Effects of storage practices on long-chain polyunsaturated fatty acids and lipid peroxidation of preterm formula milk.

Background: Preterm formula milk (FM) is often prepared in advance, potentially affecting nutritional quality. Long-chain polyunsaturated fatty acids (LCPUFAs), important for brain and immune system function, are prone to lipid peroxidation, which correlates with comorbidities of prematurity. The effects of clinical storage practices on LCPUFA content and lipid peroxidation of preterm FM were investigated.

Methods: UK liquid and powder preterm FM (2017) (from two manufacturers) were subjected to routine storage conditions (liquid: refrigeration ≤10 h; powder: weekly preparation in accordance with the manufacturer's instructions and refrigeration ≤24 h for 4 weeks). LCPUFA content, thiobarbituric acid reactive substances and 4-hydroxy-2-nonenal (HNE) content were analysed.

Results: Storage did not significantly decrease LCPUFA content. The European Society for Paediatric Gastroenterology, Hepatology and Nutrition recommended LCPUFA intake, whereas in utero accretion rates could not be achieved with both FM brands (liquid and powder). Lipid peroxidation was evident on opening, with 6× higher levels in powder. No effect of ≤10-h refrigeration on peroxidation was seen in liquid FM. In powder FM, it increased over refrigeration (HNE opening: 6.5-9.7 µg mL versus day 28, 24 h: 16.6-36.5 µg mL ) with a significant interaction between storage time and refrigeration (P = 0.015), with higher HNE at 4 h on days 0, 7, 14 and 21 (all P < 0.05).

Conclusions: The results suggest that preterm FM and storage conditions do not support in utero accretion rates for LCPUFAs. Although the results suggest different susceptibility of liquid and powder FM to peroxidation upon refrigeration, they are too preliminary to make specific recommendations. We suggest minimising storage time of fresh and prepared powder FM, wherever possible.