Location: Functional Foods Research2013 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, experiments showing a symbiotic interaction between corn and rice phytosteryl ferulates and tocopherols were conducted. Frying experiments with synthetic phytosteryl ferulates were conducted to provide information on the optimal composition for 70-80% protection of soybean oil. The synthesis of phytosteryl ferulates was also improved. For Objective 2, frying experiments demonstrated that a known compound could replace a synthetic antioxidant, tert-butylhydroquinone (TBHQ), to protect oils during frying. Many antioxidants evaporate from oil during frying, which quickly reduces their effectiveness. A strategy to combat the problem of evaporation by adding low concentrations of antioxidant at regular intervals rather than adding higher concentrations at the beginning of frying was investigated. In addition, a technology to actually reduce the volatility of antioxidants was also developed. Other progress included testing activity of antioxidants extracted from grape pomace (a byproduct of winemaking process) from Midwest grape varieties, and development of a water-soluble sage extract that is high in antioxidants like rosmarinic acid. While neither of these extracts had high antioxidant activity in frying oils, the sage extract, as well as grape pomace extracts from certain red varieties showed dose-dependent antioxidant activity in oil-in-water emulsions, indicating promise as antioxidants for use in a variety of food systems. For Objective 3, a process was developed to yield a rice bran spread from crude rice bran oil that is rich in tocopherols, tocotrienols, orzyanol, and phytosterols. This product was added to soybean oil at 0.25% levels and increased its oxidative stability at frying temperatures. At this level, taste panelists were unable to distinguish tortilla chips fried in soybean oil from chips fried in soybean oil with the rice bran oil antioxidant blend. A patent application for the extraction process has been submitted. For Objectives 1 through 3, research was conducted to investigate the types of compounds that are produced when oils oxidize at frying temperatures. Using several nuclear magnetic resonance techniques, it was demonstrated that Diels-Alder products do not form under normal frying conditions, which disproves the long-standing belief that these were some of the major polymer compounds that form in oxidized oils. For Objective 4, organogels from rice bran wax and sunflower wax in soybean oil were used to make margarines (no added hydrogenated or saturated fats). Physical properties such as melting point, solid fat content, and firmness were measured. Margarines with firmness and slip melting point similar to commercial spreads were obtained with low concentrations of wax. Firmness approaching that of commercial stick margarines could be obtained with higher wax concentrations. Also under Objective 4, the rice bran oil spread mentioned above was tested for fat replacement in bread and granola and tested for sensory threshold and acceptability by taste panelists.
1. Low saturated fat, zero trans fat margarines. Margarines and spreads used in baking, cooking, and as table margarines, are solid at refrigerator temperature, yet soften up enough to mix into a dough or to spread on bread at room temperature. These unique characteristics are facilitated by the saturated or trans-fatty acids found in tropical or hydrogenated oils. Yet nutritionists warn that consumers need to reduce the amount of saturated and trans fats in the diet. Agricultural Research Service scientists in the Functional Foods Research Unit at the National Center for Agricultural Utilization Research in Peoria, Illinois, have made margarines using soybean oil by replacing the hydrogenated soybean oil or saturated-fat containing palm oil, with a small amount of plant waxes from sunflower or rice bran. The test margarines were similar in texture, melting point, and stability to commercial margarines. This research demonstrates a new approach to removing harmful trans- and saturated fats from structured fat products like margarines, spreads, and frostings.
2. Rice bran oil spread. Three million people in the U.S. have a nut allergy and 1.5 million people have an allergy to peanuts. In addition, the number of people with allergies or sensitivity to gluten is also on the rise, so there is a need to develop ingredients that are free of allergens and gluten. An Agricultural Research Service scientist in the Functional Foods Research Unit at the National Center for Agricultural Utilization Research in Peoria, Illinois, developed an extraction procedure to produce a spreadable rice bran oil product from crude rice bran oil. This product is similar in texture to nut butters and margarine spreads, and is rich in Vitamin E, antioxidants, and phytosterols, all of which have known health benefits. The product is also allergen, gluten, and trans-fat free, and has been tested as an antioxidant in frying oils and as a fat replacer in bread and granola. Baked products using the rice bran oil spread were deemed acceptable by sensory panelists, thus this product has potential as a functional food ingredient for use by companies desiring an allergen-free, trans-fat free alternative to provide texture or fat replacement in baked goods or healthy spreads.
