Butyl Hexanoate Research Articles

Electroantennographic and behavioral responses of Bactorcera dorsalis (Diptera: Tephritidae) adults to the volatiles of plum fruits.

Fruit volatiles play a crucial role in the host localization by the oriental fruit fly, Bactrocera dorsalis Hendel (Diptera: Tephritidae). This study focused on identifying the fruit volatiles from Sanyue plum and Sanhua plum (Prunus salicina Lindl.), which are 2 varieties of the same species, and examined their impact on the behavior of B. dorsalis by using a Y-olfactometer. A total of 35 and 54 volatiles from Sanyue plum and Sanhua plum were identified, respectively. Among these, 23 volatiles elicited electroantennographic (EAG) responses by B. dorsalis adults, showing concentration-dependent effects in males and females. Ethyl butyrate, butyl acetate, butyl hexanoate, ethyl caproate, ethyl hexanoate, and hexyl acetate significantly attracted B. dorsalis compared to liquid paraffin, while nonaldehyde was avoided. There was no significant difference in the behavioral responses of both sexes to sorbitol esters, hexyl isobutyrate, and 1-tetradecene compared with the control liquid paraffin group. Interestingly, (3Z)-C-3-hexenyl acetate significantly attracted females, but not males. The above findings suggest that plum fruit volatiles are likely to facilitate the localization of host fruit by B. dorsalis adults and may even aid in mate-finding. This study opens up new avenues for exploring novel plant-based attractants that might be of value for the integrated management of B. dorsalis.

Elucidation of the sweetening mechanism of sweet orange fruit aroma compounds on sucrose solution using sensory evaluation, electronic tongue, molecular docking, and molecular dynamics simulation

Sweetness enhancement through aroma has been suggested as a strategy to mitigate sugar addition in foods, but such enhancement depends on the type of aroma. Ethyl propanoate, ethyl 2-methylbutanoate, octyl acetate, ethyl butanoate, ethyl hexanoate, butyl hexanoate, γ-terpinene, nootkatone, and acetophenone with fruity aroma from sweet orange were selected as the objects to investigate the sweetening effect of aroma compounds in a 5% sucrose solution using an artificial sensory tongue and an electronic tongue. The results showed that nine aroma compounds exerted a significant effect on the sweetness, among which ethyl butanoate, ethyl propanoate, and ethyl 2-methylbutanoate imparted a more comfortable effect. Subsequently, the mechanism of their sweetening action was studied by molecular simulation. Molecular docking results indicated that the binding free energy decreased below −5.9 kcal/mol in the presence of aroma compounds, indicating that sucrose was more tightly docked to the sweet taste receptor. Molecular dynamics (MD) further implied that under the influence of ethyl butanoate, the stable time of binding was advanced by 15 ns, and the amino acids forming hydrogen bonds changed from LYS65, ASP278, GLU302, SER165, and SER303 to SER165, ASP142, LYS65, and GLU302. The interaction depends on hydrogen bonds, water bridges, and hydrophobic forces.

The response pattern of the microbial community structure and metabolic profile of jiupei to Bacillus subtilis JP1 addition during baijiu fermentation.

Baijiu brewing is a complex and multifaceted multimicrobial co-fermentation process, in which various microorganisms interact to form an interdependent micro-ecosystem, subsequently influencing metabolic activities and compound production. Among these microorganisms, Bacillus, an important bacterial genus in the liquor brewing process, remains unclear in its role in shaping the brewing microbial community and its functional metabolism. A baijiu fermentation system was constructed using B. subtilis JP1 isolated from native jiupei (grain mixture) combined with daqu (a saccharifying agent) and huangshui (a fermentation byproduct). Based on high-throughput amplicon sequencing analysis, it was evident that B. subtilis JP1 significantly influences bacterial microbial diversity and fungal community structure in baijiu fermentation. Of these, Aspergillus and Monascus emerge as the most markedly altered microbial genera in the jiupei community. Based on co-occurrence networks and bidirectional orthogonal partial least squares discriminant analysis models, it was demonstrated that the addition of B. subtilis JP1 intensified microbial interactions in jiupei fermentation, consequently enhancing the production of volatile flavor compounds such as heptanoic acid, butyl hexanoate and 3-methylthiopropanol in jiupei. B. subtilis JP1 significantly alters the microbial community structure of jiupei, enhancing aroma formation during fermentation. These findings will contribute to a broader application in solid-state fermentation. © 2024 Society of Chemical Industry.

