Aroma Extract Research Articles

Wet Friction of Rubbers Containing DAE or TDAE Process Oil in ESBR and ESBR/BR Blends

AbstractThe inevitable need to replace conventional high aromatic process oils with new safe ones has made it critically important to investigate the extent of tire wet grip modification by process oils’ aromatic content. Here, direct measurement of wet friction is conducted on emulsion styrene butadiene rubber (ESBR) and ESBR/butadiene rubber (BR) rubber blends containing either safe treated distillate aromatic extract (TDAE) or the conventional distillate aromatic extract (DAE) oils. Interestingly, the results reveal that the wet coefficient of friction for rubbers with TDAE is comparable or even better than rubbers with the DAE. This stands in contrast with previous predictions founded on indirect methods such as the values of loss factor tan δ at 0°C. Analysis of temperature dependent dynamic properties exhibits similar values of tan δ at 0°C for two oil types; however, a higher level of loss tangent for TDAE is found near the glass transition temperature. It is hypothesized that the frequency of loading imposed by the microtexture of the concrete counterface may have dictated the temperature range in which the TDAE can surpass the DAE in terms of the wet grip performance. The difference in the wet grip of rubbers having two oils is more pronounced for the ESBR/BR blend system.

Identification and confirmation of key compounds causing cooked off-flavor in heat-treated tomato juice.

Cooked off-flavor produced by heat treatment greatly limited the acceptability of commercial tomato juice. To screen and identify the cooked off-flavor compounds, gas chromatography-mass spectrometry-olfactometry (GC-MS-O), aroma extract dilution analysis (AEDA), gas chromatography-mass spectrometry (GC-MS), and odor activity value (OAV) calculation were applied simultaneously. The results showed that there were 17 aroma-active compounds in tomato juice samples. Among them, three newly formed sulfur-containing compounds (dimethyl sulfide, dimethyl trisulfide, and methional) and 1-octen-3-one, which exhibited cooked corn/potato, onion, and mushroom odor, were proved to be responsible for the cooked off-flavor in heat-treated tomato juice (HTJ) by omission experiments and electronic nose analysis. The three newly formed sulfur-containing compounds were further confirmed to be the key compounds responsible for the cooked off-flavor in four different tomato cultivars that were commonly consumed in the market. PRACTICAL APPLICATION: Tomato is one of the most popular vegetables in the world and tomato juice is an important part of the tomato industry. However, the cooked off-flavor of tomato juice after sterilization severely restricts its industrial development. This study analyzed and compared the changes of aroma compounds before and after sterilization, and identified and confirmed the major off-flavor components. This work could provide fundamental information for the prevention of cooked off-flavor.

Potent odorants and sensory characteristics of the soft white cheese “Jben”: Effect of salt content

AbstractJben is a highly popular soft white cheese consumed in Morocco for its nutritional and health benefits. The aroma and aroma‐active compounds of salted and unsalted Jben were investigated in this study. Aroma compounds were isolated by the purge and trap extraction (PTE) method and analysed by aroma extract dilution analysis (AEDA) and gas chromatography–mass spectrometry‐olfactometry (GC–MS‐O). A total of 36 aroma compounds were characterized Jben samples, among them 30 and 32 compounds were detected in the salted Jben (260.88 mg/kg) and unsalted Jben (230.04 mg/kg) samples respectively. The alcohols, followed by acids and esters, were the most dominant aroma compounds in both samples. A total of 22 (salted Jben) and 25 (unsalted Jben) aroma‐active compounds were detected in the samples using GC–MS‐O. Based on the flavour dilution (FD) factor, the most potent aroma‐active compounds were ethyl caproate (FD = 2048, OAV = 2306, overripe fruit and pineapple odours), isoamyl acetate (FD = 2048, OAV = 2491, apple odour), hexyl acetate (FD = 1024, OAV = 1355, green odour), and isoamyl butyrate (FD = 1024, OAV = 932, green‐fruity odour) for the salted Jben sample and ethyl caproate (FD = 2048, OAV = 2388) and isoamyl acetate (FD = 1024, OAV = 880) for the unsalted Jben sample. The odour activity values (OAVs) ranged from 1 to 2491. The lowest OAVs represent the low aromatic active compounds (FD ≤ 32). The GC–MS‐O results were also consistent with the results of sensory analysis of the Jben samples.

