaluated.  The results indicated that after fat extraction, hydroponic peanut flour contained less fat than commercial and field grown peanut flowers (p<0.05).  Accordingly, hydroponic peanut flour contained higher crude protein than commercial and field grown peanut flour. In addition, peanut flours from hydroponic and field grown peanuts had darker color than commercial peanut flour with L-values for commercial, field grown, and hydrophobic peanut flour at 81, 74, and 76, respectively (P<0.05).  The results from sensory evaluation indicated that after fat and sucrose reduction, cookies containing partially deffated peanut flour had similar overall acceptance score to control.  Other sensory attributes including aroma, sweetness, and hardness showed similar trend to the overall score, but cookies with high fat content scored higher in aftertaste, mouthfeel, and color than cookies with low fat.  Instrument analysis indicated that cookies with the lowest load (treatment nine with lowest fat and sucrose content) had the highest acceptance score from sensory evaluation.  Further, cookies with the lightest color had the highest acceptance score in color. This result could help NASA to develop palatable food products using peanut as ingredient.  The results could also be used by food companies to produce peanut cookies using peanut flour, a by-product from oil production.

Physical Properties and Packaging Performance of Edible Films from Peanut Protein 

By Warren W. Wells, Jr., 2003, Major Professor: B. Wang

Research on edible film is expected to grow because they have the potential to reduce packaging waste and environmental contamination. One of the common materials for fabrication of edible film is protein from various sources.The objective of this study was to improve the formula and processing parameters for peanut protein film with different plasticizer combinations, and to examine the packaging performance of the peanut protein film in preserving the color, reducing moisture penetration, and preventing the texture deterioration of sweetpotato cookies.Peanut protein isolate based edible films containing mixed plasticizers were prepared using film-casting technique to determine the optimal formula to be used for storage. Eight films were prepared with a total of five g of glycerol/ sorbitol used with their ratio varied to obtain the optimal combinations. The packaging performance of the peanut protein film was tested on sweetpotato cookies over a 30-day period with five different time intervals. The films were evaluated for its breaking strength and displacement to identify the films that provided breaking strength of 8N-14N and displacement 8mm-26mm selected for their performance in protecting sweetpotato cookies. The cookies were tested for their change in color, weight, and breaking force to evaluate the peanut protein film capability as a compatible packaging material. The displacements of the PPI-based films combination were higher than the films containing a single plasticizer. The film with plasticizer of glycerol/sorbitol at a ratio of 4/1 had a breaking strength of 9.7N and 26 mm displacement (p<0.05). The films preserved the color of sweet potato cookies during storage. In addition, the peanut protein film was able to maintain the firmness of sweet potato cookies. The results of this study demonstrated that the peanut protein film has the potential to preserve food products such as cookies. This may have implications on NASA’s future space missions.

Production and Evaluation of a Hydroponic Sweetpotato Bread Using Macroscopic, Spectroscopic andThermal Analyses

By Jeffrey L. Greene, 2003, Major Professor: A. Bovell-Benjamin
The sweet potato [Ipomoea batatas (L.) Lam] is an important crop in many parts of the world. Sweet potatoes are very diverse and adaptable with the ability to grow in tropical areas. Sweet potatoes contain carotenoids, carbohydrates, potassium, protein, fiber and vitamin A and C. A significant amount of carotenoids in sweet potato is β-carotene. Sweet potatoes can be mixed as flour with other staples to make dishes such as bread, pancakes, and vermicelli, or with other foods in casseroles or stews.The National Aeronautics and Space Administration (NASA) Advanced life support (ALS) system has selected the sweet potato as a candidate crop to be grown on long-term space missions. Tuskegee University’s Center for environmental systems for Human Exploration of Space (CFESH) is funded by NASA to develop food candidates for use in both vehicle and planetary food systems because they are a good source of carbohydrates. A sweetpotato bread (SPB) is a feasible option for adding variety and flavor to the diets of astronauts and different consumer groups on Earth. Additionally, a SPB would add β-carotene to the diets of astronauts and consumers on Earth. The Overall objective of this research was to develop an affordable, consumer- acceptable sweetpotato bread. The specific objectives were to i) develop formulations for a SPB using varying combinations of sweetpotato flour and whole- wheat flour; ii) characterize selected macroscopic properties (proximate composition, weight loss and moisture loss, texture, loaf volume, color, sensory characteristics and consumer acceptance) of the SPB using instrumental measures, descriptive analysis and hedonic testing; iii) view selected morphological and suprastructural properties of the SPB using spectroscopic (Scanning Electron Microscopy, X-Ray Diffraction) and thermal techniques (Differential Scanning Calorimetry); and iv) characterize and quantify the residual volatiles generated during baking of the sweetpotato bread. The formulations were 50% hydroponic sweetpotato flour (HSPF)50% whole- wheat flour (WWF), 55% HSPF/ 45% WWF, 60% HSPF/40% WWF, and 65% HSPF/ 35% WWF. Overall, the HSPB65:35 had the highest moisture, β-carotene and L*, a*, and b* values over the five day storage period. The HSPB50:50 had lowest moisture, β-carotene, and L*, a*and b* values; however, it had the highest loaf volume among the HSPBs. The SEM showed that the HSPB50:50 had the highest amount of gelatinization during storage. XRD patterns showed amorphous peaks indication the freshness of the HSPBs. DSC helped confirm that HSPB50:50 had the most gelatinization compared to the other breads. SEM, XRD, and DSC provided a general picture of the staling properties of the HSPB. The volatiles released from the HSPBs were ketones, carbon dioxide, alkenes, and water. Twelve sensory attributes that could be used to differentiate the appearance, texture, and flavor of the HSPB and in the design of the consumer tests. Consumers liked the aroma of HSPBs, however further testing should be done among middle- aged and older consumers.

Development of a Meat Analog using Peanut Protein 

By Edward L. Parmer, Jr., 2003, Major Professor: B. Wang
The objectives of this study were to develop a formula and the process parameters for an acceptable meat analog using a single-screw extruder.  The effects of fed moisture, screw-speed and barrel temperature on meat analog characteristics were studied the effect of change caused by varying these parameters on the meat analog’s characteristics were determined by measuring its moisture content, expansion index, water absorption index, breaking force, protein solubility and color.  In addition, this study compared the meat analog’s from field-grown and hydroponically grown peanuts texturized with extrusion technology.The moisture content of the ingredients has a significant effects on the moisture content, breaking force, water absorption index, expansion index and Hunter L values of the texturized meat analogs (p<0.05).  Variation in screw speed caused changes in the expansion index and moisture content of the meat analogs (p<0.05). Increases in barrel temperatures led to a significant change in the moisture content, breaking force, water absorption index, and expansion index of meat analogs (p<0.05).  This study also found that hydroponically grown peanut flour had a significant effect on extrudate moisture, breaking force, water absorption index, expansion index, and color of meat analogs (p<0.05).  As a result of the conditions established in this study, acceptable meat analog using a peanut-flour-soy protein isolate mixture can be successfully produced.







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Department of Food and Nutritional Sciences, 204 Campbell Hall, Tuskegee University, Tuskegee, AL 36088 
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