Composition Of Volatile Compounds Research Articles

Composition and reactivity of volatile organic compounds in the South Coast Air Basin and San Joaquin Valley of California

Abstract. Comprehensive aircraft measurements of volatile organic compounds (VOCs) covering the South Coast Air Basin (SoCAB) and San Joaquin Valley (SJV) of California were obtained in the summer of 2019. Combined with the CO, CH4, and NOx data, the total calculated gas-phase hydroxyl radical reactivity (cOHRTOTAL) was quantified to be 6.1 and 4.6 s−1 for the SoCAB and SJV, respectively. VOCs accounted for ∼ 60 %–70 % of the cOHRTOTAL in both basins. In particular, oxygenated VOCs (OVOCs) contributed >60 % of the cOHR of total VOCs (cOHRVOC) and the total observed VOC mixing ratio. Primary biogenic VOCs (BVOCs) represented a minor fraction (<2 %) of the total VOC mixing ratio but accounted for 21 % and 6 % of the cOHRVOC in the SoCAB and SJV, respectively. Furthermore, the contribution of BVOCs to the cOHRVOC increased with increasing cOHRVOC in the SoCAB, suggesting that BVOCs were important ozone precursors during high ozone episodes. Spatially, the trace gases were heterogeneously distributed in the SoCAB, with their mixing ratios and cOHR being significantly greater over the inland regions than the coast, while their levels were more evenly distributed in SJV. The results highlight that a better grasp of the emission rates and sources of OVOCs and BVOCs is essential for a predictive understanding of the ozone abundance and distribution in California.

Chemical and volatile composition of Pálinka produced using different commercial yeast strains of Saccharomyces cerevisiae

Pálinka is Hungarian traditional alcoholic drink, and its quality is strongly depending on applied yeast strain. Unfortunately, all commercial yeast strains used the production of pálinka are selected for oenological purpose, and thus the efficacy and aroma releasing capacity are vary depending on the type and quality of fruit used. In this study, the fermentation efficacy of nine commercial yeast strains of Saccharomyces cerevisiae was focused. All strains were able to do alcoholic fermentation of apple juice quite efficiently, and the simple sugars (fructose, glucose and sucrose) were almost exhausted at the end of fermentation. Meanwhile, the alcohol production capacity and yield were no significant differences (around 9.17 v/v %–9.43 v/v %), whereas the ability of sugar consumption of strains Uvaferm Danstil A and Fermicru AR2 was stronger than others. The differences in the concentration and composition of volatile compounds were recorded. The highest levels of total volatile compounds were observed in samples fermented with Uvaferm Danstil A, Fermiblanc Arom, Vin-O-Ferm Roses, and Fermicru AR2. Meanwhile total volatile compounds, 2-methyl-1-propanol, 3-methyl-1-butanol, total higher alcohols, ethyl acetate, and total esters were considered as key parameters for describing the profile of fermented apple juices, whereas total fusel alcohols, 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, and total volatile compounds were characteristic indicators of samples fermented with Uvaferm Danstil A. This work provides very good information of commercial yeast strains for industrial pálinka production.

An in-depth multiphasic analysis of the chocolate production chain, from bean to bar, demonstrates the superiority of Saccharomyces cerevisiae over Hanseniaspora opuntiae as functional starter culture during cocoa fermentation

Hanseniaspora opuntiae is a commonly found yeast species in naturally fermenting cocoa pulp-bean mass, which needed in-depth investigation. The present study aimed at examining effects of the cocoa isolate H. opuntiae IMDO 040108 as part of three different starter culture mixtures compared with spontaneous fermentation, regarding microbial community, substrate consumption, and metabolite production dynamics, including volatile organic compound (VOC) and phytochemical compositions, as well as compositions of the cocoa beans after fermentation, cocoa liquors, and chocolates. The inoculated H. opuntiae strain was unable to prevail over background yeasts present in the fermenting cocoa pulp-bean mass. It led to under-fermented cocoa beans after four days of fermentation, which was however reflected in higher levels of polyphenols. Cocoa fermentation processes inoculated with a Saccharomyces cerevisiae strain enhanced flavour production during the fermentation and drying steps, which was reflected in richer and more reproducible aroma profiles of the cocoa liquors and chocolates. Sensory analysis of the cocoa liquors and chocolates further demonstrated that S. cerevisiae led to more acidic notes compared to spontaneous fermentation, as a result of an advanced fermentation degree. Finally, different VOC profiles were found in the cocoa beans throughout the whole chocolate production chain, depending on the fermentation process.

