|Always make sure that supplies are clean and wash your hands before handling breastmilk.|
Upon receiving breastmilk, store it in the freezer and/or the refrigerator as it is given, depending on the need. If the donor has not already done so, it is suggested that bags be labeled with name, date and phone number of donor(s). This is to ensure that milk can be returned or a donor can be contacted if need be.
Regarding raw and fresh milk, Lawrence writes: “Breastmilk can safely stand at room temperature for 6 to 8 hours and need not be discarded if the first feeding attempt is incomplete.”1
Regarding reusing milk after a feeding, Dr. Ruth Lawrence writes: “Whether you can use the remaining milk really depends on how long it sits around. Once the baby takes the bottle, there is a certain amount of saliva that gets in the bottle that creates bacteria and gets saliva enzymes in the milk. This is why it isn’t good to give milk that has been sitting around. But, if it sits for only a half hour or so, this is fine.”2 There can be confusion as to what ‘sits around’ means. Eats on Feets assumes that in this context ‘sits around’ means ‘stand at room temperature.’
See ‘How do I feed the milk to my baby?’ for cleaner and thus safer feeding options.
For raw and fresh (not frozen) breastmilk after refrigeration, this summary states: ” […] When infants do not finish a bottle of expressed breastmilk, doctors recommend unfinished portions be thrown away. This [small –ed.] study examined bacterial levels in expressed, partially consumed breastmilk that was stored for 48 hours at 4-6° C [bold –ed.]. A portion of unconsumed milk was examined as a control. Samples were taken every 12 hours for bacterial analysis. Tests were performed to identify total colony counts, pathogenic Staphylococci, coliforms and b-hemolytic Streptococci. This study showed no significant difference between bottles that were partially consumed and those that were not exposed to the baby’s mouth for 5 out of 6 participants. All milk samples had colony counts in the acceptable range of < 105 colony forming units per milliliter (CFU/ml). Although this project provides evidence that it may be safe to re-feed a child a bottle of breastmilk, due to the small sample size, further tests should be performed.”3
Most mothers reheat leftover and refrigerated milk. Dr. Ruth Lawrence writes: “If the milk is warmed up but not used, it is OK to reheat the milk once. But the more you reheat the more you decrease some of the valuable immunologic properties of the milk.”
Regarding previously frozen raw milk, it is generally accepted that thawed milk can be kept in the refrigerator for up to 24 hours. Please see ‘How can breastmilk be thawed?’ for thawing instructions. Most mothers reheat (warm) previously frozen raw milk as well (after a first feeding). It is not advisable to leave previously heat-treated milk out for longer than necessary because heat-treating affects the anti-bacterial properties of breastmilk.
According to the USDA, “Once food is thawed in the refrigerator, it is safe to refreeze it without cooking.” In this protocol, Dr. Anne Eglash, M.D. writes: “At this time, there is little information on refreezing of thawed [fresh –ed.] human milk. Bacterial growth and loss of antibacterial activity in thawed milk will vary depending on the technique of milk thawing, duration of the thaw, and the amount of bacteria in the milk at the time of expression. At this time no recommendations can be made on the refreezing of thawed human milk.”
Breastmilk, previously frozen or not, can be re-frozen after it has been heat-treated. This is the process that milk banks follow: frozen donated breastmilk is pasteurized, after which it is stored in the freezer.
Reusing heat-treated milk
In this study, the researchers discuss that after cooling “flash-heat was successful in completely eliminating bacteria in the majority of samples, and prevented substantial growth for up to 8 h when stored at room temperature.”4
To date, the safety of reheating previously heat-treated milk5 has not, to our knowledge, been studied. It should be noted that most literature speaks in terms of heating expressed milk for feeding but that mothers generally warm the (thawed) milk under running warm water or set it in a container in warm water for a short while to get the chill out of it. Gently warming should not be considered heat-treating. For optimal properties of breastmilk, reheating (warming) milk should not be done directly in a pan on the stove top nor in a container in boiling water on the stove top (which would be heat-treating it unnecessarily). It is suggested however that after a first feeding, milk that was heat-treated not be refrigerated and reheated again.
Please see this chart for length of storage guidelines.
Please also see ‘Handling Milk’ for more information on proper handling and feeding.
- Lawrence, Ruth. Breastfeeding, A Guide for the Medical Profession. P. 438. Print. [↩]
- Using alternative feeding options to a bottle and/or using small amounts at a time avoids waste and contamination. [↩]
- Brusseau, R. Bacterial Analysis of Refrigerated Human Milk Following Infant Feeding. May 1998. Web. [↩]
- Per the study “Flash-heated and unheated samples were stored at 2–8oC [35oF–46oF –ed.] overnight to be processed for microbiology assays the next morning, 18–24 h after collection. At this time, both flash-heated and unheated aliquots were placed at room temperature (23C) [73oF –ed.] and allowed to stand, in capped vials, for up to 8 h.” [↩]
- This can be the case if a donor heat-treats the milk because of high lipase or after a recipient heat-treats the milk and there is milk left over after a feeding for instance. [↩]