Since ancient times natural fats and oils have been used by humans for food and non-food purposes. The Egyptians, for example, used olive oil and fats as a lubricant for moving heavy building materials and to grease axles. Most ancient civilizations used fats and oils as fuel, typically in lamps and in the elaboration of candles that were the principal source of illumination. As understanding of the chemical nature of edible fats and oils increased, so did their commercial uses. Butter is even mentioned in the Bible, when Abraham and Sarah offer to three visiting angels a feast of meat, milk, and the “creamy yellow spread”.1 However, it was not until 1869 that the French chemist Hippolyte Mège-Mouriès invented and patented the process of elaborating margarine. The original process, developed in response to a prize offered by Napoleon III to the one who could find a substitute for butter, combined beef fat and skimmed milk (i.e. with the butter fraction removed). Later on, in 1871, Henry W. Bradley patented the process of creating margarine utilizing vegetable oil, mainly cottonseed oil, combined with animal fats. Subsequently, margarine production was limited by the availability of beef tallow, until in 1902 the German chemist Wilhelm Normann patented a process to harden oils through hydrogenation of the double bond of unsaturated fatty acids esterified to triacylglycerols (TAGs). This development greatly expanded the availability of margarine and widened the market opportunities for vegetable oils.2,3 Hydrogenation of the double bond in fats and oils still constitutes a major industrial oleochemical process. This is mainly because the original research later led to the development of the partial hydrogenation process for vegetable oils that established the grounds for the shortening industry. In turn, the shortenings provided the functionality that supported the development of food products that exposed consumers to appealing new textures, mouthfeel, and flavors. Thus, partially hydrogenated vegetable oils (PHVO) became the major functional component of baked goods such as cakes, cookies, pie crust, and crackers; snacks like corn, chips, and microwaveable popcorn; refrigerated dough used for canned biscuits, cinnamon rolls, and frozen pizza crusts; and also non-dairy coffee creamers, confectionary spreads, stick margarines, and shortenings for frying foods.
Now we know that most of the functional properties associated with lipid-based foods are due to the strong function of the nano- and meso-scale organization of major constitutive bio-molecules, its phase changes, and rheological behavior. Since TAGs are the main component of fats, vegetable oils, and subsequently PHVO, the functional properties of lipid-based foods are directly associated with the phase changes, namely crystallization, melting, and polymorphism, of the TAGs. In particular, the physical properties associated with saturated TAGs and/or those containing trans fatty acids, the last one present in high concentrations in shortenings derived from PHVO, provide the solid fat content, melting, and textural properties requested by the consumers in several processed food products. Unfortunately, there is now a well-established link between the consumption of trans fatty acids and a higher risk of coronary heart disease4 and the development of type II diabetes.5,6 Within this context, and as a result of the government's recommendations issued to limit and even eliminate trans fatty acids in processed foods, palm oil and its fractions (i.e., palm stearin) which are high in saturated TAGs (i.e., palmitic and stearic acids), have become the edible oil most used by the food industry to replace trans fatty acids in food formulations. This is mainly because palm oil and its fractions provide functional properties and oxidative stability to lipid-based foods similar to those achieved by shortenings. Unfortunately, although the relationship of saturated fatty acid intake by humans with a higher risk for atherosclerotic cardiovascular disease remains controversial,7 the consumer's response has been to move away from products high in saturated fatty acids; particularly those formulated with palm oil and its derivatives due to reports claiming that certain refined palm oil (i.e., glycidyl fatty acid esters) components might be genotoxic and carcinogenic. These negative health issues associated with the consumption of trans and saturated fats, and the legislation issued by regulatory agencies, have put considerable pressure on the food industry to resolve this health issue associated with food consumption. Therefore, the development and use of trans-free oils and fats are of the utmost interest to research groups and industries worldwide. The challenge for the industry is to produce foods containing less “bad fats” while retaining most of the functional properties associated with saturated TAGs and/or TAGs with esterified trans fatty acids. Evidently, this situation indicates that food formulation must shift toward the use of healthy unsaturated oils, a goal not easily accomplished mainly because the physical and functional properties of unsaturated oils are significantly different from those provided by “bad fats”. For instance, unsaturated edible oil remains essentially liquid under most of the temperature conditions used to produce food systems, and consequently, they do not positively contribute to food texture and mouthfeel. Additionally, the use of unsaturated edible oils in the formulation of food systems would require their protection against oxidation to avoid negative effects on the food quality and nutritional value. Thus, several research groups worldwide have investigated different mechanisms to provide structure and elastic properties to unsaturated oils. An important aspect to consider in the development of these new “structured unsaturated edible oils” is that, despite the health benefits associated with the consumption of unsaturated oils, consumers will not accept and consume a particular food if it does not meet their sensory expectations.
From the above is it understandable that the research associated with the development of strategies for structuring oils has grown extensively during the last 10 to 15 years. However, the implementation of “structured edible oils” that result in the commercialization of food systems, for instance through the use of oleogels, is still not a reality. Within this framework, there is a need for additional studies to evaluate and understand the digestion of “structured edible oils” in food systems, their oxidative stability, the interaction of the “structured edible oils” with food matrices under processing and storage conditions, and furthermore, trained sensory panels must evaluate the tentative development of off-flavors.8 In this regard, this book encompasses the work of leading researchers discussing, from a scientific and technological perspective, the latest and most innovative approaches to structure edible oils without the use of trans fats. Additionally, the authors discuss the practical uses and technical limitations associated with the use of these “structured edible oils” in different food systems. We hope that the information discussed here will contribute to the successful development of a new generation of functional “structured edible oils” that once incorporated into food systems, will have higher rates of consumer acceptance.
Jorge F. Toro-Vazquez
Facultad de Ciencias Químicas
Laboratorio de Fisicoquímica de Alimentos
Universidad Autónoma de San Luis Potosí