Profiles of Volatiles Emitted from Orange Fruits Infested by Ceratitis capitata (Diptera: Tephritidae).

The profiles of volatile organic compounds (VOCs) emitted from orange fruits infested by Ceratitis capitata were examined. VOCs were collected from the headspace of oranges immediately, 24 h, 5 days, 8 days, and 13 days after oviposition and when larvae exit the fruit by applying either static or dynamic sampling techniques. A total of 32 and 47 compounds were detected in infested orange fruits when using static and dynamic techniques, respectively. Differences in the volatile profile of oranges were observed. Classification models were employed, showing that infested fruits emitted a chemical profile distinct from that of non-infested ones. Limonene was associated with cell disruption. (E)-β-Ocimene, (E)-4,8-dimethyl-1,3,7-nonatriene, hexyl butanoate, butyl hexanoate, and hexyl hexanoate were the VOCs that were correlated with the infestation of sweet oranges by C. capitata.

Identification on regional-markers based on the flavor molecular matrix analysis of sauce-aroma style Baijiu.

Baijiu is a very complex system and its flavor substances are endogenous influenced by raw materials, starter, production process, production region and other factors. The production region directly affects the composition of flavor substances and quality of Baijiu. However, identification of Baijiu region is challenging because the corresponding relationship between the production region and Baijiu quality is not clear, and the identification of regional-markers is indeterminate. In this study, the difference on volatile components of sauce-aroma style Baijiu from four representative regions were investigated. Consequently, a total of 94 volatile compounds were identified in samples tested. Additionally, it was verified that 35 potential flavor substances had important contributions to the aroma of sauce-aroma style Baijiu. Meanwhile, 9 potential regional-markers were screened through multivariate analysis. Further, based on distribution of volatile compounds and the results of sensory evaluation combined with multivariate analysis, molecular matrix and correlation network were established according to the result of addition experiments, which showed that 6 substances had a significant impact on the flavor of the tested samples. In this study, 6 key flavor substances (including ethyl octanoate, ethyl 2-methyl propanoate, propyl acetate, ethyl heptanoate, 2-nonanone and butyl hexanoate) were considered as important regional-markers to effectively identify the production region of sauce-aroma style Baijiu. This article is protected by copyright. All rights reserved.

Changes in the VOC of Fruits at Different Refrigeration Stages of 'Ruixue' and the Participation of Carboxylesterase MdCXE20 in the Catabolism of Volatile Esters.

Aroma is a crucial quality attribute of apple fruit, which significantly impacts its commercial value and consumer choice. Despite its importance the volatile aroma substances produced by the new variety 'Ruixue' after harvest remain unclear. In this study, we utilized headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) to investigate the changes in volatile substances, fruit hardness, crispness, and related aroma synthase activity of commercially mature 'Ruixue' apples during cold storage. Our findings revealed a gradual decline in fruit firmness and brittleness of 'Ruixue' apples during cold storage, with hexyl acetate, hexyl caproate, and hexyl thiocyanate being the main hexyl esters detected. To gain a better understanding of the metabolic pathway of esters, we identified 42 MdCXE gene members that are associated with ester degradation. Through RT-qPCR analysis, we discovered that carboxylesterase MdCXE20 exhibited higher expression levels compared to other MdCXE genes during cold storage. To confirm the role of MdCXE20, we conducted a transient injection of apple fruits and observed that overexpression of MdCXE20 led to the degradation of esters such as hexyl hexanoate, butyl hexanoate, butyl 2-methylbutyrate, hexyl butyrate, and hexyl 2-methylbutyrate. The results of the study showed that the virus-induced gene silencing of MdCXE20 found the opposite results. Additionally, the esters of OE-MdCXE20 callus showed a lower content of ester VOC than the control callus, according to the homologous stable transformation of 'Wanglin' callus. Overall, these findings suggest that the MdCXE20 gene plays a crucial role in the decrease of esters in 'Ruixue' apples, which ultimately affects their flavor.

