Location: Functional Foods Research2012 Annual Report
1a. Objectives (from AD-416):
The overall objective of the project is to improve the stability and functionality of commodity vegetable oils so they can be used as alternatives to hydrogenated oils and imported tropical fats for frying and for margarines and shortenings. To achieve this goal, we will investigate the effects of several types of phytochemicals in frying oils and will explore methods to produce healthful margarines and shortenings with low or no trans fatty acids and low saturated fats. The research will focus more specifically on the following objectives: Objective 1: Develop commercially viable methods that utilize tocopherols, phytosterols and phytosteryl ferulates to synergistically improve the oxidative stability of frying oils and fried foods; Objective 2: Develop commercially viable methods that utilize naturally-derived antioxidants and anti-polymerization compounds to improve the stability of frying oils; Objective 3: Develop commercially viable methods that utilize specialty vegetable oils to enhance the nutritional properties and oxidative stability of commodity oils; Objective 4: Develop commercially viable processing technologies to reduce or eliminate trans fatty acid content in margarines, spreads, and shortenings.
1b. Approach (from AD-416):
Food manufacturers, restaurants, and bakeries that need stable oils for frying and/or oils with the appropriate functionality for shortenings are looking for alternatives to hydrogenated oils because of trans fatty acids hydrogenated oils contain. However, commodity oils such as soybean, sunflower, and corn that are processed without hydrogenation are not stable enough for frying oils nor do they have the proper functionality for margarines and shortenings. Even most oils with fatty acid compositions modified to increase oleic and/or to decrease linoleic or linolenic acids are still not as stable for frying as hydrogenated oils. This project proposes to improve the stability and functionality of commodity vegetable oils so they can be used as alternatives to hydrogenated oils and imported tropical fats for frying and margarines/shortenings. To help solve the problems of frying oil stability, we will: 1) Develop commercially viable methods that utilize tocopherols, phytosterols, and phytosteryl ferulates to synergistically improve the oxidative stability of frying oils and fried foods; 2) Develop commercially viable methods that utilize naturally-derived antioxidants and anti-polymerization compounds to improve the stability of frying oils; and 3) Develop commercially viable methods that utilize specialty vegetable oils to enhance the nutritional properties and oxidative stability of commodity oils. To help solve functionality problems for margarines and shortenings, we will develop commercially viable processing technologies to reduce or eliminate trans fatty acid content in margarines and shortenings. Based on the results of our research, we will make recommendations to food manufacturers, oil processors, and plant geneticists for developing oils with enhanced stability, functionality, and healthfulness.
3. Progress Report:
For Objective 1, ratios and amounts of tocopherols and phytosteryl ferulates were optimized to improve stability of frying oils. Tocopherols and phytosteryl ferulates protected each other and increased oil fry-life. Volunteers were recruited for an in-house sensory panel, and weekly training sessions have begun. Shelf stability studies will commence once the panel is sufficiently trained to evaluate the flavor and odor of aged fried foods. One paper was published (FY11) and one paper has been submitted for peer-review. For Objective 2, several approaches are under way to investigate natural compounds with antioxidant, metal chelating, or surfactant activity to protect frying oils from degradation and to improve the shelf-life of fried foods. At certain concentrations several plant-based lignans were demonstrated to be as effective as synthetic antioxidants at preventing degradation of oil during heating and frying. Procedures were developed to extract antioxidants from grape pomace from Midwest wineries; studies to evaluate their impact on oil quality during heating and frying are ongoing. Scientists collaborated with another Agricultural Research Service (ARS) project to develop a solvent-free, plant-based extract rich in antioxidants and rosmarinic acid (an antioxidant with possible neuroprotective activity). A variety of commercially available, naturally occurring antioxidants with varying structural features were obtained in order to systematically study the impact of solubility, thermal stability, and volatility on antioxidant activity in frying oils. One paper has been published (FY12) and two papers have been submitted for peer review. For Objective 3, specialty vegetable oils are being evaluated as blends with commodity and modified fatty acid composition oils to enhance frying stability and increase the profile of healthful phytochemicals such as phytosterols, tocotrienols, and phenolics. Oils were obtained from commercial sources and cooperators. To understand the heat stability characteristics of these oils, and to improve upon existing methodologies, a quick and solvent-free method for measuring oil degradation using pulsed nuclear magnetic resonance (NMR) was developed and validated using these oils. Recent experiments have focused on using rice bran oil, extracts from rice bran oil, and corn fiber oil with traditional frying oils. One publication was recently accepted by a peer reviewed journal. For Objective 4, plant waxes, due to their low cost and effectiveness, were demonstrated to be feasible organogel agents to increase the melting point and solidify vegetable oils without the need for hydrogenation. The properties of organogels made with soybean oil and various waxes was published. Organogels were used to make 80% liquid oil margarines with measured firmness between traditional stick margarines and tub spreads. In another approach, an extraction procedure was developed to produce a product from rice bran oil with the consistency of a spread or peanut butter. Physical, chemical, and thermal properties were measured; further work will optimize the physical and organoleptic properties.
1. Natural antioxidants for frying oil. During frying, oils that are high in polyunsaturated fatty acids are easily degraded by high temperatures and oxidation which causes thickening, darkening of the oil as well as destruction of essential fatty acids and vitamins. In addition, polymerized and oxidized oil will cause excessive foaming, incomplete cooking, and will impart off-flavors and poor sensory and nutritional quality to the fried food. Agricultural Research Service scientists in the Functional Foods Research Unit at the National Center for Agricultural Utilization Research in Peoria, IL, have found several naturally occurring antioxidants to prevent degradation reactions in frying oil, including phytosteryl ferulates isolated from corn fiber and sesamol from sesame oil. Phytosteryl ferulates were shown to reduce the formation of polymerized soybean oil by 70% and to protect the vitamin E in soybean oil by slowing destruction. Phytosteryl ferulates have anti-inflammatory and cholesterol-lowering effects, and could find valuable application as functional food ingredients in frying oils. At certain concentrations, sesamol was more effective than a commonly used synthetic antioxidant in preventing soybean oil polymerization during frying. These compounds may replace synthetic antioxidants used in frying oils and will enable oil processors, food companies, and restaurants to produce oils and fried foods with better stability and nutritional quality.
2. Trans-fat free margarines and spreads using organogels. Despite having at least 20% water and being mainly composed of liquid vegetable oils, margarines and spreads are semi-solid at room temperature mainly because they contain saturated or trans fatty acid containing triglycerides that crystallize into a solid network that surrounds liquid oil droplets. Saturated and trans fatty acids are solid at room temperature, so the solid network keeps liquid oil droplets from coalescing. The food industry is currently challenged to produce margarines and spreads that are both low in saturated fats and have no trans fatty acids. Agricultural Research Service scientists in the Functional Foods Research Unit at the National Center for Agricultural Utilization Research in Peoria, IL, demonstrated that organogels using small amounts of plant waxes can be used to make margarines or spreads without the need for saturated or trans fatty acids. This technology can be utilized to replace palm oil and hydrogenated oils to develop healthier, trans fat free margarines and spreads and will also be investigated for application in confectionary and shortening products.Hwang, H., Winkler-Moser, J.K., Liu, S.X. 2012. Structural effect of lignans and sesamol on polymerization of soybean oil at frying temperature. Journal of the American Oil Chemists' Society. 89:1067-1076.