Jonathan Beauchamp

Breath acetone represents a promising non-invasive biomarker for monitoring fat oxidation during exercise. However, its utility is limited by confounding factors, as well as by the fact that significant changes in concentration occur only hours post-exercise, which makes real-time assessment difficult. We performed an untargeted screening for volatile organic compounds (VOCs) that could serve as markers of fat oxidation beyond acetone, and investigated whether breath measurements taken during exercise could predict post-exercise changes in fat oxidation. Nineteen participants completed two 25-min cycling sessions separated by a brief 5-min rest period. VOC emissions were analysed using proton-transferreaction time-of-flight mass spectrometry (PTR-TOF-MS) during exercise and after a 90-min recovery period. Blood β-hydroxybutyrate (BOHB) concentrations served as the reference marker for fat oxidation. Among 773 relevant analytical features detected in the PTR-TOF-MS measurements, only four signals exhibited strong correlations with BOHB (ρ ≥ 0.82, p = 0.0002)—all attributable to acetone or its isotopologues or fragments. End-of-exercise measurements of these signals enabled accurate prediction of participants with substantial post-exercise BOHB changes (F1 score ≥ 0.83, accuracy = 0.89). Our study did not reveal any novel breath-based biomarkers of fat oxidation, but it confirmed acetone as the key marker. Moreover, our findings suggest that breath acetone measurements during exercise may already enable basic predictions of post-exercise fat oxidation.

The increasing popularity of plant‐based diets and snacks has led to a growing variety of alternative foods, yet these often fail to meet sensory expectations, which is a decisive factor for food acceptance. The confectionery sector has recognized this dietary transition and developed tailored products to meet consumer demands. Despite the variety of plant‐based confectioneries on the market, few studies have investigated these novel formulations for their sensory performance compared to their traditional counterparts, or how their sensory properties impact consumer acceptance. In this study, we selected fruit gum candies as a confectionery model to explore sensory perception and the modality‐specific liking in relation to overall acceptance. In addition to taste, our consumer study ( n = 147), comprising 12 commercial products including various formulations, revealed that texture is an equally important driver of overall liking for fruit gum candies. Chewy gelatine‐based candies received the highest overall liking (mean ratings up to 7.3 on a nine‐point hedonic scale). Higher stickiness in starch‐ or pectin‐based candies decreased liking, while a harder texture improved the acceptance of products that used plant‐based gelling agents. The acceptance of gelatine decreased with increasing hardness. Acceptance of starch‐ and pectin‐based products decreased with consumer age by about 0.3–0.4 points per 10‐year increase in age, while gelatine‐based products maintained popularity. The present results highlight that texture, particularly hardness and stickiness, is an important driver of liking for fruit gum candies and provide a basis for optimizing plant‐based alternatives to meet sensory expectations.

Rationale: Geosmin and 2‐methylisoborneol (2‐MIB) are odor‐active compounds responsible for earthy off‐flavors in fish, creating significant quality concerns in recirculating aquaculture systems (RAS). Their extremely low odor thresholds make rapid and highly sensitive detection essential for maintaining product quality and consumer acceptance in aquaculture production. Methods: A novel analytical method was developed using static headspace sampling combined with proton transfer reaction‐mass spectrometry (PTR‐MS) for the detection of geosmin and 2‐MIB in aquaculture water. Sample preparation was optimized by sodium chloride addition to enhance salting out , incubation at 90 °C, and maximization of headspace injection speed into the PTR‐MS system to improve analyte sensitivity. Results: The optimized method achieved detection limits of 19 ng·L⁻¹ for geosmin and 4 ng·L⁻¹ for 2‐MIB with a total sample screening time of less than 10 minutes. Detection limits were within the same low ng·L⁻¹ range as the odor thresholds of these compounds, enabling quantification at sensorily relevant concentrations associated with off‐flavor perception. Conclusions: This PTR‐MS‐based approach provides a rapid and sensitive method for objective detection of geosmin and 2‐MIB in aquaculture water at concentrations relevant to sensory off‐odor impairment. The method shows strong potential for routine monitoring in RAS and may be extended to other volatile compounds and aqueous analytical applications.

