Aroma Molecules Research Articles

Water–triglyceride interfaces limit permeability and diffusion of aroma molecules in butter

AbstractInsight into the dynamics of aroma molecules in bulk phases and at water–triglyceride interfaces is crucial for elucidating the aroma release mechanisms in complex dairy products such as butter. This study employs classical, all‐atom molecular dynamics simulations with umbrella sampling to investigate the energetics and kinetics of key aroma‐active compounds, including diacetyl, ‐decalactone, and butyric acid, at interfaces of 1,3‐dipalmitoyl‐2‐oleoylglycerol (POP) in water. The chemical properties of aroma compounds, including polarity, hydrogen bonding, and van der Waals interactions, play a pivotal role in their interaction with interfacial molecules, resulting in unique profiles of the potential of mean force and diffusivity. In particular, ‐decalactone preferentially resides at the interface and accumulates in the triglyceride phase. Aroma permeability through the complexly organized water–triglyceride interface significantly decreases from ‐decalactone to butyric acid, with a less pronounced reduction for diacetyl. Surprisingly, this trend in aroma permeability at interfaces does not coincide with trends in aroma diffusion within both pure bulk phases. This discrepancy is attributed to local, heterogeneous molecular structuring at water–triglyceride interfaces, impeding the interfacial permeation processes and leading to local aroma confinement.Practical Application: Employing a water–POP interface as a case study, the methodology investigates aroma compound diffusion within bulk phases, delineating limitations in aroma permeability in dairy products with extended water–triglyceride interfaces. This is a substep in the aroma release process, contributing to the interpretation of perception studies by sensory panels in human sensory experiments and fostering a deeper understanding of the intricate dynamics inherent to individual compounds.

An innovative device for in vivo and in vitro study of fragrance evaporation after application on skin or model surfaces

An original device has been developed to measure perfume release in the air above a surface. This device has proven its originality, effectiveness, and repeatability both in vitro on different types of model surfaces and in vivo directly on the skin of the forearm of volunteers. A perfume composed of eight fragrance molecules in ethanol was used to measure evaporation in the headspace with solid phase microextraction (SPME) and gas chromatography analysis. Temperature control, time effects, system dimensions, volume and seal integrity, and SPME optimizations were investigated for the measurement device and the analytical method setup. Finally, the system's effectiveness and modularity were demonstrated with evaporation studies carried out on four different surfaces: a chemically inert glass surface, the Strat-M® model, a perfume test strip, and the skin. This original device shows promising results in providing a better understanding of the evaporation phenomena of fragrance molecules and its link with the physicochemical properties of the skin.

Unveiling the Neurocognitive Impact of Food Aroma Molecules on Pleasantness Perception: Insights From EEG and Key Brain LFT Activation

ABSTRACTFood aroma molecules have the potential to influence people's emotions through the olfactory pathway and are anticipated to emerge as a new method for regulating emotional states, owing to their simplicity and high acceptance. Current research on food aroma predominantly centres on the physicochemical properties and formation mechanisms of aroma components, neglecting the effects of aroma molecules in emotional regulation. Moreover, the evaluation of pleasantness, a pivotal dimension of emotions, lacks objective assessment methods. In this study, sensory assessments of pleasantness for 12 aroma compounds were gathered from 45 subjects, and their correlation with the brain's activity responses in the left frontal‐temporal lobe (LFT) and right frontal‐temporal lobe (RFT) using electroencephalogram (EEG) signals was analysed. The results revealed a close relationship between brain activity in the LFT and the perception of aroma pleasantness. Furthermore, a substantial correlation was observed between the α, β and γ frequency bands in the LFT and the subjective pleasantness scores. These findings demonstrate that the LFT plays a critical role in evaluating the pleasantness of aroma molecules, and that changes in the power of the α, β and γ bands serve as important evaluation indicators. Consequently, this method offers a new objective means for assessing pleasantness to find higher pleasantness aroma molecules and the emotional regulation of food aroma.

