Monitoring aroma changes during human milk storage at +4 °C by sensory and quantification experiments

Background & aims The effect of human milk storage in the refrigerator has been investigated with regard to sensory changes and modifications to the molecular composition of the milk odour-active volatiles. Methods In the present study, characteristic odorants from fat oxidation, known from previous studies, as well as free fatty acids were quantified as representative marker substances by means of stable isotope dilution assays of fresh milk samples and milk samples stored at +4 °C for one and three days, respectively. Results Sensory evaluation showed that rancid and sweaty odour attributes were generated during storage, resulting in an unpleasant aroma profile for adults; however, odour changes were not as pronounced as those observed in our previous study for freeze storage. Fatty and buttery odour notes and a cooked milk-like smell were also generated. In total eight odorants from fat oxidation were determined and some potent odorants showed slight concentration increases. Moreover, five free fatty acids were determined and these all showed drastic concentration increases, even after storage for just one day. Conclusions These investigations support our previous findings that storage recommendations for breast milk might need to be slightly reconsidered in view of potential sensory changes; on the other hand, no negative physiological effects are to be expected from these changes.