- Freshly expressed milk may be stored at temperatures slightly below
room temperature (such as in a cooler with icepacks ) for up to 24
hours. If the milk has been kept at room temperature prior to being
placed into the cooler, safe storage time in the cooler may be
- Fresh breastmilk may be kept in a refrigerator for up to 8
days. Store milk in the back of the refrigerator rather than in the
door. If milk has been kept at room temperature or in a cooler with
icepacks prior to being placed in the refrigerator, safe storage time
may be decreased.
- Fresh milk may be placed in a
freezer compartment inside a refrigerator for up to 2 weeks. If it has
previously been kept at room temperature, in a cooler, or in the
refrigerator, storage time may vary.
- Freshly expressed breastmilk may be kept in a
self-contained freezer unit of a refrigerator for up to 3-6 months,
depending upon how often the door is opened. Store milk in the back of
the freezer. If the milk has been stored at room temperature, in a
cooler with icepacks, or in the refrigerator prior to being placed in
the freezer, safe freezing time may be decreased.
- Fresh milk may be placed in a separate deep freeze
(chest-type freezer) for 6-12 months. If previously kept at room
temperature, or stored in a cooler or refrigerator before freezing,
storage time may vary.
- Previously frozen milk may be kept in the refrigerator for up to 24 hours after it has completely thawed..
One last word about the guidelines: Although the above is the latest
published set of guidelines regarding safe storage times of breastmilk,
keep in mind that these are just guidelines. It's wise to try to stay
as close to them as possible, but milk that is older than the stated
safe age, should not be automatically discarded. Milk that is truly bad
has a very distinct sour taste and odor. Even if expressed milk is "out
of date" it should still be considered safe to give a baby as long as
it still has a fresh odor and/or taste.
CHOICE OF A STORAGE CONTAINER
When a baby is only receiving expressed milk occasionally, the type of
storage container is not a major consideration; however, if a baby is
receiving most of his nourishment from expressed breastmilk, the type
of storage container used should be considered carefully. Plastic
containers are the best
choice for storing breastmilk in the refrigerator as more of human
milk's leukocytes or white cells adhere to glass. If the milk is to be
frozen, glass is the preferred choice as it is less porous and
offers the best protection. Most of the leukocytes in human milk are
killed with freezing anyway. For this reason, milk that can be used
within 8 days of expression should be refrigerated rather than frozen,
because the antimicrobial properties of human milk are better preserved
Another good choice for refrigeration or freezing is the milk storage bags that are designed specifically for human milk (see CSF milkbags).
They are pre-sterilized and are thicker (2-ply), coated with
polyethylene, and lined with nylon which prevents the fat from adhering
to the sides. Hard plastic containers of any kind are also good choices
for both refrigeration and freezing. Other milkbags, sold specifically
as bottle liners, are not as durable, making them an unacceptable
alternative when freezing the milk as the seams may burst during the
freezing process perhaps causing a leak during thawing. Also, one study
found that there was a 60% decrease in the milk's antibodies and a loss
of fat that adhered to the sides of these bags. If this type of bag is
still chosen, the milk can be better protected by placing the liner
bags in a larger gallon size freezer bag or in a hard plastic container.
When milk freezes it expands, so it is necessary to leave about an inch
at the top of the container to allow for expansion. For this reason,
bottle caps or container lids should not be tightened until the milk is
HANDLING AND THAWING
Fresh human milk separates into milk and cream, so it is important to
gently swirl the container to mix the milk before offering it to your
While it was originally thought that a mother had to cool her fresh
breastmilk before combining it with previously expressed cooled milk,
the latest research now shows that you may pump directly into already
refrigerated or cooled milk as long as the milk is added within 24
hours of the first milk expressed. You should then follow the storage
recommendations based upon the time and date of the first milk
expressed. You may pump directly into milk that has been stored at room
temperature as long as you do so within 10 hours. This milk would need
to then be used.
You may add your fresh milk to what you have already frozen as long as
you chill the fresh milk first for about half an hour and it is a
smaller amount than the amount that you are adding it to.
When thawing milk it is best to thaw it in the refrigerator. This takes
about 12 hours.
