Location: Functional Foods Research
2021 Annual Report
Objectives
Objective 1. Stabilize sensitive and bioactive food ingredients, improve shelf-life, and reduce food waste with optimized natural antioxidants and plant extracts.
Sub-Objective 1.A. Evaluate antioxidant activity of combinations of antioxidants in frying oils and fried foods.
Sub-objective 1.B. Evaluate antioxidants or natural antioxidant extracts for protection of polyunsaturated and omega-3 oils and bioactive lipids and to extend shelf-life of whole foods and food ingredients.
Objective 2. Enable oleogel applications to reduce saturated fats in foods.
Sub-Objective 2.A. Investigate and optimize the physical and sensory properties as well as the oxidative stability of edible oleogels.
Sub-objective 2.B. Evaluate interesterified natural waxes, waxes with vegetable oils, fatty alcohols or fatty acids, as potential new oleogelators.
Objective 3. Improve commercial value and sustainable food production through recovery of healthful bioactive ingredients from food processing by-products or waste.
Approach
Approximately 30% of the food supply in the United States is wasted and the worldwide problem is even larger. This waste represents a large strain on the environment and on the entire food production enterprise. According to the Food and Drug Administration (FDA), about 20% of the food waste in the United States is due to confusion about the meaning and safety of foods labeled with “best before” and “use by” dates. This means that extending shelf-stability of foods can have an impact in reducing food waste. There is also concern about the healthfulness of processed foods, including the high content of saturated fats, which consumers are advised to limit in the diet. However, reducing the saturated fat content of foods by substituting with healthier fats can influence product texture and mouthfeel, as well as the oxidative stability and shelf-life. The research of the next five years will enable the commercial development of natural antioxidants needed to improve the oxidative stability and shelf-life of foods formulated with a lower saturated fat content. Antioxidants will improve the stability of frying oils, fried foods, and high-value foods such as nuts and protein replacement bars. Oleogels will be developed with improved physical and melting properties for margarines and shortenings and other food applications that require hard fats and will have lower amounts of saturated fats and zero trans fats. New value-added ingredients such as antioxidants and bioactive lipids will be mined and characterized from low-value agricultural inputs. This research, together with complimentary technology and policy development strategies, will contribute to efforts to reduce food waste and improve the healthfulness of the food supply.
Progress Report
Significant progress was made under Objective 1 to evaluate antioxidant activity of combinations of antioxidants in frying oils and fried foods. We conducted studies of the antioxidant activity of amino acids in a variety of frying oils and in fried foods and evaluated their antioxidant activity in combination with other natural antioxidants. Amino acids and tocopherols were found to be a highly effective combination of antioxidants for protecting frying oils. In additional experiments, we investigated modifications to amino acids using food-safe ingredients. We also studied combinations of modified amino acids with tocopherols to evaluate their antioxidant activity in frying oil. The modifications were shown to improve antioxidant activity of some of the amino acids, and they were still an effective combination with tocopherols. A new method to further increase the feasibility of commercialization of amino acids as natural antioxidants for frying was proposed and a domestic food ingredient company is interested in this new technology and a collaboration with ARS is being discussed.
Progress was also made to evaluate antioxidants or natural antioxidant extracts for protection of polyunsaturated and omega-3 oils and bioactive lipids and to extend shelf-life of whole foods and food ingredients. Tocopherols are powerful antioxidants and the most commonly used natural antioxidant added to foods since they can be easily obtained as a co-product of vegetable oil refining. There is growing interest in tocotrienols, a similar class of natural antioxidants. Vegetable oils contain up to four tocopherols, and four tocotrienols, the composition of which depends on the original source. Each component has slightly different antioxidant activities, so performance of mixtures can be improved by finding the optimum blend of components. As progress towards the first milestone under this objective, we studied the antioxidant activity of individual tocopherols and tocotrienols and three commercial tocopherol mixtures using antioxidant assays. Then we evaluated the performance of the mixtures in fish oil, fish oil ethyl esters, and high oleic sunflower oil using an accelerated testing procedure. While all of the three commercial tocopherol mixtures improved stability of the oils when added at high enough concentrations, we found that one mixture had better performance than the other two, due to the higher concentration of a tocopherol component that had higher antioxidant activity than other tocopherols. This mixture improved oxidative stability of high-oleic sunflower oil by 565% and 869% when added at 0.05% and 0.1%, and improved fish oil stability by 435% and fish oil ethyl ester stability by 530% when added at 0.15%. The results in this study can be used to prepare optimized mixtures of tocopherols to protect polyunsaturated and omega-3 oils and to extend shelf-life of whole foods and food ingredients.
