How long can you leave milk out until it goes bad?


In this article, we will answer the question “How long can you leave milk out until it goes bad?”, and how to tell If the milk has gone bad?

How long can you leave milk out until it goes bad?

Milk is perishable and should not be left out for more than 2 hours at 4°C and 1 hour if the temperature is above 32°C according to the FDA, or else the milk goes bad. The crux is to never leave your perishables for long periods of time in the ‘Danger zone’.


The extent of spoilage of the milk, that has been left on the counter, depends a lot on the milk quality. Raw milk tends to spoil quicker than pasteurized milk. Milk with a higher initial microbial load will be more prone to spoilage even after pasteurization.

How long does milk last after the sell-by date?

There is a difference between ‘Best-by’, ‘Sell-by’, ‘Use-by’, and ‘Expires on’ dates. Milk, If stored correctly, remains safe to consume even after the ‘Best-by’ date.


‘Expires on’ refers to the date on which the quality degradation speeds up and after that date, the product might not remain safe for consumption. 


The ‘Sell-by’ date is of importance to the seller. This date decides how long the product can safely stay on the shelves. Expiration dates vary with how the milk was processed, packaged, and stored.

How long is the milk safe to drink after the expiration date?

Typically, unopened milk will last for 5–7 days past the labeled date, while opened milk will stay good for at least 2–3 days past this date. UHT milk that is sold unrefrigerated is also called aseptic milk. 


This type of milk can typically stay good for 2–4 weeks past the labeled date if stored in a cool, dry place such as the pantry, and up to 1–2 months in the fridge. Once opened, UHT milk should always be kept in the fridge and consumed within 7–10 days.


UHT milk is heated above 135°C for 2-5 seconds to kill the vegetative spores. Therefore, It has an extended shelf life than HTST milk.


(Unopened) Refrigerator 
Past printed date 
Lactose-free milk 7-10
Non-fat milk 7-10
Skim milk 7
Reduced-fat  7
Whole milk  5-7
(Opened) Refrigerator 
Past printed date 
All types of milk 5-7


How to store milk to extend its shelf-life?

  1. Pasteurized milk should be kept at 3-4°C in the refrigerator.


  1. Avoid keeping the milk carton in the door to prevent temperature fluctuations.


  1. Freeze storing milk extends its shelf life for up to 6 months but it is recommended to consume within a month. Frozen milk has a grainy texture and some separated fat. It is best to use in cooking or smoothie/shakes.


  1. The refrigerator temperature should be maintained at 38°F (3°C) and 40°F (4°C).


  1. After use, the milk carton should immediately go back to the fridge.

How to tell if that milk has gone bad?

Sour milk develops a slimy and grainy texture due to the curdling of casein protein. If the appearance has not changed yet, give it a sniff. If the milk smells sour and acidic, it has gone bad and is unfit for consumption


Drinking spoiled milk in large quantities can result in food poisoning that reflects in the form of diarrhea, vomiting, and nausea.

What is pasteurization?

Pasteurization is a mild heat treatment that is used to kill the non-vegetative forms of bacteria and inactivate enzymes that cause spoilage in fluids like milk, wine, and fruit juices.


The pasteurization of milk is done at 62.8°C for 30 minutes in a batch-type process.  For the HTST. milk is heated at 71.7°C for 15 seconds.


These are the minimum temperature and holding time requirements to pasteurize milk to kill Coxiella burnetti, responsible for Q fever. Pasteurization does not kill vegetative spores of bacteria, hence, it is important to refrigerate milk after pasteurization to prevent spoilage.

Why does milk spoil?

The two species of bacteria that spoil milk are lactobacilli and streptococci. During temperature fluctuations, streptococci multiply and produce acid by fermenting the milk sugar, lactose, reducing the milk ph that inhibits the further growth of streptococcus.


After this, the lactobacillus takes hold and continues to make acid until it cannot multiply anymore due to low acidity. This low ph denatures the casein protein structure and causes it to curdle up leaving behind the hey protein liquid and the casein is filtered to make cottage cheese.


In this article, we answered the question “How long can you leave milk out until it goes bad?”, and how to tell If the milk has gone bad?



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