Olfactory Cues in Infant Feeds: Volatile Profiles of Different Milks Fed to Preterm Infants

Abstract

Background: Smell is determined by odor-active volatile compounds that bind to specific olfactory receptors, allowing us to discriminate different smells. Olfactory stimulation may assist with digestion and metabolism of feeds in the neonate by activation of the cephalic phase response of digestion. Infants' physiological responses to the smell of different milks suggest they can distinguish between breastmilk and infant formula. We aimed to describe the profile of volatile compounds in preterm breastmilk and investigate how this differed from that of other preterm infant feeding options including pasteurized donor breastmilk, breastmilk with bovine milk-based fortifier, human milk-based products and various infant formulas.Methods: Forty-seven milk samples (13 different infant formulas and 34 human milk-based samples) were analyzed. Volatile compounds were extracted using Solid Phase Micro Extraction. Identification and relative quantification were carried out by Gas Chromatography with Mass Spectrometry. Principal Component Analysis (PCA) and one-way Analysis of Variance (ANOVA) with Tukey's HSD (parametric data) or Conover's post-hoc test (non-parametric data) were used as appropriate to explore differences in volatile profiles among milk types.Results: In total, 122 compounds were identified. Breastmilk containing bovine milk-based fortifier presented the highest number of compounds (109) and liquid formula the lowest (70). The profile of volatile compounds varied with 51 compounds significantly different (adjusted p < 0.001) among milk types. PCA explained 47% of variability. Compared to preterm breastmilk, the profile of volatile compounds in breastmilk with added bovine milk-based fortifier was marked by presence of fatty acids and their esters, ketones and aldehydes; infant formulas were characterized by alkyls, aldehydes and furans, and human milk-based products presented high concentrations of aromatic hydrocarbons, terpenoids and specific fatty acids.Conclusions: Sensory-active products of fatty acid oxidation are the major contributors to olfactory cues in infant feeds. Analysis of volatile compounds might be useful for monitoring quality of milk and detection of oxidation products and environmental contaminants. Further research is needed to determine whether these different volatile compounds have biological or physiological effects in nutrition of preterm infants.

Odor-active volatile compounds in preterm breastmilk

“…Previous studies suggested that the profile of volatile compounds in BM results from degradation of milk lipids (yielding ketones, aldehydes, alcohols, free FAs, and FAe) and from maternal diet (mostly terpenoids). 30 , 38 – 41 BM from ten mothers of FT infants was found to contain higher amounts of terpenes, aldehydes, and alcohols than infant formulas, 38 although, in contrast to our findings, that study only detected SCFA in the BM. However, samples analyzed in this study were all from mature BM (>5 weeks postnatal) provided by mothers of FT infants, which may explain the different results.…”

“… 40 We previously reported that volatile compounds in 15 samples of preterm BM differed from those in infant formulas largely due to the presence of specific FA in BM that was absent from formulas. 30 Therefore, our findings are largely in agreement with previous reports and expand on the current knowledge of volatile compounds in BM by demonstrating that a variety of compounds of different chemical classes can be found in preterm BM, including MCFA and their esters, terpenoids, and VOCs.…”

“… 54 It has been demonstrated that the formation of hexanal from lipid peroxidation in BM is inversely correlated with the concentration of vitamins E and C. 54 Vitamins are powerful antioxidants and, therefore, their antiantioxidant capacity may prevent lipid oxidation of BM. 54 Thus, considering the influence of maternal diet on the distribution of volatile compounds in BM, 30 , 38 , 40 it seems possible that the elevated concentration of hexanal in BM of the mother from most deprived socioeconomic quintile could be related to reduced antioxidant components in their BM. Further research is required to confirm this association.…”

“…Untargeted analysis of volatile compounds was performed by headspace solid-phase microextraction gas chromatography with mass spectrometry (SPME-GC-MS) using a Thermo Fisher Trace GC Ultra with a Programmable Temperature Vaporizer connected to a Thermo ISQ mass spectrometer as described previously. 30 In brief, a Gerstel MPS2 autosampler was used to equilibrate samples at 37 °C, with continuous agitation, for 10 min. The SPME fiber was divinylbenzene-carboxen-polydimethylsiloxane 50/30 μm (Supelco, Bellefonte, Pennsylvania) measuring 20 mm in length.…”

“…We recently demonstrated that the profile of volatile compounds in different milk types commonly fed to preterm infants (BM, fortified BM, pasteurized donor BM, and a variety of infant formulas) are markedly distinct. 30 However, that study only analyzed a small number of samples from preterm BM, all collected in the first two weeks postpartum, as the main purpose was to compare different types of milk. Therefore, this study aims to investigate maternal and infant factors that may be associated with the profile of volatile compounds in BM produced by mothers of moderate- and late-preterm (MLP) infants enrolled in a multicenter randomized controlled trial, the DIAMOND trial.…”