Aroma Chemicals Research Articles

Potential applications of glucosyltransferases in terpene glucoside production: impacts on the use of aroma and fragrance.

The detection of glucoconjugated forms of monoterpene alcohols in rose petals in the late 1960s opened the new field of nonvolatile aroma precursors in flavor research. It is now well established that odorless glycosides represent a significant pool of aroma precursors in plants where they act as preformed but inactivated defense or attractive chemicals. Technical improvements in the separation and identification of plant secondary metabolites have provided a multitude of chemical structures, but functional characterization of glycosyltransferases that catalyze their formation lags behind. As technical efforts and costs for DNA sequencing dramatically dropped during the last decade, the number of plant genome sequences increased significantly, thus providing opportunities to functionally characterize the glycosyltransferase gene families in plants. These studies yielded the first glycosyltransferase genes that encode efficient biocatalysts for the production of monoterpene glucosides. They have applications in the food, feed, chemical, cosmetic, and pharmaceutical industries as slow release aroma chemicals.

A green and sustainable approach: celebrating the 30th anniversary of the asymmetric l-menthol process.

Takasago has been devoted to producing l-menthol since 1954, and our long history of manufacturing this important aroma chemical is reviewed here. The current asymmetric catalytic process had its 30th anniversary in 2013. Our l-menthol process is considered carbon-neutral, and, therefore, 'green' and sustainable. It uses renewable myrcene obtained from gum rosin as a starting material. In addition, the Rh-BINAP (=2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) catalytic system is highly efficient. This pathway not only leads l-menthol, but a variety of 100% biobased aroma chemical products as well. By measuring the (14) C levels in a material, one can determine the percentage of carbon that is biobased. This biobased assay, described as the ratio plant-derived C/fossil-derived C, can clarify how renewable a product really is. This will be highlighted for several of Takasago's key aroma chemicals.

Development of Quartz Crystal Microbalance Sensors for Tea Aroma Chemicals

Development of Quartz Crystal Microbalance Sensors for Tea Aroma Chemicals

Biosynthesis of Flavour-Active Esters via Lipase-Mediated Reactions and Mechanisms

Flavour active esters belong to one group of fine aroma chemicals that impart desirable fruity flavour notes and are widely applied in the flavour and fragrance industry. Due to the increasing consumer concern about health, natural products are attracting more attention than chemically synthesized substances. The biosynthesis of flavour-active esters via lipase-catalyzed reactions is one of the most important biotechnological methods for natural flavour generation. To proceed with the industrial production of esters on a large scale, it is critical to understand the enzyme properties and behaviours under different reaction conditions. In this short review, the lipase-catalyzed reactions in various systems and their mechanisms for synthesis of the esters are summarized and discussed.

An Exploration of the Perception of Minerality in White Wines by Projective Mapping and Descriptive Analysis

AbstractMinerality is a way for wine writers to associate wines with their terroir. Little research has been carried out on the concept of minerality. In this study white wines were compared by projective mapping (PM) performed by wine industry professionals to a standard sensory descriptive analysis (DA) by trained judges. The PM found minerality to be positively correlated with acid taste and citrus, fresh, wet stone, and chemical aromas, and negatively correlated to butter, butterscotch, vanilla, and oak aromas. The PM panel minerality was associated with both aroma and taste perception. The DA found minerality to be positively correlated with reduced, chalky, and grassy aromas and bitter taste, and negatively correlated with barrel, caramel, honey, juicy fruit, musty, and cat pee aromas. Wine groupings were similar between the two panels. Minerality was highly associated with malic acid, tartaric acid, and titratable acidity, and moderately associated with free and total sulfur dioxide.Practical ApplicationsThere were similar concepts for minerality between the two types of panels, but there were also differences. This gives us the hope that teasing out the exact concept of minerality in white wines should be possible.

