Objective Several data confirm benefits of mother’s milk (MM) for preterm infants, for its nutritional aspects and biologically active compounds. Oligosaccharides play an emerging role among these compounds. When MM is unavailable, pasteurized donor breast milk (DM) is considered the next best choice. Pasteurization partially affects properties of breast milk. Few data address how pasteurization affects milk concentration of oligosaccharides. Aim of this study was to evaluate the effects of Holder pasteurization on lactose concentration and on the pattern of 24 different oligosaccharides, quantitatively representing the big majority of those so far identified in human milk.

Methods Samples of MM were collected from mothers having delivered preterm. One of the samples was immediately frozen at −80°C, while the other one was pasteurized with Holder method. Then they were both analyzed with high performance anion exchange chromatography.

Results Results did not show any statistically significant variation in the total amount of oligosaccharides nor in the chromatographic pattern of the tested oligosaccharides before and after pasteurization.

Conclusions Milk oligosaccharides have prebiotic, trophic, antiadhesive and immunomodulatory effects, which play a relevant role in feeding vulnerable preterm infants with MM. Two recent meta-analysis showed a reduction in necrotizing enterocolitis incidence in preterm babies fed DM compared to those fed preterm formula. Milk oligosaccharides can play a protective role due to their above listed effects.

In conclusion, as concerns oligosaccharides our study confirms the persistence of the biological value of human milk even after pasteurization.