Hexyl Acetate Research Articles

Volatile and sensory composition of Brazilian Muscat sparkling wine and Asti

The aim of this study is to evaluate Muscat sparkling wines from the traditional Asti region (Italy) and the new geographical indication “IG Farroupilha” (Brazil). We analyzed 23 commercial Muscat sparkling wines from Asti and Farroupilha. Sample characterization of the aromatic profile by headspace-solid phase microextraction and gas chromatography detector yielded a total of 32 targeted components in Muscat wines. The multivariate analysis of data differentiates the Muscat sparkling wines based on origin: Brazilian or Italian. The main quantitative differences between wines are residual sugar, sulfite content, isoamyl acetate, hexyl acetate, limonene, rose oxide, linalool, and citronellol. The sensory analysis confirmed that Brazilian wines were less sweet with freshener aroma, whereas the Italian wines were more intense in aroma, complex, and sweet. These peculiarities can be associated with terroir, including technological processes that may be tailored to fit different wine styles for particular markets. Practical applications The chemical and sensorial characterizations of sparkling wines produced in regions with geographical indication are important to differentiate products made in different regions.

Evaluation of Physiological Characteristics, Soluble Sugars, Organic Acids and Volatile Compounds in 'Orin' Apples (Malus domestica) at Different Ripening Stages.

‘Orin’ is a popular apple cultivar, which has a yellow-green appearance, pleasant taste, and unique aroma. However, few studies on the fruit quality characteristics of ‘Orin’ apples have been reported before. In this study, changes of the physiological characteristics were measured at different ripening stages, and the soluble sugars and organic acids were determined by high-performance liquid chromatography (HPLC). Volatile compounds were identified using the headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). During the fruit ripening, the ‘Orin’ apple fruit weight, size, and total soluble solid were gradually increased by contrast with the titratable acidity, and the firmness decreased. The content of four soluble sugars reached the maximum at the 180 days after full bloom (DAFB) stage. Malic acid was measured as the most abundant organic acid in ‘Orin’ apples. Ethyl butyrate, hexyl propanoate, hexyl acetate and butyl acetate belonging to esters with high odor activity values (OAVs) could be responsible for the typical aroma of ‘Orin’ apples. The aim of this work was to provide information on the flavor characteristics of ‘Orin’ apples and promote this apple cultivar for marketing and processing in the future.

Semiochemical-Based Attractant for the Ambrosia Pinhole Borer Euplatypus parallelus

A semiochemical-based attractant for Euplatypus parallelus was identified and field-tested. Analyses of headspace volatile extracts of conspecific males revealed the presence of 1-hexanol along with lesser amounts of 3-methyl-1-butanol, hexyl acetate, 1-octanol and trans-geraniol, which were not found in equivalent extracts from females. Emission of 1-hexanol coincided with the emergence of adults of both sexes during afternoon hours. A synthetic blend of these compounds, with and without ethanol, was tested in the field. The blend alone attracted a small number of females and no males. Ethanol alone attracted a small number of females (not significantly different from the blend alone) but significantly more males than the blend alone. More females were caught with the blend combined with ethanol than the combined catch of either attractant alone, suggesting a synergistic interaction. Attraction of males appeared to be a response to ethanol alone. During the trials, two potential natural enemies of E. parallelus were caught, indicating that they might be eavesdropping on the semiochemical channels of their prey. Traps containing the male-specific volatile compounds combined with ethanol could be applied as an effective attractant for detection and monitoring of E. parallelus as well as for recruitment of its natural enemies.

Dissolution kinetics of main-chain-scission-type resist in organic developers

Main-chain-scission-type resists have been widely used for the fabrication of nanodevices. A copolymer consisting of methyl α-chloroacrylate and α-methylstyrene, known as the ZEP series of ZEON, is a popular main-chain-scission-type positive-tone resist. In this study, the dissolution kinetics were investigated using the ZEP series to clarify the effects of the molecular weight distribution and developer on the dissolution kinetics of the main-chain-scission-type resist. The thickness of the transiently swelling layer in hexyl acetate development was less than that in pentyl acetate development. The thickness of the transiently swelling layer depended on the molecular weight distribution of resist polymers.

