Location: Functional Foods Research
2019 Annual Report
Objectives
Objective 1. Enable new methods using organogels and alternative oil structuring agents to generate commercial zero trans fat, low saturated fat margarines, shortenings, confectionary fats, and other lipid ingredients.
Sub-Objective 1.A. Investigate and optimize the physical, rheological, and sensory properties of edible organogels.
Sub-objective 1.B. Evaluate the effect of organogels on the properties of structured fats composed of either modified fatty acid composition vegetable oils or fully hydrogenated soybean or cottonseed oil with vegetable oils.
Objective 2. Enable new commercial delivery systems using natural antioxidant technologies to protect frying oils, polyunsaturated oils, and bioactive lipids.
Sub-Objective 2.A. Evaluate the activity of naturally occurring antioxidants and antioxidant combinations for protection of frying oils and fried foods.
Sub-objective 2.B. Evaluate antioxidants or natural antioxidant extracts for protection of polyunsaturated and omega-3 oils and bioactive lipids.
Sub-objective 2.C. Investigate new delivery systems for antioxidants, omega-3 oils, and bioactive ingredients.
Objective 3. Quantitate and evaluate bioactive ingredients including antioxidants and bioactive lipids in commodity and non-commodity crops as well as in food and agricultural waste processing streams.
Approach
In order to tackle health issues facing the nation including obesity, heart disease, and diabetes, nutritional experts are urging U.S. consumers to limit their consumption of both saturated fats and trans fats from hydrogenated oils, and to eat a diet high in fruits, vegetables, and whole grains, in order to obtain the added benefits of the bioactive food constituents found in these foods. Food manufacturers, restaurants and bakeries are looking for alternatives to hydrogenated vegetable oils or imported palm oil that have the stability necessary for frying, or the functionality needed for margarines and shortenings. U.S. commodity vegetable oils are low in saturated fats and high in healthy polyunsaturated and monounsaturated fats. However, without hydrogenation, the majority of these oils are not stable enough for frying and do not have the proper functionality for margarines and shortenings.
The first objective of this project plan is to develop alternative methods of structuring oils in order to solve the problem of functionality for margarine and shortening applications. Low concentrations of natural, inexpensive ingredients, will be used to form organogels with liquid oils. Physical and rheological characteristics of organogels will be fully investigated and test margarines and shortenings will be developed from organogels with desirable physical and rheological properties. These will be further tested in food applications for creaming, aerating, and structuring ability, as well as sensory quality.
The second objective of this plan is to develop natural antioxidant systems to protect polyunsaturated fats and bioactive lipids from oxidation and degradation in frying and in food systems, in order to extend the shelf-life and healthfulness of lipids and foods, and to replace synthetic antioxidants. Antioxidants will be tested for activity in commodity oils during frying, in order to extend the fry life and prevent oxidation products from forming. Potential antioxidants will also be tested for their ability to extend the oxidative stability and shelf life of model food systems, such as in oil-in-water emulsions, and in whole grain food products. The potential antioxidants will also be compared to synthetic antioxidants.
The third objective of this research is to analyze byproducts of food and agricultural processing for valuable bioactive lipids and/or antioxidants, in order to develop new ingredients from these products, and to reduce waste. Spent coffee grounds, blueberry pomace, and various pulse processing fractions will be extracted and analyzed for bioactive lipids and water soluble antioxidants.
Progress Report
As progress towards Objective 1, research over the past FY has focused on oleogels (also known as organogels) made with small amounts of natural wax, mixtures of two or more waxes, and oleogels made with modified fatty acid composition oil, such as high stearic acid oil and waxes. One of the goals in this project is to develop oleogels with the melting point close to conventional solid fats so that their sensory properties, such as mouth-feel, are like conventional food products. An additional aim is to increase oleogel firmness without increasing wax content, so that the desired firmness of structured fat can be achieved with a minimal amount of wax and thus the impact of wax on sensory properties is minimized. Therefore, we studied 30 different oleogels made with binary mixtures of three waxes with differing compositions and were able to correlate the wax compositions with physical properties such as firmness and melting properties, as well as a correlation between oleogel firmness and the oleogel crystal morphology and microstructure. This knowledge is important for future ability to tailor wax combinations for oleogels with physical properties that will be useful for specific food applications. It also led to a hypothesis regarding the effect of wax components on the microstructure of the oleogels, which will be tested in future studies. A manuscript describing this research was recently accepted after minor revisions by a peer-reviewed journal, and the results were presented at the 2019 Institute of Food Technologists Annual Meeting. Among the binary wax systems that we studied, candelilla wax/beeswax mixtures showed very interesting properties. Oleogels made with these wax mixtures were firmer while their melting points were lower than those made with either individual wax. In addition, it was found that low ratios of sunflower wax with high ratios of candelilla wax resulted in firmer oleogels but did not significantly increase the melting point. From earlier studies, it was determined that the properties of an oleogel don’t always directly reflect properties of a final product such as margarine. Therefore, margarine samples from oleogels with different ratios of candelilla wax and beeswax were prepared, and we are completing studies of the properties of these margarine samples. If margarines made from oleogels from these wax combinations, (as well as other oleogels that are still under development), prove to have physical properties similar to commercial products, we will proceed with sensory evaluation, and testing as replacements for margarines in food products.
