Which of the following are protein thickeners?

• A. Gelatin, Egg Yolk, Casein
• B. Acacia, Pectin
• C. Sorbitan Esters
• D. High-Molecular Weight Alcohol

Answer: (A)

Protein thickening happens when proteins form a three‑dimensional network that traps water and resists flow, turning a liquid into a gel-like or more viscous system. Gelatin is a classic protein thickener: it swells in water and, upon cooling, forms a gel network that greatly increases viscosity. Casein, the main protein in milk, also thickens by forming networks in solution, especially under conditions that promote aggregation or gelation, contributing to the body and mouthfeel of dairy products. Egg yolk brings protein-rich components that help stabilize and thicken emulsions and gels through interactions among its proteins and phospholipids, adding to the viscosity of mixtures.

In contrast, the other options rely on different mechanisms. Acacia (gum arabic) and pectin are polysaccharides; they thicken by forming long carbohydrate networks rather than protein networks. Sorbitan esters are emulsifiers, surfactants that stabilize emulsions rather than create a protein-based network. High-molecular-weight alcohols don’t form protein gels or networks and are not used as protein thickeners.