Life Sciences Commons^™

Analysis Of Antioxidant Synergism And Its Mechanisms In Different Food Systems, Ipek Bayram

Doctoral Dissertations

Lipid oxidation results in off-flavors, toxic aldehydes, and co-oxidation of proteins and color compounds. Combining antioxidants to achieve synergistic interactions has been practiced for decades to improve oxidative stability. Nevertheless, synergism mechanisms have been poorly understood and rarely studied. This dissertation examines the mechanisms of antioxidant synergism in a model system with α-tocopherol (α-TOC) and myricetin (MYR). The interactions between α-tocopherol and taxifolin (TAX) were also tested because it has structural similarities to myricetin but has a higher redox potential. The first part of this research focused on the antioxidant interactions between α-tocopherol and myricetin in stripped soybean oil-in-water emulsions …

Antioxidant Synergism Between Α-Tocopherol And A High Phosphatidylserine Modified Lecithin, Harshika Arora

Masters Theses

Phospholipids, such as phosphatidylserine (PS) have been shown to work synergistically with tocopherols to extend the shelf life of oil-in-water emulsions. However, the high cost of PS prevents it from being used as a food additive. This work investigated the potential use of a high PS enzyme-modified lecithin to be used along with α-tocopherol to extend the lag phase of oil-in-water emulsions stabilized using Tween 20. Phospholipase D from Streptomyces sp. and L-serine were used to modify lecithin to increase PS concentration. Enzyme activity was optimized as a function of pH and temperature using a high PC soybean lecithin. The …

Antioxidant Combination Of High Phosphatidylserine (Ps) Lecithin With Mixed Tocopherol In Soybean Oil-In-Water Emulsion: Effect Of Ph And Salt, Princy Agnihotri

Masters Theses

Lipid oxidation is one of the major challenges faced by the food industry as it contributes to the loss of nutritional quality and loss of flavor in food products. Studies have shown that naturally occurring phospholipids like phosphatidylserine (PS) and phosphatidylethanolamine (PE) can regenerate oxidized tocopherols and help delay the lipid oxidation in bulk oils and oil-in-water emulsions. Since consumers desire simpler and cleaner labels, without chemically synthesized antioxidants, this research is of great interest. The combination of PS and PE with tocopherols has already been studied. However, PS was a better antioxidant in combination with tocopherols in the oil-in-water …

Application Of Flow Cytometry As Novel Technology In Studying Lipid Oxidation In Oil-In-Water Emulsions, Peilong Li

Masters Theses

The body of literature on the impact of emulsion particle size on oxidation rates is unclear. This could be because emulsions are typically polydisperse and the oxidation rate of individual droplets is impossible to discern. Flow cytometry is a technique for studying individual cells and their subpopulations using fluorescence technologies. It is possible that individual emulsion droplets could also be characterized by flow cytometry as a novel approach for studying lipid oxidation. Typical emulsion droplets are too small to be visualized by flow cytometer, so emulsions were prepared to have droplets > 2 μm; weighting agent and xanthan gum were added …

Strategies To Increase Lipid Oxidative Stability Of A Low Moisture Cracker System, Thanh Vu

Doctoral Dissertations

The first study focuses on impact of solid fat content (SFC) on lipid oxidation and micro-structure of low moisture crackers. A series of fats were formulated to have varying SFC but the same linoleic acid (18:2) and tocopherol compositions so the fats had similar susceptibility to oxidation. A comparison of the oxidative stability of interesterified soybean oil and a blend of fully hydrogenated soybean fat and soybean oil, the interesterified fat (13.7% SFC at 55 ^oC) resulted in a more oxidatively stable cracker than the fat blend (17.4% SFC at 55 ^oC). Similarly in crackers were made from …

Reactive Carbonyl Compounds: Their Control And Consequences In Foods, Michael Freund

Masters Theses

Polyunsaturated omega-3 fatty acids (n-3 PUFAs) have been suggested to reduce risk for multiple diseases but animal studies on the beneficial effects of n-3 PUFAs are conflicting, possibly due to the presence of toxic lipid oxidation products in the oils used in these studies. In order to provide guidance for future research in n-3 PUFA supplementation, this study researched lipid oxidation and its inhibition in an animal feed system enriched with fish oil. Different storage conditions were tested, and it was found that samples stored at room temperature or above were at significant risk for oxidation with lag phases of …

Tocopherol Regeneration By Phospholipids In Soybean Oil-In-Water Emulsions: Effect Of Tocopherol Homologue And Emulsifier Type, Gautam Samdani

Masters Theses

Phospholipids can regenerate oxidized tocopherols and help delay lipid oxidation. The impact of emulsifier type, tocopherol homologue and phospholipid head group on tocopherol-phospholipid interaction was investigated in this study.