Studies using 0.5 – 2% of various waxes as a replacement for fully hydrogenated oil for peanut butter stabilization were completed, and a manuscript was submitted and was recently accepted. This research was also presented at the 2019 American Oil Chemists Society Annual Meeting. We are using the knowledge that we have developed of the relationship between oleogelators and physical properties to optimize oleogel firmness and melting properties in ternary wax-based oleogels. We also have completed a preliminary evaluation of several binary wax oleogels in a prototype shelf-stable frosting, which is an application that has been proven to be challenging for the replacement of saturated and trans fats. So far, one oleogel combination has been identified to have suitable air-holding and whipping properties like a conventional shortening; this research is still in progress.
For the second objective of this project, we continued studies on the antioxidant activity of amino acids and identified some of the factors that contribute to the antioxidant activity of different amino acids, which was published in a peer-reviewed journal and presented at the 2019 Annual Meeting of the American Oil Chemists’ Society. In addition, it is known that some antioxidants have prooxidant activity when the concentration is increased. To investigate if amino acids also have prooxidant activity at high concentrations, four different amino acids, L-arginine, L-cysteine, L-Lysine, and L-methionine, were examined for their activity at concentrations increased up to 15 mM (about 3 times of the initial concentration). No prooxidant activity was observed with these amino acids up to 15 mM indicating that the concentration can be increased under a circumstance where the stronger antioxidant activity is needed. Scientists are preparing a manuscript for publication in a peer-reviewed manuscript. Blueberry pomace was extracted with two different solvents, acetone and ethanol. A preliminary heating study was conducted with stripped soybean oil at 35 and 50 °C. However, the antioxidant activity of these extracts was not as strong as spent coffee ground extracts.
For the third objective of this project, scientists analyzed spent coffee ground extracts for total phenolic content (TPC), alpha- and beta-tocopherols, and several phenolic compounds that were reported to be major antioxidative compounds in coffee and in spent coffee ground extracts including 3,4-dihydroxybenzoic acid, gallic acid, chlorogenic acid, and caffeic acid. Correlations between these compounds and antioxidant activity shown in the storage study were evaluated to understand which compound(s) are most responsible for the prevention of oil oxidation. It was determined that an acetone extract had significantly better activity in fish and soybean oil studies, even though it had lower levels of total phenolics, target phenolic compounds, and in vitro antioxidant activity compared to the ethanol extract, which had the second-best performance. This indicates that either there is an unidentified component with high activity in the acetone extract, or that there are unidentified components present in the ethanol extract that had interfering oxidant activity. The next steps in this research, therefore, are to develop a more comprehensive profile of the active constituents and to optimize the extraction procedure and solvents to maximize antioxidant activity. This work was published in a peer-reviewed journal and was presented at the 2019 Institute of Food Technologists Annual Meeting.
Under Objective 3, research in collaboration with a company was completed on the ARS side, to evaluate the content of phenolics, bioactive lipids including tocopherols, tocotrienols, carotenoids, phytosterols, and antioxidant activity of distillers grain oil (DGO) samples from 50 corn ethanol plants. DGO is extracted from distillers grains (DDGS), which are the main co-product of corn-to-ethanol production. Ethanol companies used to leave the oil in the DDGS, but in the past 10 years, ethanol companies have increased profitability by extracting the oil and selling as a separate feed component or as a feedstock biodiesel production. The overall goal of the research is to determine if there are any correlations between plant processing parameters and the oil quality, composition, and antioxidant activity, in order to improve the quality and lower the variability in the composition of this important co-product, as well as determine whether the bioactive lipid components are present in high enough concentration to be economically viable as a separate co-product.
