The impact of the olfactory sense is regularly apparent across development. The fetus is bathed in amniotic fluid (AF) that conveys the mother's chemical ecology. Transnatal olfactory continuity between the odours of AF and milk assists in the transition to nursing. At the same time, odours emanating from the mammary areas provoke appetitive responses in newborns. Odours experienced from the mother's diet during breastfeeding, and from practices such as pre-mastication, may assist in the dietary transition at weaning. In parallel, infants are attracted to and recognize their mother's odours; later, children are able to recognize other kin and peers based on their odours. Familiar odours, such as those of the mother, regulate the child's emotions, and scaffold perception and learning through non-olfactory senses. During juvenility and adolescence, individuals become more sensitive to some bodily odours, while the timing of adolescence itself has been speculated to draw from the chemical ecology of the family unit. Odours learnt early in life and within the family niche continue to influence preferences as mate choice becomes relevant. Olfaction thus appears significant in turning on, sustaining and, in cases when mother odour is altered, disturbing adaptive reciprocity between offspring and carer during the multiple transitions of development between birth and adolescence. This article is part of the Theo Murphy meeting issue ‘Olfactory communication in humans’.

Although the microbiota is considered to be the primary source of off-flavors in farmed fish, there is a lack of information about the possible contribution of feeds to fish malodor. For this reason, the current study was designed to perform comprehensive sensory and chemo-analytical characterization of fish feed constituents that can impact the quality of farmed fish, and to determine whether feeds cause malodor accumulation in fish. To this aim, odorants in four commercial fish feeds were extracted using solvent assisted flavor evaporation (SAFE) and characterized by comparative aroma extract dilution analysis (cAEDA) and multi-dimensional gas chromatography-mass spectrometry/olfactometry (MD-GC-MS/O). The odorants in the fish feed samples were correlated with their respective sensory and fatty acid profiles. The cAEDA studies revealed the presence of 81 odorants of which 55 compounds were common to all the samples. Most of these odorants are identified here for the first time in fish feeds, and include skatole, indole, (E,Z,Z)-2,4,7-tridecatrienal, 4-ethyloctanoic acid, and cresols. Additionally, geosmin and 3-isopropyl-2-methoxypyrazine, known for their contribution to fish taint, and other cyanobacterial by-products, dimethyldisulfide and dimethyltrisulfide, were identified in feed samples. The results suggest that fish feed may contribute to fish malodor. Most of these off-flavors were linked to lipid source (fish oil or plant/lard alternatives), unsaturated fatty acids contents, and protein type (plant-based or fishmeal-based sources) in the feed.

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Scope: Breast milk is repeatedly postulated to shape the first aroma and taste impressions of infants and thus impact their flavor learning. The objective of this study is to assess the transition of aroma compounds from a customary curry dish into milk. Methods and Results: The article prepares a standardized curry dish and administers the dish to nursing mothers (n = 18) in an intervention study. The participants donate one milk sample before and three samples after the intervention. Due to their olfactory or quantitative relevance in the curry dish, 1,8-cineole, linalool, cuminaldehyde, cinnamaldehyde, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, sotolone, eugenol, vanillin, and 𝜸-nonalactone are defined as target compounds, and their transition into milk is quantified by gas chromatography-mass spectrometry. A significant transition into the milk is observed for linalool, and its olfactory relevance in this respect is supported by calculated odor activity values. In contrast, no relevant levels are detected for the other eight target compounds. Conclusion: Ingestion of a customary curry dish can lead to an alteration of the milk aroma, which might be perceived by the infant during breastfeeding. The current study also demonstrates that the extent of aroma transfer differs between both substances and individuals.

Human milk odour has for long elicited research interest with regard to its function in breastfeeding initiation. The present review aims to provide an overview of the behavioural effects of human milk odour in the human neonate, considering different types of response measures in a feeding or nonfeeding context. Further, an overview of the current knowledge of odorant composition and factors influencing milk odour is provided by summarizing results from analytical studies using olfactometry, and addressing changes in milk odour due to storage, lactational stage, and maternal dietary intake of odorous substances. We finally highlight some issues for future research.

General emissions of volatile organic compounds from wood are well investigated, but only limited information is available on the odor-active substances contained therein. To close this gap, we aimed at specifically elucidating the odorous constituents of wood from incense cedar [Calocedrus decurrens (Torr.) Florin]; this material is commonly used for the production of a range of products such as pencils and interior accessories. Targeted odorant analysis requires specialized techniques combining modern odorant analytical tools with human-sensory evaluation. Following this concept, the odor profile of the wood sample was first evaluated by human-sensory analyses. Then, the most potent wood odorants were characterized by means of gas chromatography-olfactometry and ranked according to their odor potency via aroma extract dilution analysis. With use of this approach, more than 60 odorous substances were detected, and the 22 most potent odorants were successfully identified by gas chromatography-mass spectrometry/olfactometry and two-dimensional gas chromatography-mass spectrometry/olfactometry. Among the main odorants found were a series of terpenes, several degradation products of fatty acids, and a number of odorants with a phenolic core moiety. Five odorants are reported here for the first time as wood odorants, such as γ-octalactone and 3-phenylpropanoic acid; thymoquinone was demonstrated for the first time to have a pencil-like odor quality.

Volatile organic compounds of the vehicle interior are well investigated, but only limited information is available on the odorants of the passenger cabin. To close this gap, we aimed at specifically elucidating the odor, as a general proof of principle, of two new cars with different seat upholstery in a controlled environment using a targeted odorant analysis. In a first step, odor profiles were evaluated by a descriptive sensory analysis. Then, potent odorants of the passenger cabins were characterized by gas chromatography‐olfactometry and ranked according to their odor potency via odor extract dilution analysis. Using this approach, 41 potent odorants were detected, and 39 odorants were successfully identified by two‐dimensional gas chromatography‐mass spectrometry/olfactometry. In a third step, important odorants of the vehicle interior were quantified by means of internal standard addition. The most dominant odorants could be assigned to several specific substance classes comprising esters, saturated and unsaturated aldehydes, unsaturated ketones, rose ketones, phenolic and benzene derivatives, and pyrazines, occurring in a concentration range between 0.05 and 219 ng/L in air. Of these potent odorants, the aldehydes 2‐butylhept‐2‐enal, 2‐propyloct‐2‐enal, and (Z)‐2‐butyloct‐2‐enal are reported here for the first time as odorants in the environment of a passenger cabin.

Odorants are relatively small molecules which are easily taken up and distributed in the human body. Despite their relevance in everyday life, however, only a limited amount of evidence about their metabolism, pathways, and bioactivities in the human body exists. With this Review, we aim to encourage future interdisciplinary research on the function and mechanisms of the biotransformation of odorants, involving different disciplines such as nutrition, medicine, biochemistry, chemistry, and sensory sciences. Starting with a general overview of the different ways of odorant uptake and enzymes involved in the metabolism of odorants, a more precise description of biotransformation processes and their function in the oral cavity, the nose, the lower respiratory tract (LRT), and the gastrointestinal tract (GIT) is given together with an overview of the different routes of odorant excretion. Finally, perspectives for future research are discussed.