Malting procedure and its impact on the composition of volatiles and antioxidative potential of naked and covered oat varieties

Grains from four naked oat varieties (Amant, Maczo, Polar and Siwek) and one covered oat variety (Kozak) grown with three different nitrogen fertilization regimes were malted in a laboratory setting using specifications typical for barley malt production (45% moisture content, temperature of germination equal to 15 °C, germination time equal to 120 h). The goal was to determine, whether malting process could be used to improve pro-health properties and aroma of the covered oat and naked oat grain. Malting increased concentration of phenolic compounds (from 44.92 to 64.39 mg GAE per 100 g of grain to 158.06–393.69 mg GAE per 100 g of malt) and increased the antioxidative potential of grains (analysed by ABTS, DPPH and FRAP assays) by 200–300%. Malting also had an effect on the changes in composition of volatile compounds: the HS-SPME-GC-MS detected 23 compounds in grain samples and 34 compounds were detected in malt samples. The total concentration of volatiles in malts was significantly higher (1659.70–39708.33 ng per 100 g) than in grain samples (882.45–2098.74 ng per 100 g). Malting mostly increased concentration of aldehydes, such as nonanal, decanal and undecanal and pyrazines, such as trimethyl- and tetramethylpyrazine in the acquired malts.

Possibilities of Using Medicinal Plant Extracts and Salt-Containing Raw Materials from the Aral Region for Cosmetic Purposes.

The aim of this work was to study the possibility of using medicinal plants in combination with salt-containing raw materials from the Aral Sea region for cosmetic purposes. The chemical and mineralogical compositions of salts occurring in this region were studied for pharmacological and cosmetic purposes. The salt-containing raw materials were studied by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The microflora of saline-containing raw materials and flora of the Zhaksy-Klych lake were studied. Fifty-six plant species were identified, of which 25% belong to the Asteraceae family, 32% were Poaceae, 22% were Amaranthaceae, and 21% were Tamaricaceae. Using the solid-phase microextraction (SPME) method and comprehensive two-dimensional gas chromatography–mass spectrometry, the composition of volatile compounds in such plant species as Artemisia alba L., Achilleamillifolium L., Eleagus commutate Bernh. Ex Rydb., Psoraleadrupacea Bunge, Artemisia cipa O. Vegd., Thymus vulgaris L., Morus alba L., Salvia pratensis L., Glycyrhizaglabra L., Tanacetum vulgare L., Polygonumaviculare L., Alhagipseudoalhagi Gagnebin and Peganumharmala L., chosen on the basis of their herbal components for future cosmetic products, was determined. In total, 187 different volatile compounds were found in the endemic plant species Glycyrrhizaglabra L., of which the following were dominant: 1,7-octadiene-3-, 2,6-dimethyl- with a peak area of 4.71%; caryophyllenes; bicyclo[7.2.0]4,11,11-trimethyl-8-methylene-, [1R-(1R*,4E,9S*)]—3.70%; bicyclo[2.2.1] heptane-2-1,7,7-trimethyl-,(1S)—3.46%; cyclohexanone, 5-methyl-2-(1-methylethyledene)-; 2-isopropyledene-5—2.97%; menthol; cyclohexanol, 5-methyl-2-(1-methylethyl)-; p-menthane-3-ol; menthol alcohol; and 2-isopropyl-5—2.08%. The remaining compounds were detected in amounts of less than 2.0%. Tests of seven cosmetic compositions developed on the basis of plant extracts and salt-containing raw materials revealed that three samples had a moisturizing effect. Launching the production of cosmetic products in the Aral region will not only reduce social tensions but also significantly improve the environmental situation in the region.

