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Despite being present in trace amounts, ethyl esters play a crucial role as flavour compounds in lager beer. In yeast, ethyl hexanoate, ethyl octanoate and ethyl decanoate, responsible for fruity and floral taste tones, are synthesized from the toxic medium chain acyl-CoA intermediates released by the fatty acid synthase complex during the fatty acid biosynthesis, as a protective mechanism. The aim of this study was to enhance the production of ethyl esters in the hybrid lager brewing yeast Saccharomyces pastorianus by improving the medium chain acyl-CoA precursor supply. Through CRISPR-Cas9-based genetic engineering, specific FAS1 and FAS2 genes harbouring mutations in domains of the fatty acid synthesis complex were overexpressed in a single and combinatorial approach. These mutations in the ScFAS genes led to specific overproduction of the respective ethyl esters: overexpression of ScFAS1 I306A and ScFAS2 G1250S significantly improved ethyl hexanoate production and ScFAS1 R1834K boosted the ethyl octanoate production. Combinations of ScFAS1 mutant genes with ScFAS2 G1250S greatly enhanced predictably the final ethyl ester concentrations in cultures grown on full malt wort, but also resulted in increased levels of free medium chain fatty acids causing alterations in flavour profiles. Finally, the elevated medium chain fatty acid pool was directed towards the ethyl esters by overexpressing the esterase ScEEB1. The genetically modified S. pastorianus strains were utilized in lager beer production, and the resulting beverage exhibited significantly altered flavour profiles, thereby greatly expanding the possibilities of the flavour palette of lager beers. • Ethyl esters play a crucial role as flavour compounds in lager beer. • Enhancing medium chain acyl-CoA improves production of ethyl esters in lager yeast. • Alleles ScFAS1 I306A and ScFAS2 G1250S improves ethyl hexanoate production in lager yeast. • Allele ScFAS1 R1834K boosted ethyl octanoate production in S. pastorianus. • Engineering of ethyl ester synthesis aids customizing aroma profiles lager yeast. [ABSTRACT FROM AUTHOR]

Aims Ethyl hexanoate, one of the key flavor compounds in strong-flavor Baijiu. To improve the content of ethyl hexanoate in strong-flavor Baijiu, a functional strain with high yield of ethyl hexanoate was screened and its ester-producing performance was studied. Methods and results Upon identification, the strain was classified as Candida sp. and designated as ZY002. Under optimal fermentation conditions, the content of ethyl hexanoate synthesized by ZY002 can be as high as 170.56 mg L−1. A fermentation test was carried out using the ZY002 strain bioaugmented Daqu to verify the role of the strain applied to Baijiu brewing. It was found that strain ZY002 could not only improve the moisture and alcohol contents of fermented grains but also diminish the presence of reducing sugar and crude starch. Furthermore, it notably amplified the abundance of flavor compounds. Conclusion In this study, Candida sp. ZY002 with a high yield of ethyl hexanoate provided high-quality strain resources for the actual industrial production of Baijiu. [ABSTRACT FROM AUTHOR]

The current work illustrates microwave-assisted synthesis of ethyl hexanoate without a solvent system using cationic resin (Amberlyst-15) as a catalyst. The effect of various parameters was evaluated, and a maximum equilibrium conversion of 84.2% was achieved in 50 min. The optimized parameters were 1:02 mole ratio of acid to alcohol, temperature 328 K, and 9% (w/w) catalyst loading. The impact of mole ratio and catalyst loading on the reaction rate was predicted by developing an empirical correlation. The activation energy was determined as 17.63 kJ/mol. The experimental data fitted well with Eley-Rideal mechanism, in which the surface reaction was a rate-limiting step. Thermodynamic parameters were evaluated, including standard enthalpy, Gibbs free energy, and reaction entropy. The energy consumption for microwave reaction was predicted as 15.357 × 105 kJ/kg. These results have been compared with that of conventional as well as ultrasound-assisted synthesis of ethyl hexanoate. This novel technique shows an enhancement in reaction rates and higher yields. [ABSTRACT FROM AUTHOR]

ABSTRACT The phytonematodes seriously harm plants worldwide, reducing agricultural productivity, especially root-knot nematodes, genus Meloidogyne. An alternative form of control for this pathogen is the use of essential oils, which have a complex mixture of compounds with potential nematicidal activity. The objective of this work was to identify the chemical compounds present in the essential oil of pequi and to verify the efficiency of the oil in the control of Meloidogyne javanica. The identification of chemical compounds was performed by comparing the mass spectra obtained with the spectra present in the equipment library, Nist08. Eighty-second stage juveniles (J2) were incubated in the following treatments: control 0 (2 mL of distilled water) 2, 4, 8 and 16 mg L-1 of pequi essential oil (PEO). The results obtained in the experiment were significant, with a high percentage of mortality of J2 in the treatment T5 (16 mg L-1) of 82% and T3 (4 mg L-1) 66%, respectively. Among the compounds identified, 58.3% are esters, highlight for ethyl hexanoate, and 25.0% are monoterpenes, and all are nematicidal compounds. Pequi essential oil has the potential to be used in the control of M. javanica.

