How long did expressed breast milk stay stable in tropical heat?

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Researchers measured bacterial contamination and growth in expressed breast milk stored in a tropical environment with high ambient temperatures and humidity. They collected colostrum or mature milk from mothers who had delivered preterm or at term, then stored it at room temperature (27–32°C) and in a refrigerator (4°C) over a 24-hour period. The bacteria isolated were normal skin flora.

Colostrum inhibited bacterial growth more than mature milk, and term colostrum was more inhibitory than preterm colostrum. At room temperature, mature milk from mothers who delivered at term could be stored for 6 hours without a significant increase in bacterial counts, while term colostrum could be stored for 12 hours without significant bacterial growth. Milk from mothers who delivered preterm could be stored for 4 hours. The researchers said the findings could be practically useful to lactating mothers without access to refrigerators.