Climate-driven changes to taste and aroma determining metabolites in an economically valuable portunid (Portunus armatus) have implications for future harvesting

The effects of climate change on the distribution and biology of fisheries species have received substantial attention, but quantitative assessments of changes to taste and aroma determining compounds remain limited—despite sensory quality being a key driver of demand for most harvested species. Utilising the economically important blue swimmer crab (Portunus armatus), we tested the effects of temperature and salinity treatments aligned with near-future climate change projections on volatile and non-volatile sensory compounds that determine seafood flavour. Volatile compounds were analysed using solid phase microextraction and gas chromatography-mass spectrometry and non-volatiles were identified using liquid chromatography (mass spectrometry analysis). Multivariate analyses revealed that temperature, but not salinity, significantly affected the compositions of both volatile and non-volatile compounds in crab meat following a 30-day exposure period. Univariate analyses highlighted significant reductions in amino acids and amines associated with bitter and sweet organoleptic properties following exposure to elevated temperature. These results imply the potential for climate change to alter taste and aroma determining compounds in seafood, which could affect future harvesting priorities. Assessments of seafood sensory quality under climate change can produce valuable information to help predict shifts in fishing effort for harvested species that form the basis of important global fisheries.

Classification of Japanese Pepper (Zanthoxylum piperitum DC.) from Different Growing Regions Based on Analysis of Volatile Compounds and Sensory Evaluation.

The Japanese pepper (Zanthoxylum piperitum DC.) is an attractive plant that is highly palatable and benefits human health. There are several lineages of pepper plants in Japan. However, the classification of each lineage by analyzing its volatile compounds and studies on the effects of differences in volatile compounds on human flavor perception have not been performed in detail. Herein, we conducted gas chromatography (GC) and GC/mass spectrometry (GC/MS) analysis of volatile compounds and sensory evaluation of flavor by an analytical panel using 10 commercially available dry powdered Japanese pepper products from different regions. GC and GC/MS analysis detected limonene, β-phellandrene, citronellal, and geranyl acetate as the major volatile compounds of Japanese peppers. The composition of volatile compounds showed different characteristics depending on the growing regions, and cluster analysis of composition classified the products into five groups. The sensory evaluation classified the products into four groups, and the results of both classifications were in good agreement. Our results provide an important basis for proposing cooking and utilization methods that take advantage of the unique characteristics of each lineage based on scientific evidence.

Enhanced Water Resistance and Catalytic Performance of Ru/TiO2 by Regulating Brønsted Acid and Oxygen Vacancy for the Oxidative Removal of 1,2-Dichloroethane and Toluene.

The compositions of volatile organic compounds (VOCs) under actual industrial conditions are often complex; especially, the interaction of intermediate products easily leads to more toxic emissions that are harmful to the atmospheric environment and human health. Herein, we report a comparative investigation on 1,2-dichloroethane (1,2-DCE) and (1,2-DCE + toluene) oxidation over the Ru/TiO2, phosphotungstic acid (HPW)-modified Ru/TiO2, and oxygen vacancy-rich Ru/TiOx catalysts. The doping of HPW successfully introduced the 1,2-DCE adsorption sites to promote its oxidation and exhibited outstanding water resistance. For the mixed VOCs, Ru/HPW-TiO2 promoted the preferential and superfluous adsorption of toluene and resulted in the inhibition of 1,2-DCE degradation. Therefore, HPW modification is a successful strategy in catalytic 1,2-DCE oxidation, but Brønsted acid sites tend to adsorb toluene in the mixed VOC oxidation. The Ru/TiOx catalyst exhibited excellent activity and stability in the oxidation of mixed VOCs and could inhibit the generation of byproducts and Cl2 compared with the Ru/HPW-TiO2 catalyst. Compared with the Brønsted acid modification, the oxygen vacancy-rich catalysts are significantly suitable for the oxidation of multicomponent VOCs.

