Where to store milk:
1. Hard-sided containers, such as hard plastic or glass, are the preferred containers for long-term storage. These containers should have an airtight seal. Check here for tips on how to use glass containers for milk storage.
2. Choose containers that are bisphenol-A free –> not polycarbonate plastic.
3. Containers must have been washed in hot, soapy water and rinsed. People have been asking me if we sterilize the bottles. We don’t have a sterilizer and rarely sterilize. Instead, I just pour boiling or hot water on the containers after they’ve been washed. We stopped doing this when Naima turned 1.
4. Plastic bags specifically designed for human milk storage can be used for short-term milk storage. Use of plastic bags is not recommended for long-term storage as they may spill, leak or become contaminated more easily than hard-sided containers, and some important milk components may adhere to the soft plastic and be lost. Disposable bottle liners are also not recommended.

  • Although not recommended, Playtex liners are usually promoted as milk storage bags in the Philippines. I myself have used these liners since I was able to get several free bags. When I store my milk using bottle liners, I make sure that they are securely closed using those bag clips to keep snacks fresh. My refrigerator also has separate drawers and we have reserved one of the drawers exclusively for breastmilk.

Storage Tips:

  • Store milk in small portions (1-4oz.) to minimize waste. — Especially for young babies. Naima normally took 3-4 oz. of milk and was only able to go up to 5oz when she was past 1 year old. The most milk she ever took was 6oz.
  • Refrigerated milk has more anti-infective properties than frozen milk. — Naima usually consumes refrigerated milk and I donate my frozen milk.
  • Label and date the containers before storing.
  • Milk from different pumping sessions/days may be combined in one container – use the date of the first milk expressed. –> I never combine milk from several days. I combine milk pumped in different hours of the SAME day only.
  • Chill freshly expressed milk for at least 1 hour before adding it to previously chilled milk expressed on the same day. –> Milk temperature must always go down and never up. By mixing freshly expressed warm milk immediately with refrigerated milk, you cause the cold milk temperature to go up, making it more prone to spoilage.
  • Do not fill the container. Leave some room at the top because breast milk expands as it freezes.
  • If you use breastmilk storage bags, make sure that you squeeze out the excess air.  When frozen, the excess air create pockets in the storage bags which become brittle.  So when you drop your milk bags or when they get hit by sharp corners during handling, they may get broken or pierced, leading to milk leaks when thawing.  
  • If you are unsure if your milk storage bags have holes, put them inside another ziplock bag before thawing.  This way, the milk leaks will get caught and won’t get wasted. 

Thawing and Warming the Milk

  • The oldest milk should be used first.
  • 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.
  • Previously frozen milk may be kept in the refrigerator for up to 24 hours after it has finished thawing. Do not refreeze.
  • To warm milk, heat water in a cup or other small container, then place the milk container in the water to warm; or use a bottle warmer.
  • NEVER microwave human milk or heat it directly on the stove. This will leave hot spots (which may burn your baby’s mouth) and will also destroy antibodies.

*Because human milk is not homogenized, expect that the milk will separate during storage and the cream will rise to the top of the milk. Before feeding, gently swirl milk (do not shake or stir) to mix the cream back. Read this if you want to know why breastmilk should not be shaken.

Milk with a Soapy smell?
Breast milk is not spoiled unless it smells really bad or tastes sour. Sometimes thawed milk may smell or taste soapy. This is an indication that the mother’s milk is high in lipase (the enzyme that breaks down milk fats). The milk is safe and babies will still drink it. To prevent the soapy smell and taste, freshly expressed milk should be immediately scalded (bubbles around the edges, not boiling), then quickly cooled and frozen. This deactivates the lipase enzyme. Scalded milk is still healthier than infant formula. Read here for more instructions on scalding breastmilk.
You can also read my post on excess lipase in breastmilk.

The foregoing is compiled from the following sources:
1. La Leche League International
2. Australian Breastfeeding Association
3. KellyMom
4. The Academy of Breastfeeding Medicine, Protocol #8

Part I here.

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