Storage and Handling
To avoid waste and for easier thawing & warming, store milk in 1-4 ounce portions. Date milk before storing. Milk from different pumping sessions/days may be combined in one container – use the date of the first milk expressed. Breastmilk is not spoiled unless it smells really bad or tastes sour.
To thaw milk
To warm milk
If baby does not finish milk at one feeding, it may be refrigerated and offered at the next feeding before it is discarded.
My expressed breastmilk doesn't smell fresh. What can I do?
Human milk that has truly soured has a very distinct sour taste and odor - much like soured cow's milk. If your milk doesn't smell distinctly sour or rancid, then it should be safe to give to your baby.
If you repeatedly notice that your stored milk doesn't smell or taste fresh, it might help to go through your storage procedures to see if there is something you could do to improve the smell/taste of your milk:
Lipase is an enzyme that is normally present in human milk and has several known beneficial functions:
What can I do if my storage problem is due to excess lipase? Once the milk becomes sour or rancid smelling/tasting, there is no known way to salvage it. However, newly expressed milk can be stored by heating the milk to a scald to inactivate the lipase and stop the process of fat digestion. Scald the milk as soon after expression as possible.
To scald milk:
To thaw milk
- Thaw slowly in the refrigerator (this takes about 12 hours – try putting it in the fridge the night before you need it). Avoid letting milk sit out at room temperature to thaw.
- For quicker thawing, hold container under running water - start cool and gradually increase temperature.
To warm milk
- Heat water in a cup or other small container, then place frozen milk in the water to warm; or
- Use a bottle warmer.
- NEVER microwave human milk or heat it directly on the stove.
If baby does not finish milk at one feeding, it may be refrigerated and offered at the next feeding before it is discarded.
My expressed breastmilk doesn't smell fresh. What can I do?
Human milk that has truly soured has a very distinct sour taste and odor - much like soured cow's milk. If your milk doesn't smell distinctly sour or rancid, then it should be safe to give to your baby.
If you repeatedly notice that your stored milk doesn't smell or taste fresh, it might help to go through your storage procedures to see if there is something you could do to improve the smell/taste of your milk:
- Storage containers: Standard glass or plastic bottles (or any type of leak-proof food storage containers) are acceptable for storing mother's milk, as are disposable bottle liners or "mother's milk" bags. The best materials are glass or food-grade polypropylene or polybutylene (hard) plastic. Polyethylene bags (bottle liners) do not preserve nutrients and immune properties as well as glass or hard plastic. (Jones & Tully 2005)
- If you're using standard plastic bottle liners, instead try using bags specifically designed for storing human milk.
- If you're storing in plastic, try glass instead.
- Storage conditions:
- Do you plan to freeze the milk? If you're not expecting to use refrigerated milk within 5-8 days of expression, then freeze as soon as possible after expression. Use as soon as possible after thawing (but always within 24 hours).
- Make sure that all packages in your refrigerator or freezer are sealed well, so that your milk cannot absorb odors from other foods. A box of baking soda placed in the refrigerator or freezer may help to absorb odors.
- Store your milk in the BACK of the refrigerator or freezer, not in the door. Don't store your milk against the wall of a self-defrosting freezer.
- Is your freezer cold enough? If your freezer keeps ice cream hard, then the temperature is right.
Lipase is an enzyme that is normally present in human milk and has several known beneficial functions:
- Lipases help keep milk fat well-mixed (emulsified) with the "whey" portion of the milk, and also keep the fat globules small so that they are easily digestible (Lawrence & Lawrence, p. 156).
- Lipases also help to break down fats in the milk, so that fat soluble nutrients (vitamins A & D, for example) and free fatty acids (which help to protect baby from illness) are easily available to baby (Lawrence & Lawrence, p. 156).
- The primary lipase in human milk, bile salt-stimulated lipase (BSSL), "has been found to be the major factor inactivating protozoans" (Lawrence & Lawrence, p. 203).
What can I do if my storage problem is due to excess lipase? Once the milk becomes sour or rancid smelling/tasting, there is no known way to salvage it. However, newly expressed milk can be stored by heating the milk to a scald to inactivate the lipase and stop the process of fat digestion. Scald the milk as soon after expression as possible.
To scald milk:
- Heat milk to about 180 F (82 C), or until you see little bubbles around the edge of the pan (not to a full, rolling boil).
- Quickly cool and store the milk.