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Lactation Information and Discussion <[log in to unmask]>
Date:
Wed, 8 Jun 2005 23:30:11 EDT
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I am pleased to announce that my son won 3rd place at the California State 
Science Fair in the Junior Division (6-8th grade) Microbiology section with his 
breastmilk project.  His abstract is below.
 
Bacterial Activity in Fresh & Frozen Human Milk as Compared to Cow’s Milk & 
Baby Formula 
 
Microbiology
 
Objectives/Goal:  Human milk is the best food for human infants, but many 
women work and must store their milk for later use.  The objective of my project 
was to measure the bacterial activity in human milk compared to cow’s milk and 
  formula, both fresh and after freezing for different periods of time.
 
Materials/Methods: The Methylene Blue dye test was used to measure the 
relative aerobic bacterial content of various milks (fresh and pasteurized human 
milk, fresh and pasteurized cow’s milk, and infant formula) tested fresh and 
after freezing for 3, 10 and 26 days in a household freezer at approximately – 
17.5°C.  Each sample had a control.  In this test, the more rapid the color 
change, the more bacterial growth.  Color change was recorded by time and 
photographically up to 72 hrs at body temperature.  The results of the experiment were 
compared to the bacterial count and graded milks standard charts.  In Phase II 
additional samples frozen 4-5 months were tested and a simple home test kit 
was designed.
 
Results:  All milks tested exceeded the highest commercial standards for cow’
s milk.  Human milk had the greatest resistance to aerobic bacterial growth 
with no color change, except for 1 sample, for more than 72 hrs.  Raw cow’s milk 
had the greatest aerobic bacterial activity.  Freezing had no effect on the 
bacterial activity of the milks, with the exception of pasteurized cow’s milk 
that increased in bacterial activity with the length of time frozen.
 
Conclusion/Discussion: Human milk is the best food for human infants, but 
many women work and must store their milk for later use.  One of the human milk 
samples (frozen 10 days) changed color after only 10 hrs, indicating increased 
bacterial activity, possibly due to illness in the donor or contamination 
during collection or processing.  A simple home test kit was designed and tested 
to help mothers who may be concerned about the quality of their milk. Human 
milk is the safest, best food for human infants, even when frozen for extended 
periods of time.
 
Summary Statement:  Human milk inhibits bacterial growth more than cow’s milk 
or formulas, even after extended frozen storage, making it safest for infants 
whose mothers need to express and store milk for later use.
 
Help Received in Doing Project:  My mother obtained human milk samples and 
helped with the graphs.  My father helped me set up my experiment and helped 
organize the poster board.  Both parents helped edit my report.

Nancy
Nancy E. Wight MD, IBCLC, FABM, FAAP
Neonatologist, Sharp Mary Birch Hospital for Women and Children's Hospital
Medical Director, Sharp HealthCare Lactation Services
San Diego, CA
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