Sodium stearoyl lactate (and the similar calcium stearoyl lactate) is made by combining lactic acid and stearic acid, and then reacting the result with sodium hydroxide or calcium hydroxide to make the sodium or calcium salt.
Replacing the lactic acid with fumaric acid gives sodium steroyl fumarate, a compound with same uses as the other two.
Sodium stearoyl lactylate is an emulsifier used as a dough strengthener in baked goods. It has several features that combine to make it very popular with bakers.
It maintains the texture of fresh baked bread by keeping the amylose starch in its gelled state, preventing its recrystallization.
It makes the gluten in the bread stronger and more extensible, increasing the volume of the loaf.
It disperses the fats in the bread, making it softer, while allowing less fat to be used.
It absorbs water, allowing the baker to get 1 to 1.5% more loaves from the same ingredients, thus making each loaf less expensive.
It has a sweet taste, allowing less sugar to be used in the bread.