A recent inquiry to the American Bakers Association (ABA) asked what the purpose of emulsifiers are in a bakery formula. Using fundamental chemistry as a background, here is a generalized overview of lecithin in a bakery environment. (To read part one of this series, see “The fundamental chemistry of baking cookies,” which analyzes the role of sodium bicarbonate, among other factors, in a sugar cookie dough formula.)
Emulsifiers are one of the lesser-known aspects of the baking industry, and we tend to rely on “heritage formulas” and “heritage knowledge” in using emulsifiers in a bakery environment (using the rationale of “that’s the locked-in formula” and “we have always done it that way”). Lecithin is a widely used emulsifier, and there are specialized emulsifiers for specific purposes.
Specialized emulsifiers such diacetyl tartaric acid esters (DATEM) and sodium stearyl lactates (SSL) are two of the more-common emulsifiers used. These offer specific characteristics in foam formation in dough and bread quality. They are added to the formulation because they are known to improve loaf volume and stability of the dough during proving (see “Effects of emulsifiers and hydrocolloids on whole wheat bread quality: A response surface methodology study” and “Breads from white grain sorghum: Effects of SSL, DATEM, and xanthan gum on sorghum bread volume”). Little is known about the underlying mechanism, but it is thought that they replace the lipids at the surface, and perhaps even the proteins, and stabilize the gas cells against coalescence, as they are more foam-active than the wheat lipids due to their detergent-like structure (see “Breadmaking,” Second Edition, 2012).
Lecithin is a widely use emulsifier and is added to cookie formulas to improve machinability in sheeting laminated doughs and as a release agent in rotary-moulded cookies. Lecithin generally refers to a complex mixture of phosphatides obtained as byproducts in the refining process of oils by hydration and subsequent drying. Use of soy lecithin also requires an allergen declaration on the label for those individuals sensitive to soy protein.
The main commercial source of lecithin is soybean oil due to its high content in phosphatides (about 2 percent). However, lecithin can also be obtained from other vegetable oils, such as corn, cottonseed, rapeseed, rice, sunflower, and even from eggs, an animal source. The most interesting components of lecithin are the phospholipids due to their emulsifying properties. Lecithin is widely used in food processing because of its dispersing, stabilizing, and emulsifying characteristics.
Lecithin is an emulsifier made up of about five smaller molecules. It has a backbone of glycerol that bonds up to three other molecules creating a hydrophobic (water-repelling) tail, and two of the bonded molecules are fatty acids forming a hydrophilic (water-attracting) head. They give lecithin a structure similar to fats or lipids.
Lecithin is one type of emulsifier used in food application primarily to reduce surface tension at an oil and water interface and promote emulsification. Emulsifiers can, however, perform other functions when utilized in food application. ABA’s Cookie and Cracker Manufacturing Course states that emulsifiers are categorized by the following three functions:
- Reducing surface tension
- Interacting with starch and protein components
- Enhancing wetting, dispersing, and foaming
Lecithin is used in the cookie and cracker industry in several applications. It is used for the combination of oils. It also allows oils with different specific gravities to stabilize as one emulsion.
Lecithin added as an ingredient to crèmes (sandwich cookie fillings) as it increases the fluidity of the filling. However, caution must be used, as even small amounts of lecithin can have an exponential effect on the viscosity of the crème.
Lecithin can be used to reduce the overall amount fat in a product if a fat-free or low-fat claim is being made on the finished product. It is also used in the manufacture of chocolate and compound coatings by reducing the interfacial tension of the cocoa butter and any additional ingredients.
Emulsifiers play a key role in production, enabling plant efficiency and final consumer acceptability of baked products. Lecithin allows normally immiscible liquids to remain in a stable state for further processing.