Alcohol acyl transferase genes at a high-flavor intensity locus contribute to ester biosynthesis in kiwifruit.

Volatile esters are key compounds contributing to flavor intensity in commonly consumed fruits including apple (Malus domestica), strawberry (Fragaria spp.), and banana (Musa sapientum). In kiwifruit (Actinidia spp.), ethyl butanoate and other esters have been proposed to contribute fruity, sweet notes to commercial cultivars. Here, we investigated the genetic basis for ester production in Actinidia in an A. chinensis mapping population (AcMPO). A major quantitative trait loci for the production of multiple esters was identified at the high-flavor intensity (HiFI) locus on chromosome 20. This locus co-located with eight tandemly arrayed alcohol acyl transferase genes in the Red5 genome that were expressed in a ripening-specific fashion that corresponded with ester production. Biochemical characterization suggested two genes at the HiFI locus, alcohol acyl transferase 16-b/c (AT16-MPb/c), probably contributed most to the production of ethyl butanoate. A third gene, AT16-MPa, probably contributed more to hexyl butanoate and butyl hexanoate production, two esters that segregated in AcMPO. Sensory analysis of AcMPO indicated that fruit from segregating lines with high ester concentrations were more commonly described as being "fruity" as opposed to "beany". The downregulation of AT16-MPa-c by RNAi reduced ester production in ripe "Hort16A" fruit by >90%. Gas chromatography-olfactometry indicated the loss of the major "fruity" notes contributed by ethyl butanoate. A comparison of unimproved Actinidia germplasm with those of commercial cultivars indicated that the selection of fruit with high concentrations of alkyl esters (but not green note aldehydes) was probably an important selection trait in kiwifruit cultivation. Understanding ester production at the HiFI locus is a critical step toward maintaining and improving flavor intensity in kiwifruit.

The potential of Strychnos madagascariensis (Poir.) as a source of vegetable oil

A study was undertaken to quantify screw press-extractable oil in the seed coat of Strychnos madagascariensis (Poir.) fruits harvested from trees in the northern coastal plain of KwaZulu-Natal province of South Africa and to determine the physiochemical properties and fatty acid composition of the oil. The seed coat constituted 19.36% of the dry fruit biomass and contained w/w 42% oil. Thus, the oil yield of the dried fruit was approx. 8.13%. Monounsaturated oleic acid accounted for between ca.70–73% of the total fatty acids in the Strychnos oil. Palmitic acid was present in amounts ranging between 15.05 and 16.27%. Also present, but in smaller amounts were cis linoleic acid (5.76–6.03%), stearic acid (1.64–4.65%), n3 linolenic acid (1.26–1.90%), and palmitoleic acid (1.10–1.65%). The oil contained trace amounts of arachidic acid (0.45–0.54%) and eicosenoic acid (approx.0.325%). Vitamin E was present in appreciable amounts, mostly in the form of α-tocopherol (approx. 5.8–14.4 mg/100 g oil) and β-tocotrienol (approx. 8.1–15.6 mg/100 g oil) homologues. The downside was that the oil had high acid values (161–181.32 mg KOH/g) and free fatty acid content (66–81 g oleic acid/100 g oil). There were 141 volatile compounds detected in the Strychnos oil, the most dominant of which were butyl-butyrate (20%), butyl hexanoate (8.2%) and glycerol (6.1–6.7%). Overall, the results indicate that Strychnos madagascariensis has potential as a source of vegetable oil.