Genotoxicity assessment of some cosmetic and food additives

α-Hexylcinnamaldehyde (HCA) and p-tert-butyl-alpha-methylhydrocinnamic aldehyde (BMHCA) are synthetic aldehydes, characterized by a typical floral scent, which makes them suitable to be used as fragrances in personal care (perfumes, creams, shampoos, etc.) and household products, and as flavouring additives in food and pharmaceutical industry. The aldehydic structure suggests the need for a safety assessment for these compounds. Here, HCA and BMHCA were evaluated for their potential genotoxic risk, both at gene level (frameshift or base-substitution mutations) by the bacterial reverse mutation assay (Ames test), and at chromosomal level (clastogenicity and aneuploidy) by the micronucleus test. In order to evaluate a primary and repairable DNA damage, the comet assay has been also included. In spite of their potential hazardous chemical structure, a lack of mutagenicity was observed for both compounds in all bacterial strains tested, also in presence of the exogenous metabolic activator, showing that no genotoxic derivatives were produced by CYP450-mediated biotransformations. Neither genotoxicity at chromosomal level (i.e. clastogenicity or aneuploidy) nor single-strand breaks were observed. These findings will be useful in further assessing the safety of HCA and BMHCA as either flavour or fragrance chemicals.

ChemInform Abstract: Natural 4‐Hydroxy‐2,5‐dimethyl‐3(2H)‐furanone (Furaneol)

AbstractReview: 92 refs.

Comparative analysis of the aroma chemicals of Melissa officinalis using hydrodistillation and HS-SPME techniques

Headspace solid-phase micro extraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS) has been used for the chemical analysis of Melissa officinalis (leaves) cultivated in Institute Germplasm. The HS-SPME analysis led to the identification of 22 components constituting 99.1% of the total volatile constituents present in the leaves whereas its hydrodistillate led to the identification of 24 volatile constituents constituting 98.1% of the volatile material. The chemical composition of the SPME and hydrodistilled extract of M. officinalis leaves comprised mainly of oxygenated monoterpenes (78.5% and 57.8% respectively) and sesquiterpene hydrocarbons (14.9% and 29.7% respectively). The major components identified in the HS-SPME extract were citronellal (31.1%), citronellol (18.3%), β-caryophyllene (12.0%), (E)-citral (11.9%), (Z)-citral (9.6%), geraniol (3.6%), (Z)-β-ocimene (3.1%) and 1-octen-3-ol (2.0%) whereas hydrodistilled essential oil was rich in (Z)-citral (19.6%), β-caryophyllene (13.2%), (E)-citral (11.2%), citronellal (10.2%), germacrene-d (8.3%), δ-3-carene (5.0%), 6-methyl-5-hepten-2-one (3.7%) and citronellyl acetate (3.7%). The comparative analysis of volatile constituents of M. officinalis leaf extract using HS-SPME and hydrodistillation techniques shows both qualitative as well as quantitative differences. The current study is the first report involving rapid analysis of volatile components of M. officinalis by HS-SPME.

Effect of freezing method and frozen storage duration on odor-active compounds and sensory perception of lamb

The effects of different freezing methods (nitrogen freezing tunnel, air blast freezer and home freezer) and frozen storage duration (1month and 10months) have been studied by sensory analyses and chemical analyses of odor-active compounds. The sensory analyses showed that fresh meat was significantly (p<0.05) juicier than frozen meat. Meat frozen in the air blast freezer (ABF) and stored during 10months had the highest lamb flavor intensity, significantly different from meat frozen in a home freezer (stored for 1 and 10months) or in a nitrogen tunnel and stored for 1month. The fresh sample was characterized by lower levels of Strecker aldehydes, 2-phenoxyethanol, cresols and to a lesser extent 2-methylbenzaldehyde, and higher levels of furaneol, which was not even detected in frozen samples. These compounds, together with the relative levels of octanoic acid and ethyl hexanoate, could be used as markers to detect whether lamb meat has been frozen. In chemical terms, the ABF samples were the most similar to fresh meat. Remarkably, in most cases the relative chemical aroma composition had no significant differences as a result of freezing. This helps explain the high sensory similarity observed. Only pyrazine levels changed significantly with frozen storage duration. No oxidation aromas or rancidity have been detected in fresh or frozen lamb.

