Effect of Holder pasteurization and frozen storage on macronutrients and energy content of breast milk

The aim of this study was to explore the effect of Holder pasteurization and frozen storage at -20°C after pasteurization on fat, total nitrogen, lactose, and energy content of breast milk. Both procedures are routinely practiced in human milk banks.

A total of 34 samples of frozen breast milk, donated by 28 women, were collected. Once thawed, an aliquot of each sample was analyzed before pasteurization; the remaining milk was pasteurized (Holder method) and split into 8 aliquots. One aliquot was analyzed after pasteurization and the remainder frozen at -20°C and analyzed 30, 60, 90, 120, and 180 days later. For every aliquot, fat, total nitrogen, lactose, and energy content were determined using the device human Milk Analyzer.

We observed a significant reduction in fat (3.5%; -0.17 (-0.29; -0.04) g/dL) and energy content (2.8%; -2.03 (-3.60; -0.46) g/dL) after pasteurization. A significant decrease over time was observed for fat, lactose and energy content. No significant changes were observed for nitrogen content. Mean differences between day 0 postpasteurization and day 180 were -0.13 (-0.21; -0.06) g/dL for fat, -0.08 (-0.13; -0.03) g/dL for lactose, and -1.55 (-2.38; -0.71) kcal/dL for energy content. The relative decreases were 2.8%, 1.7%, and 2.2%, respectively. Overall (postpasteurization + frozen storage), a 6.2% and 5% decrease were observed for fat and energy, respectively.

Holder pasteurization decreased fat and energy content of human milk. Frozen storage at -20°C of pasteurized milk significantly reduced fat, lactose, and energy content of human milk.