Scientist Mom Shows That Breast Milk Is Not Sterile…and That Pasteurization is Amazing
Áine Blanchard Quimby, scientist, breastfeeding mom, and woo fighter extraordinaire, decided to do some science for fun and to prove a point about raw milk and pasteurization.
Caveat: While she does have experience in sterility labs and culturing bacteria, food science is not her area of specialization.
I conducted this experiment with raw versus pasteurized breast milk. It shows why pasteurization is important, and why people-to-people raw breast milk sharing could potentially be dangerous.
I used sterile collection techniques with alcohol wipes to clean my nipple after letdown, then gathered milk by manual expression with gloved hands into a sterile microcentrifuge tube.
I separated and heated 50 microliters of milk at 65 degrees Celsius for 30 minutes, a classic Pasteurization method. The other was left alone. I then plated them onto LB culture plates (I streaked the first area with 30 ul of breastmilk, then did the remaining segments with ten fold dilutions), and left them to grow overnight at 37 degrees Celsius.
Results and Findings:
After overnight growth at 37 degrees Celsius, the raw milk sample without pasteurization had significant bacteria growth – approximately 200 colonies. The pasteurized sample had no visible bacteria growth.
I was not able to categorize the bacteria, because that’s not possible in my lab. Consequently, the bacteria found in my milk could potentially be harmless. We may never know. One doesn’t know what bacteria or viruses they have in their body at a given time, never mind what another person might have. I can almost guarantee that someone donating breast milk isn’t using sterile collection techniques in a lab. I wanted to show that even using sterile techniques bacteria can survive to be passed along. It’s possible that the milk may have been contaminated through the collection process, but however the bacteria got into the sample, pasteurization fixed it.
Conclusions and Recommendations:
Raw breast milk is not sterile. You don’t know what might be living in someone else’s breast milk. Or in raw cow’s milk. Pasteurization kills bacteria. Peer-to-peer raw milk sharing is not safe and should not be recommended over milk bank donor milk or formula, if a mother is unable to breast feed or needs to supplement.
Images: Áine Blanchard Quimby, all rights reserved.