Risk factors associated with sensitization to hydroxyisohexyl 3‐cyclohexene carboxaldehyde

Hydroxyisohexyl 3-cyclohexene carboxaldehyde (HICC) is a synthetic fragrance chemical and an important contact allergen, at least in Europe. Despite this importance, little is known about risk factors associated with this allergen. To examine factors from the history and clinical presentation of patch tested patients associated with HICC sensitization. Contact allergy surveillance data of 95 637 patients collected by the Information Network of Departments of Dermatology (IVDK, www.ivkd.org) in 2002-2011 were analysed. Point and interval estimates of the relative risk were derived from multifactorial logistic regression modelling. The overall prevalence of HICC sensitization was 2.24%. The strongest risk factors were polysensitization and dermatitis of the axillae, followed by dermatitis at other sites. No consistent and significant time trend was observed in this analysis. As compared with the youngest patients, the odds of HICC sensitization increased approximately three-fold in the 52-67-year age group, and strongly declined with further increasing age. The risk pattern with regard to age and affected anatomical site differed from that observed with other fragrance screening allergens. Cosmetic exposure, as broadly defined here, was a stronger and more prevalent individual risk factor than occupational exposure.

Natural 4-Hydroxy-2,5-dimethyl-3(2H)-furanone (Furaneol®)

4-Hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF, furaneol®) and its methyl ether 2,5-dimethyl-4-methoxy-3(2H)-furanone (DMMF) are import aroma chemicals and are considered key flavor compounds in many fruit. Due to their attractive sensory properties they are highly appreciated by the food industry. In fruits 2,5-dimethyl-3(2H)-furanones are synthesized by a series of enzymatic steps whereas HDMF is also a product of the Maillard reaction. Numerous methods for the synthetic preparation of these compounds have been published and are applied by industry, but for the development of a biotechnological process the knowledge and availability of biosynthetic enzymes are required. During the last years substantial progress has been made in the elucidation of the biological pathway leading to HDMF and DMMF. This review summarizes the latest advances in this field.

Diffusion and performance of fragranced products: Prediction and validation

The design of fragranced products is a combination of art, technology, and scientific knowledge, although the former still predominates in the industry. For that reason, a theoretical model to assess their performance considering the release and diffusion together with the predicted odor intensity over time and distance from the source was developed and validated. Diffusion profiles were experimentally measured in a diffusion tube, similar to the Stefan tube, and predicted with a model for pure fragrance chemicals, binary, quaternary, and multicomponent (11 chemicals) mixtures. A very good agreement between our purely predictive model and experimental concentration data was observed. Fragrance concentrations in air were then converted into odor intensities using models from psychophysics, making it possible to evaluate the evolution of the odor with time and distance using a performance plot. Accordingly, the performance of these mixtures was modeled and experimentally validated, which constitutes a landmark for fragrance design. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3943–3957, 2013

Bioproduction of Natural Isoamyl Esters from Coconut Cream as Catalysed by Lipases

&lt;p&gt;This study investigated the bioproduction of isoamyl esters in coconut cream by lipases. Five lipases (palatase 20000 L, lipase AYS “Amano”, lipase A “Amano” 12, piccantase A and piccantase AN) were used to biosynthesize isoamyl esters in coconut cream supplemented with isoamyl alcohol. The lipases have different abilities to synthesize isoamyl esters with lipase AYS “Amano”, palatase 20000 L and piccantase A showing the highest potential. Bioproduction of isoamyl octanoate by palatase 20000 L was further examined under different conditions of temperature, pH, isoamyl alcohol concentration and lipase amount. Biosynthesis of isoamyl octanoate by palatase was not significantly affected at 30-50°C or pH of 4 to 7 and its maximum bioproduction was obtained at isoamyl alcohol concentration of 4% (v/v) and lipase amount of 6 mg 100 mL&lt;sup&gt;-1&lt;/sup&gt; reaction mixture. The lipase-treated coconut cream may serve as a bioflavouring ingredient for food applications or for extraction of pure aroma chemicals.&lt;/p&gt;

Hydrogenation of Styrene Oxide to 2-Phenyl Ethanol over Polyurea Microencapsulated Mono- and Bimetallic Nanocatalysts: Activity, Selectivity, and Kinetic Modeling

