Breast milk is a dynamic substance, rich with components that actively support an infant’s growth and development. Among these components is lipase, an enzyme naturally present in the milk that plays a functional role in fat digestion. Understanding this enzyme is important for parents who pump and store milk, as its activity can lead to a noticeable change in the milk’s sensory qualities. This natural variation is easily managed once its cause is understood, helping parents preserve their milk supply.
The Essential Function of Lipase
Lipase is a digestive enzyme that breaks down fats (triglycerides) into smaller, more easily absorbed components. Breast milk contains two main types of lipase: lipoprotein lipase (LPL) and bile salt-stimulated lipase (BSSL). BSSL is activated in the infant’s digestive system by bile salts, significantly increasing the baby’s capacity to digest fat, which is especially helpful since a newborn’s own pancreatic lipase production is limited.
The enzyme releases free fatty acids and glycerol, crucial for the infant’s energy and growth. This process aids the absorption of fat-soluble vitamins (A, D, E, and K) and essential fatty acids needed for brain development. Lipase essentially begins fat digestion, making the nutrients more bioavailable for the baby’s still-maturing digestive system.
Understanding High Lipase Activity
The term “high lipase activity” refers to a natural variation where the enzyme continues to break down fats rapidly after the milk has been expressed and stored. This accelerated breakdown is a characteristic of some mothers’ milk composition, not a flaw. The enzyme’s continued work releases a higher concentration of free fatty acids over time, particularly when milk is refrigerated or frozen.
These released fatty acids alter the milk’s flavor and odor, causing the sensory change that parents often notice. The stored milk can develop a taste and smell described as soapy, metallic, or sometimes slightly sour. This chemical change is entirely safe for the infant to consume and is not a sign of bacterial spoilage, though some babies may reject the altered taste.
Methods for Managing Lipase Activity
If a baby refuses milk with the altered taste, the most effective method for managing high lipase activity is to deactivate the enzyme shortly after expression. This is accomplished through scalding, which uses heat to stop the enzyme from breaking down fats further. Scalding must be done with freshly expressed milk, as the flavor change is irreversible once it occurs.
Scalding Breast Milk
To scald breast milk, gently heat it on a stovetop in a clean pot until it reaches approximately 180°F (82°C). At this temperature, small bubbles will begin to form around the edges of the pan, but the milk should not be allowed to boil vigorously. Immediately after reaching this temperature, the milk must be cooled rapidly, typically by placing the container in an ice bath. This heat treatment inactivates the lipase, preventing the development of the soapy or metallic taste during storage.
Parents can also experiment with other storage strategies to mitigate the issue. Freezing the milk immediately after expression may slow the enzyme’s activity compared to refrigeration, though the effect may still occur over time. Another tactic is to mix the stored, high lipase milk with freshly expressed milk to dilute the altered flavor, making it more palatable for the infant.
Nutritional Value of High Lipase Milk
A common concern for parents is whether milk with high lipase activity retains its nutritional value. High lipase breast milk remains fully nutritious and safe for a baby to drink. The enzyme’s activity does not diminish the overall fat content; it simply changes the chemical form of the fat from triglycerides into free fatty acids.
The milk still provides necessary calories, antibodies, and growth factors. While scalding is a practical solution for taste preference, heat treatment may reduce a small fraction of the milk’s heat-sensitive components. Therefore, freshly expressed milk is ideal, and scalded milk can be used to safely preserve a freezer stash.