Milk Storage Guidelines

This page provides information about milk storage guidelines. Guidelines for milk storage can be confusing. Many common recommendations are not evidenced-based or practical, differ for term and preterm infants, and can lead to families wasting precious milk.

• Containers. Mothers should aim for cleanliness but realize milk is a biologic substance and full of probiotic and commensal bacteria. Hand washing, using clean or new containers, minimizing milk transfers (which waste fat and calories), and pumping directly into storage containers are recommended. Plastic or glass containers are fine, no evidence supports one over the other.
• Cold storage. Milk has biology that leads it to maintain its nutrient value and discourage bacterial growth when kept at room temperature or in the refrigerator. Raw milk likely has better biology than frozen with intact milk fat globules and maternal cells. After 4 hours at room temp or 4 days in the refrigerator it may be best to freeze milk for long term storage. Milk is generally considered safe for feeding for up to 12 months of freezer storage. The colder the freezer temperature the better and the less exposure to high temperatures the better. A deep freezer is better than the door of a standard freezer.
• Free fatty acid build up. Human milk contains lipases that continue to break down triglycerides even in frozen milk. These free fatty acids (FFA) can give the milk an unpalatable taste, but cause no GI upset, no additional bacteria, or altered nutrition. Some babies however will reject the taste of the milk, others do not seem to care. Keeping the milk colder may help slow down the process, and mothers can consider a mini pasteurization or scald step after expression but before freezing expressed milk. Lipase is very heat sensitive and will be eliminated thus preventing the FFA build up and frustration over lost milk due to taste alone. While heating may alter some of the biology of the milk, it is better than the baby rejecting the untreated milk. For more information see the Healthy Children Article Tips for Freezing and Refrigerating Breastmilk, CDC Proper Storage and Preparation of Breastmilk, and the AMB Clinical Protocol Human Milk Storage Information for Home Use For Full-Term Infants.