Expressed breast milk often requires specific handling for storage and feeding, and one technique sometimes necessary is called scalding. This process involves heating the milk just until small bubbles appear around the edges, typically reaching a temperature between 140°F and 180°F (60°C and 82°C). The primary purpose of this quick, controlled heat treatment is to preserve palatability, allowing the milk to be stored for later use without being rejected by the infant. The central question for parents is whether this necessary thermal intervention compromises the exceptional nutritional quality of the milk.
The Reason for Scalding: Managing High Lipase
Scalding is performed specifically to address the activity of the naturally occurring enzyme, lipase, which is present in all human milk. Lipase’s function is to break down milk fats, or triglycerides, into easily digestible fatty acids, which is a beneficial process for the infant. However, some parents produce milk with an unusually high level of lipase activity, known as high lipase.
When this highly active milk is stored, the rapid breakdown of fats causes the milk to develop a distinctly soapy, metallic, or rancid odor and taste. While this change does not make the milk unsafe, many infants will refuse to drink it. By heating the milk to 180°F (82°C), the lipase enzyme is deactivated, which immediately halts the fat breakdown process and prevents the development of the unpalatable flavor.
Degradation of Heat-Sensitive Vitamins and Immune Factors
The primary trade-off for preventing taste changes is the impact of the heat on specialized, biologically active components. The scalding temperature of 180°F is high enough to cause molecular changes in numerous heat-sensitive proteins and micronutrients. This heat denaturation significantly affects the immunological factors, which are proteins that provide anti-infective properties.
Specific immune components, such as Secretory Immunoglobulin A (sIgA) and Lactoferrin, are highly susceptible to heat damage, reducing the milk’s protective capacity. Similarly, water-soluble vitamins, including Vitamin C and some B vitamins like Thiamine, are prone to degradation from heat and oxidation. The concentration of these vitamins may decrease significantly due to the thermal process.
Stability of Macronutrients and Caloric Content
While the specialized protective components are diminished, the bulk nutritional components of the milk remain largely stable after scalding. Macronutrients—fat, protein, and carbohydrates (lactose)—are not significantly altered by the short duration of the heating process. The overall caloric density of the milk is maintained, meaning the baby still receives the energy needed for growth and development.
The total fat content, the main source of calories, does not vary by more than approximately 10% through most storage and heating practices. Similarly, the overall quantity of crude protein and the carbohydrate content are generally unaffected by the heat treatment.
Practical Guidelines for Minimizing Nutritional Compromise
For parents who must scald, minimizing the heat exposure is the best way to protect the remaining nutrients. It is important to scald the milk as soon as possible after expression, before the lipase has time to change the flavor. Heating the milk to the absolute minimum temperature necessary, typically 180°F (82°C), and removing it from the heat source immediately is crucial to avoid further degradation.
Using an accurate thermometer to monitor the temperature is recommended, as boiling the milk will increase nutrient loss. Following the scalding, the milk should be cooled rapidly using an ice bath before storage. A final strategy is to mix scalded milk with fresh or frozen un-scalded milk, ensuring the baby receives the benefit of all the milk’s components.