Identification of potential odorant markers to monitor the aroma formation in kilned specialty malts

Specialty malts are strategic ingredients regarding their contribution to colour and flavour of beer. Malts with the same colour may present distinct flavour characteristics and intensities. Contradictorily, colour is the benchmark in practical quality control. To investigate the correlation between colour and flavour of kilned barley specialty malts, odorants of commercial products of pale ale (5–9 EBC), Vienna (6–10 EBC), Munich (11–35 EBC) and melanoidin malts (80–90 EBC) were screened via solvent-assisted flavour evaporation (SAFE) and compared via comparative aroma extract dilution analysis (cAEDA). Subsequently, selected odorants were quantified using solid-phase microextraction (SPME). A total of 34 odorants were detected, of which 12 exhibited a concentration increase as the coloration increased, whereas 4 suggested the influence of temperature and modification degree on aroma formation. Such odorants are thus elected as potential markers for monitoring the influence of process variations on the formation of aroma in commercial kilned specialty malts.

Characteristic of aroma components and antioxidant activity of essential oil from Ocimum tenuiflorum leaves

AbstractOcimum tenuiflorum has a characteristic spicy, sweet and green aroma and has been used as a medicinal herb for various diseases in Ayurveda systems. This study aimed to investigate the aroma‐impact components and antioxidant activity of the essential oil from O. tenuiflorum leaves, grown in Sri Lanka, which was obtained by hydrodistillation. The volatile compounds in the essential oil were measured by gas chromatograph–mass spectrometry. The major components were caryophyllene oxide (23.8%), β‐caryophyllene (18.2%), germacrene D (14.6%), α‐copaene (14.4%) and eugenol (10.0%). The characteristics of aroma components of the essential oil were determined by gas chromatography–olfactometry and aroma extract dilution analysis. Eleven compounds, including eugenol, rotundone, β‐damascenone, linalool and geraniol, were identified as aroma‐impact components of the essential oil. Among them, the dominant components were identified as eugenol, rotundone, 3‐hydroxy‐4,5‐dimethyl‐2(5H)‐furanone, coumarin and vanillin, which were quite different from the results of chemical analysis. The antioxidant activity of the essential oil was evaluated by 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging activity, 2,2′‐azino‐bis (3‐ethylbenzothiazoline‐6‐sulfonic acid) radical cation scavenging activity and β‐carotene bleaching assays. All results showed that the essential oil exhibited strong antioxidant activity, and antioxidant‐active components were proved to be eugenol by column chromatography. Furthermore, the presence of new antioxidant compounds other than eugenol, which had previously been reported, was also revealed. Therefore, the essential oil from O. tenuiflorum leaves has great potential as a resource in the cosmetics and food industries.

Elucidation of aroma compounds in passion fruit (Passiflora alata Ait) using a molecular sensory approach.

In this experiment, Guangxi passion fruit was used as the raw material for natural aroma extraction using the spinning cone column (Spinning Cone Column, SCC) technique. In combination with the semi-quantitative method, the aroma characteristics of the raw pulp (raw whole-fruit puree, PU) before SCC processing, residue (Residue, RS) and extract (Extract, EX) after SCC processing, and passion fruit juice (Juice, JU) were evaluated for their aroma characteristics using headspace gas chromatography-mass spectrometry (HS-SPME-GC-MS), gas chromatography-ion mobility spectrometry (GC-IMS), electronic nose, and sensory evaluation. As a result, a total of 110 aroma substances were detected in four samples, and 33, 38, 73, and 28 aroma components were detected from PU, RS, EX, and JU, respectively. There are 50 compounds in EX with concentrations greater than 10 μg/kg, and 19 of them had OAV values greater than 1, including β-Ionone and linalool, which contributed significantly to the aroma. The aroma profiles and characteristics were further analyzed for JU and EX using the e-nose sensor, and it was found that both showed similar aroma profiles. The sensory evaluation results were also in general agreement with the results obtained from the electronic nose, with EX having mainly "floral", "fruity," and "sweet" aromas. The results demonstrated that the spinning cone column technique can increase the fresh and natural fruity aroma of passion fruit in the extract, which has the effect of enriching the aroma and improving the aftertaste. This study will make a foundation for passion fruit SCC extract application in drinks. PRACTICAL APPLICATIONS: Compared with traditional extraction technology, spinning cone column technology has the advantages of high mass transfer efficiency, short extraction time, a wide range of temperature control, and the most complete extracted flavor substances, which greatly reduces the damage degree of heat-sensitive flavor substances and condense aroma. It is widely used in beverages, wine, dairy products, fruit and vegetable, spice essential oil, and other industries. Passion fruit flavor prepared by SCC technology has the advantages of high purity and high concentration, which can be used in solid drinks, baked food, convenience food, tobacco, perfume, and other products. Besides, GC-IMS is an efficient and rapid new analytical technique, which has been widely used in the flavor analysis of volatile organic compounds in food and traditional Chinese medicine samples.