Volatile compounds in Chinese steamed bread influenced by fermentation time, yeast level and steaming time

The aim of this work is to investigate how volatile compounds of Chinese steamed bread (CSB) are influenced by yeast level (0.5, 1 and 1.5%, flour weight basis), fermentation time (20, 40 and 60 min) and steaming time (5, 10, 20 and 30 min). The volatile compounds were extracted by headspace-solid phase microextraction and analyzed by gas chromatography-mass spectrometry. Higher yeast level and longer fermentation time promoted the formation of yeast-metabolism-derived compounds, including 2-methyl-1-propanol, 3-methyl-1-butanol, phenethyl acetate, hexyl acetate and 2-octanone. Increased fermentation time decelerated the generation of lipid oxidation compounds (octanal, nonanal, decanal, (E)-2-nonenal, and (E,E)-2,4-decadienal). Prolonged steaming time facilitated the production of benzaldehyde and 2-pentylfuran and promoted the loss of alcohols and esters. Network analysis showed that 2-pentylfuran contributed to wheat-like aroma of CSB while 3-methyl-1-butanol was related with alcoholic odor. This study was helpful for improving the understanding of CSB aroma evolution profile and may contribute to the aroma improvement of commercial CSB.

Comparison of Aroma Compounds and Some Pomological Characteristics of Local Apple Genotype Called ‘Gelin’ and ‘Mondial Gala’ Cultivated in Canakkale

Volatiles directly affect the sensorial quality of fresh fruits and therefore consumer preferences. The types and concentrations of volatile compounds show great variability in different apple types and varieties. In this experiment some pomological characteristics and aroma potential of local apple genotype called ‘Gelin’ or ‘Yazlik Elma’ and commercial standard apple cultivar ‘Mondial Gala’ were evaluated. Fruit length and diameter (mm), fruit weight (g), soluble solid content (% Brix), pH, titratable acidity (malic acid ml 100 ml-1), skin and flesh color (L, hue, chroma) were investigated within scope of pomological characteristics. The identification of volatile constituents was performed by Gas Chromatography/Mass Spectrometer (GC/MS) instrument by liquid–liquid extraction using diethyl ether solvent. The amount of the aroma volatile determined with a gas chromatograph-mass spectrometer (Shimadzu® QP2010 GC/MS) fitted with a DB-WAX column (30 m x 0.25 mm ID, 0.25 μm film thickness; J & W, USA). According to the obtained results, 23 volatile constituents including 9 aldehydes (45.56%), 7 esters (46.78%), 6 alcohols (6.85%), and 1 other compound (0.81%), were detected in ‘Gelin’ genotype; 20 volatile constituents including 6 esters (56.08%), 7 aldehydes (34.76%), 6 alcohols (8.13%) and 1 other compound (1.03%), were detected in ‘Mondial Gala’ cultivar. Aldehydes and esters are main volatiles to fruity and floral aroma especially for apples. Especially, E-2-Hexenal and acetaldehyde for aldehydes and butyl acetate and hexyl acetate for esters are the main volatile compounds detected for the fruits studied. The high contents of these compounds that give pleasant flavor and aroma in fruits play very important part in the preference of fruits by consumers. In addition, the ‘Gelin’ genotype population can represent a novel source of breeding materials for improvement of aroma characteristics of standard cultivars.

