Lemon juice thickens primarily due to its acidity interacting with proteins, especially in dairy-based mixtures. This acidic reaction causes the proteins to denature and coagulate, increasing the mixture's viscosity.
Here's a breakdown of the process:
- Acidity: Lemon juice is highly acidic, containing citric acid.
- Protein Interaction: When lemon juice is added to a mixture containing proteins (like milk or cream), the acid disrupts the protein's structure.
- Denaturation: The acidic environment causes the proteins to unfold or "denature."
- Coagulation: The denatured proteins then clump together, forming a network. This process is called coagulation.
- Increased Viscosity: This coagulation increases the thickness of the mixture. This is similar to how vinegar curdles milk.
Think of it like making ricotta cheese. Acid (often lemon juice or vinegar) is added to milk, causing the milk proteins to coagulate and separate from the whey, creating a thicker curd. The same principle applies, albeit on a smaller scale, when lemon juice thickens a sauce or custard.