Unravelling the key aroma compounds in the characteristic fragrance of Dendrobium officinale flowers for potential industrial application

Dendrobium officinale Kimura et Migo, one of the most important orchids because of its medicinal and edible value, has a typical Dendrobium Sw. flora scent, which has great application potential and commercial value to be characterized. The aroma-active compounds originating from D. officinale fresh flowers (DFF) were investigated using a sensomics approach. A combined solid phase microextraction and solvent-assisted flavor evaporation method were used to accurately capture the overall aromatic profile. Exactly 34 odorants were detected and identified by aroma extract dilution analysis (AEDA) coupled with gas chromatography/olfactometry−mass spectrometry (GC/O−MS) in DFF, of which nine odorants had a flavor dilution (FD) factor ≥27. All 34 odorants were further quantified. The odor activity values (OAVs) were calculated with the highest value of 7444, in which 18 compounds were confirmed to be key odorants, including 1-octen-3-ol, hexanal, nonanal, phenylacetaldehyde, linalool, 4-oxoisophorone, theaspirane, methyl salicylate, etc. Among the studies above, 42 out of 78 volatiles and 14 out of 34 odorants were identified in DFF for the first time. Then, the aroma profile of the DFF was simulated successfully by aroma recombination experiments based on the quantitation results, and the omission test suggested that alcohols are the decisive type of compounds in the DFF key odorants. In addition, a progressive addition test showed that the aroma recombinate prepared with 18 reference key odorants was able to reconstruct the characteristic aroma of DFF. In comparison, the recombinate constituted by mixing all 34 reference odorants in the same concentrations as determined in the DDF sample could mimic the flower scent and closely match the sensory attributes of the original D. officinale fresh flower.

Total phenolic content and antioxidant capacity of Greek medicinal and aromatic plant extracts using pulsed electric field followed by ultrasounds extraction process

The aim of this study was to evaluate an advanced water extraction method applying pulsed electric field followed by ultrasound. For this purpose, antioxidant capacity (AC) and total phenolic content (TPC) of Olea europaea L. leaves and unripe fruit, Melissa officinalis L. leaves, Cistus incanus L. ssp. creticus leaves, Vitis vinifera L. cv. “Xinomavro” leaves, marc, and fruits, Aronia melanocarpa L. fruits, Punica granatum L. peel, and Crocus sativus L. petals were analyzed. The results showed that a ratio of 1/20 g plant material/ml water, 5 min pulsed electric field and 30 min ultrasounds presented the maximum extraction efficiency. Melissa officinalis L. and Punica granatum L. had high TPC exhibiting 155 mg GAE/g DW (DW: dry weight) and 208 mg GAE/g DW, respectively, comparing to Vitis vinifera L. marc (31 mg GAE/g DW). All aqueous extracts studied, had high AC approaching 90% (except 32% in Crocus sativus L. petals and Vitis vinifera L. marc). Practical applications The beneficial use of medicinal and aromatic plants extracts in human health has been widely accepted. However, the efficiency of the process for the extraction of phenolic compounds from plants constitutes a challenge, since it is highly depended on the applied technique itself and the imposed operating conditions. In this regard, this work studies the application of a novel combined process of pulsed electric field extraction followed by ultrasounds assisted extraction for the recovery of polyphenols from selected Mediterranean plants. The evaluated process showed high extraction yields at short processing time and at moderate temperatures, which in conjunction with the use of water as a “green” extraction solvent lead to bioactive compounds stability and increased applicability of aqueous extracts.

