Fat: It’s a household word and a necessary ingredient in baked foods. In industrial applications, solid fats such as butter, lard and shortenings based on partially hydrogenated oils (PHOs) have historically been preferred to liquid vegetable oils because of their structural integrity and resistance to oxidation. But over time, this functionality has come with some undesirable nutritional traits, namely saturated fatty acids and trans fatty acids, both of which are associated with increasing the risk of heart disease.
Some disagreement exists over the heart health effects of saturated fats, and not all researchers agree that they pose risks. With a growing number of consumers scrutinizing product labels, bakers are seeking out better-for-you oils that have been strategically modified to provide functionality and improved nutrition.
The science of structure
Lipid scientists and oilseed breeders have learned how to manipulate the fatty acid composition of vegetable oils to enhance their stability while maintaining attractive nutrition labels on finished products. To better understand such advancements, one must consider the chemistry of fats and oils.
Fats and oils are classified as triacylglycerols (more familiarly known as triglycerides); they have a glycerol backbone esterified to three fatty acid chains consisting of carbon atoms connected to hydrogen atoms. Their physical state is determined by the types of fatty acids and the acids’ position on the backbone.
In common parlance, solid triglycerides are called fats and liquids termed oils. Bakery shortening, because it combines both physical states, is a plastic fat, but that term is rarely used by bakers.
Although the genetics of the source determine which fatty acids make up a given fat, the three fatty acids connected to the backbone are seldom identical. One fatty acid may be saturated (no double bonds), while the other two might be unsaturated (one or more double bonds). A fatty acid with one double bond is referred to as monounsaturated while one with two or more double bonds is referred to as polyunsaturated (PUFA).
If the triacylglycerol has undergone partial hydrogenation, the unsaturated fatty acids may be in the “trans” configuration, rather than in the naturally occurring “cis” configuration. Although trans fats occur naturally in animal fats, none are found in unprocessed vegetable oils. The trans orientation makes the fatty acid less flexible, with more solid-like properties. Because of health concerns, such man-made trans-fatty acids are being phased out of the food supply and may very soon be stripped of their generally recognized as safe (GRAS) status. (See “Ban on trans gets political” below.)
Saturated fatty acids are typically solid at room temperature and inherently the most stable type of fatty acid. Stability refers to susceptibility to oxidation, which takes place when a double bond breaks and an oxygen molecule attaches. Thus, the least stable fatty acids are those that have a long carbon chain with multiple double bonds.
The majority of unsaturated fatty acids in the human diet contain 18 carbons; however, they can contain as few as 10 carbons and as many as 22, with the former mostly found in animal fats and the latter in marine oils.
Scientists use an “omega” nomenclature system that identifies the fatty acid according to position of the first carbon double bond counting from the methyl end of the fatty acid. This helps categorize fatty acids in terms of function and nutrition.
For example, of the 18-carbon fatty acids, oleic acid has one double bond starting on the ninth carbon from the methyl end and is appropriately referred to as an omega-9 fatty acid. The length of this carbon chain, coupled with a single double bond, renders oleic acid a much more stable unsaturated fatty acid than many of the others that are abundant in the food supply. This includes linoleic acid and linolenic acid, also often referred to as alpha-linolenic acid (ALA). Both of these are 18-carbon fatty acids with linoleic having two double bonds. The first occurs at the sixth carbon double bond (from the methyl end) and is referred to as an omega-6, while ALA has three double bonds and is classified as an omega-3, with the first double bond occurring at the third carbon.
Two other popular omega-3 fatty acids are eicosapentaenoic acid (EPA), which has a 20-carbon chain and five double bonds, and docosahexaenoic acid (DHA), which has a 22-carbon chain and six double bonds. This abundance of double bonds renders these fatty acids highly unstable in certain food applications where high heat accelerates oxidation, such as in an oven. Unfortunately, these are two of the more healthful fatty acids for humans.
Choosing more healthful oils
In efforts to improve the fatty acid profile of baked foods, many bakers try to keep saturated fatty acids low and artificial trans fatty acids absent. To do this, bakers minimize animal fats and palm kernel and coconut oils because they are concentrated sources of saturated fatty acids. Likewise PHOs, which contain trans-fatty acids, are avoided more and more. Because vegetable oils vary in their fatty acid profile, smoke point and organoleptic properties, bakers must choose their oils wisely.
Having only one double bond, oleic acid is very stable, making high-oleic fatty acid oils desirable for baking applications. Oleic acid is naturally abundant in highly flavorful vegetable oils such as olive and peanut, but their intense flavor profiles and high prices often limit their use in commercial baking.
Recognizing the value of high oleic acid content, oilseed breeders have been aggressively working to heighten the fatty acid profile of bland-flavored oilseeds such as soy and canola that are more accessible and affordable. Mid- and high-oleic canola and sunflower oils were the first to market, with soybean oils following. Though compositions vary by source and breeder, these oils generally have significantly higher concentrations of oleic acid — in some instances, even higher levels than olive oil. They also have reduced levels of highly unstable linolenic acid.