Engineering of Saccharomyces cerevisiae towards synthesis of linalool using linalool synthase from Magnolia champaca

Linalool is one of the commercially important fragrance molecule usually extracted from Lavandula angustifolia (lavender) and Ocimum basilicum (basil) plants. In the present study, efforts were made to produce this molecule in microbial system to meet demand-supply imbalance. Linalool synthase (LIS) gene from Magnolia champaca (Mc) and Coriandrum sativum (Cs) were successfully cloned and expressed in Saccharomyces cerevisiae CEN PK2–1 C. It was observed that expression of full-length LIS (fLIS) resulted in lesser linalool when compared to truncated LIS (tLIS) devoid of plastid signal for both Mc and Cs. In terms of linalool yield, MctLIS resulted in 1.27-fold higher linalool when compared to CstLIS. Later, when two more genes viz., TPI1 and ALD6 which presumably increase sterol pathway flux were overexpressed, actually resulted in lower linalool and increased acetate production. However, multicopy expression of MctLIS and tHMG1 in this strain has reversed the above phenomenon due to presumptive push-pull strategy. Finally, this engineered strain was cultivated in the 2 L bioreactor in fed-batch mode to obtain 10.85 µg/mL of linalool. Docking studies of homology model of MctLIS with geranyl pyrophosophate (GPP) revealed V387, Y361, T434, R427 and R249 as key interactions sites. The study reports the linalool production using LIS gene from Magnolia champaca for the first time and could be a potential chassis for further studies.

Metabolic engineering of the oleaginous yeast Yarrowia lipolytica for 2-phenylethanol overproduction

The rose fragrance molecule 2-phenylethanol (2-PE) has huge market demand in the cosmetics, food and pharmaceutical industries. However, current 2-PE synthesis methods do not meet the efficiency market requirement. In this study, CRISPR-Cas9-related metabolic engineering strategies were applied to Yarrowia lipolytica for the de novo biosynthesis of 2-PE. Initially, overexpressing exogenous feedback-resistant EcAROGfbr and EcPheAfbr increased 2-PE production to 276.3 mg/L. Subsequently, the ylARO10 and ylPAR4 from endogenous genes were enhanced with the multi-copies to increase the titer to 605 mg/L. Knockout of ylTYR1 and enhancement of shikimate pathway by removing the precursor metabolic bottleneck and overexpressing the genes ylTKT, ylARO1, and ylPHA2 resulted in a significant increase of the 2-PE titer to 2.4 g/L at 84 h, with the yield of 0.06 g/gglu, which is the highest yield for de novo synthesis in yeast. This study provides a valuable precedent for the efficient biosynthesis of shikimate pathway derivatives.

Novel fragrant aldehydes from (1R,5R)-sabinene: An experimental study supported by DFT calculations revealing an unusual hydroformylation mechanism

The fragrance industry continually searches for compounds that introduce new scent notes or improve existing ones. Herein, we report a methodology for obtaining two novel aldehydes, potentially interesting for application in fragrance formulations, via rhodium-catalyzed hydroformylation of (1R,5R)-sabinene, a biorenewable monoterpene available in many essential oils. One of the aldehydes, which retained the original sabinene skeleton, was derived from the hydroformylation of the exocyclic C-C double bond through the accepted hydroformylation mechanism. The other aldehyde arose from the interaction of rhodium with the cyclopropane ring through an unusual mechanism, which resulted in the cyclopropane ring cleavage, forming a product that shares structural similarities with established fragrant molecules. The selectivity was controlled by adjusting the reaction conditions (temperature, pressure, P-ligand, and P/Rh ratio). Each aldehyde was obtained in a 70–80 % yield, depending on the reaction conditions. Combining our experimental findings with DFT calculations allowed us to propose an unusual hydroformylation reaction mechanism involving cyclopropane moiety in vinylcyclopropanes.

Molecular interaction of cyclodextrins with cellulose nanocrystals: A new venue for improving the functional properties of Pickering emulsions