Metabolomic Profile of Citrus limon Leaves (‘Verna’ Variety) by 1H-NMR and Multivariate Analysis Technique

The elaboration and definition of “metabolic fingerprints” can subsidize both the identification and determination of plant varieties, as well as the increase in knowledge about the responses and adaptations of plants to external and/or internal factors. The lemon tree (Citrus limon Burm.) is one of the most important crops in the Spanish southeast and is often consumed around the world. Although the study and characterization of its fruits are common due to its economic interest, its leaves are limited to specific functionalized studies related to the objective of the work (extraction of essential oils, stabilizing agent, aromatic extracts, etc.). So, this study aimed to identify the primary and secondary metabolites of Citrus limon Burm. (‘Verna’ variety) leaf samples cultivated under different conditions (three rootstocks and three culture media). In total, 19 metabolites were identified for all samples, of which 9 were amino acids, 5 organic acids, 3 sugars and 2 intermediate metabolites. The results pointed to a limited influence, both of the substrate and of the crop rootstock, on the metabolomic differentiation of lemon leaves. Knowledge and foliar metabolomic differentiation can offer important information that supports the application of crop foliar treatments but also helps in the management of diseases and pests.

Changes in Serum Blood Parameters in Farmed Rainbow Trout (Oncorhynchus mykiss) Fed with Diets Supplemented with Waste Derived from Supercritical Fluid Extraction of Sweet Basil (Ocimum basilicum)

The antimicrobial and immunostimulant proprieties of aromatic plant extracts have been widely described, but their effects on serum blood biochemistry in fish have not. For this study, we assessed the changes in serum blood biochemical parameters in rainbow trout fed with a fish diet supplemented with a basil supercritical extract (F1-BEO). Our hypothesis was that treatment and time would be associated with changes in 10 serum blood biochemical parameters. F1-BEO was added to a commercial feed (0.5, 1, 2, 3% w/w). The fish were fed for 30 days, and the blood samples were collected at 2 time points (15 and 30 days). A two-way ANOVA showed a significant effect of treatment, time, and interaction treatment × time on creatinine, urea, total protein, albumin, magnesium, and phosphorus (p < 0.05), a significant effect of both time and interaction treatment × time on cholesterol (CHOL), glutamic oxaloacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) levels, and a significant effect of time on triglycerides (p < 0.05). While changes in several of the parameters were observed, the levels remained within the normal range for rainbow trout. Notably, after 30 days there was a significant decrease in CHOL in fish treated with 0.5% and 1% w/w F1-BEO (p < 0.05). The statistically non-significant increase in GOT and GPT in the fish fed with F1-BEO up to 3% w/w indicated a positive effect of basil on liver health. Our findings suggest a potential use for basil extracts (for example., F1-BEO) in fish feed to reduce antibiotic use and improve fish welfare.

Cytotoxicity, early safety screening, and antimicrobial potential of minor oxime constituents of essential oils and aromatic extracts

Due to market and legislative expectations, there is a constant need to explore new potential antimicrobial agents for functional perfumery. In this study, we evaluated the antimicrobial activity of 53 low molecular oximes and the corresponding carbonyl compounds against Escherichia coli, Enterococcus hirae, Pseudomonas aeruginosa, Bacillus cereus, Staphylococcus aureus, Aspergillus brasiliensis, Legionella pneumophila and Candida albicans. The most potent compound was α-isomethylionone oxime, which exhibited a minimum inhibitory concentration (MIC) of 18.75 µg/mL against E. hirae. The evaluation of the MICs for bacterial and fungal strains was performed for selected compounds, for example, the MIC of 2-phenylpropionaldehyde, cis-jasmone oxime, and trans-cinnamaldehyde measured against A. brasiliensis was 37.50 µg/mL. ADME-Tox (Absorption, Distribution, Metabolism, Excretion, and Toxicity) and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) cell viability assays were performed to assess the cytotoxicity of tested compounds. ADME-Tox indicated the safety and promising properties of selected compounds, which enables their usage as nontoxic supporting antibacterial agents. The results of the in vitro MTS assay were consistent with the ADME-Tox results. None of the compounds tested was toxic to Human Embryonic Kidney 293T (HEK293T) cells, with all cell viabilities exceeding 85%.

