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The length of time breast milk can be stored depends whether it is kept at room temperature, in a fridge or frozen. This article shares the recommendations for storing breast milk at different temperatures, and answers frequently asked questions about collecting and using expressed breast milk. The Academy of Breastfeeding Medicine’s (ABM) Clinical Protocol #8:
Human Milk Storage Information for Home Use for Full-Term Infants is a reputable guide to storage times and was revised in 2017. Their information and the thoughts of others are summarised below: Note: Historically, researchers have speculated that breast milk can be stored longer than four hours. Nwanko et
al1 say six hours for storage of mature milk and 12 hours for colostrum at 27-32ºC; Ajusi et al2 say eight hours at room temperature and Igumbor et al3 say breast milk may be acceptable for up to eight hours at 15-27ºC or four hours at 30-38ºC. Based on a single study by Hamosh et al in 1996 human milk may be safe to use for 24 hours in an insulated cool bag at an average temperature of 15 °C 4. At 4 °C (39 °F) or below, the optimal storage time is 4 days, but 5–8 days may be acceptable for breast milk collected under very clean conditions and stored towards the back of the fridge (ABM, 2017). According to some researchers, the bactericidal activity of refrigerated fresh milk remains unchanged for the first 48
hours56. At temperatures below -4 °C
(24.8°F) the optimal storage time is 6 months however 12 months is acceptable (ABM, 2017). Older sources often quote freezer temperatures of -18 °C. Note that little freezer “ice compartments” within an old style fridge only have a recommended storage time of two weeks
78. Can I keep milk longer than 12 months in the freezer?More research is needed to determine whether frozen milk is safe to use after 12 months. The Academy of Breastfeeding Medicine explains that foods frozen at -18°C are indefinitely safe from bacterial contamination however the quality of the milk may deteriorate. Collecting breast milk for storageHygiene
Cleaning your pump equipment after useThe UK’s National Health Service recommends sterilising all feeding equipment after use until a baby is 12 months old, see Sterilising Baby Bottles (NHS website) for comprehensive information on cold water sterilising, steam sterilising and boiling. However the American based Academy of Breastfeeding Medicine and US Food and Drug Administration state sterilising is not necessary for milk storage containers and pump parts:
Breast milk storage containersBreast milk can be stored in glass or food grade plastic containers with secure lids, or special freezer bags for breast milk. There are concerns about chemicals leaching from plastic containers into foods or liquids they contain 9. Although moves to use BPA free (bisphenol A) plastics such as polypropylene are helpful there are still many other chemicals in plastics. Glass bottlesSome parents choose to avoid the potential dangers of plastic altogether by using glass containers. Glass is said to be the least damaging to human milk10. If freezing glass, use special glass containers designed to withstand freezing, leave space for expansion and thaw milk slowly e.g. overnight in a refrigerator. Plastic bagsIf using plastic storage bags, use those that are strong and sturdy and specifically made for storing breast milk. Take care the bags of milk are in a suitable container and can’t get punctured by other food packages. As with the hard sided containers, leave space for expansion and squeeze air out of the top of the bag before sealing. Storage tips
Breast milk doesn’t need any special handling and can sit in a work place refrigerator that is used to store food (ABM, 2017). Handling breast milk, mixing layersIt’s normal for expressed breast milk to separate into a milk layer and a cream layer and to look blueish, yellow or even brownish. Simply mix the layers back together before feeding the milk to your baby 13. Gently swirl or give a good shake?You may have heard that breast milk that has separated into layers should be gently swirled together and never vigorously shaken in case it damages the milk. As breast milk is quite robust, damage seems unlikely by the force of an average hand shaking a container of milk 14. In some situations breast milk is centrifuged at high speed to separate the layers—apparently without concerns about damaging the milk 15 16. Using frozen breast milkWhat is the best way to thaw frozen breast milk?The Academy of Breastfeeding Medicine recommends that breast milk can be defrosted:
A microwave is not a good way to thaw milk. It can create hot spots in the milk and decreases the milk’s anti infective and health qualities. And heating milk above 40°C can damage enzymes and the immunologically active factors in breast milk (ABM, 2017). How long does thawed breast milk last?There are a mix of opinions ranging from advice to use thawed milk immediately 17 to within a few hours if left at room temperature (ABM, 2017) to use within 24 hrs in a fridge 1819. Frozen milk is thought to be less able to inhibit bacterial growth compared to fresh refrigerated milk as it loses some of its immune properties (Sears, 2016). However Fogelman et al20 found that human milk might be stable at longer storage times than these quoted in two small pilot studies. They call for more research on previously frozen leftover milk before making new recommendations. Can thawed milk be refrozen?The Academy of Breastfeeding Medicine states that it cannot make any recommendations regarding refreezing thawed breast milk due to insufficient research. However Rechtman et al21 found that breast milk was very robust and suggested that human milk that has thawed in a fridge for up to eight hours can safely be refrozen. Kelly Bonyata concludes from their research that if breast milk still contains ice crystals it can be refrozen:
How does freezing affect the quality of milk?Nutritional valueThere may be some small changes to the nutritional value of frozen stored breast milk e.g. a reduction in vitamin C content, and a reduction in fat, protein, calories and some of the anti-infective properties 22.
