The Chemical Reaction That Creates Acidity
Acidity in cheese curds is a result of fermentation by lactic acid bacteria (LAB) starter cultures introduced to pasteurized milk. These cultures convert lactose, the sugar in milk, into lactic acid. While milk has a near-neutral pH of about 6, this process lowers the curd's pH to an acidic range, typically 4.5–5.5. This drop in pH is crucial for subsequent cheesemaking steps and the final product's characteristics.
The Role of Lactic Acid Bacteria
The type of LAB culture used affects the final cheese properties:
- Mesophilic Bacteria: Used for milder cheeses, like fresh cheddar curds, and thrive at moderate temperatures.
- Thermophilic Bacteria: Used for sharper, more acidic cheeses and prefer higher temperatures.
Cheesemakers control these bacteria to manage the acidification process.
Acidity's Impact on Flavor and Texture
Acidity is a key factor influencing the flavor and texture of cheese curds. The tangy taste comes directly from lactic acid. It also affects the physical structure.
The Science of the Squeak
The characteristic "squeak" of fresh cheese curds comes from the casein protein network held together by calcium phosphate bonds. Acidity breaks down this network as the cheese ages, causing the squeak to fade and altering the texture. Cheesemakers aim for a balance to achieve the desired squeaky texture and tangy flavor.
Comparison of Acidity's Influence on Curd
| Property | High Acidity (Low pH) | Low Acidity (High pH) |
|---|---|---|
| Flavor | Sharper, tangier, more pronounced acidic taste. | Milder, sweeter, more buttery or milky. |
| Texture | Firmer and potentially more brittle or grainy. | Softer, more elastic, and springier. |
| Squeak | Squeak diminishes more quickly as acid breaks down the protein network. | Retains its squeak for a longer period due to a more intact protein structure. |
| Calcium Retention | Less calcium is retained in the curd, as the acid solubilizes the minerals. | Higher calcium content is retained, contributing to elasticity and better melting properties. |
Cheesemaking Techniques for Controlling Acidity
Cheesemakers use several techniques to manage acidity:
- Measuring and Monitoring pH: pH meters are used throughout the process to ensure the correct acidification curve is followed.
- Timing of Curd Cutting: Cutting curds affects moisture and acidity; smaller curds heated to a higher temperature can reduce moisture and minimize excessive acidity.
- Curd Washing: This technique removes whey containing lactic acid and replaces it with water, which increases the curd's pH and reduces acidity.
Conclusion: The Final Verdict on Cheese Curd Acidity
Cheese curds are indeed acidic. This acidity stems from the fermentation of lactose by bacteria, producing lactic acid. This process is fundamental to their signature tangy flavor, texture, and squeak. Cheesemakers precisely manage factors like starter cultures and pH levels to achieve the desired balance of tang and texture. The controlled acidic environment is key to the characteristic qualities of fresh cheese curds. Further information on the science behind these processes and acidity control in cheesemaking can be found at the Center for Dairy Research.
