How long does it take for milk to go bad?
In this brief article, we will answer the question, “How long does it take for milk to go bad?” shelf-life of milk, tips to store milk, and detect spoilage in milk.
How long does it take for milk to go bad?
Milk can last for 4 days to a week without going bad if it is stored well. If the milk is opened, the shelf-life would reduce to 2-3 days.
Total consumption of all milk types in US schools declined by 14.2% from 2008 to 2017, and the percentage of children participating in the school lunch program has also declined. This decline has also been driven by declining average daily participation in the school meal program and may also reflect children’s dissatisfaction with the sensory characteristics and the form of milk offered in schools (1).
There are various labels present on the milk carton. The best-by date would indicate how long the milk would remain in the best quality. The use-by date would be an indicator of how long the milk would be safer to consume. It is not a purchase or safety date (2).
The sell-by date is used by shopkeepers and is not an indication of the safety of the milk. The sell-by date indicates the date by which the milk can be bought by the consumers beyond which the quality of the milk can get affected. It is not a safety date (2).
During milk pasteurization, not all bacteria are killed. Sources of the initial microflora in raw milk include the interior of the udder, udder surfaces, milking equipment, transport lines, storage tank, environment (such as air and water), and workers. Raw milk may also be contaminated from the animal manure and flies (3).
You can refer to these dates to check the safety and quality of the milk.
The shelf-life of other types of milk is stated below (4). Once milk is opened, it will last about 3-5 days after the sell-by date on the label. Spoiled milk has a strong, sour odor and lumpy texture caused by excess bacteria producing lactic acid, which curdles the protein in milk and produces off-odors (5).
|Type of milk||Shelf-life of milk|
|Reduced-fat milk/ skimmed milk||1 week|
|Whole milk||5-7 days|
|Lactose-free milk||7-10 days|
Can milk be consumed past its expiry?
If the milk is pasteurized, it means most of the harmful microbes have been killed. This does not mean that all microbes have been killed. Some microbes would still be present in the milk and can contribute to the spoilage of the milk.
The temperature of the fridge can play a major role in regulating the quality of the milk. If the temperature of the fridge is below 40 degrees Fahrenheit, the shelf-life of the milk would be extended. If it has been stored at room temperature for two hours or longer, it is recommended to discard it. Although pasteurization kills much of the bacteria in milk, any remaining bacteria can grow quickly in milk at room temperature or warmer (5).
If the milk has not been pasteurized, the shelf-life would reduce considerably. Aseptic milk produced using Ultra High Treatment (UHT) can also last for 2-4 weeks past the printed date. UHT processing is a method of milk preservation by which both the microorganisms and enzymes are reduced to a commercially acceptable level (commercial sterility). UHT milk is bacteriologically stable for months at ambient temperatures; its shelf life is often affected by age gelation (3). Opened UHT milk can last for only 7-10 days (4).
It is essential to check the milk for signs of spoilage especially if you are planning to consume them post their expiry.
The most common fermentative spoilage of fluid milk products is souring caused by thermoduric LAB. Lactic acid by itself has a clean pleasant acid flavor and no odor. The unpleasant “sour” odor and taste of spoiled milk result from formation of small amounts of acetic and propionic acid. Sour odor can appear before an acid flavor when the microbial population reaches 106 cells per milliliter of fluid milk products. Pasteurized milk spoils by the growth of heat resistant Streptococcus utilizing lactose to reduce pH (3).
How to store milk?
- Milk should not be stored at room temperature for more than 2 hours as this can attract the growth of microbes in the milk.
- Keep the milk in the refrigerator immediately after you have bought it. Store at a temperature below 40 degrees Fahrenheit.
- Place the milk on the back of the fridge as the back would be the coolest place in the fridge. Avoid placing the milk at the door of the fridge as it is subject to fluctuations in temperature.
- Seal the milk properly and place them in the fridge.
- For longer shelf-life milk can also be kept in the freezer. It is important to remember though that freezing followed by thawing can alter the texture and color of the milk. It would still be fine to drink it.
- If the room temperature goes above 90 degrees Fahrenheit, avoid keeping the milk out for long.
- If you are buying milk from a shopkeeper, make sure to check whether the milk has been chilled. Ensure that the milk has been kept in a fridge or cool place.
- To thaw the milk kept in the freezer, place them in the fridge overnight. Thawed milk is less stable than fresh milk and can spoil faster (3). You can also thaw the milk by placing it in cold water as well.
- If you have placed milk alternatives in the freezer, it would be best to consume them within 3 months (6). If you wish to quickly freeze them, place the milk in ice cube trays.
- Avoid defrosting milk at room temperature.
How to detect spoilage in milk?
- Smell the milk. If the milk gives off a bad odor, it is better to discard it immediately. Sour odor or other off-flavors, such as sour or acid flavor, bitter, burn or caramel flavor, barny, soapiness, fruity, fishiness, putrefaction, alcoholic and coconut-like flavor.
- The texture of spoilt milk can also change. It can show the appearance of lumps. Ropiness (sliminess), increase in viscosity are also signs of spoilage.
- The color of the milk might change to pale yellow which can also be another indicator of spoilage. Blueish, brown and red colors can also occur.
- Spoilt milk can taste sour. In such a case, throw the milk away.
The methods to check for spoilage in plant milk is similar to the one listed above.
Other FAQs on milk that you might be interested in.
How to make condensed milk from evaporated milk?
Can coconut milk be substituted for milk? (+13 substitutes)
What happens if you consume spoilt milk?
Consumption of spoilt milk can result in the development of symptoms of food poisoning. The symptoms of food poisoning would include diarrhea, nausea, vomiting, and bloody urine.
Extreme cases of food poisoning can cause dehydration as well.
Other FAQs about Milk that you may be interested in.
When did humans start drinking cow milk?
Which plant-based milk is better: coconut milk or almond milk?
How to prepare condensed milk in the microwave?
In this brief article, we have answered the question, “How long does it take for milk to go bad?” shelf-life of milk, tips to store milk, and detect spoilage in milk.
- Sipple, Lauren R., David M. Barbano, and MaryAnne Drake. Invited review: Maintaining and growing fluid milk consumption by children in school lunch programs in the United States. J dairy sci, 2020, 103, 7639-7654.
- Food Product dating. United States Department of Agriculture. 2013.
- Erkmen, Osman, and T. Faruk Bozoglu. Spoilage of Milk and Milk Products. Food Microbiology, Principles into Practice. John Wiley & Sons, 2016, 307-336.
- FSIS’ FoodKeeper. Food Safety and Inspection Service.
- Milk. The Nutrition Source. School of Public Health, Harvard. 2022.
- Maddox, M. Freezing milk and dairy products. 2020. University of Florida.