Taste and smellSome mothers notice that their previously frozen breast milk tastes or smells soapy, sour or rancid. For more information to explain this and tips to avoid it see My Breast Milk Smells Soapy or Sour. Milk storage for premature or poorly babiesBecause premature or poorly babies are more vulnerable to infection, greater care over milk handling and sterilisation is usually recommended. Check with your doctors what they advise. Breastfeeding and Human Lactation, Fifth Edition p 484 in the chapter “The use of human milk and breastfeeding in the NICU” advises:
FAQs about stored milkIf my baby doesn’t finish their bottle, how long can I keep the leftovers?General advice varies slightly for the handling of a partly drunk bottle of breast milk. Once the milk has been in contact with baby’s saliva there is a risk of bacterial contamination but few studies are available. The UK’s National Health Service recommends partly drunk breast milk be used within an hour and then discarded23 and The Academy of Breastfeeding Medicine recommends discarding milk within 1-2 hours after baby has finished feeding (ABM, 2017). Breastfeeding author Nancy Mohrbacher recommends discarding leftover milk at the end of the feed24 and for further discussion see Kelly Bonyata’s Reusing Expressed Breastmilk. More recently, Fogleman et al discuss a small study with 12 women that indicated the bacteriological and immunological characteristics of left over milk were stable when stored in a fridge at 4ºC for six days and say more research is needed to determine safe storage times of leftover milk25. Why does my breast milk smell soapy or sour?If you are worried that your breast milk smells or tastes like soap, smells sour or like garlic, onion or other food see My Breastmilk Smells Soapy or Sour for further information. Milk that seems to have gone off should not be fed to your baby. Can I use milk collected in breast shells (drip milk)?Drip milk collected from one breast while feeding from the other is said to be lower in fat with more skin bacteria and rather than storing this, Mohrbacher 26 advises it should be discarded. Can I store breast milk if I have thrush (fungal infection)?The Academy of Breastfeeding Medicine says milk pumped through a thrush episode can still be stored:
However in Breastfeeding Answers Made Simple the author says that as freezing does not kill Candida it is not clear whether reinfection is possible, but boiling the milk will kill fungal cells (Mohrbacher 2010). SummaryOpinions vary slightly but most sources agree that the ideal storage times for breast milk are four hours in a sealed container at room temperature, four days in the back of a cold fridge, and six months frozen in a stand alone deep freezer. Although these are the “ideal times”, they err on the side of caution because actually breast milk is so full of antibacterial agents that it can often last longer than these times when collected under clean conditions and fed to healthy term babies. Browse by CategoryNow Reading How Long Does Breast Milk Last? 20 Jun, 2019 Can I use breastmilk that has been in the fridge for 5 days?Freshly expressed breast milk can be stored in the back of the refrigerator for up to four days in clean conditions. However, it's optimal to use or freeze the milk within three days.
Can I put breast milk back in fridge after baby drinks from it?If your baby did not finish the bottle, the leftover breast milk can still be used within 2 hours after the baby is finished feeding. After 2 hours, leftover breast milk should be thrown away. To avoid wasting unfed milk, consider storing, thawing, and warming milk in smaller amounts.
How will I know if breast milk is spoiled?Some people describe a “soapy” smell or taste in their milk after storage; others say it is a “metallic” or “fishy” or “rancid” odor. Some detect a “sour” or “spoiled” odor or taste. Accompanying these changes are concerns that the milk is no longer good for the baby.
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