Styrene oxide is an important precursor to prepare 2-phenyl ethanol (2-PEA) of high quality for its use as a fragrance chemical. Styrene oxide was selectively hydrogenated to 2-PEA with polyurea-microencapsulated (EnCat) Pd, Pd–Rh and Pd–Cu nanocatalysts with methanol as solvent and NaOH as promoter. The catalysts were fully characterized to understand their activity, selectivity, and stability. Pd–Cu EnCat was used for further studies. Complete conversion of styrene oxide with 92% selectivity to 2-PEA was obtained over Pd–Cu EnCat at 333 K and 607.8 kPa. Effects of various parameters were studied to understand the product profile. A bifunctional Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanistic model was proposed. The kinetics of reaction was established and tested against experimental data. The results are new and provide a green and cost-effective process for the synthesis of 2-PEA.

Controlled biosynthesis of odd-chain fuels and chemicals via engineered modular metabolic pathways

Microbial systems are being increasingly developed as production hosts for a wide variety of chemical compounds. Broader adoption of microbial synthesis is hampered by a limited number of high-yielding natural pathways for molecules with the desired physical properties, as well as the difficulty in functionally assembling complex biosynthetic pathways in heterologous hosts. Here, we address both of these challenges by reporting the adaptation of the butanol biosynthetic pathway for the synthesis of odd-chain molecules and the development of a complementary modular toolkit to facilitate pathway construction, characterization, and optimization in engineered Escherichia coli. The modular feature of our pathway enables multientry and multiexit biosynthesis of various odd-chain compounds at high efficiency. By varying combinations of the pathway and toolkit enzymes, we demonstrate controlled production of propionate, trans-2-pentenoate, valerate, and pentanol, compounds with applications that include biofuels, antibiotics, biopolymers, and aroma chemicals. Importantly, and in contrast to a previously used method to identify limitations in heterologous amorphadiene production, our bypass strategy was effective even without the presence of freely membrane-diffusible substrates. This approach should prove useful for optimization of other pathways that use CoA-derivatized intermediates, including fatty acid β-oxidation and the mevalonate pathway for isoprenoid synthesis.

Fragrance chemicals lyral and lilial decrease viability of HaCat cells’ by increasing free radical production and lowering intracellular ATP level: Protection by antioxidants

We investigate in this study the biochemical effects on cells in culture of two commonly used fragrance chemicals: lyral and lilial. Whereas both chemicals exerted a significant effect on primary keratinocyte(s), HaCat cells, no effect was obtained with any of HepG2, Hek293, Caco2, NIH3T3, and MCF7 cells.Lyral and lilial: (a) decreased the viability of HaCat cells with a 50% cell death at 100 and 60nM respectively; (b) decreased significantly in a dose dependant manner the intracellular ATP level following 12-h of treatment; (c) inhibited complexes I and II of electron transport chain in liver sub-mitochondrial particles; and (d) increased reactive oxygen species generation that was reversed by N-acetyl cysteine and trolox and the natural antioxidant lipoic acid, without influencing the level of free and/or oxidized glutathione. Lipoic acid protected HaCat cells against the decrease in viability induced by either compound. Dehydrogenation of lyral and lilial produce α,β-unsaturated aldehydes, that reacts with lipoic acid requiring proteins resulting in their inhibition. We propose lyral and lilial as toxic to mitochondria that have a direct effect on electron transport chain, increase ROS production, derange mitochondrial membrane potential, and decrease cellular ATP level, leading thus to cell death.