Characterization of a traditional ripened cheese, Kurdish Kope: Lipolysis, lactate metabolism, the release profile of volatile compounds, and correlations with sensory characteristics

Kope cheese has been characterized based on gross chemical composition, free fatty acids (FFAs), organic acids (OAs), volatile compounds (VCs), and sensory attributes (SAs) during 187 days of the ripening period. C16:0, C18:1cisΔ9, and C14:0 were the most abundant FFAs. Lactic and acetic acids were the most prevalent OAs affecting sensory properties. principal component analysis (PCA) indicated that butanoic acid, butyl hexanoate, and 2,3-butanediol were as key VCs. Protein contents, pH (based on FFA and OA), salt in the moisture (S/M), andwater activity (aw )(based on VC and SA) were highly correlated with PC2, resulted in two distinct groups. Based on lipolysis and glycolysis studies, early-ripened cheese samples showed lipolysis and lactate metabolism more intensely compared to medium and old-ripened ones. Based on the data of VC and SA, the samples may be classified into three groups: (1) early-ripened cheeses with a salty taste, waxy to cheesy odor, and rubbery texture, (2) medium-ripened cheese with a sweet taste and cheesy odor, and (3) old-ripened cheese with a bitter taste, cheesy to pungent odor, a firm and fragile texture. Textural attributes were highly correlated with proteolysis indices and pH. The results of sensory desirability indicated a significant correlation with pungency, bitterness, and OAs. The cheese samples ripened on the day 127 were selected as the most desirable product. Ripening time had a significant effect on the chemical composition, especially on S/M, pH, andaw parameters, which determine the pattern as well as the intensity of biochemical pathways and the final sensory attributes. PRACTICAL APPLICATION: The current study intends to characterize and develop a standardized procedure for producing a traditional cheese called "Kope cheese" by determining the appropriate duration time for the ripening process, determining the main chemical/biochemical compounds that are highly correlated with its unique flavor and texture and distinguishing the key processing factors (such as curd salting, pH values during brining) that have to be altered or controlled carefully during the manufacturing process. The data would help cheese manufacturers determine the optimum time of ripening in order to achieve the best flavor and texture attributes in the final product.

Development of multi‐component non‐sex pheromone blends to monitor both sexes of Cydia pomonella (Lepidoptera: Tortricidae)

AbstractNineteen host plant volatiles (HPVs) were screened for attractivity to adult codling moth Cydia pomonella (L.) as a fourth component of core blends (3K) including (E,Z)‐2,4‐ethyl decadienoate, (E)‐4,8‐dimethyl‐1,3,7‐nonatriene and acetic acid. Each new quaternary combination was compared with a previously reported attractive bisexual lure (4K), consisting of the 3K blend plus 6‐ethenyl‐2,2,6‐trimethyloxan‐3‐ol (pyranoid linalool oxide, pyrLOX). All lure evaluations were conducted in apple, Malus domestica (Borkhausen). Several compounds were found to significantly lower total and/or female catches when added to the 3K blend, including (Z)‐3‐hexenol, (E)‐2‐hexanal and hexyl butanoate (female and total moths), and (Z)‐3‐hexenyl acetate and linalool (female moths). Other compounds when added to the 3K blend did not increase or decrease moth catches, including methyl salicylate, (E)‐β‐ocimene, limonene, β‐caryophyllene, butyl hexanoate, farnesol, terpineol, terpinen‐4‐ol and α‐pinene. A few added compounds significantly increased moth catches compared with the 3K blend, including β‐pinene (male moths), (Z)‐jasmone (male and total moths), (E)‐β‐farnesene and β‐myrcene (female and total moths), and (E,E)‐α‐farnesene (male, female, and total moths). In addition, each of these five compounds when added to the 3K core blend performed similarly to the 4K lure (male, females, and total moths). Further studies should expand these results through tests of these and other new blends with a range of component ratios and total loading amounts. Field trials should also be replicated within all host crops of codling moth and across major geographical production regions.