Accomplishments
1. Antioxidants from spent coffee grounds. Spent coffee grounds (SCG) are the residue generated from coffee brewing. It is estimated that over 9 million tons of SCG are discarded in landfills. Therefore, ARS researchers in Peoria, Illinois, used three methods for the extraction of SCG, and evaluated their use as potential antioxidants for the protection of fish oil and soybean oil from oxidation. Target antioxidant compounds, such as total phenolics, 3,4-dihydroxybenzoic acid, gallic acid, chlorogenic acid, caffeic acid, and tocopherols were also analyzed in the extracts. An acetone extract of the defatted SCG protected soybean oil and fish oil from oxidation as well as a synthetic antioxidant, butylated hydroxytoluene (BHT), which demonstrates that SCG can be utilized as a source of antioxidants to replace synthetic antioxidants for protection and shelf-life extension of foods and oils with omega-3 fatty acids. This may reduce the mass of SCG discarded in landfills, and foster the development of naturally-based, clean label antioxidants to replace undesirable and potentially harmful synthetic antioxidants in foods.
2. Stabilized peanut butter. Peanut butter and other nut and seed butters require the use of a stabilizer to bind liquid oil and prevent it from leaking to the surface, to improve the texture and spreadability, and to allow for room temperature storage by consumers. Fully hydrogenated oil or a solid fat such as palm oil are often used as stabilizers, but companies are under pressure to replace these ingredients with more natural and sustainable alternatives. Therefore, ARS researchers in Peoria, Illinois, studied the oil binding capacity, long-term stability, and sensory quality of peanut butter stabilized with natural waxes including beeswax, candelilla wax, rice bran wax, and sunflower wax. It was found that 0.5 to about 1.5 % of the wax, depending on the wax source, had good long-term stability and similar texture and mouthfeel compared to hydrogenated cottonseed oil, indicating that they could be used as natural, label-friendly stabilizers. Using this knowledge, food companies may apply this oil stabilization technology in peanut butter, nut and seed butters, as well as in many other food applications to replace palm oil and fully hydrogenated oils that are high in unhealthy saturated fats with oils stabilized with food-grade natural waxes.
3. Factors affecting antioxidant activity of amino acids in frying. Frying oil rapidly degrades due to the high temperatures used which accelerates oxidation. This results in the production of unhealthful compounds, off-flavors and odors, and increased cost to restaurants and food manufacturers due to the need to replace frying oil and because of the reduced shelf-life of fried foods. It is difficult to find suitable replacements for synthetic antioxidants for frying because most natural antioxidants are not soluble in oil and are also susceptible to degradation at high temperatures. ARS researchers in Peoria, Illinois, previously demonstrated that a variety of natural amino acids may be effective replacements for synthetic antioxidants for frying, despite their low oil solubility. Understanding the factors affecting their antioxidant activity is critical for the selection of the best candidates for utilization of these antioxidants in frying. Therefore, the scientists determined that two factors, higher lipophilicity (affinity to oil) and higher free radical scavenging ability, were the most critical factors for higher antioxidant activity whereas metal chelation was ruled out as a significant factor influencing antioxidant activity during frying. This knowledge will be used by ingredient suppliers and by oil processors to formulate effective antioxidants for frying oil applications and frying oils with higher stability to frying. More effective antioxidants for frying will result in healthier fried foods with longer shelf-life, which can impact consumer health, and save money for restaurants and food manufacturers.
Review Publications
Blake, A.I., Toro-Vazquez, J.F., Hwang, H.-S. 2018. Wax oleogels. In: Marangoni, A.G., Garti, N., editors. Edible Oleogels, Structure and Health Implications. 2nd edition. Cambridge, MA: Elsevier. p. 133-171. https://doi.org/10.1016/C2017-0-00541-4.
Hwang, H.-S., Winkler-Moser, J.K., Doll, K.M., Gadgil, M., Liu, S.X. 2019. Factors affecting antioxidant activity of amino acids in soybean oil at frying temperatures. European Journal of Lipid Science and Technology. https://doi.org/10.1002/ejlt.201900091.
Hwang, H.-S., Winkler-Moser, J.K., Kim, Y., Liu, S.X. 2019. Antioxidant activity of spent coffee ground extracts toward soybean oil and fish oil. European Journal of Lipid Science and Technology. https://doi.org/10.1002/ejlt/201800372.
Hulke, B.S., Winkler-Moser, J.K. 2019. Registration of genetic stocks TOCO B1, TOCO R1, and TOCO R2 with high gamma- and delta-tocopherol and altered fatty acid composition in the seed oil. Journal of Plant Registrations. https://doi.org/10.3198/jpr2018.10.0070crgs.