Functional Analysis of Odorant-Binding Proteins 12 and 17 from Wheat Blossom Midge Sitodiplosis mosellana Géhin (Diptera: Cecidomyiidae)

Simple SummarySitodiplosis mosellana is one of the most destructive pests of wheat. Adults rely highly on wheat spike volatiles to search and locate oviposition sites. Insect odorant-binding proteins (OBPs) are important in binding and transporting host plant volatiles to the olfactory receptors. Therefore, OBP-based behavioral interference is believed to be a novel and effective pest management strategy. The objectives of this study were to clone two S. mosellana female antenna-enriched OBP genes (SmosOBP12 and SmosOBP17), determine the functions of the encoded SmosOBP proteins in binding wheat volatiles, and investigate behavioral responses of female S. mosellana to odorant molecules. Results indicated that SmosOBP12 had a broader ligand-binding spectrum than SmosOBP17 to wheat volatiles. Female S. mosellana showed intensive response to 3-hexanol, 1-octen-3-ol, D-panthenol, 3-carene, (Z)-3-hexenylacetate, hexyl acetate, methyl salicylate, heptyl acetate, ethyl heptanoate, α-farnesene, and ocimene. Notably, all these compounds except α-farnesene exhibited strong affinity to SmosOBP12. In conclusion, SmosOBP12 may play more crucial roles than SmosOBP17 in perception and transportation of biologically active host volatiles. This information has enhanced our molecular understanding of the S. mosellana olfaction, which could also serve as an important reference for developing attractants or repellents to control this pest.The wheat blossom midge Sitodiplosis mosellana, one of the most disastrous wheat pests, depends highly on olfactory cues to track suitable plants. To better understand the olfactory recognition mechanisms involved in host selection, in the present study we cloned two S. mosellana adult antenna-specific odorant binding protein (OBP) genes, SmosOBP12 and SmosOBP17, and evaluated bacterially expressed recombinant proteins for their selectivity and sensitivity for host wheat volatiles using the fluorescence-based ligand binding assay. The results showed that both SmosOBPs effectively bound alcohol, ester, ketone, and terpenoid compounds. Particularly, SmosOBP12 had significantly higher affinities (Ki < 10.5 μM) than SmosOBP17 (Ki2 > 0.1 μM) to 3-hexanol, 1-octen-3-ol, D-panthenol, 3-carene, (Z)-3-hexenylacetate, hexyl acetate, methyl salicylate, heptyl acetate, and ethyl heptanoate. Consistently, S. mosellana females were attracted to all these chemicals in a behavioral assay using Y-tube olfactometer. SmosOBP12 also bound aldehyde, but neither bound alkanes. Notably, SmosOBP12 exhibited strong affinity to ocimene (Ki = 8.2 μM) that repelled S. mosellana. SmosOBP17, however, was insensitive to this compound. Taken together, our results indicate that SmosOBP12 may play a greater role than SmosOBP17 in perceiving these biologically active plant volatiles.

Free and Bound Volatile Aroma Compounds of ´Maraština´ Grapes as Influenced by Dehydration Techniques

Dehydration or drying of grapes is one of the most important steps in the production of Croatian traditional dessert wine Prošek. The natural sun drying of grapes is the traditionally used method in Prošek production. Alternative methods, such as dehydration under controlled conditions, have been studied as safer and faster methods than the traditional sun drying but without precise knowledge of the effect on volatile compounds. The objective of this work was to study how dehydration of grapes carried out in a greenhouse and an environmentally controlled chamber impacts on the free and glycosidically bound volatile compounds of native grape cv. ‘Maraština’. The 36 volatile compounds were identified and quantified using headspace solid-phase micro extraction coupled with gas chromatography-mass spectrophotometry (HS-SPME-GC/MS). The results showed that the aroma profile of dehydrated grapes was significantly different from that of fresh grapes. Regarding free forms, significant increases in the concentration of 2-methyl-1-propanol, 1-butanol, 2-hexen-1-ol, 1-hexanol, ethyl hexanoate, hexyl acetate, o-cymene, linalool oxide, and terpinen-4-ol and geraniol were found in greenhouse-dried grapes, whereas increases in cis-limonene-epoxide, trans-limonene epoxide, and γ-hexalactone were higher in chamber-dried grapes compared to greenhouse-dried grapes. Glycosidically bound forms of o-cymene, linalool oxide, linalool, and terpinen-4-ol were increased in both types of drying, whereas β-damascenone was increased only in greenhouse-dried grapes.

