Comparison of oxidative status of human milk, human milk fortifiers and preterm infant formulas

Preterm and low birth weight infants require specific nutrition to overcome the accumulated growth deficit, and to prevent morbidities related to postnatal growth failure. In order to guarantee an adequate nutrient-intake, mother's milk, when available, or donated human milk, are usually fortified with additional nutrients, in particular proteins. Fortification with processed ingredients may result in additional intake in oxidative compounds, deriving from extensive heat treatments that are applied during processing. This study aims to compare the in vitro antioxidant activity and oxidative compound content conveyed by different preterm infant foods and fortifiers, namely raw and pasteurized human milk, two different preterm infant formulas, two bovine milk-based fortifiers and two experimental donkey milk-based fortifiers. The antioxidant activity of the infant foods and human milk fortifiers considered in the present research were evaluated as Trolox equivalent antioxidant capacity (TEAC), radical scavenging activity on the radical DPPH and in vitro antioxidant activity using red blood cells as indicators (CAA-RBC). As far as the oxidative content is concerned, the formation of malondialdehydes and protein carbonyls were assessed by HPLC and UV-spectrophotometric method respectively. Univariate and multivariate statistical analyses revealed significant differences between the different products. In particular, the choice of the protein source (hydrolysed vs. whole proteins) may greatly impact the resulting total antioxidant capacity of the preterm meal. The addition of fortifiers to human milk may result in higher antioxidant capacity; among bovine milk proteins, hydrolysed whey proteins resulted to provide higher antioxidant capacity than whole proteins. In general, the use of human milk minimizes the amount of oxidative compound in the diet in comparison to infant formulas, irrespectively of pasteurization or fortification, especially when malondialdehyde content is taken into account. The characterization of macro and micronutrients, bioactive compounds, as well as contaminants, deriving from food alteration, is of primary importance in order to guarantee high quality food products and adequate protein intake, especially when intended for infants, as formulas and fortifiers.