Browsing by Author "Dr. Van-Den Truong, Committee Member"

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Characterization of the Glycemic Index of Raw and Thermally Processed Sweet Potatoes (Ipomea batatas L.)
(2008-08-13) Corbitt, Alexis Danielle; Dr. Van-Den Truong, Committee Member; Dr. Leon C. Boyd, Committee Member; Dr. Jon C. Allen, Committee Chair
Diabetes mellitus is one of the more common and serious chronic diseases across the globe. There are 20.8 million children and adults in the United States, or 7% of the population, who have diabetes. While an estimated 14.6 million have been diagnosed, 6.2 million people are unaware that they have the disease. Type-2 non insulin-dependent diabetes mellitus diabetes (NIDDM), formerly adult-onset diabetes, is a disease that occurs when the body produces enough insulin but cannot use it effectively. This form of diabetes has primarily been observed to develop in adults over the age of 40, but is gradually becoming a threat across all age groups. About 90% to 95% of people with diabetes have type 2; of which 80 percent are overweight. Diabetes is a life-long disease, but it can be self-managed if people take responsibility of their daily care. Through diet management, exercise, self-testing of blood glucose and in many cases oral medication and/ or insulin, people with diabetes can assist their bodies to keep blood glucose near normal levels. The objective of our study was to investigate the short term glycemic effect of Beauregard sweet potato impomea batatas in normal subjects through measuring the glucose response of sweet potato with and without skin, and of skin alone, in comparison with the more commonly consumed white potato. The study investigated the decrease in glycemic response of white potato vs. white potato plus Caiapo, an antidiabetic acidic glycoprotein component in Japanese sweet potato cultivars. The first study focused on C-peptide and insulin analysis via ELISA (ALPCO Diagnostics) from subjects at 0, 60, and 120 minutes after consumption of potato samples. Glucose levels were measured at times 0, 30, 60, 90, 120 minutes post prandially with glucometers (Freestyle). These data illustrated that differences in insulin, C-peptide response due to potato were constant over time resulting in graph parabola trends similar to glucose response. The comparison of C-peptide, serum insulin, and glucose response showed that the mechanism for the hypoglycemic effect in sweet potato or Caiapo is not due to improved insulin production, response to blood glucose, or increased insulin uptake by target cells. The study suggested that the blood glucose lowering effects occur in the small intestine (duodenum) by retarding absorption of glucose to the bloodstream. The subsequent study investigated the thermo-stability, through cooking, of the low glycemic index effect previously determined in Beauregard sweet potato by measuring the glycemic index after baking at 375o F for 1 hour, steaming at 100o C for 45 minutes, dehydration at 40o C overnight, and microwaving for 5 minutes. Participants consumed 25g of available carbohydrate, determined through AOAC proximate analysis of lipid, ash, moisture, and total dietary fiber levels in each preparation method. Comparing the heat treatments (steaming, baking, dehydrating, and microwaving) of Beauregard sweet potato skin and flesh illustrated the extent to which cooking affects the glycemic index. Results showed that steamed skin, baked skin, and dehydrated flesh do not have statistically different glycemic indices (p> 0.05) from those of raw sweet potatoes (n=12). Dehydrated sweet potato flesh, along with the aforementioned cooked sweet potatoes, retained the low glycemic index of raw sweet potatoes. The glycemic index of steamed flesh elevated to that of a medium glycemic index food. Baked and microwaved flesh also elicited blood glucose responses to those of medium glycemic index foods. This information will lead to further understanding of preferred foods for diabetics to assist in blood glucose management. Understanding the glucose response and glycemic index elicited by NC sweet potatoes will improve recommendations for their health promoting properties, such as reducing the risk of diabetes or insulin resistance.
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.
