Costco customers claim their milk doesn’t spoil for weeks after expiration date — here’s the surprising reason why

There’s a reason Costco fans think the brand’s milk is legendairy.

People who buy their milk at the retail giant have noticed that the Kirkland-brand milk stays fresh longer than other brands — way past its sell-by date.

“I find that with Costco milk it isn’t even spoiled a week after the expiration date most times,” one person wrote on the r/Costco subreddit page.

“I prefer Costco milk because it does last longer than anything else,” someone chimed in.

This may be because Costco’s milk undergoes more testing and quality control than what’s required by government standards, according to Food & Wine.

All Grade A milk sold in the United States must meet the basic safety standards set by the Food and Drug Administration’s Pasteurized Milk Ordinance.

These safety standards include keeping the somatic cell count below 750,000 per milliliter, limiting total bacteria to fewer than 100,000 colonies, and chilling the milk to below 45°F within two hours of milking.

Testing for the basic rules typically occurs once or twice per year, and most dairies meet these standards through standard practices.

But Costco’s inspections go above that.

According to Costco’s 2023 Food Safety & Quality Audit Expectations, suppliers that produce Kirkland-brand milk have to undergo surprise inspections at least once a year — and if the facility is in China, twice a year.

Suppliers are expected to pass inspection — which covers both the farm and the milk processing plant — with zero critical issues. If the facility scores below 85%, it will be re-audited within 60 days. If a supplier skips the additional audit requirements, inspectors will return at the supplier’s expense.

Every batch of Kirkland milk also has to go through a testing policy where 60 microbial tests are run before anything is shipped out, and if just one of those tests fails, the product doesn’t go out.

Additionally, the water used during processing is monitored more closely than required by the FDA.

By federal standards, public water systems are tested annually for E. coli while private wells are checked each quarter. Costco, in an effort to keep its production error-free, rotates lead auditors every three years to avoid any carelessness and ensure that nothing goes unnoticed.

The careful examination is likely the reason Costco milk tends to last a few days after its printed expiration date.

Cleaner milk from healthier herds that is processed under precise inspection generally lasts longer once it’s jugged — especially when left unused for several days.

Milk from herds with lesser somatic cell counts usually stays fresh longer, according to the Penn State Extension, so if your Kirkland milk is still good after a few days, that’s likely due to the lower bacteria and cell counts that Costco verifies with its strict scrutiny.

The practices ultimately lead to less food waste and customers saving money, not having to buy milk as often.