[Display omitted] • Application of cellar mud-sourced acid-producing bacteria and acid-tolerant esterifying yeast. • Co-culture solid-state fermentation of functional microbial to improve key flavor ethyl esters. • Ethyl hexanoate and ethyl butyrate were correlated with a cluster of interactions dominated by lactic acid bacteria. • Positive synergistic relationship between Clostridium tyrobutyricum and Saccharomyces cerevisiae. • Conversion of acids to esters by microorganisms in a high-acid fermentation system by stress reactions. Ethyl hexanoate and ethyl butyrate are indispensable flavor metabolites in strong-flavor Baijiu (SFB), but batch production instability in fermenting grains can reduce the quality of distilled Baijiu. Biofortification of the fermentation process by designing a targeted microbial collaboration pattern is an effective method to stabilize the quality of Baijiu. In this study, we explored the metabolism under co-culture liquid fermentation with Clostridium tyrobutyricum DB041 and Saccharomyces cerevisiae YS219 and investigated the effects of inoculation with two functional microorganisms on physicochemical factors, flavor metabolites, and microbial communities in solid-state simulated fermentation of SFB for the first time. The headspace solid-phase microextraction-gas chromatography-mass spectrometry results showed that ethyl butyrate and ethyl hexanoate significantly increased in fermented grain. High-throughput sequencing analysis showed that Pediococcus , Lactobacillus , Weissella , Clostridium _ sensu _ stricto _12, and Saccharomyces emerged as the dominant microorganisms at the end of fermentation. Co-occurrence analysis showed that ethyl hexanoate and ethyl butyrate were significantly correlated (|r| > 0.5, P < 0.05) with a cluster of interactions dominated by lactic acid bacteria (Pediococcus , Lactobacillus , Weissella , and Lactococcus), which was driven by the functional C. tyrobutyricum and S. cerevisiae. Mantel test showed that moisture and reducing sugars were the main physicochemical factor affecting microbial collaboration (|r| > 0.7, P < 0.05). Taken together, the collaborative microbial pattern of inoculation with C. tyrobutyricum and S. cerevisiae showed positive results in enhancing typical flavor metabolites and the synergistic effects of microorganisms in SFB. [ABSTRACT FROM AUTHOR]

Targeted biofortification is an effective way to regulate the microbial community succession and the production of flavor metabolites in the Baijiu fermentation. However, the high organic acid present in the Baijiu brewing process causes the gradual succession of exogenous functional microorganisms to be less dominant, ultimately resulting in defective flavor substances. In this study, a strain of Saccharomyces cerevisiae YS219 with high production of ethyl hexanoate and excellent organic acid tolerance was excavated, and the effects of this strain on the microbial composition and flavor metabolites during the fermentation of strong-flavor Baijiu were investigated. The microbial community was analyzed using the Illumina Miseq Pe300 Sequencing Platform, and at the genus level, Saccharomyces , Lactobacillus , and Pediococcus became the dominant genera after biofortification. A total of 77 flavor substances were detected in the biofortified fermented grains, and the contents of total esters and alcohols increased significantly. Among them, ethanol and ethyl hexanoate were significantly increased. Mantel test showed significant positive correlation between lactic acid and Pediococcus. Moreover, lactic acid, acetic acid, and ethanol were negatively correlated with most of the fermenting microorganisms. Following inoculation with S. cerevisiae YS219, Saccharomyces and Pediococcus exhibited a positively significant link with ethyl hexanoate, according to Spearman's correlation analysis. Taken together, the results demonstrate that the addition of S. cerevisiae with excellent organic acid tolerance and high ethyl hexanoate production helps to promote the change of microbial community and the elevation of ethanol and ethyl hexanoate. [Display omitted] • Excavation of a Saccharomyces cerevisiae strain with high ethyl hexanoate production and excellent organic acid tolerance. • Biofortification drives Saccharomyces , Lactobacillus , and Pediococcus to become the dominant genera. • Correlation analysis showed that biofortification induced ethyl hexanoate production by utilizing lactic acid and acetic acid. [ABSTRACT FROM AUTHOR]