For example, high-oleic sunflower oil is usually defined as having a minimum of 80% oleic acid. The oil has a neutral taste and provides excellent stability in bakery applications. The patent on high-oleic sunflower oil and seed has expired, prompting more companies to produce and merchandise it, according to the National Sunflower Association, Mandan, ND.
A new sunflower oil from Nutrisun, a business unit of Advanta Technologies, a seed company based in Buenos Aires, Argentina, is within a year or two of commercialization, according to Fernanda Filgueira Risso, the company’s marketing and communications leader. “We are currently having both preliminary and advanced commercial conversations with leader food companies in the world,” she said. “This first-of-its-kind oil has unique physicochemical and functional properties, which offer a healthy alternative to bakers.
“Basically we achieved a novel natural oil in the sunflower seed, which has 18% stearic and 70% oleic acids,” she said. Stearic acid is an 18-carbon saturated fatty acid, which, unlike other saturated fatty acids, has not been shown to raise serum levels of low-density lipoprotein (LDL), which is the so-called bad cholesterol.
“The higher levels of stearic and oleic acids yield a product with a higher level of solids, which works well for tropical fat replacement,” Ms. Filgueira Risso said. “It has been used successfully in croissants, breads and biscuits, using 100% pure product and blends with butter. Other bakery applications include cookies and crackers where it can be used in the dough or as spray oil. It is useful in fillings for sandwich cookies and layered wafers, too.”
High-oleic soybean oil has made many inroads in the baking business, allowing bakers to increase shelf life with a better-for-you ingredient “while still maintaining the soy-based flavor that consumers prefer,” according to Susan Knowlton, senior research manager, DuPont Pioneer, a DuPont Company, Wilmington, DE.
It can be used as an ingredient or spray oil for products such as crackers, snack bars, breads, cookies and more. “It has exceptional stability, similar to partially hydrogenated soybean oil, but with lower saturated fat and no trans fat,” Ms. Knowlton said. “It naturally provides a long shelf life for baked goods, allowing manufacturers to remove synthetic antioxidants from their ingredient labels.” This is because soybean oil has inherently high antioxidant content in the form of tocopherols, reaffirming its use in commercial applications.
“High-oleic soybean oil delivers three times the amount of monounsaturated fatty acids, which helps reduce LDL levels in the blood when substituted for saturated fatty acids, reducing the risk of heart disease and stroke,” said Don Banks, oils expert and consultant to Qualisoy and the United Soybean Board, Chesterfield, MO, adding that the neutral flavor lends itself well to product development.
John Janssen, vice president-regulatory, quality and innovation, Bunge Oils, St. Louis, MO, suggested more consumers are gravitating to high-oleic products because of their high content of monounsaturated fatty acids. “Manufacturers also like these same products because they are extremely stable and enhance the shelf life of finished products on the grocery shelf,” he noted.
New trait-enhanced sunflower is conventionally bred while similar soy and canola varieties are more likely to be derived through bioengineering.
Fatty acid makeover
The physical state of oils is not only determined by the types of fatty acids but also by their position on the glycerol backbone. Interesterification is a process that shifts the positions of fatty acids within the triglyceride molecule to improve structural integrity and functionality.
“Enzymatic interesterification is accomplished by physically blending a liquid oil with a fully hydrogenated oil and enzymatically rearranging the fatty acids predominately at the one and three positions on the glycerol backbone, with some conversion at the sn-2 positions as well,” said Tom Tiffany, senior technical manager, ADM Oils, Decatur, IL. He reported that enzymatically interesterified vegetable oils have been very successful replacing PHOs in baked foods.
“Typically the same usage level is applied, and in some cases, such as tortillas and cookies, the enzymatically interesterified oil can be used as a drop-in replacement,” Mr. Tiffany said. “By varying the level of fully hydrogenated vegetable oil in the base stock (a blend of soybean oil and fully hydrogenated soybean oil) prior to enzymatic interesterification, we can tailor the melting and functional characteristics of the blend for the desired application. Shortenings produced from this process are very low in trans fatty acids and are moderate in saturated fatty acids, in which the saturates are predominately stearic acid, which has been shown to be cholesterol neutral.”
A quick trans fix
In addition to high-oleic and interesterified oils, palm oils have been a go-to for many bakers whose main objective is to remove trans-fatty acids from nutritional profiles.
Palm oil is obtained from the flesh of the fruit of the palm tree, not the fruit’s kernel. The oil, which is a naturally solid fat, is extracted by a steam treatment followed by expeller pressing. The crude palm oil is refined using non-chemical processes.
“We developed a functional crystallization process that allows a zero-trans-fat palm oil to function more like partially hydrogenated soybean-based shortenings,” said Roger Daniels, vice-president, research, development and innovation, Stratas Foods LLC, Memphis, TN. “Shortenings created through this process, compared with typical palm shortenings, are smoother, creamier, more workable, more consistent cube-to-cube, able to work over a wider temperature range and are functional throughout their shelf life.”
Palm oil works well in combination with high-oleic oils and interesterified oils. Such blends are the future of formulating in baking industry.