If you need a quicker method you may hold the container under water
that is gradually warmed or you may place it in a bowl of water that
again is gradually warmed. Another, newer method that affords a faster
warm is the Avent bottle warmer.
This warmer allows for a gradual warm and has been tested on breastmilk
and not shown to affect any of the milk's properties. Regardless of the
method of warming you choose, shake the container before testing the
temperature. Human milk should NEVER be microwaved or heated
directly on the stove! These heating methods alter the composition of
the milk and may result in hot spots in the milk that could perhaps
burn your baby!
Once thawed, breastmilk should not be refrozen. It also should not be reheated once heated.
It is best to store in portions of 2-4 ounces to avoid less waste. These smaller portions also thaw and warm more quickly.
Extensive research has not yet been done to determine if it is safe to
give a baby milk that was left over from a previous feeding or milk
that was previously warmed, but not used. However, most lactation
experts agree that milk that is not finished at one feeding may be
offered at one more feeding before needing to be discarded. Human milk
has antibacterial and antimicrobial properties that result in slower
spoilage as compared to other foods.
WHAT ABOUT SOURED or "OFF" MILK?
Milk is not spoiled unless it has a sour odor or tastes bad.
Some moms find that their milk seems to spoil rather quickly despite
careful attention to proper storage and handling. This is thought to be
a result of the milk having an excess of lipase, an enzyme which helps
break down the fats in human milk. One way to keep milk from spoiling
so quickly is to halt the breakdown of fats by scalding the milk just
prior to storing it. This is done as soon after expression as possible
and over a stove eye. Scalding the milk involves allowing small bubbles
to appear on its surface but removing it from the heat before an actual
boil occurs. The milk should then be stored immediately either in the
refrigerator or freezer.
Other mothers have reported a soapy smell to their frozen milk
after it is thawed. This change in smell has been attributed to changes
in the milk fats related to storage in self-defrosting
refrigerator-freezers. It has not been found to be harmful to the baby.
Sometimes odors from the refrigerator or freezer can enter
stored breastmilk. To avoid this, be careful about your choice of
storage containers (review the information above), consider adding a
box of baking soda to the unit, throw out old leftovers and make sure
any newer food is covered or wrapped tightly, and check that the
temperature of your refrigerator or freezer is set low enough.
APPEARANCE OF STORED MILK
The appearance of stored milk can take on many forms. Most moms notice
that after a while the fats in the milk begin to separate from the body
of it. They may rise to the top or settle on the sides of the storage
container. Before emptying the milk into your baby's bottle or cup and
right before serving it to baby, be sure to gently swirl the milk so
that the fats can be redeposited back into the rest of the milk.
Milk that has been expressed can look thin and some moms may
think this appearance means that their milk is low in fat. Human milk
does not look like cow's milk in its container. Cow's milk has been
homogenized giving it a more white appearance than cow's milk that has
not been homogenized or expressed human milk.
At other times, the milk may take on different tints of color.. This
can be in relation to something mom has eaten or a medication she is
taking. The color of the milk is not harmful to the baby. And keep in
mind that if the milk was not expressed, noone would be any wiser as to
its appearance as it left the breast straight into baby's mouth.
WHY DO THESE GUIDELINES DIFFER FROM OTHER INFORMATION BOOKLETS?
Be careful about your source for information concerning storage
and handling of breastmilk. It's wise to disregard most information
contained in booklets published by formula companies in regards to
expressed human milk. Often this information is inconsistent and
outdated. It is also not in the best interest of the formula companies
for a mother to have plenty of safe, expressed breastmilk on hand
should she need to offer her baby a bottle or cup. Other literature,
books, etc. offering information on storage and handling should be
up-to-date and from an authority on breastfeeding; ie. lactaction
consultant, La Leche League, medical professional with expertise in
Written by Becky Flora, BSed, IBCLC
Last revision: July 31, 2002
Source: La Leche League's, "The Breastfeeding Answer Book" (1997) by Nancy Mohrbacher, IBCLC and Julie Stock, BA, IBCLC
More info at other sites:
"Common Concerns When Storing Human Milk"