Breast milk is a complex biological fluid that contains enzymes that play a direct role in a baby’s digestion and nutrient absorption. One such enzyme is lipase, which naturally works to break down the fats in the milk. This process is beneficial for infants, whose digestive systems are still developing, allowing them to more easily utilize the essential fatty acids present in the milk. For some, this fat-breakdown process continues at an accelerated rate once the milk is expressed and stored, leading to high lipase activity. This enzyme activity causes the fat molecules to break down into free fatty acids, resulting in a noticeable change in the milk’s flavor and odor upon thawing.
Understanding High Lipase Milk
Lipase is present in all human milk, functioning to hydrolyze triglycerides, the primary fats in breast milk, into their simpler forms. This initial digestion starts in the milk itself. The term “high lipase” does not necessarily mean an abnormal amount of the enzyme is present, but rather that the enzyme is unusually active in storage conditions. This accelerated activity speeds up the breakdown of lipids even while the milk is refrigerated or frozen, which is why the change is often discovered only when the milk is thawed. The resulting free fatty acids are responsible for the milk developing a distinct soapy, metallic, or sometimes rancid smell and flavor. This change is a chemical reaction and a natural variation in human milk composition, not a sign of spoilage.
Safety and Palatability of Affected Milk
Milk affected by high lipase activity is completely safe and retains all of its nutritional value. The process does not diminish the calorie count, vitamins, or antibodies that make breast milk so beneficial. The sole issue with high lipase milk is the change in palatability, which can lead to feeding refusal. Some babies may not mind the altered taste and will drink it without hesitation. However, others may strongly reject the soapy or metallic flavor, as this rejection is purely a preference for the baby and is the only challenge that high lipase milk presents.
Strategies for Using Existing Frozen Supplies
Once high lipase activity has altered the flavor of frozen milk, the change cannot be reversed, but there are practical ways to make the existing supply usable.
Feeding Strategies
Mix the thawed high lipase milk with fresh milk or milk that has a low lipase level. Begin by using a small portion of the affected milk, such as one part high lipase milk to three parts fresh milk, and gradually increase the ratio if the baby accepts the taste. Serving the thawed milk chilled rather than warmed may also help, as colder temperatures can mask the off-flavor more effectively. Adding a small drop of pure, alcohol-free vanilla extract to the bottle can successfully camouflage the soapy or metallic notes for a sensitive baby.
Non-Feeding Uses
For milk that a baby completely refuses to drink, there are non-feeding uses that ensure the effort of pumping is not wasted. High lipase milk can be mixed into solid foods, such as purees or oatmeal, once the baby begins complementary feeding. Additionally, the milk’s beneficial properties make it excellent for topical use, such as adding it to a baby’s bath to help soothe skin conditions like eczema or diaper rash.
Preventative Measures for Future Pumping
The long-term solution for parents dealing with high lipase activity is to stop the enzyme from breaking down fats before the milk is frozen. This is accomplished through a simple heat-treatment process known as scalding, which deactivates the lipase enzyme. The scalding process involves gently heating the freshly expressed milk to a temperature of approximately 180°F (82°C).
The milk should be heated on a stovetop in a clean saucepan until small bubbles begin to form around the edges of the pan, but it must not be brought to a full, rolling boil. Using an instant-read thermometer is the most accurate way to ensure the milk reaches 180°F, which is the temperature required to successfully deactivate the enzyme. Once the target temperature is reached, the milk must be removed from the heat immediately.
Following the heating, it is necessary to cool the milk rapidly to stop any further heat-related effects before storing or freezing it. This can be done by placing the saucepan into a bowl filled with ice and cold water, also known as an ice bath. The entire scalding procedure must be performed as soon as possible after pumping, ideally within the first few hours, before the lipase has had time to significantly alter the fats. To confirm the process is effective, a small test batch of scalded milk should be frozen, thawed, and tasted before committing a large volume of milk to the freezer.