The design of functional delivery systems is essential for storing and releasing active components. Inspired by the structure of Nepenthes mirabilis, cellulose nanocrystals (CNC) cooperate with cyclic α-cyclodextrins (α-CD), β-cyclodextrins (β-CD), and γ-cyclodextrins (γ-CD) to form nanocomposites at different mass ratios for the delivery the Mosla chinensis essential oils (EO)-loaded Pickering emulsions (PE), respectively. Characterization methods including FT-IR, TG, XPS, AFM, XRD, and three-phase contact angle were used to analyze the structure of the nanocomposites. The molecular docking and molecular dynamic simulation results revealed that the most hydrogen bonds were formed between β-CD and CNC, but the tendency for γ-CD and CNC to bond with hydrogen bonds was stronger in the molecular dynamic simulation. Subsequently, the physicochemical properties of emulsions stabilized by CNC/CDs nanocomposites were characterized through particle size, potential, microstructure, long-term stability, rheology, and aqueous phase distribution indexes. The results showed that the different mass ratios CNC/α-CD and CNC/β-CD nanocomposites stabilized PE had smaller droplet scales and better stability. While CNC/γ-CD nanocomposites had a negative effect on the emulsion. The in vitro release results showed that the emulsions stabilized by CNC/CDs nanocomposites had a slow-release rate for EO by diffusion. The simulated gastrointestinal release showed that CNC/β-CD-PE had the highest bioavailability. Moreover, CNC/β-CD-PE reduced the minimal inhibitory concentration of EO by a mechanism that disrupts the membrane structure of bacteria. Therefore, the introduction of β-CD may be an effective alternative in regulating the physical properties, function, and stabilization of CNC-based PE. These findings provide a scientific basis for the rational structural design of delivery systems for the encapsulated aroma molecules.

Stabilization and sustained release of fragrances encapsulated by layered double hydroxides

To stabilize the fragrances with high volatility and chemical instability, various carriers or matrix have been employed to encapsulate the fragrance molecules. However, it is still a challenge to acquire high-loading and long-lasting fragrances due to the complicated reaction procedure or the lack of the efficient interactions between the matrix and fragrances. Herein, we have introduced layered double hydroxides (LDHs) to localize the fragrant vanillin molecules through the electrostatic interaction and hydrogen bonds between aldehyde group of vanillin and hydroxyl groups on the LDHs, and the loading contents of vanillin in the composites reached 1208 mg/g. The as-prepared composites showed high stability, and the fragrance retention ability of vanillin was significantly promoted in a long-term preservation due to the stabilization of LDHs. Moreover, the fragrant vanillin in the composites could be sustainably released upon the thermal treatment. Therefore, we have provided a long-lasting fragrant composite by encapsulating the fragrances into the inorganic LDHs through electrostatic interaction and hydrogen bonds, and it is anticipated that this strategy could provide insights into stabilization and controlled release of fragrances.

Environmentally friendly calcium carbonate-polydopamine microcapsules with superior mechanical, barrier, and adhesive properties

There is a rising need to deliver perfume molecules to fabric surfaces during washing cycles to enhance consumers' perception. With upcoming regulations phasing out intentionally produced microplastics by 2027, the focus is on sustainable alternatives to conventional non-biodegradable synthetic microcapsules (e.g. melamine-formaldehyde). Calcium carbonate (CaCO3) has shown promise to form the microcapsule shells due to its environmental benignity, inexpensiveness, and potential for liquid formulations, particularly detergents. Notwithstanding, its inherent porosity undermines the performance of the ensuing microcapsules. Bio-inspired by the adhesive properties of mussel proteins, dopamine is proposed for forming a protective organic coating on CaCO3-based microcapsules. This research aims towards developing primary microcapsules with CaCO3 shells encapsulating hexylsalicylate (HS) as a perfume oil, applying a polydopamine (PDA) coating via oxidative auto-polymerisation of dopamine-hydrochloride (pH 8.5), and conducting a comprehensive analysis of morphological, mechanical, barrier, and adhesive properties through advanced techniques, namely fluorescent-sensing/scanning electron microscopy (SEM), micromanipulation, UV–Vis spectrometry, and a microfluidic chamber fitted with polyethylene-terephthalate (PET) fabrics. The obtained microcapsules (D[3, 2]=31.2 ± 0.4 μm) exhibited a spherical core-shell structure with a smooth PDA-coated surface. Mechanical assessments reveal remarkable rupture stress (2.2 ± 0.3 MPa) comparable to that of commercial microcapsules. After one month in water, ∼40% of HS was released from PDA-coated microcapsules, while the primary ones released the entire amount within 4 h. When mimicking washing conditions (pH 9), the PDA-coated microcapsules demonstrated improved retention (∼60%) on the PET substrate at hydrodynamic shear stress of ∼1 Pa, whereas that of the primary microcapsules was below 10%. Overall, this study suggests the successful fabrication of eco-friendly microcapsules featuring a hybrid inorganic-organic shell, with enhanced mechanical strength, reduced leakage, and improved adhesion, showcasing their potential in applications within the fast-moving consumer goods industry.

