Recipient Organization
RUTGERS, THE STATE UNIVERSITY OF NEW JERSEY
3 RUTGERS PLZA
NEW BRUNSWICK,NJ 08901-8559
Performing Department
Food Science
Non Technical Summary
This project is determining molecular details of how lipid, protein, and antioxidant reactions are involved in oxidative degradation of foods, and then using this information to develop innovative solutions and more effective stabilization strategies to maintain food sensory and nutritional quality while limiting or blocking formation of toxic products.This research is critical because, oxidative degradation is the greatest chemical threat to food shelf life, quality, safety, and wholesomeness. Oxidation leads to loss of palatability and sensory qualities (flavor, aroma, texture, color), destruction of critical nutrients, and potential formation of toxic products. Preventing oxidation is a key hurdle and significant cost for the food industry, and it causes loss of millions of tons of food each year. Traditional practices of just adding synthetic antioxidants for control are not working in contemporary foods reformulated with high polyunsaturated fatty acids for health, largely because oxidation in complex food systems involves more molecules than just lipids.This research is novel in addressing in detail our outdated understanding of lipid oxidation and our limited knowledge of total food oxidation. Nearly all analyses in industry or research concentrate on how fast a food oxidizes while ignoring how it oxidizes and what types of damage results. Current analyses miss key lipid oxidation products and do not account for broadcasting oxidation to other molecules, particularly proteins. Established dogma that antioxidants only quench lipid oxyl radicals overlooks reactions with other lipid oxidation products and other food molecules that divert antioxidant actions in ways that may be both protective and detrimental. This project will provide detailed fundamental information to unravel the complex molecular changes involved in oxidative degradation of foods and then integrate this knowledge to learn what factors most actively drive oxidation in foods, what products must be analyzed to most accurately measure food degradation, how antioxidants interact with food molecules, why natural antioxidants don't always work in foods, how best to use natural antioxidants and which ones are most effective, and more.This new information about how oxidations occur, what products are generated, and how damage may be diverted or blocked is obtained by studying reactions of unsaturated lipids alone and in combination with food proteins and/or antioxidants in model systems under controlled conditions, and many products are measured over time to determine how fast oxidation occurs and what molecular changes occur under different conditions. We start studies with pure molecules in clean model systems to provide simple reactions where molecular products are easier to analyze and identify accurately with minimal side reactions. Integrating results here allows us to develop reaction maps and identify arrays of products that provide key markers for degradation of lipids, proteins, and antioxidants under different conditions. These molecular markers can then be singled out among thousands of products in real foods to diagnose how oxidation occurs and what damage results. Analyzing these markers in studies extended to foods can suggest important intervention points and allow us to target specific reactions to increase food stability by formulation revisions, processing modifications, and selective antioxidant use.
Animal Health Component
10%
Research Effort Categories
Basic
80%
Applied
10%
Developmental
10%
Goals / Objectives
This project seeks to elucidate lipid, protein, and antioxidant reactions involved in oxidative degradation of foods, and then to use this information to contribute innovative solutions and devise more effective strategies for limiting and controlling oxidative degradation in foods.The overall goal of this program and all of its sub-projects is to provide new advanced fundamental knowledge about the chemistry of lipid oxidation, protein oxidation, and antioxidant actions of phytonutrients, as well as the interactions of these processes, and then integrate this information to develop more effective strategies to prevent and control oxidative deterioration of foods, thereby maintaining high levels of sensory quality, functionality, safety (freedom from toxic products), and nutritional value.SPECIFIC OBJECTIVES:1. Continue studies of alternative pathways of lipid oxidation, focusing on pathway and product shifts induced by lipid structure (mono vs polyunsaturated fatty acid methyl esters vs triacylglycerols/oils) and reaction conditions (bulk oil vs dispersed on molecular surfaces vs emulsions). Give special attention to tracking epoxides (toxic and potential precursors of previously unidentified products) and hydroxy lipids (markers of pathway shifts and product not previously measured) and to identifying products that have been previously ignored.2. Determine roles of antioxidants in lipid oxidation - do phenols just quench lipid radicals, or do they also shift oxidation pathways and product distributions? Can such shifts explain apparent pro-oxidant behaviors of high concentrations of phenols? Can antioxidant reactions be used to block formation of products known to be toxic?3. Determine reactions involved in antioxidant interactions with proteins. Distinguish protein oxidation from heat and shear processing stresses vs lipid oxidation and determine whether any of this damage can be limited or repaired by antioxidants.4. Determine interactions among antioxidants, oxidizing lipids, and proteins in mixed systems. Do antioxidants limit only lipid oxidation, or do they also protect proteins against degradation? Does protein protection interfere with lipid protection by antioxidants, are the two actions parallel and independent, or are they complementary and synergistic?5. Integrate results from these studies to develop improved stabilization approaches for lipid-containing foods.