Aromatypicity of Austrian Pinot Blanc Wines

Pinot blanc is a grape variety found in all wine-growing regions of Austria. However, there are only few scientific studies which deal with the aroma of wines of this variety. In the course of this project, the relationship between aroma profile and the typicity of Austrian Pinot blanc wines was studied. The aim was to describe the typicity and to find significant differences in aroma profiles and aroma descriptors of typical and atypical Pinot blanc wines. Since the typicity of a jointly anchored prototype is embedded in the memory, typical attributes for Austrian Pinot blanc wines were first identified by consumers and experts or producers. According to this, 131 flawless commercial Austrian wines of the variety Pinot blanc of the vintages 2015 to 2017 were analysed for more than 100 volatile substances. The wines of the vintages 2015 to 2017 were judged by a panel of producers and experts for their typicity; furthermore, the wines of the vintage 2017 were also evaluated by a consumer panel and a trained descriptive panel. Subsequently, typical and atypical wines were described by the trained descriptive panel. It was found that Pinot blanc wines typical of Austria showed significantly higher concentrations of the ester compounds ethyl hexanoate, ethyl butanoate, ethyl octanoate, ethyl decanoate, methyl hexanoate, hexyl acetate and isoamyl acetate, while atypical wines had higher concentrations of free monoterpenes such as linalool, trans-linalool oxide, nerol oxide, nerol and alpha-terpineol. The sensory description of typical Pinot blanc wines was significantly more pronounced for the attribute “yellow pome fruit”, and tended to be more pronounced for the attributes “green pome fruit”, “pear”, “walnut”, “pineapple”, “banana” and “vanilla”, while the atypical Pinot blanc wines were described more by the attribute “citrus”. These findings could help to ensure that, through targeted measures, Austrian Pinot blanc wines become even more typical and distinguish themselves from other origins such as Germany or South Tyrol through a clear concept of typicity.

Polyphenols, Antioxidant Activity and Volatile Compounds in Fermented Leaves of Medicinal Plant Rosebay Willowherb (Chamerion angustifolium (L.) Holub).

At present, the consumption of medical plants and functional foods is growing in the whole world. Rosebay willowherb (Chamerion angustifolium (L.) Holub) is an important medicinal plant that has various pharmacological effects (antioxidant, anti-inflammatory, anticancer, and others), can improve the state of health and well-being, and reduce the risk of various diseases. The aim of this work was to investigate volatile compounds, polyphenols, and antioxidant activity in rosebay willowherb leaves fermented for 24 and 48 h in solid state fermentation under aerobic and anaerobic conditions. High-performance liquid chromatography (HPLC) for polyphenols and the spectrophotometric method for antioxidant activity determinations were used. To recognize and identify the leaves’ fragrances, electronic nose (Alpha M.O.S) measurement technology was used. The results showed that the highest amounts of total polyphenols in dried matter were after 48 h aerobic solid state fermentation (SSF). Antioxidant activity was higher under 48 h SSF compared to the control. The most abundant flavoring compound groups were esters, terpenes, and aldehydes. In unfermented leaves, (z)-3-hexen-1-ol, acetate, hexyl acetate, and trans-hex-2-enyl acetate prevailed, characterized by fragrances of greenery, flowers, and fruits. The undesired esters group compounds, ethyl butyrate and butyl acetate, with pungent odor, were detected after 48 h anaerobic SSF.

Preliminary study of the effect of cation-exchange resin treatment on the aging of tempranillo red wines

This research reports the effect of the cation exchange treatment in Tempranillo wines during the aging period in oak barrels. The control wine and the mixtures with different percentages (5, 10 and 20%) of wine treated by a cation exchange resin (permeate wine) were evaluated. In general, a greater acidity, color and tartaric stability, and a lower mineral content were observed in the treated wines, especially in those with 20% of permeate wine. In addition, during the entire aging time, the decrease in potassium and magnesium cations stood out. A higher concentration of aromatic compounds such as hexyl acetate, isobutanol, 2-phenylethyl alcohol, ethyl isovalerate and diethyl succinate was observed in treated wines after six months of aging. The two last compounds reached the highest concentrations when the percentage of permeated increased and reached values up to 23 μg/L for ethyl isovalerate and up to 3186 μg/L for diethyl succinate. In addition, the perception thresholds of these esters were exceeded in all wines. The use of cation exchange resins seems to be an effective industrial alternative to produce balanced red aged wines in a climate change scenario.

