Which of these agents is used for stabilizing emulsions?

Acacia is a natural gum derived from the sap of the Acacia tree, and it is widely recognized for its effectiveness as an emulsifying agent. Emulsifying agents are substances that help to stabilize mixtures of oil and water by reducing the surface tension between the two immiscible liquids, thus preventing them from separating. Acacia achieves this through the formation of a protective layer around oil droplets, which helps to keep them dispersed within the aqueous phase.

While options like xanthan gum, agar, and bentonite have their respective uses in food science and other applications (such as thickening or gelling), they are not primarily known as emulsifying agents. Xanthan gum is mainly used as a thickening agent and stabilizer but it doesn't have the same emulsifying properties as Acacia. Agar serves as a gelling agent, particularly in microbial culture or as a vegetarian substitute for gelatin. Bentonite, a type of clay, is often used in products for clarifying and thickening but is not specifically known for emulsion stabilization.

Thus, Acacia stands out as the most effective choice for stabilizing emulsions due to its unique properties that facilitate the even distribution of oil and water phases.