Project Methods
EffortsAlternative pathways of lipid oxidationTo follow pathway/product shifts induced by lipid structure, high purity methyl linoleate, methyl oleate, and their respective triacylglycerols are incubated in 10 ml headspace vials at different temperatures and headspace oxygen in the dark with shaking. Samples are withdrawn periodically and analyzed for lipid oxidation products --conjugated dienes, hydroperoxides, epoxides, non-volatile carbonyls, alcohols, and volatile products. Length of incubation varies with how fast and how extensively the lipid oxidizes.Analyses include both class assays for quantitation and by separation of total oxidation products for determination of non-volatile product profiles and identification of individual products. Parallel samples incubated identically are analyzed by GC-MS for volatile products.To determine effects of matrix, the same lipids are incubated on filter paper or microcrystalline cellulose to model dispersion in thin films on foods, and also in emulsions. The goal here is to determine specific effects of matrix and high water on lipid oxidation pathways and product distributions, although kinetic data will be collected in the process. Samples are incubated as initial pure lipid studies, and are analyzed periodically after extraction of the lipids.Role of antioxidants in lipid oxidationOleic and linoleic acid methyl esters are incubated as described above in the absence and presence of antioxidants. Initial studies will test effects of α-tocopherol and mixed tocopherols at 100, 500, and 1000 ppm. Samples will be withdrawn periodically, then product distributions will be analyzed directly by normal phase HPLC with ultraviolet and corona discharge detection as well as by chemical assays of each product class to track shifts in product distributions. Subsequent studies will test effects of other antioxidants frequently used in foods but with a range of structures and redox potentials to identify structural features associated with low vs high reactivity and specificity.Protein oxidation from processing stresses vs lipid oxidationFull experimental details cannot be provided here because this study is being funded by a company. However, to provide a general picture, several food proteins that can be obtained pure in large quantities are subjected to heat and shear stress then analyzed by EPR to detect free radical formation, by HPLC to detect peptide fragmentation and crosslinking patterns, and by chemical assays to quantitate specific amino acids oxidized on the proteins. This will establish damage caused by processing stresses. The same proteins will then be incubated with oxidizing lipids and analyzed periodically to track development of protein oxidation that parallels measured lipid oxidation. Damage patterns and kinetics will then be compared to assess whether oxidizing lipids augment the same damage caused by processing or add a second layer of different damage and to also determine which damage affects food quality most extensively.Interactions among antioxidants, oxidizing lipids, and proteins in mixed systems.Each protein experiment described above is repeated with α-tocopherol to test ability of antioxidants to protect proteins against processing and oxidative stress. Lipid oxidation, protein oxidation, and tocopherol transformation will be measured in a three-way system containing oxidizing lipid, protein, and antioxidant to track competitions among the interactions and determine reaction shifts that may result when all three molecules are present.Evaluation, Milestones, and Indicators of SuccessThe key output from this project will be new data and its use, the major indicator of the success in generating this new information will be publication of scholarly research papers and chapters and acceptance of papers for presentation and scientific meetings, both of which require peer review.An additional indicator of success may be ability of the research results to attract research collaborations from industry and to support additional federal research grants, although both of these are affected by factors unrelated to quality and relevance of the research.