The Traditional Method: A "Recooked" Process
In Italy, the birthplace of ricotta, cheesemakers developed a resourceful method to produce a second cheese from the whey, or the leftover liquid, of their first batch. The word ricotta literally translates to "recooked," a direct reference to this process. After making a cheese like Pecorino, the cheesemaker takes the residual whey, allows it to become more acidic, and then heats it to near-boiling temperatures. The combination of heat and acidity causes the remaining proteins in the whey—primarily albumin and globulin, not the main milk protein casein—to clump together and rise to the surface. These fine, soft, and milky white curds are then scooped out and drained, resulting in the creamy, fresh cheese known as ricotta. This traditional method has no need for rennet, as the heat and acid perform the necessary coagulation naturally.
Modern Variations: Milk-Based Ricotta
For most home cooks today, obtaining leftover whey from a previous cheesemaking endeavor is not practical. Instead, they make a fresh cheese that mimics ricotta using a more accessible method that starts with whole milk. This process is different from traditional ricotta, though it yields a similar product in texture and flavor. To make this modern, milk-based ricotta, whole milk (and often some cream for richness) is heated and an acid is introduced to prompt coagulation. This method coagulates both casein and whey proteins, technically making it a fresh cheese and not a true whey-based ricotta. A variety of acidulating agents can be used:
- Lemon juice: Provides a subtle citrus flavor.
- White distilled vinegar: A very common choice that is easy to measure and produces consistent results.
- Buttermilk: Can be used to acidify the milk during the heating process.
- Citric acid: A powdered form of acid favored by some cheesemakers for consistent curd formation.
Like the traditional method, this modern approach also relies on acid and heat, and the use of rennet is generally unnecessary and omitted in home recipes.
The Role of Rennet in Some Commercial Production
While traditional ricotta is rennet-free, the question of "is rennet used to make ricotta cheese?" becomes more nuanced when considering large-scale commercial production. Some industrial producers may add rennet, microbial coagulants, or other thickeners to their recipes for several reasons, including increasing yield, ensuring a consistent texture, and standardizing the production process.
- Increased Yield: Adding a small amount of rennet can help coagulate more proteins, leading to a higher yield of product.
- Consistency: The use of specific coagulants can ensure that every batch has the same consistency and texture, a crucial factor for a mass-market product.
- Vegetarian Concerns: For those following a vegetarian diet, it is essential to check the label on store-bought ricotta. Some brands will specify "vegetable rennet" or "microbial coagulant" if a non-animal source is used.
Casein vs. Whey Proteins: The Science of Coagulation
To understand why rennet is typically not needed for ricotta, one must grasp the difference between milk's two main protein types and how they coagulate.
- Casein Proteins: These make up about 80% of the protein in milk. Rennet is an enzyme that specifically acts on casein, causing it to form solid curds. This is the basis for most ripened cheeses, like cheddar, mozzarella, and gouda.
- Whey Proteins: This group includes albumin and globulin and constitutes the remaining 20% of milk protein. These proteins do not respond to rennet. Instead, they require a combination of heat and acid to coagulate and form curds. Since traditional ricotta is made from whey, which contains only these leftover proteins, the heat and acid combination is the only coagulant needed.
Traditional vs. Modern Ricotta Comparison
| Feature | Traditional Ricotta | Modern (Milk-based) Ricotta |
|---|---|---|
| Base Ingredient | Leftover whey from cheesemaking | Whole milk (or milk/cream mix) |
| Primary Coagulant | High heat (near-boiling) and acid | High heat and acid (e.g., lemon juice) |
| Use of Rennet? | No, typically not needed | No, acid is used instead |
| Protein Type | Whey proteins (albumin, globulin) | Casein and whey proteins |
| Flavor Profile | Subtly sweet, milky | Milky, potentially with a slight tang from acid |
| Name Meaning | "Recooked" | Technically a fresh cheese, not true ricotta |
The Verdict: When is Rennet Used for Ricotta?
The final word on whether rennet is used to make ricotta cheese depends entirely on the method. The centuries-old Italian tradition of making ricotta from recooked whey does not involve rennet, relying instead on high heat and acid to coagulate the remaining whey proteins. This is the most important distinction. For modern homemade versions, a similar process using acid to curdle whole milk is common, and rennet is also not typically included. However, in some large-scale commercial settings, rennet or other non-traditional coagulants may be used to increase efficiency and yield, making it essential for conscientious consumers to check the label. Ultimately, for authentic, freshly made ricotta, the need for rennet is not part of the process.
Wisconsin Cheese offers further insights into the world of cheesemaking and the distinctions between various dairy products.