Composition, seasonal variation and sources attribution of volatile organic compounds in urban air in southwestern China

The composition, seasonal variation and sources attribution of volatile organic compounds (VOCs) were investigated in a plateau city in China. Air samples were collected simultaneously by canister at three sites and covered four seasons. 113 VOCs species were determined by GC–MS–FID. Higher concentration of α-pinene (0.98 ± 2.25 ppb) in urban central site was observed in this study than in most others reported. Results of the ratios of α-pinene/isoprene, source profile of VOCs and backward trajectory of air mass identified that both biogenic emission and wooden furniture manufacturers were contributors to the significant high concentration of α-pinene. And high concentration of α-pinene (>2 ppb) accompanied by significant high concentration of isopentane, for air mass passing through the dense area of both wooden furniture factories and gas stations. In addition, the highest concentrations of alkanes, anthropogenic alkenes, alkynes, aromatics and halohydrocarbons appeared in winter, caused by the lowest temperature and mixed layer height in winter. For biogenic alkenes, the highest concentration was found in spring or summer as plants flourishing. Finally, results of the ratios of species and PMF model showed that local vehicle, fuel evaporation and household were the dominant VOCs source with contribution to 42.7%–53.5% of the total VOCs concentration.

Validating the Use of Amputated Limbs Used as Cadaver Detection Dog Training Aids

Cadaver detection dogs (CDDs) are trained to locate human remains and/or objects associated with human remains. This is possible due to their extraordinary olfactory capabilities compared to those of humans. To reinforce this capability, CDDs must be trained and regularly exposed to the target odor in the form of training aids which include—chemical formulations, animal remains, and/or human remains. Currently, the Ontario Provincial Police (OPP) use amputated limbs/feet from consented surgeries performed on diabetic patients as cadaver detection dog training aids. There is limited knowledge about the volatile organic compound (VOC) composition of these training aids and their appropriateness as an alternative to human remains for CDD training purposes, which formed the aim of the current study. VOCs were collected from amputated lower limbs/feet repeatedly using thermal desorption (TD) tubes and analyzed with comprehensive two-dimensional gas chromatography—time-of-flight mass spectrometry (GC×GC-TOFMS). The response of cadaver detection dogs to these training aids was also recorded to understand their alert in the context of the detected VOCs. VOC classes including acids, alcohols, aldehydes, ketones, ester and analogues, ethers, aliphatic, cyclics, sulfur-containing, nitrogen-containing, and halogen-containing VOCs were identified. Of these classes, cyclic VOCs were most abundant followed by nitrogen-containing VOCs while ethers were the least abundant. The most prominent VOCs identified in amputated limbs/feet were decomposition related however, one VOC—sevoflurane, originated from anaesthesia during the surgeries. It was determined that the VOC profile of aged and relatively recent training aids were variable. The aged training aids sampled over time had less variability (compared to more recent training aids). Additionally, the VOC profiles of samples was not found variable owing to the storage conditions—room temperature, refrigerator or freezer. Overall, a 98.4% detection rate was observed for amputated limbs/feet used as CDD training aids and the presence of non-decomposition related VOCs such as sevoflurane did not appear to impact the CDDs’ detection capability. This study highlights that the presence of decomposition VOCs in amputated limbs/feet and their high detection rate by CDDs validates their use as alternative CDD training aids.

Articles of Significant Interest in This Issue

Baiome et al. (e00155-22) investigated the composition and antifungal properties of volatile organic compounds (VOCs) produced by the worm symbiont Xenorhabdus indica strain AB. Methyl anthranilate in the VOC mix was particularly effective against fungal phytopathogens. The secretion of these antifungal compounds allows the bacteria to kill fungal competitors and can be harnessed in biocontrol applications.

