Browsing by Author "George L. Catignani, Committee Member"

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Beta-lactoglobulin Complexed Vitamins A and D in Skim Milk: Shelf Life and Bioavailability
(2003-11-18) Liu, Ying; Jonathan C. Allen, Committee Chair; George L. Catignani, Committee Member; Leon C. Boyd, Committee Member; sarah_ash@ncsu.edu, Committee Member
As reduced fat dairy products became popular in the U.S., the reduction of vitamins A and D in these products rendered a nutritional concern. Beta-lactoglobulin has been reported capable of binding fat-soluble vitamins. In order to justify the potential of beta-lactoglobulin as a stable and protective carrier for the vitamins, stability and bioavailability of beta-lactoglobulin complexed vitamins A and D in skim milk were investigated in this study. The first objective of this research was to observe the stability of vitamin A palmitate and vitamin D₃ in fortified skim milk during storage. The fortifiers included regular oil-based vitamins, Roche dry vitamins, and spray-dried and freeze-dried protein-based vitamins. Milk was stored in different packaging materials including glass test tubes, plastic bottles, and paperboard cartons. The effect of High Temperature Short Time (HTST) and Ultra High Temperature (UHT) pasteurizations on shelf life was also studied. Vitamin A palmitate and vitamin D₃ were extracted by organic solvents and assayed by High Performance Liquid Chromatography (HPLC). Results showed that vitamin D₃ was relatively stable in all milks during the 4 weeks of shelf life. Vitamin A concentrations remained stable in most HTST milk except for those fortified with Roche dry vitamin A. A significant decrease in retinyl palmitate was detected in UHT protein-based vitamin-fortified skim milk. The second objective was to test the ability of different forms of fortified skim milk to boost vitamin levels in vitamin-depleted rats. Serum, liver and bone tissues were assayed for both vitamins and calcium. Data indicated that oil-based vitamin A-fortified skim milk was as efficient as positive AIN-93G pelleted rodent diet in raising the vitamin A levels in the tissues and protein-based vitamin D₃ fortified skim milk most effectively boosted the serum 25-OH D level. In conclusion, beta-lactoglobulin complexed vitamin A palmitate is not an appropriate fortifier for UHT skim milk while beta-lactoglobulin complexed vitamin D₃ is a more stable and effective fortifier than the regular oil-based fortifier.
Effects of Muscadine Grape Products on Healthy and Type 2 Diabetic Subjects: Blood Chemistry, Antioxidant Capacity and Membrane Lipids
(2004-08-30) Banini, Akpene Esi; Brenda Alston-Mills, Committee Member; Hengameh G. Allen, Committee Member; George L. Catignani, Committee Member; Jonathan C. Alllen, Committee Co-Chair; Leon C. Boyd, Committee Co-Chair
Red wines and grape juices contain phenolic compounds with antioxidant properties that are protective against oxidative stress conditions such as hypertension, insulin resistance and Type 2 Diabetes (T2D). This study evaluated the effects of muscadine grapes processed as juice (MJ), wine (MW) and dealcoholized wine (DzW) on blood constituents, antioxidant capacity, and erythrocyte membrane lipids of free living T2D and control, non-diabetic subjects. Two Control groups, MJ- group and control without supplementation (CS); and three T2D groups, MJ, DzW and MW each consumed 150 ml of the grape product daily (except for CS) with meal for 28 days. Dietary information, anthropometry and blood sample analysis for erythrocyte membrane lipids, antioxidant capacity, glycated hemoglobin, insulin and electrolytes were carried out. Liver, renal and cardiac function tests were also evaluated. All tests performed at baseline were repeated 28 days post-treatment. Decreased levels of blood glucose and glycated hemoglobin post supplementation suggest better glycemic control, especially in the T2D- wine group. Low dietary chromium and biotin in all subjects indicate insulin inefficiency in stimulating glucose uptake. Reduced serum sodium and chloride levels among T2D- wine group after supplementation suggest reduced risk for hypertension. High folate and vitamin B12 levels in T2D- DzW indicate a favorable environment for homocysteine clearance and increased insulin sensitivity. Lowered triglyceride, total cholesterol and low density lipoprotein cholesterol in T2D taking DzW and MW suggest improved lipid metabolism. Decreased alanine aminotransferase (ALT) and aspartate transaminase (AST) in T2D- wine group indicate better insulin sensitivity and reduced risk of impaired liver function. In conclusion, T2D- wine and DzW groups exhibited improved serum lipids, ALT, AST and glutathione compared to T2D- juice group. Also, improved serum electrolyte and cardiac function in T2D- wine group, and greater responses in insulin, folate and vitamin B12 in T2D- DzW group were observed. Moderate amounts of wine and dealcoholized wine intake may therefore improve diabetic metabolic functions.
