Which of the following food additives acts as an emulsifier?

An emulsifier is a substance that helps to stabilize mixtures of oil and water, allowing them to blend together rather than separate. Mono and diglycerides are derived from glycerol and fatty acids and serve as effective emulsifiers in various food products. They lower the surface tension between oil and water, creating a stable emulsion, which is essential in foods like salad dressings, margarine, and baked goods.

Other options do not function as emulsifiers. Monosodium glutamate is primarily used as a flavor enhancer. Ascorbic acid acts as an antioxidant, preventing spoilage by inhibiting oxidative processes. Carboxymethyl cellulose is a thickening agent and stabilizer but does not particularly serve the function of an emulsifier. Therefore, mono and diglycerides stand out as the correct answer in the context of food additives that act as emulsifiers.