Significant progress was made under Objective 2 to investigate and optimize the physical and sensory properties as well as the oxidative stability of edible oleogels. To meet the 12-month milestones, we conducted experiments showing that by adding a small amount of one wax to binary mixtures of two other waxes, we were able to improve the firmness of oleogels without impacting the melting properties. This is an important discovery, as one of the goals of the research is to develop gels with textures similar to conventional solid fats and hydrogenated oils, without the high melting point that can make the product taste or feel waxy when consumed. This work was presented at the annual meeting of the American Oil Chemists’ Society and a manuscript is being prepared. We also published a paper on the physical properties of margarines made with binary wax mixtures, which also had firmer texture than margarines made from one-wax oleogels. In collaboration with scientists at Sejong University (Seoul, Korea), physical properties and crystal structures of grapeseed oil oleogels prepared with binary systems of two oleogelators, candelilla wax and glyceryl monostearate, were also investigated. We studied the minor ingredients in commercial glyceryl monostearate using nuclear magnetic resonance (NMR) and found that a minor ingredient positively affected the physical properties of oleogels. The binary blends of candelilla wax and glyceryl monostearate at varying ratios were also incorporated in canola oil oleogels, which were used to replace shortening in the preparation of filling creams. The hardening effect by mixing two oleogelators was also observed in the filling creams. The optimum blending ratio was 60:40 (candelilla wax: glyceryl monostearate), which had the highest firmness as well as the lowest melting temperature. The level of saturated fatty acids in the filling creams prepared with oleogels was reduced from 36.2% to 10.3% compared to that with a conventional shortening, bringing the values in alignment with food industry goals and nutritional recommendations for lower saturated fats in the diet.
Also under Objective 2, we evaluated interesterified natural waxes, waxes with vegetable oils, fatty alcohols or fatty acids, as potential new oleogelators. One of the major components in natural waxes are wax esters, which are composed of a chemically bonded fatty acid and fatty alcohol. The chain lengths of each these can range from 16 to 22 carbons, and natural waxes contain mixtures of wax esters with different chain lengths for each component. Oleogel properties are significantly affected by the chain lengths of the components of wax esters. Interesterification is a process that rearranges the components within a mixture using either chemicals or enzymes, and it may improve the physical properties of wax-based oleogels. To meet the 12-month milestone for this objective, chemical interesterification was conducted with six combinations of four waxes (beeswax, sunflower wax, rice bran wax, and candelilla wax). The resulting materials were incorporated in 5% wax-soybean oil oleogels, and their firmness was measured. Among six combinations, two interesterified waxes (products from beeswax and candelilla wax, and those from rice bran wax and sunflower wax) had increased firmness from oleogels with pure wax. This study indicates that physical properties of oleogels can be improved by interesterification of natural waxes. This may allow food companies to produce oleogels with an increasing and improved range of physical properties using these waxes as the building blocks.
Objective 3 is to improve commercial value and sustainable food production through recovery of healthful bioactive ingredients from food processing by-products or waste. Soybean hulls are by-products from soybean processing that are currently used as an inexpensive animal feed additive. As progress towards the first milestone, oil was extracted from soybean hulls and the composition of the fatty acids, tocopherols, phytosterols, and total phenolics were studied to determine the total content of these bioactive components. For further studies on possible valuable substances in soybean hulls, additional oil was extracted, and we plan to next characterize soybean hull wax for potential use as an oleogelator, and to test different extraction conditions to improve the antioxidant activity of extracts and the hulls for use as bioactive food ingredients. Corn bran is a by-product derived from the production of corn flakes and other food products. It is currently used as a fiber additive in food products, but it may have better marketability if other bioactive components in the bran are identified and quantified or if new ingredients are developed with enhanced content of bioactive components. Therefore, corn bran was extracted with different solvents ranging from low to high polarity. The yield, content of phytosteryl ferulates, lipid composition, and total phenolics were measured as a first step in this research. In addition, the oils were tested as antioxidants in preliminary heating studies in canola oil. These preliminary studies have helped to narrow down the potential extraction solvents and conditions for further research. We also collaborated with other ARS scientists on a project to evaluate the in vitro digestibility of pea protein isolates and determined the impact of particle size on digestibility. The information collected in this study will be used to recover valuable bioactive ingredients and antioxidants from food processing by-products or wastes.