Towards Greener and More Cost-efficient Biosynthesis of Pharmaceuticals and Fragrance Molecules.

Enzymes are natural catalysts which are gaining momentum in chemical synthesis due to their exquisiteselectivity and their biodegradability. However, the cost-efficiency and the sustainability of the overall biocatalytic process must be enhanced to unlock completely the potential of enzymes for industrial applications. To reach this goal, enzyme immobilization and the integration into continuous flow reactors have been the cornerstone of our research. We showed key examples of the advantages of those tools for the biosynthesis of antivirals, anticancer drugs, and valuable fragrance molecules. By combining new strategies to immobilize biocatalysts, innovative bioengineering approaches, and process development, the performance of the reactions could be boosted up to 100-fold.

Harnessing graph neural networks to craft fragrances based on consumer feedback

In this research, we present a comprehensive methodology to categorize perfumes based on their fragrance profiles and subsequently aid in creating innovative odoriferous molecules using advanced neural networks. Drawing from data on Parfumo (2008) and The Good Scents Company (2021) webpage, the study employs web scraping techniques to gather diverse perfume attributes. Following this, a k-means algorithm is applied for perfume clustering, paving the way for recommending similar scents to consumers. The process then bridges customer preferences to molecular design by incorporating their feedback into generating new molecules via graph neural networks (GNNs). Through converting the Simple Molecular Input Line Entry System (SMILES) representation into graph structures, the GNN facilitates the creation of new molecular designs attuned to consumer desires. The proposed approach offers promising avenues for consumers to pinpoint similar perfume choices, incorporating feedback, and for manufacturers to conceptualize new fragrant molecules with a high likelihood of market resonance.

Machine Learning-Assisted Portable Microplasma Optical Emission Spectrometer for Food Safety Monitoring.

To meet the needs of food safety for simple, rapid, and low-cost analytical methods, a portable device based on a point discharge microplasma optical emission spectrometer (μPD-OES) was combined with machine learning to enable on-site food freshness evaluation and detection of adulteration. The device was integrated with two modular injection units (i.e., headspace solid-phase microextraction and headspace purge) for the examination of various samples. Aromas from meat and coffee were first introduced to the portable device. The aroma molecules were excited to specific atomic and molecular fragments at excited states by room temperature and atmospheric pressure microplasma due to their different atoms and molecular structures. Subsequently, different aromatic molecules obtained their own specific molecular and atomic emission spectra. With the help of machine learning, the portable device was successfully applied to the assessment of meat freshness with accuracies of 96.0, 98.7, and 94.7% for beef, pork, and chicken meat, respectively, through optical emission patterns of the aroma at different storage times. Furthermore, the developed procedures can identify beef samples containing different amounts of duck meat with an accuracy of 99.5% and classify two coffee species without errors, demonstrating the great potential of their application in the discrimination of food adulteration. The combination of machine learning and μPD-OES provides a simple, portable, and cost-effective strategy for food aroma analysis, potentially addressing field monitoring of food safety.

QM/MM Study Into the Mechanism of Oxidative C=C Double Bond Cleavage by Lignostilbene-α,β-Dioxygenase.

The enzymatic biosynthesis of fragrance molecules from lignin fragments is an important reaction in biotechnology for the sustainable production of fine chemicals. In this work we investigated the biosynthesis of vanillin from lignostilbene by a nonheme iron dioxygenase using QM/MM and tested several suggested proposals via either an epoxide or dioxetane intermediate. Binding of dioxygen to the active site of the protein results in the formation of an iron(II)-superoxo species with lignostilbene cation radical. The dioxygenase mechanism starts with electrophilic attack of the terminal oxygen atom of the superoxo group on the central C=C bond of lignostilbene, and the second-coordination sphere effects in the substrate binding pocket guide the reaction towards dioxetane formation. The computed mechanism is rationalized with thermochemical cycles and valence bond schemes that explain the electron transfer processes during the reaction mechanism. Particularly, the polarity of the protein and the local electric field and dipole moments enable a facile electron transfer and an exergonic dioxetane formation pathway.