ЛЕТУЧИЕ СОЕДИНЕНИЯ СВЕЖЕГО PTERIDIUM AQUILINUM (L.) KUHN, ПРОИЗРАСТАЮЩЕГО В КРАСНОЯРСКОМ КРАЕ

The results of a comparative analysis of the individual composition of volatile compounds of vegetative parts of fresh bracken growing in different regions of the Krasnoyarsk Territory are presented for the first time. The collection of samples was carried out in May 2021, using an unopened plant with a size of 30 cm. Using chromatography-mass spectrometric analysis, 43 volatile components were identified, of which 30 were identified. It was revealed that in the composition of volatile components, the largest number of 12 compounds belong to the class of aldehydes, slightly less than 11 substances are represented by alcohols, the remaining 7 components belong to different classes of compounds. It was found that the predominant components in the composition of the bracken in terms of content are benzaldehyde, which accumulates up to 44% and hexanal - up to 23% of the total amount of substances. It was determined that the vayi plants differ in a large number of volatile compounds and their content, compared with the stems. Among the studied samples, in terms of the content of volatile components 98% in the wars and 94% in the stems, the fern collected in the southern part of the western Sayans (Shushenskoye settlement) prevails. Phenanthrene was identified in volatile components in samples No. 1 and No. 2 in an amount from 0.2% to 0.9%. The technique used did not allow the identification of ptaquiloside in fresh bracken.

Effect of Six Different Feedstocks on Biochar’s Properties and Expected Stability

Biochar (BC) is often proposed as a tool for climate change mitigation, due to the expected long lifetime in the environment. However, BC’s stability can vary depending on feedstock type and the presence of labile carbon fractions. In this study, we verify the recent methods with new possible tools for biochar stability assessment on six different biochars derived from commonly available Europe biomass sources. Elemental composition (CHNO), dissolved organic carbon (DOC) and water-soluble carbonates content (WSC), volatile organic compounds (VOCs) composition, and mid-infrared spectra (MIR) were performed to estimate the persistence of biochars. Under similar conditions of pyrolysis, biochar properties can vary depending on a feedstock origin. Less aromatic structure and higher contents of labile carbon fractions (DOCs and WSC) in food waste biochars affected the lower stability, while biochars derived from high lignocellulose materials (straw, wood, and grass) were strongly carbonized, with persistent, aromatic structure. Labile carbon pool content (DOC, WSC) and spectral analysis can be useful tools for biochar stability assessment, giving similar information to the standard molar ratio method. Biochars obtained from agriculture and forestry management biomass should be considered as highly stable in soil and are appropriate for long-term carbon sequestration purposes.

Switchable GC/GC × GC–olfactometry–mass spectrometry system for the analysis of aroma components of infant formula milk-based on cow and goat milk

The study sought to characterize the composition of volatile compounds and key aroma-active compounds of infant formulas (IF), which derived from cow's milk and goat's milk. The volatile aroma compounds were analyzed by the solid-phase microextraction (SPME) combined with a new switchable GC/GC × GC–olfactometry–mass spectrometry (SGC/GC2-O-MS) system, which can switch between one-dimensional and two-dimensional analysis modes and can realize the sniffing function under two-dimensional analysis conditions. The key aroma-active compounds were analyzed by the aroma extract dilution analysis (AEDA) and odor activity value (OAV). A total of 118 volatile compounds were identified in IF samples from 12 brands, of which 66 had aroma activity. These results revealed that hexanal had the highest FD factor but was not responsible for the difference between GS and CS. According to the results of OPLS-DA and VIP, it was helpful to screen for more important volatile compounds. (E)− 2-octenal, (E,E)− 3,5-octadien-2-one, (E,E)− 2,4-decadienal, 3-methylbutanal and 2-pentylfuran helped distinguish GS from CS.