Effect of pepsin hydrolysis on amylase activity and lack of amylase inhibitory activity of sweet potato protein
(2008-12-02) Patterson, Katherine Worth; Dr. Van-Den Truong, Committee Member; Dr. Sarah Ash, Committee Member; Dr. Jonathan C. Allen, Committee Chair
Caiapo, an extract of Japanese white-skinned sweet potato, has been shown to possess antidiabetic properties. Caiapo treatment has been associated with a decrease in fasting plasma glucose, an increase in insulin sensitivity, and a decrease in HbA1c. A 22 kDa acidic glycoprotein has been isolated and deemed the active component of Caiapo. Beauregard sweet potatoes, one of the most common commercial cultivars in the United States, have been shown to elicit a low glycemic response and may possess antidiabetic properties similar to Caiapo. Protein band patterns of Caiapo and protein isolated from Beauregard sweet potato were found to be almost identical. Inhibition of pancreatic amylase by sweet potato protein was proposed as a possible mechanism for the low glycemic response to sweet potatoes because the addition of Caiapo to white potato decreased the glycemic response while the addition of Caiapo to glucose did not decrease the glycemic response. The first objective of this study was to determine the most efficient method for extracting protein from Beauregard sweet potato. Protein in solution after homogenization with buffers of varying concentrations of sodium phosphate (0.05 M and 0.025 M) and sodium chloride (0.3 M, 0.2 M, and 0.1 M) was compared to homogenization with distilled water by BCA assay. The concentration of protein in solution was similar for all buffers. Protein in solution after precipitation of protein with calcium chloride and resuspension was also compared by BCA assay. The highest concentration of protein in solution was achieved with the use of the 0.05 M sodium phosphate and 0.1 M sodium chloride buffer, however, none of the protein concentrations were statistically different. The second objective of this study was to determine the effect of digestive conditions on sweet potato protein. In order for a protein to inhibit pancreatic amylase in the small intestine the active portion of the protein must not be destroyed by the acidic conditions of the stomach or pepsin digestion. Sweet potato protein was subjected to pepsin digestion under acidic condition and then run on a gel next to protein not subjected to digestive conditions. Proteins resistant to pepsin digestion were found in Beauregard sweet potato flesh, peel, and leaf. The third objective of this study was to quantify the native amylase activity of Beauregard sweet potato protein. Protein extracted from the flesh exhibited higher amylase activity (32.7 Â± 5.93 units/mg protein) than protein extracted from the peel (13.0 Â± 1.12 units/mg protein). Digestion with pepsin eliminated amylase activity in the flesh (0.013 Â± 0.812 units/mg protein) and peel extracts (0.609 Â± 0.795 units/mg protein). No amylase activity was found in the leaf extract (-1.40 Â± 0.469 units/mg protein) or the leaf extract treated with pepsin (-0.625 Â± 0.179 units/mg protein). The fourth objective of this study was to determine if proteinaceous amylase inhibitors are present in Beauregard sweet potato. The amylase activity of pancreatic amylase and sweet potato protein were determined separately and then in combination by measuring the degradation of starch over time with a dinitrosalicylic acid (DNS) reagent. DNS reacts with sugar reducing ends to produce a compound that absorbs at 540 nm. The amylase inhibitory activity was calculated by subtracting the sum of the individually determined pancreatic and sweet potato amylase activities from the amylase activity of the combination determined experimentally. Amylase inhibitors were not apparent in any of the fractions.
Evaluation of the Importance of Enzymatic and Non-enzymatic Softening in Low Salt Cucumber Fermentations
(2006-03-13) Maruvada, Rashmi; Dr. Roger F. McFeeters, Committee Chair; Dr. Van-Den Truong, Committee Member; Dr. Allen E. Foegeding, Committee Member
Retention of a firm, crisp fruit texture is a major consideration for pickled vegetables including pickles made from fermented cucumbers. Cucumbers fermented in low salt (3% or less NaCl) without added calcium soften rapidly. However, it is not clear if softening of cucumbers in low salt occurs as a result of enzymatic or non-enzymatic mechanisms. The objective of this research was to assess the relative importance of non-enzymatic and enzymatic reactions in cucumbers in the softening that occurs when cucumbers are fermented and stored at a low salt concentration. Fermentation of cucumbers in 6.0% NaCl plus 18 mM calcium maintained firmness better than any treatment with reduced salt. Heat treatment of cucumbers sufficient to inactivate cell wall degrading enzymes before fermentation helped reduce firmness loss during fermentation and storage. However, heat treatment of cucumbers after fermentation did not prevent firmness loss during storage at 30°C. This suggested that reactions that resulted in softening of the cucumber tissue during storage had occurred during the fermentation period and that heating after fermentation could not prevent those changes. Polygalacturonase activity could not be detected in the cucumbers used in these experiments. α-D-galactopyranosidase and β-D-glucopyranosidase lost their activity completely in cucumbers blanched at 65°C. Other enzymes detected in the cucumbers that hydrolyzed p-nitrophenylglycosides lost ~60 to 80% of their activity at this blanch temperature. Pectinesterase retained over 70% of its activity in cucumbers blanched at 65°C. Pectinesterase along with all of the glycosidases detected in fresh cucumbers lost all detectable activity when cucumber slices were blanched at 85°C. At equal ionic strength, α-D-galactopyranosidase and β-D-galactopyranosidase were inhibited to a greater extent by calcium ions than sodium ions. However, for β-D-glucopyranosidase, the inhibition was dependent primarily on the ionic strength of the solution. During the first week of fermentation in 1.75% NaCl, there was a complete loss of activity of all the glycosidases assayed. The fact that cucumbers heated sufficiently to inactivate all the enzymatic activities measured and fermented at a low salt concentration lost firmness compared to cucumbers fermented in 6% salt with 18 mM calcium chloride showed that non-enzymatic reactions were important in low salt softening. In three of four lots of cucumbers fermented there was additional softening if the cucumber tissue did not receive a heat treatment. This suggested that enzymatic reactions can also contribute to the softening that occurs during fermentation and storage of cucumbers at low salt levels. However, it was not possible to associate softening with specific enzymatic reactions.