Reactive extraction for synthesizing long chain ester butyl hexanoate intensified by deep eutectic solvent

Butyl hexanoate (BuHE) is an important long-chain ester that is widely used in the food, beverage and cosmetic industries. In this work, reactive extraction concept was proposed to intensify the BuHE formation in a biphasic system, in which deep eutectic solvent (DES) comprising 2-methylimidazole (2-MIm) and p-toluenesulfonic acid (PTSA) was used as dual solvent-catalyst. First, the effect of 2-MIm to PTSA molar ratio on esterification was investigated to determine the optimum DES of [2-MIm:2PTSA], which was characterized by FT-IR and TGA. Then, the liquid–liquid equilibrium (LLE) and esterification experiments were carried out to confirm the extraction and catalytic effect of [2-MIm:2PTSA], respectively. Afterwards, the pseudo-homogeneous kinetic model was employed to describe the esterification kinetics. Finally, the intensification mechanism of reactive extraction for BuHE formation was proposed according to the experiments and interaction effect analysis.

Identification of Volatiles From Plants Infested With Honeydew-Producing Insects, and Attraction of House Flies (Diptera: Muscidae) to These Volatiles.

House flies (Musca domestica L.) are mechanical vectors of food-borne pathogens including Salmonella spp., Escherichia coli O157:H7, and Shigella spp., resulting in increased risk of diarrheal disease in areas where flies are abundant. Movement of house flies into food crops may be increased by the presence of honeydew-producing insects feeding on these crops. Using gas chromatography-electroantennogram detection (GC-EAD) and gas chromatography-mass spectrometry (GC-MS), volatile odors that elicited house fly antennal response were identified from naval orange (Osbeck) (Sapindales: Rutaceae) and Marsh grapefruit (Macfad.) (Sapindales: Rutaceae) leaves infested with whitefly (Hemiptera: Aleyrodidae) and from whole faba (L.) (Fabales: Fabaceae) bean plants infested with aphids (Hemiptera: Aphididae). Volatiles identified included benzaldehyde, butyl hexanoate, β-caryophyllene, Δ3-carene, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), (Z)-3-hexenyl acetate, myrcene, limonene, linalool, and naphthalene. This was followed by semifield bioassays of volatile blends and individual volatiles to determine house fly attraction to these volatiles. Although fly capture rates in the semifield setting were low, benzaldehyde and (Z)-3-hexenyl acetate were consistently attractive to house flies as individual compounds and as components of volatile blends.

Spatial distribution of flavor components and antioxidants in the flesh of ‘Conference’ pears and its relationship with postharvest pathogens susceptibility

The spatial distribution of dry matter, ethylene production, respiration rate, organic acids, sugars, antioxidants, volatiles and fungal (Penicillium expansum and Rhizopus stolonifer) growth was evaluated analyzing four different slices of ‘Conference’ pear flesh taken along an equatorial radius. A common spatial distribution trend was found for ethylene emission, CO2 production, antioxidant capacity and total phenolic compounds with a minimum in the slice under the skin and a maximum in the slice near the core. Fructose, which was the dominant sugar followed by sucrose and glucose, showed a quasi-linear decreasing profile from the outer slice towards the core. Malic and ascorbic acid had the highest content in the outer slice while citric remained practically constant over the different slices. Twenty-nine volatile organic compounds (VOCs) were identified using solid-phase microextraction (SPME), yet only six of them showed significant differences between flesh slices. The content in VOCs was further related to the tissue susceptibility to the above-mentioned postharvest pathogens using a multivariate approach. Fruit flesh from inner sections was more prone to P. expansum whereas flesh from the slice under the skin presented the highest incidence of R. stolonifer. A Partial Least Square (PLS) model showed that P. expansum growth was negatively correlated with malic acid, dry matter content, 2-ethyl-hexanal and butyl hexanoate concentrations and R. stolonifer was negatively correlated to sucrose and some volatiles such as hexanal and 1-butanol. Based on the results from the PLS, selected volatiles naturally present in the pear flesh were tested in vitro, at different concentrations, in order to investigate their effectiveness to control blue mold caused by P. expansum and soft rot caused by R. stolonifer. A completely control of P. expansum was found with 2-ethyl-hexanal application and hexanal while 1-butanol showed a total fungicide effect against R. stolonifer. This study is a step towards a better understanding of how biochemical compounds are spatially distributed among different slices of ‘Conference’ pears as well as in the development of natural compounds to fight major postharvest pathogens in pear fruit.