3. Metering out frying oil antioxidants. Synthetic antioxidants are sometimes added to deep-fat frying oils to prolong the amount of time the oil can be used before being thrown away. Agricultural Research Service scientists in the Functional Foods Research Unit at the National Center for Agricultural Utilization Research in Peoria, Illinois, have been searching for natural antioxidants to replace synthetic antioxidants, which have come under scrutiny for having possible negative health effects. Food companies are very interested in replacing synthetic antioxidants with natural antioxidants. One problem is that at the high temperatures used for deep fat-frying, antioxidants evaporate from the oil and lose their effectiveness. Agricultural Research Service scientists in the Functional Foods Research Unit at the National Center for Agricultural Utilization Research in Peoria, Illinois, studying a natural antioxidant, found that adding small doses to maintain low concentration levels of the antioxidant, was more effective in protecting the oil than adding a higher dose of either this compound or a synthetic antioxidant at the beginning of frying. The scientists hope to develop a way to automate release during frying, which may solve the problem of antioxidant evaporation, and open the door to the use of sesamol or a number of other natural antioxidants, in frying.
4. Antioxidants to increase frying oil life. During frying, oils that are high in healthy polyunsaturated fatty acids, like soybean oil, quickly react with oxygen and polymerize, which causes darkening, foaming, and a reduction in the nutritional value. Synthetic antioxidants are used as one way to protect oils like soybean oil during frying, but many synthetic antioxidants have come under scrutiny because of potential negative health effects, and food companies are very interested in replacing synthetic antioxidants with natural antioxidants. Agricultural Research Service scientists in the Functional Foods Research Unit at the National Center for Agricultural Utilization Research in Peoria, Illinois, have been investigating phytosteryl ferulates, natural antioxidants found in corn, rice, wheat, and rye, combined with Vitamin E, another important antioxidant found in oils. The researchers found that phytosteryl ferulates and Vitamin E protect each other, and work together to protect the oil during frying, so that both the oil and the antioxidants last longer. With this combination, soybean and other healthy oils can be use for a longer time for frying which saves money for food processors and restaurants. For consumers, fried foods will absorb more Vitamin E because it has been maintained in the oil for a longer period of time resulting in healthier fried foods.
5. New understanding of oil chemistry. Understanding the reactions that oils undergo when heated is important to food chemists, who want to protect and preserve healthy oils, as well as to industrial chemists, who use soybean and other oils as a starting material to produce industrial lubricants, paints, and other products. There are hundreds of different compounds that can form in oil during heating and frying, which makes it difficult to identify compounds and evaluate the safety of their consumption, and for industrial chemists to predict the composition of products generated using oils as a starting material. A popular misconception is that specific classes of polymers, known as Diels-Alder reaction products, are formed by polyunsaturated fatty acids in heated oils. Agricultural Research Service scientists in the Functional Foods Research Unit and the Bio-Oils Research Unit at the National Center for Agricultural Utilization Research in Peoria, Illinois, teamed up to disprove this theory. Using sensitive nuclear magnetic resonance techniques, the researchers proved that these compounds are not found in oils that are heated either with oxygen (as with food and frying systems) or without oxygen (as with reactions used to produce industrial products). This research leads to a better understanding of the complex chemistry of heated and fried oils. It will allow food and industrial scientists to better understand and control the reactions that occur when oils are heated as well as lead to a better understanding of the safety and nutritional quality of fried foods.
6. Fast method for measuring frying oil degradation. During deep-fat frying, it is important to monitor oil quality so that food processors and restaurants know when to replace the oil. While there are several instruments available for quick measurements, they are usually inaccurate and unreliable. Traditional methods require more time and the use of large amounts of solvents. Agricultural Research Service scientists in the Functional Foods Research Unit at the National Center for Agricultural Utilization Research in Peoria, Illinois, discovered that an instrument called a low resolution nuclear magnetic resonance (NMR), which is commonly used by oil companies and in quality assurance environments, may be used as a substitute for traditional methods for measuring oil degradation. The advantages of the new method are that once it is calibrated, it correlates with standard methods, it requires no solvents and minimal sample preparation, and it is easy and fast to use so that anyone could be trained to measure frying oil degradation.
Hwang, H.-S., Winkler-Moser, J.K., Bakota, E.L., Berhow, M.A., Liu, S.X. 2013. Antioxidant activity of sesamol in soybean oil under frying conditions. Journal of the American Oil Chemists' Society. 90:659-666.