Previously, spent coffee ground extracts obtained by Soxhlet extraction with acetone as solvent was found to have stronger antioxidant activity than other commercial natural antioxidants in soybean oil and fish oil. The extract at 0.25% had similar or stronger antioxidant activity than a synthetic antioxidant, butylated hydroxytoluene, at its legal limit (0.02%). This fiscal year, a preliminary study was conducted on the modification of the extract from spent coffee ground. The extract was treated with a base, sodium bicarbonate, and examined for its antioxidant activity in soybean oil during storage at 35 °C. The results showed that the treatment of the extract with a base could further improve the activity of the extract. Since natural antioxidants generally have inferior antioxidant activity to their synthetic counterparts, improving the efficacy of natural antioxidants is critical to their practical application. The method developed in this study can be applied to other natural antioxidants to enhance their activity.
We also collaborated with scientists at the University of Illinois to improve the recoveries of oil and hydrolyzed sugars from corn germ meal by different hydrothermal and fermentations treatments. This work enables the development and optimization of the yield of co-products of energy crop utilization.
Accomplishments
1. Natural antioxidants extracted from Osage orange fruits. Oxidation of vegetable or fish oils, or the natural oils in foods, causes off-flavors and odors, destroys essential fatty acids and other nutrients, and reduces the shelf-life of the oils and foods. There is a strong desire by the food industry and proponents of clean labels and natural foods to develop natural antioxidants to replace synthetic antioxidants that are currently used in foods. Osage orange tree is common throughout the midwestern and southwestern regions of the United States, and the fruits from this tree are underutilized despite high content of osajin and pomiferin, two potent antioxidants. ARS scientists at Peoria, Illinois, developed a very efficient extraction method to isolate a high-concentration mixture of osajin and pomiferin. These scientists studied the antioxidant activity of this extract in soybean oil and fish oil during storage at 25 and 40 °C. The antioxidant activity of Osage orange fruit extract was stronger than commercial natural antioxidants such as rosemary extract and Vitamin E (mixed tocopherols) and similar to or stronger than the most commonly used synthetic antioxidant, butylated hydroxytoluene (BHT). These results indicated that the Osage orange fruit extract was effective as an antioxidant and prevented the off-flavors and odors that occur when oils are oxidized. Although these extracts should be further tested to determine their safety this study demonstrated that the Osage orange fruit extract has great potential as an antioxidant for edible oils.
2. Making margarines with lower saturated fat. Margarines are traditionally prepared using mixtures of hard fats, such as palm oil or hydrogenated oils, liquid vegetable oils, water, and other ingredients. They are used as table spreads and for baking and cooking. Current recommendations call for reducing saturated fats in the diet because their consumption increases the risk of high cholesterol, atherosclerosis, and heart disease. Therefore, ARS scientists at Peoria, Illinois, are developing replacements for the high saturated fats that are used in margarines using oleogels made from small amounts of natural waxes mixed with liquid oil. The scientists previously found that mixtures of oil with candelilla wax or beeswax provided oleogels with increased firmness but lower melting points. To improve on these mixtures, margarines made with oil and mixtures of candelilla wax and beeswax, and they had higher firmness and lower melting points than margarines made with each single wax. Reducing the melting point will allow the margarine to melt in the mouth, which is preferred by consumers. This study showed that properties of oleogel-based margarines such as firmness and melting properties could be improved by mixing two waxes, and that these oleogels could be used to replace saturated fats to prepare margarines.
Review Publications
Hwang, H., Moser, J.K. 2020. Properties of margarines prepared from soybean oil oleogels with mixtures of candelilla wax and beeswax. Journal of Food Science. 85(10):3293-3302. https://doi.org/10.1111/1750-3841.15444.
Jia, Y., Kumar, D., Moser, J.K., Dien, B.S., Singh, V. 2020. Recoveries of oil and hydrolyzed sugars from corn germ meal by hydrothermal pretreatment: a model feedstock for lipid-producing energy crops. Energies. 13(22). Article 6022. https://doi.org/10.3390/en13226022.
Byars, J.A., Singh, M., Kenar, J.A., Felker, F.C., Moser, J.K. 2021. Effect of particle size and processing method on starch and protein digestibility of navy bean flour. Cereal Chemistry. 98(4):829-839. https://doi.org/10.1002/cche.10422.
Hwang, H-S., Winkler-Moser, J.K., Tisserat, B., Harry-O'kuru, R.E., Berhow, M.A., Liu, S.X. 2020. Antioxidant activity of Osage orange extract in soybean oil and fish oil during storage. Journal of the American Oil Chemists' Society. 98(1):73-87. https://doi.org/10.1002/aocs.12458.