Orthonasal aroma characteristics of Spanish red wines from different price categories and their relationship to expert quality judgements

Background and Aims: Research aimed to define the olfactory sensory spaces of Spanish red wines from different price segments and to determine relationships between sensory descriptors and quality as evaluated by experts. Methods and Results: A trained panel using a frequency of citation method assessed the orthonasal sensory characteristics of 96 Spanish wines belonging to three price segments (premium; high standard; low standard). Eleven robust sensory terms were built by combining similar terms using statistical criteria. A panel of experts consistently assessed quality. Negative aroma profiles, some of them very skewed, were identified in the different sets with ‘animal’, ‘undergrowth’, ‘vegetal’, ‘dried fruit’ or ‘evolved/oxidized’ notes. While skewed aroma profiles were not necessary for achieving low quality, the role of some terms was highly dependent on the category. ‘Dried fruit’ was positive in premium wines and negative in the other categories, in which its role was played by ‘berry’. The low standard wines had to be segmented into wooded and unwooded samples to find clear relationships with quality. Satisfactory models for quality could be built in all segments. Conclusions: Orthonasal aroma can explain wine quality. The sensory pair ‘woody/animal’ was confirmed as the most relevant and influential for wine quality. The role of the other terms depended on the category. Oxidation-related attributes are particularly detrimental to younger wines. Significance of the Study: The results provide a reliable and complete sensory database. They identified aroma profiles related to quality, provided an insight into the hierarchies of terms and provided information that will assist in the identification of the aroma chemicals potentially involved.

Contact sensitization to common haptens is associated with atopic dermatitis: new insight

It has been much debated whether atopic dermatitis (AD) is associated with contact sensitization as past findings have been conflicting. A positive association might change our clinical practice. To investigate the association between AD and contact sensitization taking the likely route of allergen exposure into account. Questionnaire and clinical data from a cross-sectional study performed in a general population in Copenhagen. In total, 3202 adults aged 18-69 years were patch tested, filaggrin genotyped for 2282del4 and R501X and questioned about AD. The variable 'contact sensitization to at least one allergen, but not nickel and thimerosal' was significantly associated with AD (odds ratio 2·53, 95% confidence interval 1·59-4·04). The higher prevalence of contact sensitization was driven mainly by fragrance chemicals. In a subanalysis in nonpierced women, a positive association was also found for nickel sensitization. Nickel and thimerosal sensitization may introduce bias in data analysis as these allergies often develop following skin piercing where the skin compartments are bypassed. We suspect that individuals with self-reported AD from this study mainly had mild disease. However, clinicians should be aware of increased levels of contact sensitization in individuals with AD. Patch testing should therefore be considered at an early point in individuals with a history of AD and active disease. The fundamental relationship between atopic disease and environmental chemical exposure may be of a more complex and intimate nature than previously supposed.

The role of the skin irritation response in polysensitization to fragrances

Contact allergy to fragrance chemicals is an increasing problem. Polysensitization is likely to be a phenotype of increased susceptibility to contact allergy. The factors that play a role in polysensitization are largely unknown. Identifying these risk factors is important with regard to future studies on the aetiology of contact allergy. To investigate whether enhanced skin irritability is a risk factor for the development of polysensitization to fragrance chemicals. One hundred participants characterized by fragrance contact allergy were included in our study. The participants were patch tested on the back with 25 individual fragrance chemicals and fragrance mixes I and II, and on the upper arm with sodium lauryl sulfate (SLS) (consisting of SLS concentrations of 0.45%, 0.67%, 1%, and 1.5%). Reading of both tests was performed during the following visits at days 2, 3, and 7. The response to SLS was monitored by measuring transepidermal water loss (TEWL). Polysensitization was defined as three or more allergic reactions to non-cross-reacting fragrance chemical allergens. Individuals with polysensitization showed significantly higher irritation responses to SLS 1% and 1.5% as assessed by TEWL. We found an enhanced skin irritation response to be a risk factor for the development of polysensitization to fragrance chemicals.

Characterization and Assessment of Flavor Compounds and Some Allergens in Three Iranian Rice Cultivars during Gelatinization Process by HS-SPME/GC-MS

A combined gas chromatography mass spectrometry with headspace solid-phase microextraction method has been utilized for the analysis of the flavor volatiles of three different rice cultivars including two modified Iranian rice cultivars and Hashemi rice cultivar during gelatinization. As a result, while gelatinization would progress, the amount of the volatile compounds would be also increased. Altogether, 74, 55 and 66 components were identified for Hashemi, HD5 and HD6 rice samples, respectively, which 56 unique compounds were not identified, previously. Subsequently, seven fragrance chemicals have been detected, which were most frequently reported as contact allergens in the European Union.