Sensory Quality Evaluation of Korla Pear from Different Orchards and Analysis of Their Primary and Volatile Metabolites.

Metabolites play vital roles in shaping the quality of fresh fruit. In this study, Korla pear fruit harvested from twelve orchards in South Xinjiang, China, were ranked in sensory quality by fuzzy logic sensory evaluation for two consecutive seasons. Then, gas chromatography-mass spectrometry (GC-MS) was applied to determine the primary metabolites and volatile compounds. Sensory evaluation results showed that the panelists were more concerned about ‘mouth feel’ and ‘aroma’ than about ‘fruit size’, ‘fruit shape’ and ‘peel color’. In total, 20 primary metabolites and 100 volatiles were detected in the pear fruit. Hexanal, (E)-2-hexenal, nonanal, d-limonene, (Z)-3-hexen-1-yl acetate and hexyl acetate were identified as the major volatile compounds. Correlation analysis revealed that l-(+)-tartaric acid, hexanoic acid, trans-limonene oxide and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate were negatively correlated with sensory scores. Furthermore, OPLS-DA results indicated that the fruit from three orchards with lower ranks in quality could be distinguished from other samples based on the contents of l-(+)-tartaric acid and other eight metabolites, which were all associated with ‘mouth feel’ and ‘aroma’. This study reveals the metabolites that might be closely associated with the sensory quality attributes of Korla pear, which may provide some clues for promoting the fruit quality in actual production.

Olfactory and behavioral responses to acetate esters in red imported fire ant, Solenopsis invicta.

The red imported fire ant, Solenopsis invicta Buren, is one of the most successful invasive ants in the world. Previous studies indicated that benzyl acetate and prenyl acetate elicited significant electroantennography (EAG) response in S. invicta and exhibited as attractants at certain concentrations. In addition, the easy commercial availability, low cost, and low mammalian toxicity make acetate esters ideal candidates to screen for potential use in S. invicta control. We examined the EAG and behavioral responses to 26 acetate esters in all castes of S. invicta. Our results demonstrated a large diversity of EAG tuning and behavioral responses to acetate esters in S. invicta. For linear alkyl acetate esters, EAG response was clearly affected by the carbon chain length of the alkyl group. Linear alkyl acetates with five to seven carbon chain length of the alkyl group elicited significant EAG response in S. invicta, whereas those with shorter (C1 to C4) or longer (C8 to C12) carbon chain lengths did not. Different substitutions also exhibited large variety of EAG and behavioral responses in S. invicta. Our works explored the olfactory and behavioral response of S. invicta to structurally different acetate esters, and identified two potential fire ant attractants, pentyl acetate and tran-2-hexenyl acetate, and two potential repellents, hexyl acetate and cis-3-hexenyl acetate. These compounds may be useful in developing new products for fire ant management. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Characterization of odour‐active compounds of sour guava (Psidium acidum[DC.]Landrum) fruit by gas chromatography‐olfactometry and odour activity value

AbstractVolatile compounds in sour guava (Psidium acidum [DC.] Landrum) were isolated by headspace‐solid‐phase microextraction (HS‐SPME) and solvent‐assisted flavour evaporation (SAFE). Analyses were performed by GC‐FID and GC‐MS. By GC‐O, the HS‐SPME extract was evaluated by frequency analysis, whereas the SAFE extract was assessed by aroma extract dilution analysis (AEDA) and odour activity value (OAV) to find the most odour‐active components. Twenty‐four volatiles were found as odour‐active compounds and contribute to the typical sour guava aroma, from which hexyl acetate, 3‐methylbutyl butanoate, (Z)‐3‐hexenyl acetate, (Z)‐3‐hexenyl hexanoate, nonanal and (E)‐β‐ionone presented the highest aroma contribution in sour guava fruit. Results demonstrated a good resemblance between the typical aroma of the fruit and the aroma model.

