Plant sterols are shown to lower cholesterol and are easy to include in bakery products, but consumers remain unfamiliar with the term and its benefits.
Plant sterols may pose one solution to combating the growing epidemic of high cholesterol in the United States, where an estimated 106.7 million adults have total blood cholesterol levels considered either high risk or borderline high risk. Present in many fruits, vegetables, nuts, seeds, cereals and vegetable oils, plant sterols are shown to reduce LDL “bad” cholesterol without affecting good cholesterol. But just eating fruits and vegetables doesn't get the job done. You would need to eat about 100 small potatoes to consume enough plant sterols to reap a cholesterol lowering benefit, notes Pam Stauffer, global marketing and communications manager, Cargill, Health and Nutrition, Wayzata, Minn. Therefore, plant sterols are being isolated and incorporated at concentrated levels into baked products, among other food applications, to appeal to cholesterol-conscious consumers and help bakers achieve FDA label claims about reducing cholesterol.
“Plant sterols act as the cholesterol of the plant world in that they help provide structure and rigidity to cell walls. Additionally, they are very similar in molecular structure to animal cholesterol,” says Charles Barber, technical service manager, Cognis Nutrition and Health, LaGrange, Ill. When consumed, plant sterols compete with and impede the absorption of dietary and endogenous cholesterol, preventing absorption in the bloodstream, he adds.
Two types of plant sterol products exist: free sterols and sterol esters. Free sterols are a waxy material with a high melting point of 245°F (135°C ) to 293°F (145°C). Free sterols are sold in finely ground powders, which manufacturers sometimes add to a carrier before introducing them into a food application. A sterol ester is formed when a fatty acid is esterified onto the sterol molecule. Sterol esters have the consistency of petroleum jelly and a melting point of 95°F (35°C) and can be used to replace part of the fat in formulas. They usually are sold in powder or semi-liquid forms. In their pure form, sterol esters are a liquid, when refrigerated they become solid and at ambient temperature they are a yellow or white paste. Food manufacturers heat sterol esters until they form a clear oil and then incorporate that oil into baked products.
“Sterol esters are mainly used in margarine-type products,” says J.J. Mathieu, ADM Technical Services, Decatur, Ill. “In baked products, one could use either product, but bakers may choose to use the more convenient free sterols powder product.”
Plant sterols' main benefit is that they help lower cholesterol and thus reduce the risk of heart disease. According to the FDA, “Foods containing at least 0.4 g per serving of plant sterols (0.65 g sterol esters), eaten twice a day with meals for a daily total intake of at least 0.8 g (1.3 g sterol esters), as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.”
Plant sterols have a 94 percent purity, while sterol esters have a 60 percent sterol content, notes Carol Lowry, senior applications scientist, Cargill, Heath and Nutrition. The daily intakes noted above are based on these differences in purity.
Studies continue to show the cholesterol lowering benefits of plant sterols. A Mayo Clinic meta-analysis, for example, showed that 2 g per day of plant sterols have been shown to lower LDL by 10 percent.
Plant sterols also benefit consumers because they are natural and, because they are being incorporated into everyday foods, such as breads and juice, they are easy for consumers to access on a daily basis. The key to reaching consumers is adding plant sterols to products they already buy, Stauffer says. This way, consumers don't have to make major adjustments to their diet to incorporate plant sterols.
“Sterol-containing baked products can also be complementary to other ingredients that are known to reduce cholesterol, such as soluble fibers and soy protein,” Mathieu adds.
Plant sterols typically are derived from soybeans, although in Europe where non-genetically modified forms are often required, the plant sterols can be derived from rape seed or from a byproduct of the lumber and paper milling industry known as “tall oil” (oil from pine trees), Barber says.
As companies process vegetable oil, they crush oilseeds and extract the crude oil. The oil is further refined, resulting in edible vegetable oils. The refining process yields a byproduct known as vegetable oil distillate (VOD). Plant sterols, natural vitamin E and other fatty acids are located within this VOD. Additional processing steps can be taken to separate these components yielding among others, purified plant sterols, Barber says.
Plant sterols do not have any baking functionality, so they do not impact baking quality or properties. Inert, bland, insoluble and used at relatively low addition levels, plant sterols can be added at any time to baked product formulas with no effect on flavor or texture. Powdered sterols and sterol esters are usually incorporated with the dry ingredients and semi-liquid sterol esters enter the mix with fats and oils.
Baking temperatures will not affect the functionality or stability of sterols because they have a high melting point. Because of the oil-like nature of plant sterol esters, their functionality and stability is similar to traditional baking fats and oils, Lowry says. Plant sterol esters are stored refrigerated and need to be heated prior to use to assist dispersion and for ease of use with processing equipment. “If bakers are using a plant sterol ester in the pure oil form, there is a melting step involved to make it a flowable oil — typically around 110°F (43°C) to 115°F (46°C),” Barber says.
As aforementioned, plant sterols have a 94 percent purity, and sterol esters have a 60 percent sterol content. To meet the FDA heart health claim level of sterols in baked products, 0.43 g sterol ingredient is needed per serving. This is 0.83 percent for bread with a 51-g serving size. To achieve the heart health claim level using sterol esters, 0.67g sterol ester ingredient is needed per serving. Using the same bread example, this would be 1.3 percent, Lowry notes.
Bakers working in small and large capacities alike can use plant sterol-containing margarines as a way to add plant sterols to bakery products. To start, Wendy Miller, registered dietition and president RD Foods, Kenilworth N.J., suggests determining the amount of plant sterols needed for a health claim versus the amount present in the sterol containing fat substitute. “Because it's an expensive product, you're not going to want to use more than you need,” she notes. A less expensive option might be to determine if your formula requires a one-for-one replacement, or if it is possible to use only a partial replacement and still achieve the label claim. Miller is the co-inventor of Right Direction Cookies, which contain plant sterols.
Overall, experts agree that formulating with plant sterols or plant sterol esters is fairly easy, but small challenges can exist. Pure plant sterols are often micro-ground into a form usable in food products. This form is highly concentrated, but very fine, similar to talcum powder, Barber says. “Food manufacturers who use large blending operations may need to be aware that microfine plant sterols may cause dusting issues and can be somewhat challenging to mix.” Bakers often prefer to use a plant sterol that has been incorporated onto a carrier because it has better mixability and a greatly reduced tendancy to dust.
“We're just at the tip of the iceberg with plant sterols and educating consumers about them,” Miller says.
Many companies avoid using the term “plant sterols” directly, instead referring to “plant extracts” or focusing on the cholesterol reducing properties that consumers better understand. “The term ‘plant sterol’ is not very friendly with consumers — they think of steroids or being sterile,” Stauffer says. Cargill's Corowise™ naturally sourced cholesterol reducer features a logo with a heart and leaf with no direct mention of plant sterols.
Still, some manufacturers feel it is necessary to use the name “plant sterols” in order to familiarize consumers with the term and its benefits. “We're hoping to be part of educating the consumer about how we can now isolate such a great component of health that comes from a food source and be able to use concentrated sources of it, so you can get enough of it to make a difference in your health,” Miller says.
More products containing plant sterols, including a variety of bakery foods, are being introduced to the market, Barber says. “I'm anticipating that the market will start to see more of that as consumer awareness picks up on plant sterols, and they start to see the true value of having them as a natural way to lower cholesterol instead of prescriptions.”