Design, synthesis, olfactory evaluation and molecular docking study of Isoxazoline carboxylate derivatives as fragrance molecules

AbstractIn this research, a wide range of aldoxime derivatives with aromatic and aliphatic substituents were synthesized as precursors to nitrile oxide in cycloaddition reactions. The aldoximes were synthesized with good to high yields and showed a lack of diastereoselectivity, as confirmed by 1H NMR measurements. These aldoximes were then utilized as precursors of nitrile oxide in 1,3‐dipolar cycloaddition reactions and were treated with dipolarophilic reagents, namely methyl methacrylate (MMA) and glycidyl methacrylate (GMA), to produce isoxazoline carboxylate derivatives with high regioselectivity. The obtained compounds were characterized using various techniques, including NMR, FT‐IR, GC–MS and TOF‐LCMS analyses. The study also targets the molecular docking analysis, using Autodock 4.2.6 software, targeting the OR51E2 protein. This protein has drawn recent attention, with the hypothesis that propionic acid activates OR51E2, making it a suitable candidate for the carboxylate group within the obtained isoxazoline skeleton. Through these multifaceted investigations, this research contributes to the design and development of fragrant molecules with potential applications in the fragrance industry, offering a promising avenue for future olfactory innovations.

The behavioral sensitivity of mice to acyclic, monocyclic, and bicyclic monoterpenes.

Monoterpenes are a large class of naturally occurring fragrant molecules. These chemicals are commonly used in olfactory studies to survey neural activity and probe the behavioral limits of odor discrimination. Monoterpenes (typically in the form of essential oils) have been used for centuries for therapeutic purposes and have pivotal roles in various biological and medical applications. Despite their importance for multiple lines of research using rodent models and the role of the olfactory system in detecting these volatile chemicals, the murine sensitivity to monoterpenes remains mostly unexplored. We assayed the ability of C57BL/6J mice to detect nine different monoterpenes (the acyclic monoterpenes: geraniol, citral, and linalool; the monocyclic monoterpenes: r-limonene, s-limonene, and γ-terpinene; and the bicyclic monoterpenes: eucalyptol, α-pinene, and β-pinene) using a head-fixed Go / No-Go operant conditioning assay. We found that mice can reliably detect monoterpene concentrations in the low parts per billion (ppb) range. Specifically, mice were most sensitive to geraniol (threshold: 0.7 ppb) and least sensitive to γ-terpinene (threshold: 18.1 ppb). These estimations of sensitivity serve to set the lower limit of relevant monoterpene concentrations for functional experiments in mice. To define an upper limit, we estimated the maximum concentrations that a mouse may experience in nature by collating published headspace analyses of monoterpene concentrations emitted from natural sources. We found that natural monoterpenes concentrations typically ranged from ~1 to 1000 ppb. It is our hope that this dataset will help researchers use appropriate monoterpene concentrations for functional studies and provide context for the vapor-phase delivery of these chemicals in studies investigating their biological activity in mice.

Inclusion complexes of β-cyclodextrin with isomeric ester aroma compounds: Preparation, characterization, mechanism study, and controlled release

Cyclodextrins (CDs) have been discovered to provide an efficient solution to the limited application of ester aroma molecules used in food, tobacco, and medication due to their strong smell and unstable storage. This work combined molecular modeling and experimental to analyze the conformation and controlled release of isomeric ester aroma compounds/β-CD inclusion complexes (ICs). The investigation revealed that ester aroma compounds could be effectively encapsulated within the β-CD cavity, forming ICs with low binding affinity. Furthermore, the key driving forces in ICs were identified as hydrogen bonds and van der Waals interactions through theoretical simulation. Results from the Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and Isothermal titration calorimetry (ITC) experiments confirmed the intermolecular interaction predicted by the molecular model. Notably, the release rate of aroma compounds from L-menthyl acetate/β-CD (LMA/β-CD) IC exceeded that of terpinyl acetate/β-CD (TA/β-CD) IC. This difference is attributed to the length of the chain of aroma molecules and the variation in the position of functional groups, influencing the stable formation of ICs with β-CD. These findings hold potential implications for refining the application of ICs across diverse industries.