Effects of a Small Increase in Carbon Dioxide Pressure during Fermentation on Wine Aroma.

The present study tested the effect of a slight increase in pressure (from 0 to 1 bar) during the fermentation on the wine aroma profile. Fermentations were carried out with a commercial dry yeast on Sangiovese juice in the absence of berry skins. The wine samples fermented under slight overpressure conditions were found to be significantly different from the control samples produced at atmospheric pressure in relation to several chemical compounds. Concentrations of many esters (i.e., isoamyl acetate, ethyl acetate, ethyl hexanoate, hexyl acetate, ethyl dodecanoate, and ethyl tetradecanoate), and acids (i.e., hexanoic acid, octanoic acid, and decanoic acid) increased, while concentrations of two acids (i.e., isobutyric and isovaleric acid) decreased. These differences, notably the higher concentration of esters, are usually associated with a more intense fruity attribute. Triangular sensory tests revealed that the significant chemical differences were also perceivable; hence, introducing a slight pressure increase during the alcoholic fermentation could be a useful tool in managing the aroma profile of wine.

Peach volatile emission and attractiveness of different host plant volatiles blends to Cydia molesta in adjacent peach and pear orchards

The oriental fruit moth (OFM), Cydia (= Grapholitha) molesta, is a highly damaging pest; peaches are its primary host, and pears serve as post-peach secondary hosts during the late season in China. We collected volatiles from detached peach shoots and fruits, and identified them with gas chromatography–mass spectrometry (GC–MS). Antennally active compounds were identified by gas chromatography-electroantennogram detection (GC-EAD), and these were further tested in the laboratory and field. We detected consistent electroantennographic activity was for ten compounds. Significantly more C. molesta females were caught with a mixture of female EAD-active compounds identified from the detached matured peach fruits (nonanal, butyl acetate, 3-methylbutyl acetate, hexyl acetate, (Z)-3-hexenyl acetate, linalool and farnesene) than other mixtures mimicking the volatile profile from detached matured fruits or shoots. We identified a new GC-EAD active mixture from intact peach shoots composed of nonanal, (Z)-3-hexenyl acetate, (E)-β-ocimene, and 6-methyl-5-hepten-2-one. In the field test, the background odour of orchards could affect trap catches, and two peach-derived blends together with two previously known pear-derived blends were proven to be able to monitor the seasonal OFM population dispersal in adjacent orchards. These host plant blends will be effective for further designing candidate attractants for season-long C. molesta population dynamic monitoring.

Antagonistic fungal endophytes and their metabolite-mediated interactions against phytopathogens in rice

Endophytes regulate physiological activities of host plants by conferring resistance against abiotic stress, insect, nematode, and diseases. Besides, they produce novel natural bioactive compounds with potential applications in agriculture, medicine, and food industry. In the present study, seven antagonistic fungal endophytes showing anti-fungal and anti-bacterial activities were isolated from rice leaves and identified as Paecilomyces tenuis EF1, Talaromyces pinophilus EF2, Nigrospora sphaerica EF3, Nigrospora oryzae EF4, Trichoderma longibrachiatum EF5, and EF7 and Aspergillus terreus EF6. Of these, T. longibrachiatum EF5 had the highest growth inhibition activity against the tested fungal (23%–82%) and bacterial plant pathogens (13%–46%). Soluble metabolites such as aliphatic organic acids, (e.g., lactic, acetic, hydroxyl-methyl valeric acids, ethyl hexyl acetate, salbutamol sulfate, dodecanone, octadecanoic, octaheptanoic and butanenoic acids), aromatic nitroamino compounds (Benzyl glycinate), and volatile metabolites, (e.g., 2,3- butanediol dinitrate, pentadecane, tetramethyl hexahydro napthalenone, 1-iodo-2-methylundecane) were detected through FT-IR and GC-MS–TD, respectively. The metabolite induced antagonistic activity of EF5 was much pronounced against phytopathogens such as Magnaporthe grisea, Rhizoctonia solani, and Macrophomina phaseolina. Also, the volatile organic compounds (VOCs) of T. longibrachiatum EF5 enhanced the lateral root formation by modulating auxin biosynthesis.

