Unfinished Milk in the Bottle?

Formula is expensive, and expressing breastmilk is time-consuming and sometimes challenging. You would hate to just throw that money and time down the drain if your baby doesn’t finish the bottle you have prepared. What are the guidelines you should adhere to, however, to keep your baby safe?

Let’s start with the basic recommendations from health professionals:

For formula

  • unopened can: finish by manufacturer’s “use by” date
  • opened can: liquid concentrate or ready-to-feed use within 48 hours; powder use within 1 month
  • formula in bottle:
    • unfed, at room temperature: 2 hours
    • in the refrigerator: 24 hours
    • in the freezer: do not freeze formula
    • left in bottle after feeding: discard immediately, do not re-feed

For expressed breastmilk

  • at room temperature: 4 to 8 hours, refrigerate as soon as possible if not planning to use soon after pumping,
  • in a cooler with ice packs: 24 hours
  • in the refrigerator: 4 to 8 days
  • in the freezer: 3 to 6 months (freezer compartment of refrigerator) or 6 to 12 months (chest or deep freezer)
  • thawed but not fed: keep refrigerated for up to 24 hours, do not refreeze
  • heated but not fed: within 1 hour
  • left in bottle after feeding: discard any unfed milk after 1 hour

It’s not as clear-cut as it may seem, though. Where did these “rules” come from? The assumption is that the times are based on how long it takes before the milk becomes unsafe for consumption, or when bacterial contamination might lead to illness if the milk was consumed. Some suggest, however, that the antimicrobial properties of human milk may keep bacterial contamination to a minimum. It turns out there’s not much solid scientific evidence about any of it, especially when it comes to whether or not you can feed your baby milk that’s left in the bottle after a feeding.

The theory is that if your baby doesn’t finish the bottle, that milk should be discarded immediately due to the greater possibility of bacterial contamination over time. According to the Academy of Breastfeeding Medicine, though:

Once an infant begins drinking expressed human milk, some bacterial contamination occurs in the milk from the infant’s mouth. The length of time the milk can be kept at room temperature once the infant has partially fed from the cup or bottle would theoretically depend on the initial bacterial load in the milk, how long the milk has been thawed, and the ambient temperature. There has been insufficient research done to provide recommendations in this regard.

They conclude that current evidence supports discarding the milk within 1 to 2 hours, but go on to say that there’s no agreement about the level of contamination that makes the milk unfit for consumption.

It’s likely that these guidelines come from general food safety information. According to the United State Department of Agriculture (USDA), leftover food items need to be kept out of the “danger zone” – between the temperatures 40 degrees F and 140 degrees F. At these temperatures, bacteria can multiply quickly, making food unsafe to consume and increasing the risk of food poisoning. So, if you plan to eat the leftovers, it’s better to refrigerate (less than 40 degrees F) or keep warm (greater than 140 degrees). And they recommend discarding foods left at room temperature for more than 2 hours (or less if the room is very hot).

The most important rule with formula or expressed milk seems to be making sure you are handling the milk safely when you’re pumping or when you’re mixing the formula. Contamination is more likely to happen at these times rather than when baby is feeding.

In addition, other safety suggestions for milk handling and storage include:

  • Practice good hand hygiene before pumping or mixing formula.
  • Be sure pump parts and feeding equipment are properly cleaned. Clean your pump after every use - with soap and water or in the dishwasher using a basin and brush specifically for that purpose (not in the sink with a sponge used for the family dishes). The US Centers for Disease Control and Prevention (CDC) has recently updated the guidelines for cleaning pump parts. These recommendations step from a case where an infant was infected with the cronobacter bacteria, and the source was traced back to the sink where pump parts were cleaned.
  • Mix formula according to directions, using water hot enough to kill contaminants. Or use ready-to-feed formula.
  • Prepare only as much milk as you need at a single feeding.
  • Store milk in small batches for less waste. Freeze expressed breastmilk in 2 ounce increments - it’s pretty easy to thaw more if needed, and less likely that you’ll need to waste much if baby doesn’t finish the bottle. If you’re mixing formula bottles for the day, make them only a few ounces each.
  • Finally, use common sense. Would you want to eat a sandwich that has been sitting out all afternoon? And definitely, if it smells bad, get rid of it. How old is your baby? Once solids are introduced, your baby has the potential for exposure to pathogens from sources other than bottles of milk. Does your baby have any health problems? If so, you will likely use more caution when making decisions like this.

Sometimes just keeping track of when you mixed the bottle can be challenging. The BlueSmart mia system’s expiration warning will give you peace of mind by letting you know when your bottle has been out too long, keeping your baby thriving and safe!







Posted by:
Michelle Roth

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