Over the past 30 years, many different shortenings have been tailored for specific applications using partial hydrogenation, a process that gives rise to trans fats. Palm oil can help supply similar functionalities without hydrogenation. Although palm oil is a single natural product, it is highly versatile due to a physical process called fractionation. During fractionation, the fat is melted and cooled slowly to produce a slurry of high-melting-point crystals suspended in liquid oil. The crystals are separated from the liquid component by filtration, and the resultant “fractions” have completely different physical properties compared to the original palm oil. The high-melting-point fraction, palm stearine (MP approximately 55°C), is a hard, waxy solid, while the palm olein fraction is a liquid at room temperature (MP approximately 25°C). Fractionating these fractions again gives additional components with different physical characteristics. Blending the fractions in different proportions generates an unlimited variety of shortenings, matching the functionality of almost any kind of partially hydrogenated vegetable oil.
Palm oil naturally resists oxidation and provides a long shelf life to baked goods and deep-fat-frying operations. It contains no linolenic acid (the most-unstable fatty acid in vegetable oil), and the total content of polyunsaturates is 10%, compared to 60% in soybean oil. The remaining fatty acids are oleic and palmitic acids, both of which are highly stable. Palm oil stability is further increased by the presence of natural antioxidants. Shelf-life and fry stability of all palm oil products are comparable to partially hydrogenated vegetable oil.
When replacing a partially hydrogenated shortening, comparing the solid-fat profile and melting point to the corresponding palm oil product is a useful first step. However, it is not realistic to expect an exact match, because of the large differences in fatty acid compositions. Palm oil, or a slightly harder or softer version of palm oil, is usually a drop-in solution for typical all-purpose shortenings used, for example, in cakes and cookies.
Some applications, including pies, Danish and puff pastries, require a more-sophisticated shortening. Regular palm oil tends to become brittle when cool, and softens excessively as it warms up. These applications need a fat that remains soft at lower temperatures and resists melting at high temperature. For these, appropriate blends of palm fractions provide the temperature tolerance needed for demanding applications.
Gerald P. McNeill, Ph.D., is director of research and development for the oils and fats division of Loders Croklaan NA, Channahon, IL, with responsibility for the roll-out of Loders’ comprehensive line of zero-trans fats and oils products.