Enzyme-induced Gelation of Whey Proteins
(2005-03-16) Doucet, Dany; E. Allen Foegeding, Committee Chair; Robert M. Kelly, Committee Member; Harold E. Swaisgood, Committee Member; George L. Catignani, Committee Member
There is currently an array of whey protein hydrolysates on the market. The applications for these products include but are not limited to: improved heat stability; reduced allergenicity; production of bioactive peptides; tailoring amounts and size of peptides for special diets; and altering the functional properties of gelation, foaming and emulsification. With functional properties applications, hydrolyzed proteins offer advantages over unmodified proteins in increased solubility, heat-process stability, foaming and emulsification. Customers who are buying whey protein hydrolysates for nutritional applications (sports nutrition, enteral formulas, hypoallergenic infant formulae, etc.) are looking for products with a high degree of hydrolysis (generally >10%) and a high content in short peptides. Extensive enzymatic hydrolysis is required, preferentially with an endoprotease, in order to avoid the presence of free amino acids in the final product. However, some endoproteases (e.g. Alcalase 2.4L) produce peptides that aggregate and form a gel during the course of hydrolysis. This creates a hurdle when a high degree of hydrolysis is desired. Because the array of endoproteases commercially available is not very exhaustive, and some enzymes and hydrolysis conditions cause gelation problems, it is important to understand the gelation mechanism in order to solve it and ultimately produce hydrolysates with a high degree of hydrolysis. The first objective of this study was to compare enzyme-induced gelation of extensively hydrolyzed whey proteins by Alcalase with the plastein reaction by determining the types of interactions. The average chain length of the peptides did not increase during hydrolysis and reached a plateau after 30 min to be about 4 residues, suggesting that the gel was formed by small molecular weight peptides held together by non-covalent interactions. The enzyme-induced gel network was stable over a wide range of pH and ionic strength, and therefore showed some similarities with the plastein reaction. Disulfide bonds were not involved in the gel network. The gelation seems to be caused by physical aggregation, mainly via hydrophobic interactions with hydrogen bonding and electrostatic interactions playing a minor role. Peptides released were characterized in order to better understand this gelation phenomenon. The apparent molecular mass distribution indicated that aggregates were formed by small molecular mass peptides (< 2,000 Da). One hundred and thirty peptides with varying lengths were identified by reversed-phase high performance liquid chromatography coupled with electrospray ionization mass spectrometry. Alcalase was observed to have a high specificity for aromatic (Phe, Trp, Tyr), acidic (Glu), sulfur-containing (Met), aliphatic (Leu, Ala), hydroxyl (Ser), and basic (Lys) residues. Most peptides had an average hydrophobicity of 1-1.5 kcal/residue and a net charge of 0 at the pH where gelation occurs (6.0). Therefore, intermolecular attractive force such as hydrophobic interaction suggests the formation of aggregates that further leads to the formation of a gel. The very complex peptide system identified previously for whey proteins was simplified by using beta-lactoglobulin. Dynamic rheology, aggregation measurements, isoelectrofocusing as well as chromatography and mass spectrometry were used to understand the gel formation. A transparent gel suggesting a fine-stranded network is formed above a critical concentration of peptides while non-covalently linked aggregates appear with increasing time of hydrolysis. Extensive hydrolysis is needed for gelation to occur as indicated by the small size of the peptides. Isoelectrofocusing was successful at separating the complex mixture and nineteen main peptides were identified with molecular weight ranging from 265 to 1485 Da. Only one fragment came from a beta-sheet rich region of the beta-lactoglobulin molecule and a high proportion of peptides had proline residues in their sequence.