Emissions of volatile organic compounds (VOCs) from consumer products into the indoor air can lead to the inhalation exposure of consumers to potentially hazardous chemicals. This investigation compared two analytical approaches to quantitatively screen VOC emissions from consumer products. A microchamber was used to examine the emissions of two selected products─a rain poncho and a skipping rope─under controlled conditions (temperature, air change rate), with a focus on the initial short-term emissions. Volatiles were sampled from the chamber either on sorbent tubes, with subsequent offline analysis by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS), or with online analysis by proton transfer reaction-mass spectrometry (PTR-MS). The products emitted several compounds of toxicological relevance, including cyclohexanone, xylene, phenol, isophorone, and naphthalene. Data from the two approaches yielded similar emission curves for most compounds, with maximum concentrations observed within 30 min. Isophorone exhibited the highest peaks, with concentrations of ∼1.2 mg m^-3 and ∼1.6 mg m^-3 from TD-GC-MS and PTR-MS analysis, respectively. Discrepancies in the maximum concentrations between the methods ranged between 25% and 50% for most of the investigated compounds. Total amounts of emitted compounds were calculated as an alternative metric to single concentration values, which allow the assessment of inhalation exposure. This study demonstrates the utility of the two approaches in characterizing short-term VOC emissions from consumer products. PTR-MS analysis offers rapid quantitation of VOCs but has limitations in identifying individual compounds, highlighting the need for complementary analyses by TD-GC-MS. Despite inherent offline sampling, TD-GC-MS was shown to be well-suited to monitoring short-term emissions.

Geosmin is a volatile sesquiterpenoid with an ‘earthy’ odour that negatively affects the flavour of aquaculture fish. While bioconcentration models for this compound in fish exist, there is an absence of studies that account for physiological kinetics across different organs and stress‐related biochemical variables. A deeper understanding of geosmin kinetics is crucial for refining models of its absorption, elimination and metabolic transformation in fish to improve predictions of its impact on flavour quality and clarify its effect on fish stress response and welfare. This study examines the waterborne absorption and distribution of geosmin in rainbow trout ( Oncorhynchus mykiss ) in blood, liver and fillet, as well as in aquaculture water, and assesses stress responses via biochemical markers. Trout were exposed to a single dose of 0.4 ng/mL geosmin ( n = 28; plus no exposure, n = 28, as a control) under static water conditions. The concentrations of geosmin in water and fish tissues were measured at five intervals over 144 h (all fish in one exposure and one control tank for each interval) using gas chromatography‐mass spectrometry (GC‐MS) analysis. Concomitant evaluations of eight biochemical stress indicators were undertaken. No significant stress response to geosmin exposure was observed, but biological tissues exhibited varying concentrations of geosmin, characterised by an initial increase followed by a decline. Strong effects of tissue‐specific properties and exposure duration on distribution kinetics and concentrations were observed. Second‐order polynomial regressions effectively captured the concentration dynamics of geosmin across all fish tissues and water. Cumulatively, over 88% of the geosmin dose remained unaccounted for, with only minor proportions of geosmin detected in water and animal biomass. This suggests primarily hepatic metabolic biotransformation in the fish, with a possible contribution from unsampled biomass and minor analytical/compartmental losses. These results advance the understanding of geosmin distribution dynamics in fish, with implications for aquaculture practices.

The organoleptic quality of aquaculture products is often diminished by off‐flavours described as ‘earthy’ or ‘mouldy’, typically associated with the odour compound geosmin. While compartmental bioconcentration models for geosmin exist, a physiologically based toxicokinetic (PBTK) multi‐compartment model that maps its organ‐specific distribution has not been established to date. This study proposes a PBTK model for waterborne geosmin uptake in liver, blood, fillet and residual biomass of rainbow trout ( Oncorhynchus mykiss ) using a hybrid machine learning approach. To address initial data limitation, polynomial regression coefficients from sparse experimental data (Part I) were used to generate interpolating synthetic time‐series data via Monte Carlo sampling. Empirical and synthetic datasets were combined to train three machine learning models, whereby random forest (RF) regression showed the best predictive performance and was selected to validate the expanded dataset. A PBTK ordinary differential equations (ODEs) model was formulated, incorporating literature‐derived physiological parameters for blood, liver, fillet and unsampled residual biomass. The RF regression model provided data to solve the ODEs, and rate constants for uptake, excretion and metabolic biotransformation of geosmin, interpreted as intrinsic tissue‐based kinetic parameters, were optimised through R‐based DEoptim and Optim algorithms. The numerically solved model refined kinetic parameters from prior compartmental models, highlighted the central role of liver in geosmin metabolism and allowed a detailed characterisation of organ‐specific geosmin distribution in fish. The hybrid approach improved descriptive accuracy and enhanced the understanding of geosmin bioconcentration dynamics, with implications for aquaculture practices and geosmin mitigation strategies.

