Technical Talk: May 2012
Mastering oil and water
Written by Dr. John Michaelides
Emulsifiers, also known as surfactants, are often referred to in the baking industry as crumb softeners, dough conditioners, or even anti-staling agents. Basically, they are chemical substances that, when used in a liquid mixture, change the surface behaviour of liquids and provide functionality. They are either hydrophilic (water-loving/attracted to water) or hydrophobic (water-fearing, but more accurately, water-repelling), which is also called lipophilic (fat-loving).
Emulsifiers are categorized in broad terms based on certain characteristics, such as ionic charge, solubility in solvents, and hydrophilic-lipophilic balance. The hydrophilic-lipophilic balance (HLB) determines the ratio of the molecular weight of the hydrophilic portion of the emulsifier divided by the total molecular weight of the emulsifier. This determines the ratio of polar (water-loving) to non-polar (fat-loving) portion in the emulsifier, and therefore determines whether it has an affinity to water or oil. The values for HLB range from zero (completely lipophilic) to 20 (totally hydrophilic) for each type of emulsifier. For example, monoglycerides have an HLB value of about three and are considered fairly lipophilic. Emulsifiers with HLB below eight are typically used for water-in-oil emulsions, while those with values above eight will be used for oil-in-water emulsion.
Emulsifiers interact with gluten protein to stabilize the dough with their hydrophilic or hydrophobic groups. This contributes to dough elasticity, oven spring and volume. Crumb-softening happens when the emulsifiers form complexes with the gelatinizing starch. This also prolongs shelf life of by slowing staling. Emulsifiers such as diacetyl tartaric acid esters of mono- and diglycerides (DATEM) are very good stabilizers, whereas monoglycerides are more effective as crumb softeners. A combination will provide both effects, if required. On the other hand, sodium stearoyl-2-lactylate (SSL) is an emulsifier with both good dough-stabilizing activity and crumb-softening effect.
Most emulsifiers are synthetic chemicals. Lecithin, however, which is a naturally occurring compound, was one of the first emulsifiers to be used extensively in the baking industry.
Mono- and diglycerides are the emulsifiers used most extensively by bakers. Most fats are mainly made up of triglycerides, which contain three chains of fatty acids attached to a central glycerol molecule. Fats also contain small amounts of monoglycerides and diglycerides. Their functionality is dependent on the nature and characteristics of their fatty acid content. Mono- and diglycerides may also be classified as natural because they are found naturally in various fats and oils. However, modified ones, such as ethoxylated mono- and diglycerides that are produced by reacting with ethylene oxide, or DATEM, produced by the reaction with diacetyl tartaric acid, will not be considered natural. Other emulsifiers that are widely used include sodium stearoyl-2-lactylate (SSL) and calcium stearoyl-2-lactylate (each of which is produced by the reaction of stearic and lactic acid) and sodium stearoyl fumarate (a product of the reaction between stearic and fumaric acid).
Emulsifiers are multifunctional. For example, in yeast-raised products, the appropriate use of emulsifiers will create higher volume, result in better crumb, delay staling, increase brightness and improve the crust. In cakes, emulsifiers will improve volume, texture and mouth feel, as well as extend the shelf life. With icings and fillings, emulsifiers can better the grain and texture, as well as increase stability. Quite often, emulsifiers that are very good for one attribute are not as good for another. For example, where dough stability is of importance (such as in the case of frozen dough or in products with high fibre where the fibre interferes with gluten development), DATEM can be used to alleviate these problems and produce good-quality, yeast-raised baked goods. In addition, DATEM may help produce good-quality breads from flours with lower-quality protein.
Hydrophilic emulsifiers (HLB value higher than 13) are recommended for cake batters because they result in a uniform dispersion of very small fat particles, and therefore create a very large number of small sites for water vapour to expand. The fat-entrapped air in these sites expands to contribute to the cake volume. The smaller the air bubbles, the larger the resulting cake volume.
Today’s consumers demand food products that are more natural, with fewer synthetic ingredients. Most emulsifiers are considered unnatural and the demand for natural ones will almost certainly increase. Unfortunately, most natural emulsifiers are not as effective as the synthetic ones. New enzymes have recently been introduced that can modify the naturally occurring fat in various ingredients and increase their emulsification capacity. Enzymes are now available that can modify parts of the egg yolk as an ingredient in order to provide them with ability to exert a higher emulsifying action.
This may reduce the use of eggs and other emulsifiers. Another enzyme recently introduced is a lipase that can be used in bread making. This enzyme modifies the natural lipids in the flour so they act as emulsifiers and reduce need for additional emulsifiers without compromising the product quality.
For more information, or fee-for-service help with food technical and
processing issues and needs, please contact Dr. John Michaelides at
John Michaelides & Associates at 519-743-8956, or at Bioenterprise
519-821-2960 ext. 226, or by e-mail at
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