Comparison of the Aroma Composition and Sensory Properties of Dark Chocolates Made with Moist Incubated and Fermented Cocoa Beans.

In a previous investigation, "moist incubation" was described as a novel postharvest treatment for cocoa and the aroma composition of the resulting cocoa nibs was compared to unfermented and fermented cocoa nibs. For this treatment, unfermented and dried nibs are rehydrated with an aqueous solution containing lactic acid and ethanol to adjust the pH value and are subsequently incubated at 45 °C under aerobic conditions for 72 h before drying. The aim of the present study was to investigate the sensory properties and aroma composition of dark chocolates made of these materials after roasting. Therefore, gas chromatography-olfactometry (GC-O) in combination with aroma extract dilution analysis (AEDA), quantitation with isotopically labeled standards, odor activity value (OAV) determination, and sensory analysis were performed. The three different chocolates had distinct sensory and OAV profiles. The sensory profiles showed a higher intensity of fruity aroma notes and a lower intensity of bitterness and astringency in the chocolate made with the moist incubated cocoa, while the chocolate made of fermented cocoa reached higher scores in the roasty aroma notes. Furthermore, higher OAVs were determined for the Strecker aldehydes in the chocolate made of the moist incubated cocoa, whereas higher OAVs for the pyrazines and the acids were detected in the chocolate made of fermented cocoa. In contrast, the chocolate produced with the unfermented cocoa showed low cocoa specific aroma notes and high levels of astringency and bitterness. The detected differences reveal interesting insights into the influence of different postharvest treatments on the resulting aroma composition in the final chocolate. Furthermore, the alternative postharvest treatment was demonstrated to result in chocolates with a pleasant sensory profile.

Characterization of aroma active volatile components in roasted mullet roe

Mullet roe is a popular global delicacy that derives its unique roasted flavor from several odors, including savory, rich, salty, and fishy attributes. Despite the nutritional significance of mullet roe, studies on their volatile components are yet to be reported. Headspace-solid-phase microextraction coupled with gas chromatography–olfactometry and aroma extract dilution analysis was applied to determine the volatile components of roasted mullet roe. Analysis of roasting time and temperature revealed that both are important parameters on aroma generation. Volatiles, including acetic acid, methional, hexanoic acid, and benzeneacetaldehyde were identified as the most potent odorants of raw mullet roe, while 2-ethyl-5-methylpyrazine, 2-ethyl-3,5-dimethylpyrazine, 5-methyl-2-phenyl-2-hexenal, and sulfurol were the primary odorants in roasted mullet roe. Reaction models using the water extract and defatted residue had the most similar flavor profile to that of roasted mullet roe, with Maillard reaction as the key flavor generator in roasted mullet roe.

Molecular characterisation of an atypical coconut-like odour in cocoa

Parallel application of an aroma extract dilution analysis (AEDA) to the volatiles isolated from a sample of fermented cocoa with an atypically pronounced coconut note and to the volatiles isolated from a reference cocoa sample revealed coconut-like smelling compounds δ-octalactone, δ-2-octenolactone, γ-nonalactone, γ-decalactone, δ-decalactone, and δ-2-decenolactone as potential causative odorants. Quantitation of these six compounds and calculation of odour activity values as ratios of the concentrations to the odour threshold values suggested δ-2-decenolactone as the crucial compound. Chiral analysis showed the presence of pure (R)-δ-2-decenolactone, commonly referred to as massoia lactone. Its key role for the coconut note was finally demonstrated in a spiking experiment: the addition of (R)-δ-2-decenolactone to the reference cocoa in an amount corresponding to the concentration difference between the two samples was able to provoke a coconut note in an intensity comparable to the one in the atypically smelling cocoa. To avoid an undesired coconut note caused by (R)-δ-2-decenolactone in the final products, the chocolate industry may consider its odour threshold value, that is 100 µg/kg, as a potential limit for the acceptance of fermented cocoa in the incoming goods inspection.

