Costco’s Kirkland Signature milk boasts an impressively long shelf life compared to other brands, with many customers noticing that it remains fresh well beyond its labeled expiration date.
One user on the Costco subreddit of the social news site and forum Reddit wrote, “I’ve found that Costco’s milk often doesn’t go bad even a week after the expiration date.” Others agreed, with one saying, “I love Costco’s milk because it stays fresh longer than any other milk.”
According to a report by the American food and wine magazine “Food & Wine,” this could be attributed to Costco subjecting their milk to more stringent tests and quality control measures than the government standards.
All Grade A milk sold in the United States must adhere to the basic safety standards set by the Food and Drug Administration (FDA) under the Pasteurized Milk Ordinance, including controlling somatic cell (cells typically found in milk including lymphocytes, macrophages, neutrophils, and a small amount of epithelial cells) counts to below 750,000 per milliliter, limiting total bacteria to below 100,000 colony-forming units, and cooling the milk to below 45°F (approximately 7°C) within two hours of milking.
Most dairy plants meet these standards through regular operations and undergo testing only once or twice a year. However, Costco’s standards far exceed these requirements.
Based on Costco’s 2023 Food Safety and Quality Audit Expectations, suppliers producing Kirkland brand milk must undergo at least one surprise inspection per year, or two if their facilities are in China, covering farms and processing plants, with a zero-defect requirement for major issues.
Facilities scoring below 85% must undergo a reevaluation within 60 days, and if still not compliant, the supplier is responsible for subsequent inspection costs.
Furthermore, every batch of Kirkland milk undergoes 60 microbial tests before shipping, with any failed test resulting in the batch not being shipped.
Costco also enforces stricter monitoring of processing water than federal standards.
Federal standards require public water systems to test for E. coli annually, while private well water must be tested quarterly. To ensure accuracy, Costco rotates its chief auditors every three years to maintain a high level of vigilance and prevent any oversights.
According to information from Penn State University’s Extension, milk with lower somatic cell and bacterial counts, especially when unopened, has a longer shelf life.
“Food & Wine” also notes that Costco’s practices help reduce food waste, and customers save money by not having to frequently purchase milk.