VOLATILE ORGANIC COMPOUNDS FROM GREEN WASTE ANAEROBIC DEGRADATION AT LAB-SCALE: EVOLUTION AND COMPARISON WITH LANDFILL GAS

The chemical composition of volatile organic compounds (VOCs) in landfill gas from municipal waste (MW) landfills primarily depends on the type of degrading waste. To provide first insights into the relationship between VOC chemistry (in landfill gas) and specific waste components, a lab-scale experiment on anaerobic digestion (AD) of green waste (GW) was carried out. The composition of the released C4+ VOCs was semi-quantitatively determined and indirectly compared to that generally expected for the overall MW landfill gas. The generated biogas from degrading GW during AD time showed up to 29 different VOCs, mainly including terpenes, followed by alkanes, alkenes, cyclics, aromatics, and halogenated compounds. O- and S-substituted compounds were sporadically detected. Overall, speciation and total concentration of VOCs fluctuated over AD time, likely due to changes in microbial populations and metabolism, as well as substrate depletion, during the AD evolution. As expected, VOC speciation in the GW biogas was lower than that of the typical MW landfill gas, since the latter is generated by a large variety of organic and synthetic waste components following different sequential degradation processes. These results highlighted that, when disposed of at MW landfill sites, the specific GW component may (i) potentially concur to the overall odour charge and toxic effects of MW landfill gas and (ii) detrimentally impact the energy exploitation of MW landfill gas by releasing terpenes, aromatics, and halogenated compounds.

Composition and correlation of volatile organic compounds and odor emissions from typical indoor building materials based on headspace analysis

Volatile organic compounds (VOCs) released from indoor building materials are one of the main causes of deterioration in indoor air quality and along with odor emissions, directly affect the physical and mental health of humans. In this study, we used headspace analysis to measure VOCs and odor emissions from 19 types of building materials, including floors, furniture boards, wall coverings, and adhesives. An untrained panel was used to assess the acceptability and intensity of building materials' odor. The total VOC (TVOC) of “dry” (e.g. floors, furniture boards, and wall cloths) and “wet” (e.g. wall paints and adhesives) materials ranged from 278.3 to 869.6 μg/m3 and 219.0–3060.0 μg/m3, with median TVOC values of 501.8 μg/m3 and 252.9 μg/m3, respectively. The sum of its odor activity value (OAVsum) ranged from 0.6 to 51.7 and 0.5–17.0, with a median OAVsum of 5.1 and 7.0, respectively. Hexanal was the dominant odor-active VOC in most building materials. Median odor intensity of “dry” and “wet” materials was 3.25 and 3.08, respectively. Substantial differences were presented for TVOC but not for odor intensity. Odor could still be perceived in air mixtures with low TVOC concentration and OAVsum < 1. A combination of multiple linear regression and principal component analysis was used to establish a model for the prediction of odor intensity based on OAV (R2 = 0.746). The model shows that the OAV of aldehydes, esters, alkanes, aromatics, and phenols can predict the overall odor intensity, and phenols contribute the most to the odor.

Study on the potential contribution of bacterial community on the volatile flavour of Yongfeng chilli paste

SummaryThe study aimed to explore the contribution of the microbial community on flavour formation by measuring physicochemical properties, volatile compounds composition and bacterial community of Yongfeng chilli paste. A similar amino acid nitrogen level and different pH, total acid and salt content were observed in five brands of Yongfeng chilli paste. A total of 106 volatile compounds were identified, wherein, ethyl palmitate, ethyl trans‐4‐decenoate, phenylethyl alcohol were the common volatile compounds with high content in all samples. Additionally, Oxyphotobacteria‐unclassified, Mitochondria‐unclassified, Pediococcus, Bacillus, Lactobacillus and Weissella were the dominant genera. Lactobacillus was related to the production of some alcohols and terpenes. Whereas, Bacillus, Pediococcus and Weissella, which showed higher salt tolerance, could affect the formation of esters, such as ethyl salicylate, ethyl lactate. Thus, this study provided a basis for further research on the mechanism of flavour formation and some guidance for the improvements of the quality of traditional fermented chilli paste.