The Influence of Pasture and Non-pasture-Based Feeding Systems on the Aroma of Raw Bovine Milk.

Aroma-active compounds in raw bovine milk produced from cows fed perennial ryegrass (GRS) or total mixed ration (TMR) consisting of grass silage, maize silage, and concentrates were identified by direct immersion sorptive extraction (DI Hi-Sorb), coupled with gas-chromatography-mass spectrometry and olfactometry using odour intensity (OI) and aroma extraction dilution analysis (AEDA). Ninety-nine volatile organic compounds (VOC) were identified in these raw GRS and TMR milk samples; 33 of which were also present in the feed and rumen samples from these diets. Only the abundance of 13 VOC varied significantly based on diet. However, the odours of both raw milks were quite distinct as aroma perception is not influenced by abundance alone but also by the odour activity of each VOC. Approximately, 30% of the VOC influenced the aroma perception of these raw milks. This study clearly highlighted the significant impact of VOC transferring from the diet that influenced the aroma perception of both raw GRS and TMR milk. The aroma of the raw TMR milk was more complex than that of the raw GRS milk, and many of the key dietary-derived-odour-active VOC likely arose during the production of the TMR feed as most were either derived from Maillard reactions or impacted by heat. Seventeen of the 44 odour activities detected differed between both sample types. This study has clearly demonstrated the impact of diet on the aroma perception of raw bovine milk.

Characterization of key aroma-active compounds in Hanyuan Zanthoxylum bungeanum by GC-O-MS and switchable GC × GC-O-MS

The present study sought to characterize the composition of volatile aroma compounds and key aroma-active compounds of dried Hanyuan Zanthoxylum bungeanum. The volatile aroma compounds were analyzed by the solid-phase microextraction (SPME) combined with gas chromatography–olfactometry-mass spectrometry (GC-O-MS) and two-dimensional comprehensive gas chromatography–olfactometry-mass spectrometry (GC × GC-O-MS). The key aroma-active compounds were analyzed by the aroma extract dilution analysis and odor activity value. A total of 72 volatile compounds were identified by GC-O-MS, of which 28 were aroma-active. Meanwhile, 116 volatile compounds were identified by GC × GC-O-MS, of which 43 were aroma-active. These results revealed that myrcene, (+)-limonene, (E)-β-ocimene, β-cubebene, Germacrene D, cineole, linalool, and linalyl acetate were the key aroma-active compounds of dried Hanyuan Zanthoxylum bungeanum.

Multi-objective evaluation of freshly distilled brandy: Characterisation and distribution patterns of key odour-active compounds.

The characterisation and distribution patterns of key odour-active compounds in head, heart1, heart2, tail, and stillage cuts of freshly distilled brandy were investigated by gas chromatography–olfactometry-mass spectrometry coupled with aroma extract dilution analysis (AEDA) and chemometrics analysis. Results from AEDA showed that there were 50, 61, 48, 25, and 18 odour-active compounds in the head, heart1, heart2, tail, and stillage cuts, respectively. Besides, 19, 22, 11, 5, and 4 quantified compounds with odour activity values ≥ 1, respectively, were considered to be potential contributors to the aroma profile of different distillation cuts. Especially, the chemometrics analysis illustrated the heart1 fraction was characterized by 3-methylbutanol, ethyl hexanoate, 1-hexanol, ethyl octanoate, benzaldehyde, ethyl decanoate, and 2-phenylethyl acetate; (E)-hex-3-en-1-ol, (Z)-hex-3-en-1-ol, and 2-phenylethyl acetate greatly contributed to the characteristics of the heart2 cut. Furthermore, different volatile compounds with a variety of boiling points and solubilities followed diverse distillation rules during the second distillation. Our findings may provide a rational basis for concentrating more pleasant aroma components contributing to brandy.