High-level expression of codon-optimized Thielavia terrestris cutinase suitable for ester biosynthesis and biodegradation

A codon-optimized cutinase gene (TtCutopt) from Thielavia terrestris was over-expressed in Pichia pastoris. An extracellular activity reached 10,200 U/mL using high cell density fermentation. The optimal pH and temperature of TtCutopt were 7.0 and 50 °C, respectively. It displayed high stability over a wide range of pH from 3.0 to 11.0 and up to 85 °C. Among tested p-nitrophenyl esters and triglycerides, TtCutopt showed the highest activity towards p-nitrophenyl butyrate and tributyrin, with specificity activity of 2322.4 U/mg and 1152.5 U/mg, respectively. It was extremely stable in organic solvents and surfactants. TtCutopt efficiently catalyzed the synthesis of butyl butyrate, hexyl butyrate, butyl hexanoate and hexyl hexanoate with esterification efficiency of >95%. Furthermore, it catalyzed the degradation of >90% of dimethyl phthalate, diethyl phthalate, dipropyl phthalate and dibutyl phthalate to release their corresponding monoalkyl phthalates within 24 h. Thus, high yield, high stability, and esterification efficiency of TtCutopt make it an attractive candidate for ester biosynthesis and biodegradation.

Ionic liquid [BMIm][HSO4] as dual catalyst-solvent for the esterification of hexanoic acid with n-butanol

Abstract Butyl hexanoate (BuHE) is currently synthesized through the Fischer esterification with mineral acid as catalyst, which suffers from the problems of side reaction, difficult recycling, and corrosion. To overcome these disadvantages, ionic liquid 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIm][HSO4]) is employed as dual catalyst-solvent for the esterification of hexanoic acid (HeAc) with n-butanol (BuOH) in a reactive extraction process. The dual functions of [BMIm][HSO4], extraction and catalysis, were confirmed by liquid-liquid equilibria for the two systems {[BMIm][HSO4] + HeAc + BuHE} and {[BMIm][HSO4] + BuOH + BuHE}, and by the comparison of esterifications with or without [BMIm][HSO4], respectively. Moreover, the optimal reactive extraction conditions for BuHE formation were obtained. Finally, the possible mechanism of intensification of [BMIm][HSO4] on BuHE formation in reactive extraction process was proposed.

Degradation of sex pheromone and plant volatile components by an antennal glutathione S-transferase in the oriental fruit moth,Grapholita molesta Busck (Lepidoptera: Tortricidae).

Insect antennae have a primary function of perceiving and discerning odorant molecules including sex pheromones and host plant volatiles. The assumption that genes highly expressed in the antennae may have an olfactory-related role associated with signal transduction. Here, one delta subfamily glutathione S-transferase (GST) gene (GmolGSTD1) was obtained from an antennal transcriptome of Grapholita molesta. Quantitative real-time polymerase chain reaction results revealed that GmolGSTD1 was mainly expressed in antennae and the expression levels were significantly higher in female antennae than in male antennae. The recombinant GmolGSTD1 (rGmolGSTD1) showed glutathione-conjugating activity toward 1-chloro-2,4-dinitrobenzene (CDNB) as substrates. The pH range for optimal rGmolGSTD1 enzyme activity was 6.0-6.5, and rGmolGSTD1 enzyme activity had maximal peaks at 35-40°C. Spectrophotometric analysis indicated that insecticides had weak inhibitory effects on the activity of rGmolGSTD1 with the inhibitory rates of 28.82% for chlorpyrifos, 22.27% for lambda-cyhalothrin, 18.07% for bifenthrin, 20.42% for acetamiprid, 17.57% for thiamethoxam, 25.67% for metaflumizone, 27.43% for abamectin, and 7.24% for chlorbenzuron. rGmolGSTD1 exhibited high degradation activity to the sex pheromone component (Z)-8-dodecenyl alcohol and the host plant volatile butyl hexanoate with the degradation efficiency of 75.01% and 48.54%, respectively. We speculate that GmolGSTD1 works in inactivating odorant molecules and maintaining sensitivity to olfactory communication of G. molesta.