Characterization of the Berry Quality Traits and Metabolites of ‘Beimei’ Interspecific Hybrid Wine Grapes during Berry Development and Winemaking

The development of grape varieties with cold resistance can be an advantage for the wine industry. ‘Beimei’, an interspecific hybrid wine grape variety with cold resistance and pleasant rose aroma, is now extensively cultivated in China. In the present study, the berry quality traits and metabolites of ‘Beimei’ and other “Bei” varieties were characterized. The sugar (234 g/L–391 g/L) and acid (6.2–8.3 g/L) contents of ‘Beimei’ and four additional “Bei” varieties, i.e., ‘Beihong’, ‘Beixi’, ‘Beixin’, and ‘Xinbeichun’ berries were smilar to that of traditional Vitis vinifera varieties. ‘Beimei’ grapes has the highest volatile compounds composition, especially the content of rose aroma compounds (2-phenyl-ethyl alcohol and neryl alcohol), which was significantly higher than that of the other “Bei” wine grape varieties. After fermentation, ‘Beimei’ wines showed improved quality, with a high resveratrol content (18 mg/L) compared to traditional Eurasian wines. In addition, the high content of main rose aroma compounds (acetic acid 2-phenylethyl acetate, phenylethyl alcohol, neryl alcohol and beta-damascenone) contribute to a pleasant rose aroma in ‘Beimei’ wines. In summary, these results indicate that ‘Beimei’ grapes could be used as a winemaking grape variety considering global climate changes.

Synthesis of Bio Hydrocarbon from Palm Olein through Pyrolysis at Various Temperature

The synthesis of biofuels through the pyrolysis of vegetable oil is studied as an alternative to the biodiesel process because it produces bio hydrocarbons that have similar properties to fossil fuels. This study uses palm olein as raw material reacted at gradually increasing temperatures ranging from 225, 250, 275, and 300°C, using zeolite as catalyst at atmosferic pressure. The volatiles compounds are condensed and collected according to the fraction and analyzed for density, viscosity, calorific value, moisture content and composition of volatile compounds using GC-MS. Palm olein as raw material had the characteristics of moisture content of 0.095% (w/w), viscosity of 41.25 mm2/s, calorific value of 39.93 MJ/kg and pour point of 20°C. The hydrocarbon fractions of various temperatures had a red to bright yellow color, liquid phase and only the 300°C fraction which had a solid fraction. The density was in the range of 0.8452 - 0.8527 g/cm3(40°C), viscosity of 3.0726 - 3.8137 mm2/s, moisture content of 0.0801 - 0.1878% (w/w) and pour point of 4 - 22 ° C. Density, viscosity and pour point from a temperature fraction of 225 – 275°C met national biodiesel standards. The composition of volatile compounds mainly consisted of n-decanoic acid, undecanoic acid, dodecanoic acid, 8-heptadecene, heptadecane, tetradecanoic acid, 2-heptadecanone, and n-hexadecanoic acid. The main volatile compounds were still in the form of fatty acids where n-hexadecanoic acid was the dominant compound (42.8 - 71.6%). In general, the characteristics and profiles of the volatile compounds of 225, 250 and 275°C fractions were similar and different from the 300°C fraction.

Olfactory discrimination of fat content in milks is facilitated by differences in volatile compound composition rather than odor intensity

The mechanisms underlying the ability of humans to olfactorily discriminate fat content in milks remain unknown. In this study, we found that fat contents (0.5, 1.5 and 3.5% fat) can be discriminated by olfaction in commercially available pasteurized milks (p < 0.05) but not in ultra-high temperature processed (UHT) milks. The composition of volatile compounds of pasteurized milks differed with fat content, whereas that of UHT milks differing in fat content was similar. Principal component analysis revealed that differences in volatile compound composition of pasteurized milks differing in fat content contribute to olfactory discrimination. In UHT milks, acetoin and 2-heptanone may mask odor differences leading to indistinguishable odors. No differences were observed regarding perceived odor intensity of pasteurized milks or UHT milks differing in fat content. We conclude that the olfactory discrimination of fat content in pasteurized milks is facilitated by differences in volatile compound composition rather than odor intensity.