Although most consumers have learned that the particulars of dietary lipid sources are a far more complex subject than the "all fat is bad" trope that used to rule, they still cast an occasionally wary eye at oils. At minimum, they are demanding oils work harder on multiple levels. Ingredient makers are employing technical prowess to fulfill those demands.
One of the newer products in this category is high-oleic acid canola oil, which joins palm oil as a growing industry favorite. Oleic acid is the fatty acid that is dominant in olive oil, a staple food in the Mediterranean diet. Early studies found that foods rich in oleic acid tend to lower LDL cholesterol without lowering HDL cholesterol, thus reducing risk factors for heart disease. More recently, a study published in the Journal of Internal Medicine reported that rapeseed oil (canola oil), when substituted for dairy fats in the diets of subjects with high cholesterol, lowered blood cholesterol and triglycerides.
Fatty acids are the carbon chains that make up fats and oils and give them their specific properties. Three fatty acids make up one fat (triglyceride) molecule.
There are two broad categories of fatty acids, saturated and unsaturated. Saturated fatty acids are "saturated" with hydrogen. Unsaturated fatty acids are not. That's because in unsaturated fatty acids one or more pairs of carbon atoms are linked together with a double bond, which naturally excludes some hydrogen.
The double-bonded carbon atoms make the fatty acid chain bend, decreasing the melting point of the fat, allowing it to remain liquid at a lower temperature, depending upon the number of double bonds. Unsaturated fatty acids can have one or more double bonds and thus are termed monounsaturated or polyunsaturated. Oleic acid is the common name for a monounsaturated fatty acid that is dominant not only in olive oil but also in avocados, macadamia nuts, almonds, pecans, hazelnuts, pistachios, peanuts and cashews.
In the body, having many double bonds in the fatty acids of the cells and tissues helps organisms adapt to cold weather. That's good for the plant or animal, but not so good for processed foods, especially baked goods. The more double bonds in a fatty acid, the more it is susceptible to oxidation or rancidity, which translates into compromises in taste and smell. Oils rich in saturated and monounsaturated fatty acids are more stable than fats rich in polyunsaturated fatty acids, i.e. the omega-6 and omega-3 classes of fatty acids.
Stability depends on the total distribution of fatty acids in the oil. An oil may be rich in monounsaturated fatty acids and at the same time carry significant amounts of polyunsaturated fatty acids as part of the mix, making them a poor choice for stability. Lack of stability does not mean that the oil is unhealthy. Certainly omega-3 fatty acids are healthy, and it's to our advantage to increase their presence in our diet. They are however quite volatile and will spoil faster in certain applications where shelflife is critical to the economic success of the product.
All those double bonds have another disadvantage when it comes to processed foods: Since they affect the melting point of the fats, they can compromise the texture of the final processed product, leaving it less crispy or flaky.
When it comes to selecting a suitable oil formulation that meets the stability test, smoke point is a critical factor. This is the temperature at which the oil begins to break down and the fatty acids are released from the fat molecule. This affects the quality of the finished product. Oils with a high smoke point include avocado and safflower oils, with smoke points of more than 500ºF.
Refining oils tends to increase the smoke point temperature. For example, unrefined soybean oil has a smoke point of 320ºF, while semi-refined oil is 350°F, and the refined oil breaks down at 460ºF. Total saturated fatty acids also make a difference. Classic refined canola oil has a smoke point of 400ºF, while the high-oleic canola oil has a smoke temperature of 475ºF.
High-oleic oil is any oil that is high in monounsaturated fats. Olive and canola oil are naturally high in monounsaturated fat, but they are also high in polyunsaturated fats, which reduces stability. High-oleic canola oil is thus marketed as a high-stability oil suitable for applications involving high temperatures, such as baking and frying.
Bunge North America, St. Louis, markets its Nutra-Clear as a high-stability canola oil, rich in oleic acid, low in linolenic acid, specifically developed for extensive deep frying. Nutra-Clear is non-hydrogenated, low in saturated fatty acids, and trans fatty acid-free. It can be used in a wide range of applications other than deep frying, including as a salad, ingredient, spray or griddle oil. It's highly stable and offers minimal flavor transfer.
Richardson International, Winnipeg, Manitoba, markets its Pure high-oleic, low-linolenic omega-9 canola oil as "Canola Harvest." It's suitable for high heat exposure and longer shelflife applications. It is non-hydrogenated, trans fat-free and also has high stability properties and a high smoke point — an ideal frying oil. Naturally stable properties make this suitable for spray applications and shelf-stable packaged goods, such as, croutons, crackers, cereals, snacks and potato chips. It has the lowest saturated fat level of any culinary oil.
Scientists have developed plants bred to be high in monounsaturated fats and low in polyunsaturated fats so they can be used in products that need to be shelf stable. Hi-oleic canola oil is the most recent of these products. The process of creating stable oils for food processing differs from hydrogenation in that the double bonds are bred out of the oils rather than destroyed by chemical treatment. That means these newer oils can be marketed as naturally healthy.