Yes, boiled milk can go bad.
While boiling milk can kill harmful bacteria, it does not prevent spoilage entirely. According to Professor Saurabh Gupta from the Food Corporation of India (FCI), further boiling milk after pasteurization can actually reduce its shelf life. This is because the heat treatment changes the proteins in the milk and can alter its ability to resist spoilage over time.
Why Does Boiled Milk Go Bad?
- Bacterial Growth: Although boiling kills most bacteria, spores of certain bacteria can survive. These spores may germinate and grow when the milk cools to a favorable temperature.
- Enzymatic Activity: Milk contains enzymes that can cause spoilage, and while boiling deactivates them, this is not permanent and they may become reactivated over time, especially at room temperature.
- Contamination: After boiling, milk can be re-contaminated if not stored properly, leading to further bacterial growth.
How Quickly Does Boiled Milk Go Bad?
The speed at which boiled milk spoils depends on several factors:
- Storage Temperature: Milk will spoil faster at room temperature. Storing boiled milk in the refrigerator can significantly extend its shelf life.
- Hygiene: Reusing dirty utensils, containers, or not practicing good hygiene can increase the rate of spoilage.
- Exposure to Air: Leaving boiled milk uncovered can allow bacteria and other contaminants to enter, leading to spoilage.
How to Extend the Shelf Life of Boiled Milk
- Refrigerate Promptly: After boiling, cool the milk quickly and refrigerate it within two hours.
- Use Clean Containers: Store boiled milk in clean, airtight containers to prevent re-contamination.
- Consume Quickly: Ideally, consume boiled milk within a few days for best quality.
- Boiling only when needed: Don't re-boil pasteurized milk unless it is absolutely necessary.
Summary Table
| Factor | Effect on Boiled Milk Spoilage |
|---|---|
| Storage Temperature | Faster at room temperature |
| Hygiene | Faster if unhygienic practices |
| Air Exposure | Faster when exposed to air |
| Repeated Boiling | Reduced Shelf Life |
| Refrigeration | Slows down spoilage |
Therefore, even though boiling kills bacteria initially, it is crucial to store boiled milk properly to prevent spoilage. Remember, boiling milk reduces its shelf life rather than extending it.
