What are Emulsifiers?
When water and oil both exist in a system, the oil eventually separates and floats to the top. To prevent this, emulsifiers are used to act as an intermediary for water and oil. In bread making, they are used for dough conditioning and shelf life extension.
Emulsifiers are molecules with two distinct ends.1 One hydrophilic end prefers water, and the other lipophilic end is partial to oil. In baking and food applications, the water-friendly end of an emulsifier is deemed the ʻhydrophilic head,ʼ while the oil-friendly end is referred to as the ‘hydrophobic tail,’ as shown in figure 1.
Many food products are emulsions, or stable mixtures of components that do not normally exhibit immiscibility. Emulsifiers allow this stability by reducing the surface tension between the two immiscible components. The most common natural example of an emulsifier is portrayed in milk, a complex mixture of fat suspended in an aqueous solution.
Commercial emulsifiers were introduced to the food industry in the 1930s in the form of mono- and diglycerides.1 Before their commercial introduction, the emulsification properties found within eggs were utilized. Egg yolks contain lecithin and other phospholipids that act as natural emulsifiers in food. The market for them the food industry was around $2.1 billion in 2012 and is predicted to rise to around $2.9 billion by 2018.7
In bread making, the function of emulsifiers are crucial to final product quality and attributes as they stabilize the dough to be processed in the bakery, and reduce the rate of retrogradation (staling). In addition, they serve as a dough conditioner by interacting with gluten to strengthen the protein network resulting in a desirable texture. In fact, their two major functions in yeast-raised products are dough conditioning, or strengthening, and shelf life extension, or “crumb softening.”2 A recent study with fiber enriched breads shows advantages in an increase in volume and crumb texture when SSL and DATEM were used.3
In cake products or pastries, emulsifiers improves gas bubble stability, resulting in a light, tender and moist product. When used in batters, they improve water binding and decrease the fluidity of the batter.4 Without them, dough or batter appears greasy and has a shine with the fat dispersed in large, coarse, irregularly shaped particles. Incorporation of emulsifiers enables aeration, foam stabilization, emulsification and crumb softening. Crumb softening does not entail actual softening of the grain, but rather slows the firming of the crumb or retrogradation. By inhibiting the rate of staling, they help generate a higher quality product with longer shelf life for consumers.
Emulsifiers can be classified by their ratio of the molecular weight of their hydrophilic polar end to the molecular weight of the lipophilic nonpolar end by means of the Hydrophilic-Lipophilic Balance, or HLB rating. Values within the HLB range from 0 to 20, with 0 being an entirely lipophilic molecule, and 20 representing an entirely hydrophilic substance. Emulsifiers, which rank in the range of 10 on the HLB scale, exhibit properties in equal balance.
Common emulsifiers that condition dough or batter via strengthening the protein network, resulting in better gas retention, improved texture, and increased volume are:
- Lecithins: First emulsifiers used in commercial baking applications. Phospholipids within the egg itself exhibit the necessary emulsifying properties. Two fatty acid component exhibit a great affinity for fat molecules when concurrently the hydrophilic phosphoric radical exerts a strong affinity for water, thereby leading to emulsion. Using Lecithin in bread dough has been proven to increase fermentation tolerance, exhibit better dough machinability, produce a better crumb color, tenderize crust, and smooth texture, while maintaining grain uniformity and lengthening shelf life.
- Sodium- and calcium stearoyl lactylate (SSL5 and CSL): HLB value of 21 & 10. Shows dough-conditioning properties as well as soften crumb effectively. Dough performance is also strengthened, attributed to the capability of forming a protein complex once mixing begins and then later during baking to form a starch complex, consequently retarding staling resulting in the softening of the crumb.
- Ethoxylated mono- and diglycerides (EMG): HLB value in between 9-10. In today’s baking industry, these are the most widely used emulsifiers. Imparts great dough strengthening properties.
- Polysorbates (PS): HLB value in between 14-16. Very surface active. Improves crumb color and strength, increases volume, and improves shelf life.
- Succinylated monoglycerides (SMG): HLB value 5.3. Interacts with flour proteins as a result of monoglyceride reacting with succinic anhydride. Greatly effective as a dough conditioner via enhancing crumb softening while increasing volume and shelf life.
- Diacetyl tartaric acid esters of monoglycerides (DATEM): HLB value 9.2. Denotes excellent handling properties as well as increased volume and lengthened shelf life.
- Mono & Diglycerides: HLB value 2.8 to 3.5. One of the most popular emulsifiers used in the bakery as a dough strengthener and crumb softener. They also aid fat and oil dispersion in batter systems.
With the popularity of clean label trend, the identification of natural alternatives to synthetic emulsifiers has considerable economic implications. Examples of the natural ones are amphiphilic proteins, polysaccharides, biosurfactants, phospholipids, and bioparticles.
FDA lists the allowed emulsifiers and their limitations for food usage in the Code of Federal Regulations (Title 21 Part 178.3400).6
- Steven R. Baker “Maximizing the Use of Food Emulsifiers.” Dept. of Animal Science, Kansas State University, A Thesis (2010)
- Indrani, Dasappa, and Gandham V. Rao. “Functions of Ingredients in the Baking of Sweet Goods.” Food Engineering Aspects of Baking Sweet Goods. By Servit Gulum. Sumnu and Serpil Sahin. Boca Raton: CRC, 2008. 31-47.
- Analía, Gómez, Buchner Diana, Tadini Carmen, Añón María, and Puppo María. “Emulsifiers: Effects on Quality of Fibre-Enriched Wheat Bread.” Food and Bioprocess Technology 6.5 (2013): 1228-1239.
- Sahi, Sarabjit S., and Juan M. Alava. “Functionality of emulsifiers in sponge cake production.” Journal of the Science of Food and Agriculture (2003) 58:92-95
- Stauffer, C. E. “Emulsifiers for the Food Industry.” Bailey’s Industrial Oil and Fat Products. By Fereidoon Shahidi. New York: Wiley, 2005. 229-67.
- “21CFR178.3400” CFR-Code of Federal Regulations Title 21. N.p. 1 Apr. 2016. http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?fr=178.3400. Accessed 30 Nov. 2016.
- Mcclements, David Julian, and Cansu Ekin Gumus. “Natural Emulsifiers â Biosurfactants, Phospholipids, Biopolymers, and Colloidal Particles: Molecular and Physicochemical Basis of Functional Performance.” Advances in Colloid and Interface Science 234 (2016): 3-26.