Identification of a New Blend of Host Fruit Volatiles from Red Downy Hawthorn, Crataegus mollis, Attractive to Rhagoletis pomonella Flies from the Northeastern United States.

A new blend of volatiles was identified for the fruit of downy red hawthorn, Crataegus mollis, that is attractive to Rhagoletis pomonella flies infesting this host in the northeastern USA. The new blend was as attractive as the previously identified mixture but is more complex in the number of odorants (six in the old versus ten in the new) and differs significantly in the ratio of three volatiles, 3-methylbutan-1-ol, butyl hexanoate, and dihydro-β-ionone, that are common to both blends and exerted agonist or antagonist effects on behavior in a flight tunnel assay. However, behavioral results with the old and new northern hawthorn blends, as well as modified blends with substituted ratios of 3-methylbutan-1-ol, butyl hexanoate, dihydro-β-ionone, indicated that the 'agonist' or 'antagonist' effects of these volatiles depended on the ratio, or balance of compounds within the blend. In addition, the new blend contains a number of esters identified from the headspace of domesticated apple, Malus domestica, that are attractive to apple-origin R. pomonella, and present in the five other blends from southern hawthorns, including the southern C. mollis var. texana blend, but are not part of the previously identified blend from northern C. mollis fruit. This finding supports the hypothesis that in addition to providing specificity to the odor blends of the northern and southern hawthorn populations, the presence of the significant amounts of ester compounds in the new northern hawthorn blend might have provided a source of standing variation that could help explain the shift in host preference by C. mollis-infesting flies to introduced apple in the mid-1800's.

Optimization of key aroma compounds for dog food attractant

Although several investigations devoted to dog food attractants (DFAs) have been conducted, these studies fell short in identifying the key aroma compounds that could improve the palatability performance of pet foods. The aim of this study was to identify the key aroma compounds in the DFA using headspace-solid phase micro-extraction, gas chromatography-mass spectrometry and Partial Least Squares Regression (PLSR) analysis. Seven DFAs with different aroma compounds obtained by Maillard reaction were employed in the study. A total of 53 aromatic compounds were identified categorized as follows: 7 alcohols, 11 aldehydes, 4 ketones, 4 organic acids, 7 esters, 2 ethers, 10 heterocycle compounds, 4 phenols, 2 terpenes and 2 polycyclic aromatic hydrocarbons. Eight adult beagle dogs were used for the preference test (two-pan test) and acceptance test (one-pan test) to rank these seven DFAs. PLSR was performed to correlate the instrumental data with the preference results. Twenty-three aroma compounds of hexanoic acid, acetaldehyde, heptanone, butyl hexanoate, heptyl formate, methyl pyrazine, 2,5-dimethyl pyrazine, 2-heptanone, pentanal, ethyl decanoate, heptanal, octanal, pentanol, acetone, ethyl caprylate, 3-methyl butanal, anisole, 2-ethyl hexanol, 2-pentyl furan, 2,3-butanediol, benzaldehyde, ethyl vanillin and vanillin correlated with the preference data. Benzaldehyde, vanillin and 2, 5-dimethyl pyrazine were added to dry dog foods in order to validate the PLSR results. The presence of three aroma compounds significantly increased the preferences of the samples (dry dog foods). The validation study involving the three compounds suggests that the 23 compounds selected by the PLSR model are aroma compounds which influence palatability. Therefore the manipulation of these flavor compounds could improve the palatability of dog foods.