Constructing a green oleaginous yeast cell factory for sustainable production of the plant-derived diterpenoid sclareol

This study provides a green oleaginous yeast cell factory for sustainable production of sclareol, a significant precursor of fragrance molecules.

The Essential Oils Obtained from (Lonicerae japonicae Flos) Flower Buds Could Affect the Deposition of Sunflower Oil under Common High Temperature Conditions and the Traditional Frying Process in Maye.

The essential oil extracted from the flower buds of Lonicerae japonicae (LJEO) was employed in the high-temperature (65℃) accelerated preservation of sunflower oil. In the present investigation, the addition of the essential oil at a concentration of 800 ppm significantly inhibited the decrease in the oxidative stability of sunflower oil. This positive effect was achieved by significantly hindering the reduction in acidity value (AV), peroxide value (PV), p-anisidine value (AnV), the total oxidation value (TOTOX) (p < 0.01), and the levels of thiobarbituric acid reactive substance (TBARS), the absorbance at 232/268 nm (K232/K268) and total polar compounds (TPC) (p < 0.01). Besides, it also significantly enhances the sensory attributes of Maye, including taste, flavor, and appearance, improving its overall acceptability through the addition of certain potential fragrance molecules (p < 0.01). Furthermore, one of the primary chemical compounds in LJEO, eugenol, has demonstrated significant natural antioxidant properties in the traditional deep-frying procedure for the product, Maye. Consequently, together with eugenol, the essential oil LJEO could be employed as a possible effective antioxidant for the typical long-term preservation and even the traditional deep-frying procedures, and developed as effective antioxidant extracted from plants for the whole food industry.

Investigating the Vapor-Phase Adsorption of Aroma Molecules on the Water-Vapor Interface using Molecular Dynamics Simulations.

Surfactants are amphiphilic additives primarily used to reduce the surface tension of water and manipulate its wettability on various surfaces. Recent reports suggest that volatile surfactants, such as aroma molecules, diffuse more quickly to the interface from the vapor-phase than conventional surfactants typically used in the aqueous phase. The ability to adsorb from the vapor phase, in addition to their use as cosurfactants, expands the potential applications of volatile surfactants, particularly in situations where adding surfactants from the liquid phase is difficult. Here, we present a molecular level understanding of the adsorption kinetics of linalool, a common aroma molecule, on the water interface using molecular dynamics simulations. We note that the value of surface tension while adsorption from vapor and liquid phases is dependent only on the surface coverage. A minimum surface tension of 32 ± 1.8 mN/m is obtained in both cases at a maximum surface coverage of 4.88 μmol/m2 at 300 K. We observe the extent of decrease of the H-bonds between linalool-water and linalool-linalool molecules at various surface coverages to explain the mechanism of surface tension reduction. We solve Gibb's adsorption equation to establish a correlation between the surface coverage of linalool and the corresponding bulk concentration in experiments. We investigate the free energy profile of linalool's adsorption behavior at different surface coverages and temperatures. Our report suggests that linalool adsorption onto the water interface is an enthalpy-driven process primarily dependent on the strength of the interaction between the hydroxyl group of linalool and water molecules. These insights are crucial for selecting a suitable aroma molecule for various applications that target the vapor-phase adsorption mechanism.

Sensomics-assisted key aroma molecules decoding of ginger-infused stewed beef

The utilization of ginger (Zingiber officinale Rosc.) is prevalent in beef cuisine for the purpose of flavor modification in China. The key aroma molecules in ginger-infused stewed beef were identified by sensomics methods. GC-MS (gas chromatography-mass spectrometry) identified 54 compounds. Nonanal, citral, β-bisabolene, α-terpineol, geraniol and endo-borneol were responsible for remarkable difference of stewed beef after ginger additions by orthogonal partial least squares-discriminant analysis (OPLS-DA). Seven aroma attributes were chosen for sensory analysis by check-all-that-apply (CATA) and free choice profiling method (FCP). Then, 23 compounds were perceived by gas chromatography-olfactometry (GC-O), and further quantified. Of these, 20 aroma-active compounds presented odor activity values (OAV) ≥ 1. Combined with aroma recombination and omission experiments, 19 compounds, including hexanal, β-myrcene, 2-acetylthiazole et al. were identified to be key contributors to characteristic aroma.