Have you noticed your stored breast milk developing a soapy or metallic smell? If so, you might be dealing with high lipase milk. Lipase is a natural enzyme in breast milk that breaks down fats for your baby’s digestion. Some mothers have higher lipase activity in their milk, which causes the fats to break down rapidly during storage. This can lead to an odd soapy, sour, or metallic smell and taste in expressed milk after it’s been refrigerated or frozen. It’s understandably alarming to find that yesterday’s pumped milk smells “off.”
The good news: High-lipase milk is still perfectly safe and nutritious for babies. The changed smell is due to fat breakdown, not spoilage. Many babies will drink high-lipase milk with no issue. However, some babies refuse milk that tastes soapy or rancid. The altered taste can make them pull away from the bottle, which is how many moms discover the issue in the first place.
What can you do about it? The primary strategy is to inactivate the lipase enzyme by scalding the milk right after pumping. Scalding means heating the milk until small bubbles form around the edges (about ~180°F/82°C, just below boiling), then quickly cooling it. For example, you can heat the freshly expressed milk in a small pan on the stove; once you see tiny bubbles (before a rolling boil), remove from heat and cool the milk in an ice water bath. Scalding breast milk stops the enzyme activity that causes the taste change. Just be careful not to boil the milk or heat it too long, as that can destroy more of the beneficial nutrients. After scalding and cooling, store the milk as usual. Many mothers report scalded milk no longer develops the off-taste (or it’s much reduced).
Other tips to manage high lipase milk include:
- •Chill or freeze milk immediately after pumping. Lipase works fastest at warm temperatures, and its activity slows when milk is cold or frozen. So, refrigerate or freeze milk promptly to minimize the enzyme’s action. Don’t let pumped milk sit out at room temp if you know lipase is an issue.
- •Use freshly pumped milk first. If your baby is sensitive to the taste of stored milk, try to use milk within 24 hours if possible, before the flavor changes. You can also mix high-lipase thawed milk with some freshly expressed milk to dilute the soapy taste – some babies will accept it that way.
- •Avoid the “pitcher method” for long-term storage. This method (collecting multiple pumping sessions into one container to freeze later) gives lipase more time to affect the milk’s taste. Instead, freeze in smaller batches soon after each session.
- •Test and learn your milk’s timing. Some moms find their milk’s taste changes after just 12–24 hours, others after a few days. By doing a sniff/taste test at different ages of stored milk, you can figure out the window before your milk develops the flavor – and aim to use or scald it before that time.
Importantly, remember that high lipase milk is not harmful to your baby. The enzyme actually aids baby’s digestion when nursing. It only becomes an issue for pumped milk storage. If your baby happily takes the milk despite the taste, there’s no need to intervene. But if your baby refuses it, implementing the above steps (especially scalding) can be a game-changer so that none of your “liquid gold” goes to waste.