What Is Sodium Stearoyl Lactylate?
Sodium stearoyl lactylate is the sodium salt of an long-chained carboxylic acid containing two ester linkages. SSL has the chemical formula C₂₄H₄₄O₆Na, and has a molecular weight of 451.6. It is extremely useful in the commercial baking of breads and pastries. It is also used in formulating icings, puddings, toppings, artificial creamers, dehydrated potatoes, snack dips, cheese and imitation cheese products, gravies, and sauces.
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Synthesis
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Overall, the chemical preparation of sodium stearoyl lactylate involves three basic steps.
The first is the reaction between two lactic acid molecules. Besides having an acid group (-COOH), lactic acid has a hydroxyl group (-OH). The hydroxyl of one lactic acid molecule can combine with the acid group of another molecule of lactic acid, producing an ester linkage, while eliminating a water molecule. This leaves a longer chained substance with one hydroxyl and one acid group remaining at opposite ends of the molecule.
The remaining hydroxyl group is then reacted with the acid group of a stearic acid molecule, forming another ester linkage, while eliminating another water molecule. This leaves only one acid group remaining.
That acid group is reacted in step three with an alkali to form the sodium salt, eliminating a final water molecule (see Figure 1 for the overall reaction).
Emulsifier
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Sodium stearoyl lactylate is a useful emulsifier in the manufacture of baked goods for many reasons. It disperses the fats in the bread, thus allowing less fat to be used, while softening the bread. Coupled with iota-carrageenan, SSL is being investigated for use in the emulsification of "meat batters".
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Moisture
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SSL, although dispersing fat, is also a humectant allowing the use of additional water in a recipe. It prevents separation, thus acting as a stabilizer. This allowed increase in moisture in the recipe makes it possible to increase the number of loaves produced by perhaps one to one-and-a-half percent.
Sweetness
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Sodium stearoyl lactylate imparts a sweetness of its own, thus decreasing the need of sugar in recipes.
Gluten
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Sodium stearoyl lactylate strengthens bread gluten, and increases its extensibility (a property of gluten proteins), increasing loaf volume.
Starch
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Starch crystallinity, such as is found in straight-chained amylose starch, is considered a problem after baking. As starch recrystallizes, bread and other baked goods are said to "go stale". The process by which the crystalline regions of starch molecules are kept from recrystallizing is called "gelatinization" (vitrification of the gluten network). Gelatinization is enhanced by the extra moisture sodium stearoyl lactylate allows in the recipe. Because of gelatinization, baked goods made with SSL seem to remain fresh, longer.
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References
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