Quick answer
Yes, milk needs to be refrigerated to prevent bacteria growth and spoilage. The proteins and sugars in milk provide an ideal environment for bacteria to multiply rapidly at room temperature. Refrigeration slows this bacterial growth by lowering the temperature. For optimal freshness and food safety, milk should be kept at 40°F or below.
What happens if you don’t refrigerate milk?
If milk is left unrefrigerated, bacteria present in the milk will begin to rapidly multiply due to the warm temperature. This bacteria growth causes milk to spoil much faster than if it was stored in the refrigerator.
Room temperature milk will start to develop an unpleasant sour smell and taste within 2 hours. At around the 4 hour mark, the milk will curdle and become lumpy as acidity increases. By 6 to 8 hours sitting out, milk will be completely spoiled and unsafe to drink.
Drinking milk that has been left out too long can cause food poisoning symptoms like nausea, vomiting, and diarrhea. This is caused by harmful bacteria like E. coli, Salmonella, and Listeria that can grow along with the spoilage bacteria.
Does the type of milk matter?
All types of milk need refrigeration to stay fresh, including:
Whole milk
The high fat content of whole milk (around 3.25%) provides more nutrients for bacteria to feed on, so it will spoil faster than low-fat or skim milk when unrefrigerated. Whole milk should always be kept chilled.
2% and 1% milk
Reduced fat milk varieties also need refrigeration. The lower levels of fat (2% has 2% fat, 1% has 1% fat) may slow spoilage times slightly compared to whole milk, but these types will still spoil within hours if left out at room temperature.
Skim and nonfat milk
With little to no fat content, skim milk (less than 0.5% fat) will spoil slightly slower than whole milk at room temperature. However, it still provides a good environment for bacterial growth and should always be refrigerated for optimal quality and safety.
Lactose-free milk
Lactose-free milk, which contains added lactase enzyme to break down lactose sugars, should always be refrigerated like regular milk. The lactase enzyme does not prevent bacterial growth.
Raw milk
Raw (unpasteurized) milk is widely considered more risky than pasteurized milk in terms of foodborne illness risk. This is because the pasteurization process eliminates dangerous bacteria that may be present. Raw milk must always be refrigerated, as leaving it out provides more opportunity for bacteria to multiply to hazardous levels.
Non-dairy milks
Non-dairy milk substitutes made from plants like almonds, coconuts, oats, and soy also need refrigeration after opening. Unopened, most non-dairy milks can be stored in the pantry since they have been commercially sterilized. But once opened, these products will spoil within a week if left unrefrigerated.
How long does milk last in the fridge?
Properly stored in the refrigerator at 40°F or below, the shelf life of milk is:
| Type of Milk | Refrigerator Shelf Life |
|---|---|
| Pasteurized milk | 5-7 days past the sell-by date or about 1-2 weeks total |
| Ultra-pasteurized milk | Up to 30 days past the sell-by date due to higher heat processing |
| Raw milk | Up to 10 days |
| Non-dairy milk | 7-10 days past best by date |
Milk should be consumed by its use-by date for best quality and food safety. Over time in the fridge, milk gradually loses nutrients, develops off-flavors, and is more likely to contain higher bacteria levels.
How to tell if refrigerated milk has gone bad
Even when stored in the refrigerator, milk can eventually spoil. Signs that refrigerated milk has gone bad include:
– Sour smell
– Thick, ropy, or lumpy texture
– Discoloration, such as yellowing cream at the top
– Off flavors like sour, bitter, or metallic taste
– Mold growth around lid or bottom of container
Milk that displays any of these characteristics should be discarded. Do not drink or cook with spoiled milk, as it can cause food poisoning.
Does freezing extend the shelf life of milk?
Freezing milk can significantly extend its shelf life past the sell-by date, to around 3-6 months. However, freezing and thawing may cause some changes to milk’s texture and flavor:
– Milk fat globules may clump together, causing a grainy or waxy texture
– Water separates from other components, yielding a watery layer at the top
– Flavor changes like a flat or stale taste
To freeze milk:
– Make sure milk is not past its sell-by date. Freeze as fresh as possible.
– Leave about 1 inch of headspace in the container for expansion.
– Store at 0°F or below. Consume within 1 week after thawing in the fridge.
Tips for keeping milk fresh longer
Follow these tips for maximizing the shelf life of your refrigerated milk:
– Purchase milk before its sell-by date and refrigerate it promptly at 40°F or below. Keep the temperature consistent.
– Give milk a sniff test when first opening the container to ensure it is fresh.
– Check sell-by and use-by dates and follow them.
– Store milk towards the back of the fridge, away from the door where temperature fluctuates.
– Keep the lid tightly sealed to prevent fridge odors from tainting milk flavor.
– Pour off only the amount of milk needed and return the carton to the fridge right away to limit temperature changes.
– Rotate containers with older dates towards the front to make sure they get used first.
– Clean the fridge regularly to avoid cross-contamination between foods.
Can you safely re-freeze thawed milk?
Previously frozen milk that has been thawed in the fridge can be safely re-frozen, although the texture and taste may further degrade. Limit re-freezing milk to only once after the initial thaw.
To re-freeze milk:
– Make sure milk was thawed in the fridge at 40°F or below, not left out at room temperature.
– Give the thawed milk a sniff test – it should not smell sour or off.
– Pour into a freezer-safe container, leaving 1 inch of headspace.
– Re-freeze at 0°F or below right away, within about 1-2 days max.
– Upon re-thawing, use within 1 week.
Milk that was left thawed for over 2 days or at room temperature should not be re-frozen and should be discarded. The multiple thaw cycles will reduce milk’s quality and safety.
In summary
All milk varieties should be stored refrigerated at 40°F or below after opening. Refrigeration prevents bacterial growth that can rapidly spoil milk and potentially cause foodborne illness if consumed. For best quality and safety, drink refrigerated milk by the expiration date listed on the package. Freezing can significantly extend milk’s shelf life for up to 6 months. Handle thawed and re-frozen milk properly, consuming within 1 week or less upon thawing. Follow proper refrigerated storage guidelines to maximize milk’s freshness.
