The pH scale measures acidity or alkalinity, ranging from 0 (most acidic) to 14 (most alkaline), with 7 being neutral. Milk has a specific pH that is closely related to its quality. This value is not static and can shift due to various biological factors.
The pH Range of Different Milk Types
The pH of fresh cow’s milk is between 6.5 and 6.9, making it slightly acidic. This acidity results from components like carbon dioxide, citrates, and phosphates present in the milk. This value serves as a useful baseline for comparison with other types of milk.
Goat’s milk has a pH similar to cow’s milk, falling between 6.6 and 6.8. Human breast milk shows more variability; its pH changes with lactation, starting around 7.45 and settling between 7.0 and 7.4. Plant-based milks also differ, with oat milk being more acidic at a pH of 6.0 to 6.5, while almond milk ranges from 6.9 to 7.6.
Factors That Change Milk pH
The most common reason for a change in milk’s pH is microbial activity. As milk ages, bacteria like Lactobacillus ferment the milk’s sugar, lactose, producing lactic acid. The accumulation of this acid causes the pH to drop, leading to the sour taste and curdled texture of spoiled milk.
An animal’s health can also influence the pH of its milk. For instance, if a cow has an udder infection known as mastitis, its milk can become more alkaline. Monitoring pH can therefore be a method for dairy farmers to check the health of their herd.
Why Milk pH is Important
Measuring the pH of milk is a standard practice in the dairy industry as a reliable indicator of freshness and safety. A drop in pH can signal the beginning of spoilage before a consumer would notice. This allows processors to ensure only high-quality milk is used for bottling or other products.
The pH of milk is also important for food production. In cheesemaking, acidification is a necessary step to coagulate milk proteins to form curds, with most cheese varieties having a final pH between 4.4 and 5.3. Similarly, yogurt production relies on fermentation that lowers the milk’s pH to between 4.0 and 4.6, creating its tangy flavor and thick consistency.