Three µmol tocopherol/kg emulsion and 15.0µmol/kg emulsion of PE or PS were dissolved in oil and emulsions were prepared. Tween 20 or bovine serum albumin(BSA) was used as emulsifier and the continuous phase contained 10mM imidazole/acetate buffer at pH 7. Lipid hydroperoxides and hexanal were measured as lipid oxidation products and the lag phase was determined. With Tween 20 as the emulsifier, α and δ-tocopherol had a hexanal lag phase of …

Understanding The Impact Of Oxygen Concentration And Active Packaging On Controlling Lipid Oxidation In Oil-In-Water Emulsions, David Johnson

Doctoral Dissertations

Consumer concern over synthetic food antioxidants have led researchers to seek alternative natural, or ‘clean’ label, solutions to prevent lipid oxidation. Unfortunately, natural antioxidants are often not as effective as their synthetic counterparts. As a result, there remains a need to develop active packaging strategies and maximize current antioxidant strategies in food applications. Active packaging, or packaging that has a function beyond being an inert barrier, is an attractive strategy to limit lipid oxidation in foods. Active packaging performs the work of an antioxidant without appearing on the package label. The work presented here builds upon active packaging development as …

Utilization Of Natural Emulsifiers And Their Derivatives To Formulate Emulsion-Based Delivery Systems For Hydrophobic Nutraceuticals, Cansu Gumus

Doctoral Dissertations

There is increasing consumer demand for food products that are more natural, sustainable, and environmentally friendly. Industry has responded by trying to identify natural alternatives to synthetic functional ingredients within these products. In this study, the ability of Maillard conjugation products, and several legume proteins were investigated to act as nature-derived or natural emulsifiers in oil-in-water emulsions fortified with hydrophobic nutraceuticals. Casein-coated oil droplets enriched with lutein were highly unstable to flocculation near their isoelectric point due to the reduction in electrostatic repulsion. However, casein-dextran-coated droplets were stable, which was attributed to strong steric repulsion by the dextran moiety. The …

Utilizing Nutritive Sweeteners To Control Lipid Oxidation In Low Moisture Baked Goods, Samantha Vieira

Masters Theses

In this study, we determined the effect of nutritive sweeteners at 0 to 0.50 moles/kg on lipid oxidation in a model cookie system. Confocal microscopy using Bodipy 493 as a fat soluble dye showed that the fat formed a continuous phase surrounding the starch granules regardless of sugar type. The impact of glucose concentration on lipid oxidation was monitored by lipid hydroperoxides and headspace hexanal during storage at 55°C. Low concentrations of glucose (0.09) were strong inhibitors. At equal molar concentrations, reducing sugars (glucose and fructose) inhibited lipid oxidation, greater than a two months increase in lag phase compared to …

Impact Of Surface Active Minor Components On Physicochemical Properties Of Association Colloids And Lipid Oxidation In Bulk Oil, Ketinun Kittipongpittaya

Doctoral Dissertations

Lipid oxidation is a great concern for food manufacturers and consumers as it negatively impacts not only food quality and nutritive values of food lipids, but also consumer health. Lipid oxidation in bulk oil is impacted by chemical factors, such as, prooxidants and antioxidants, and is also related to the existence of physical structures. Bulk oils contain a variety of surface active minor components which are able to form physical structures known as association colloids. These physical structures create oil-water interfaces which seem to be an important site where lipid oxidation occurs in bulk oil. Thus, this research focused on …

Strategies To Improve The Performance Of Antioxidants In Oil-In-Water Emulsions, Atikorn Panya

Open Access Dissertations

Due to the limited number of approved antioxidants for food applications, several alternative strategies to improve antioxidant performance have been developed by focusing on synergistic antioxidant interactions. Susceptibility to lipid oxidation in food systems is the result of the summation of antioxidative and prooxidative mechanisms. Understanding the sometimes paradoxical behavior of antioxidants and prooxidants is a vital key to design synergistic antioxidant systems suitable for particular foods. This research focused on 3 main strategies to improve the performance of antioxidant activity in oil-in-water emulsions.

The first part of this research has been focused on inhibition of lipid oxidation by a …

Antioxidant Distribution And Effectiveness In A Model Muscle System, Ann T Ballesteros

Doctoral Dissertations 1896 - February 2014

Gallic acid esters (GAE) of varying alkyl chain length were used to determine how antioxidant physical location and partitioning influence hemoglobin-catalyzed lipid oxidation. Specific GAE used were propyl gallate (PG), octyl gallate (OG), and lauryl gallate (LG). GAE partitioning experiments were performed with either isolated cod muscle membranes or washed cod muscle, which primarily contain polar membrane lipids and myofibrillar proteins. Canola oil was used in some experiments to determine how neutral lipids impact partitioning behavior. GAE distribution was determined spectrophotometrically in the recovered membranes, aqueous phase, and oil layer after employing differential centrifugation. Oxidation was monitored by measuring thiobarbituric …