Insights into profiling of volatile ester and LOX-pathway related gene families accompanying post-harvest ripening of ‘Nanguo’ pears

‘Nanguo’ pear is particularly renowned for its fragrance. Esters are the main components of its aroma, which are synthesized primarily by the LOX pathway. We identified the main volatile esters and critical gene family members involved in the LOX pathway by monitoring their variation accompanying post-harvest ripening and examining their roles through principal component analysis (PCA), partial least-square regression (PLSR), and correlation analysis. In pears ripening to the optimum taste period (OTP), components and contents of volatile esters reached a peak, of which ethyl butanoate, ethyl hexanoate, and hexyl acetate were most prominent. Linoleic acid and linolenic acid contents rose greatly until OTP and then declined; the activities of LOX, alcohol dehydrogenase (ADH), and alcohol acyltransferase (AAT) increased progressively until the OTP. Among the genes involved in LOX-pathway, the expressions of PuLOX3, PuADH3, and PuAAT contributed most to changes of total ester and main esters in ‘Nanguo’ pears.

Experimental study of the effect of C8 oxygenates on sooting processes in high pressure spray flames

Oxygenated compounds have the ability to reduce soot emissions and to improve the combustion efficiency in engines. Most studies have focused on the soot reduction potential of shorter carbon chain oxygenates, whilst longer carbon chain oxygenates are still relatively unexplored. In this work, the soot reduction potential of long carbon chain oxygenates having similar thermo-physical and chemical properties to those of diesel have been studied, viz., 2-octanone (ketone), 1-octanol (alcohol), hexyl acetate (ester) and octanal (aldehyde). These oxygenates were injected at high pressure into a constant volume chamber maintained at high ambient temperature conditions, and their spray flames were investigated using a high-speed, two-colour pyrometry system. It was found that for the same injected fuel mass, the oxygenates reduced the overall soot when compared to diesel. Small differences in sooting tendencies were observed between different oxygenated moieties but these were smaller than those relative to diesel. The absence of aromatic groups and the presence of oxygen directly bonded to carbon atoms seemed to have a larger effect on soot reduction than the oxygenated functional group. The oxygenates altered the local oxygen equivalence ratio in the spray, influencing the soot formation and its distribution in the flame. Under the high pressure conditions studied, the average sooting tendency of the long carbon-chain oxygenates studied increased in the order of: ester< aldehyde ~ alcohol<ketone.

Relationship of ripening parameters of “Alexander Lucas” pears according to orchard location, maturity stage and storage conditions

The aim of the present study was to evaluate the effect of maturity stages at harvest (MS) on the inhibitory effects of 1-methylcyclopropene (1-MCP) and the ultralow oxygen (ULO) on the ripening and synthesis of aroma volatiles of “Alexander Lucas” pears, and if this effect remains in different orchards. Results show that 1-MCP inhibited ripening and aroma production in pears harvested early (MS1) from all orchards. The most suppressed character-impact compounds were ethyl (2E.4Z)-deca-2.4-dienoate, hexyl acetate, and pentyl acetate. Generally, significantly less of these compounds were found in MS1 pears from orchard 2 and more of these compounds were found in pears harvest delay (MS2) from orchard 3. Fruits MS2 treated with 1-MCP enabled the development of melting flesh and resulted in increased accumulation of esters to levels similar to fruits stored under CS. ULO storage also decreased the production of aromatic compounds but less strongly than 1-MCP. Practical applications There are few studies about the ripening and storage conditions of “Alexander Lucas” pear. The results of this investigation show that the orchard location is important and should be considered when choosing the storage condition. Furthermore, the reported results are important for establishing the proper storage conditions of “Alexander Lucas” pears in terms of achieving suitable quality during shelf life.