Compound specific stable isotope analysis of aromatics in diesel fuel to identify potential cocktailing

Estimates suggest billions of dollars are lost annually in the US due to fuel tax fraud. One method of fuel fraud is called “cocktailing” and involves blending products that are non-taxed, lower value, taxed at a lower rate, or unwanted/less-refined petroleum to diesel fuels. The goal of this study was to investigate compound specific isotope analysis (CSIA) using isotope ratio mass spectrometry (IRMS) for small aromatics contained in diesel fuel to determine whether this approach could be used to identify cocktailing and potentially fingerprint possible sources. However, the high chemical complexity of diesel fuels complicates CSIA owing to the need to fully separate individual compounds for effective isotope analysis. Therefore, different methods were investigated to selectively isolate aromatics for CSIA and evaluate these methods for isotopic fractionation. Analyses indicate that there is enough variability in isotopic ratios (δ2H and δ13C) between toluene samples obtained from different sources to use CSIA to differentiate/identify the origin of potential fuel adulterants. Three isolation methods were identified that provided sufficiently pure aromatic fractions for CSIA: selective solvent extraction, ionic liquid coated solid phase microextraction (SPME), and a combination of the two. However, due to the labor-intensive nature of selective solvent extraction, ionic liquid coated SPME represents the best method to quickly isolate aromatics from diesel fuel, without sacrificing selectivity or sensitivity. All methods tested can result in isotopic fractionation, but this can be compensated for by applying a correction factor. Furthermore, the chemical composition of a sample appeared to be important in the degree to which fractionation occurred during isolation. While the tested approaches for aromatic extraction from diesel showed promise, additional studies are required to refine and validate the methods prior to routine use in fuel cocktailing investigations.

Fast and simplified determination of PCA and aromatic carbon content of treated distilled aromatic extract (TDAE) by NMR.

Aromatic oils obtained during lubricant production (DAE) have high value as rubber extenders in tire manufacturing, but they have high carcinogenic potential due to the content of polycyclic aromatic compounds (PCAs). Legislation on PCA content requires additional treatment to reach treated oils (TDAE) with a PCA content lower than 3% according to the IP 346 method. IP 346 is a highly time-consuming and high uncertainty method, and several proposals have tried to replace it, but nowadays, there is no standard alternative. In this work, an extensive collection of samples covering a broad PCA content were obtained and characterized by physical properties, NMR, and aromatic and PCA content. Several correlations were tested to establish an optimum procedure to estimate the aromatic and the PCA content according to the requirement of high accuracy and low time and effort. The combination of several properties does not improve the accuracy of the correlation, and simpler equations were preferred. Integrated spectra appear as an acceptable characterization method as NMR percent of the total aromatic proton and polycyclic aromatic proton correlates satisfactory with the number of aromatic carbons and PCA content, respectively. The refractive index yields the best results for the correlation to PCA content. Obtained deviations compare favorably with methods previously described in the literature and with the uncertainty involved in the experimental method. They can be considered adequate methods to analyze such magnitudes routinely.

Multi-omics discovery of aroma-active compound formation by Pichia kluyveri during cider production

Pichia kluyveri is a promising non-Saccharomyces yeast that can be used in winemaking, but is not well characterized. In this study, aroma-active compounds were identified in cider fermented by P. kluyveri X31-10 using gas chromatography–olfactometry (GC-O) analyses combined with aroma extract dilution analyses (AEDA). Further, genomic and transcriptomic analyses were used to elucidate the potential molecular mechanisms of aroma formation. Aroma-active compounds identified in the cider included 3-methylbutyl acetate, β-damascenone, ethyl 2-methylbutanoate, and 2-phenethyl acetate. A 10.97 Mb complete genome sequence of P. kluyveri X31-10 was determined that contained an estimated 5130 predicted genes. RNA-seq showed numerous differentially expressed genes related to the formation of aroma compounds in P. kluyveri during cider fermentation. Integrative analysis of multi-omics (genomic, transcriptomic, and exometabolomic) data indicated the presence of multiple copies of several genes (e.g., ADH6, ADH7, LEU4) involved in the production of aroma-active compounds, with many uniquely present in the genome of P. kluyveri, but not that of Saccharomyces cerevisiae. The high expression levels of some of these genes could implicate their contributions to producing characteristic alcohol and ester aromas. These data provide new characterization insights into the aroma-active compounds of ciders and genes associated with their formation in non-Saccharomyces yeasts.