Adding milk to coffee balances its flavor and reduces unpalatable notes (e.g., burnt aroma, bitterness), but research on how adding milk affects in vivo aroma release and perception is limited. This study analyzed the impact of adding cow or oat milk (30% w/w) on in vivo aroma release and flavor perception in medium and dark roasted Arabica coffees. Temporal dominance of sensations showed that medium roast had bitter and roasted flavors, while bitter and burnt flavors dominated the dark roast. The milks elicited their own inherent notes (dairy-like or caramel-like/vanilla-like) and decreased the perception of coffee-related flavors. Aroma release analysis by proton transfer reaction-mass spectrometry provided data on 47 volatiles, with quantitative differences between roasting levels being indicative of the changes in perception. While milk addition strongly affected perception, it did not systematically affect in vivo release of coffee-related volatiles, highlighting the challenges in aligning analytical and sensory data sets.

The consumption of seafood is driven by flavour, yet achieving its high quality remains a challenge for many species reared in recirculating aquaculture systems (RAS). A comprehensive knowledge of off‐odour sources in aquatic foods is indispensable in ensuring flavour quality standards. At the beginning of the production chain, early post‐harvest lipid oxidation products develop into endogenous off‐odours and accumulate over time. These malodours add to those already absorbed exogenously, namely from the water and feeds, although the information on the interactions between these sources is currently scarce. Despite geosmin and 2‐methylisoborneol receiving significant attention in relation to fish off‐flavour, only limited knowledge on the molecular and ecological mechanisms driving their production in aquatic environments has been reported. Moreover, RAS‐hosted bacteria have been associated with a wide range of other odour‐active compounds, such as pyrazines, terpenoids, and other degradation byproducts that are frequently overlooked when studying flavour taint in fish. The influence of aquaculture feeds on the flavour of fish flesh has been underestimated, too, both as a source of off‐odours but also as a novel modulator strategy to achieve desirable aquatic food flavours. Finally, the influence of water treatment processes widely used in RAS operations, such as advance oxidation process, ozone, ultraviolet and hydrogen peroxide disinfections, is greatly underexplored with respect to odour quality. This article reviews the current scientific evidence with supporting data on the chemical diversity of off‐odours found in aquaculture fish worldwide and their potential sources and highlights knowledge gaps that should be addressed in future research.

In this perspective, we review the evidence for the efficacy of face masks to reduce the transmission of respiratory viruses, specifically severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and consider the value of mandating universal mask wearing against the widespread negative impacts that have been associated with such measures. Before the SARS-CoV-2 pandemic, it was considered that there was little to no benefit in healthy people wearing masks as prophylaxis against becoming infected or as unwitting vectors of viral transmission. This accepted policy was hastily reversed early on in the pandemic, when districts and countries throughout the world imposed stringent masking mandates. Now, more than three years since the start of the pandemic, the amassed studies that have investigated the use of masks to reduce transmission of SARS-CoV-2 (or other pathogens) have led to conclusions that are largely inconsistent and contradictory. There is no statistically significant or unambiguous scientific evidence to justify mandatory masking for general, healthy populations with the intention of lessening the viral spread. Even if mask wearing could potentially reduce the transmission of SARS-CoV-2 in individual cases, this needs to be balanced against the physical, psychological and social harms associated with forced mask wearing, not to mention the negative impact of innumerable disposed masks entering our fragile environment. Given the lack of unequivocal scientific proof that masks have any effect on reducing transmission, together with the evident harms to people and the environment through the use of masks, it is our opinion that the mandatory use of face masks in the general population is unjustifiable and must be abandoned in future pandemic countermeasures policies.