Evaluation of volatile compounds from Chinese dwarf cherry (Cerasus humilis (Bge.) Sok.) germplasms by headspace solid-phase microextraction and gas chromatography–mass spectrometry

The types and amounts of volatiles in denucleated fruit of 30 Chinese dwarf cherry germplasms were determined by headspace solid-phase microextraction and gas chromatography–mass spectrometry to assess the genotypic variation. Eighty-five volatiles were identified; hexyl acetate, 4-penten-1-yl acetate, prenyl acetate, (Z)-pent-2-enyl hexanoate, geranyl acetate, n-butyl acetate, (3Z)-3,7-dimethylocta-1,3,6-triene, geraniol, pent-2-enyl butanoate, ethyl caprylate, butyl hexanoate, and linalool were the main volatiles. The type and content of volatile varied with genotype. Red fruits had the most abundant aroma and vinicolor fruits exhibited the least. Principal component analysis clustered the 30 Chinese dwarf cherry germplasms into four groups: (1) 2 germplasms (NM2 and HN3) had high ester content, (2) 24 germplasms (BJ1–BJ6, HB1, HB2, HN1, HN2, NM1, NM3, SX1, SX2, SX4–SX6, SX8–SX10, SX12, SX13, SX15, and SX16) contained mainly esters, lactones, and terpenes, (3) 2 germplasms (SX11 and SX14) had high ester and lactone content, and (4) 2 germplasms (SX3 and SX7) had high ester and terpene content.

Application of AlkBGT and AlkL from Pseudomonas putida GPo1 for Selective Alkyl Ester ω-Oxyfunctionalization in Escherichia coli.

The enzyme system AlkBGT from Pseudomonas putida GPo1 can efficiently ω-functionalize fatty acid methyl esters. Outer membrane protein AlkL boosts this ω-functionalization. In this report, it is shown that whole cells of Escherichia coli expressing the AlkBGT system can also ω-oxidize ethyl nonanoate (NAEE). Coexpression of AlkBGT and AlkL resulted in 1.7-fold-higher ω-oxidation activity on NAEE. With this strain, initial activity on NAEE was 70 U/g (dry weight) of cells (gcdw), 67% of the initial activity on methyl nonanoate. In time-lapse conversions with 5 mM NAEE the main product was 9-hydroxy NAEE (3.6 mM), but also 9-oxo NAEE (0.1 mM) and 9-carboxy NAEE (0.6 mM) were formed. AlkBGT also ω-oxidized ethyl, propyl, and butyl esters of fatty acids ranging from C6 to C10 Increasing the length of the alkyl chain improved the ω-oxidation activity of AlkBGT on esters of C6 and C7 fatty acids. From these esters, application of butyl hexanoate resulted in the highest ω-oxidation activity, 82 U/gcdw Coexpression of AlkL only had a positive effect on ω-functionalization of substrates with a total length of C11 or longer. These findings indicate that AlkBGT(L) can be applied as a biocatalyst for ω-functionalization of ethyl, propyl, and butyl esters of medium-chain fatty acids. Fatty acid esters are promising renewable starting materials for the production of ω-hydroxy fatty acid esters (ω-HFAEs). ω-HFAEs can be used to produce sustainable polymers. Chemical conversion of the fatty acid esters to ω-HFAEs is challenging, as it generates by-products and needs harsh reaction conditions. Biocatalytic production is a promising alternative. In this study, biocatalytic conversion of fatty acid esters toward ω-HFAEs was investigated using whole cells. This was achieved with recombinant Escherichia coli cells that produce the AlkBGT enzymes. These enzymes can produce ω-HFAEs from a wide variety of fatty acid esters. Medium-chain-length acids (C6 to C10) esterified with ethanol, propanol, or butanol were applied. This is a promising production platform for polymer building blocks that uses renewable substrates and mild reaction conditions.