Salt is a critical ingredient in processed meat and poultry products because of its multiple functions that affect product quality and safety. Although salt is a functional ingredient in food products, sodium reduction continues to be an important topic within the food industry due to interests in reducing dietary sodium intake. Previous work has shown that soy sauce addition may potentiate saltiness perception in processed meats and thus allow for novel formulations with reduced sodium content. Two studies were conducted to further elucidate these effects. First, trained panel sensory char- acteristics, relevant quality parameters, and selected chemical profiles were determined comparing frankfurters containing flake salt and traditionally brewed soy sauce. Seven aqueous compounds were found to be more abundant (P < 0.001) in the soy sauce – containing treatment, and 56 volatile compounds were identified. Principal component analysis of the sensory and selected chemical profiles led to the consideration that ethyl hexanoate (EHEX) may be a causative agent of the saltiness-potentiating phenomenon. Thus, a second study further evaluated concentrations of EHEX, revealing that trained sensory panelists perceived frankfurters containing EHEX as saltier (P < 0.05) and these frankfurters had higher scores for fermented/sour aromatic score (P < 0.05) than the control (Control: 100% NaCl from flake salt). This research demon- strated the ability of EHEX to potentiate saltiness in frankfurters with minimal effects on quality.

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Kinetics of lipase-catalyzed esterification of hexanoic acid and ethyl alcohol using the solvent-free system, surface coated lipase from Candida rugosa, had been studied. The effect of various parameters such as reaction time, reaction temperature, reaction kinetics, water removal and feasibility of solvent-free system had been focused. Candida Rugosa lipase was more effective than other lipases when ethyl hexanoate was synthesized in n-hexane. The highest esterification yield after 72 h (93 %) was achieved at a pH of 5.2 and the esterification yield was reduced to 73% at pH 4.0. The values of the apparent kinetic parameters were computed as Vmax= 0.146 μmol/min/mg enzyme; KM, Acid = 0.296 M; KM, Alcohol = 0.1388 M; Ki, Acid = 0.40 M; and Ki, Alcohol = 0.309 M. The reaction rate could be described in terms of the Michaelis–Menten equation with a Ping-Pong Bi-Bi mechanism and competitive inhibition by both the substrates.

The use of interspecific hybrids during the industrial fermentation process has been well established, positioning the frontier of advancement in brewing to capitalize on the potential of Saccharomyces hybridization. Interspecific yeast hybrids used in modern monoculture inoculations benefit from a wide range of volatile metabolites that broaden the organoleptic complexity. This is the first report of sake brewing by Saccharomyces arboricola and its hybrids. S. arboricola x S. cerevisiae direct-mating generated cryotolerant interspecific hybrids which increased yields of ethanol and ethyl hexanoate compared to parental strains, important flavor attributes of fine Japanese ginjo sake rice wine. Hierarchical clustering heatmapping with principal component analysis for metabolic profiling was used in finding low levels of endogenous amino/organic acids clustered S. arboricola apart from the S. cerevisiae industrial strains. In sake fermentations, hybrid strains showed a mosaic profile of parental strains, while metabolic analysis suggested S. arboricola had a lower amino acid net uptake than S. cerevisiae. Additionally, this research found an increase in ethanolic fermentation from pyruvate and increased sulfur metabolism. Together, these results suggest S. arboricola is poised for in-depth metabolomic exploration in sake fermentation. [ABSTRACT FROM AUTHOR]

Carob liqueur is an alcoholic drink (minimum 15% v/v of ethanol and 100 g/L of sugar) typical for the Mediterranean countries. In the current work, carob macerate produced by maceration of carob pods in hydroalcoholic base at different maceration conditions was characterized for the first time based on its aroma compounds/profile, physicochemical parameters, and chromatic characteristics. The results confirm the migration process of bioactive compounds, aroma compounds, and sugars flowing from the carob pod to the hydroalcoholic base. Changes in ethanol concentration modify the physical properties of the solvent and influence the phenolic and aroma compounds extraction, color, and acidity of the obtained samples. The higher content of phenolic compounds was determinate in the samples obtained in the darkness. The amounts of phenols were in the range of some red fruit liqueurs or walnut liqueurs, and sugars (mostly sucrose) ranging between 96 and 107 g/L. Twenty‐six (out of total 94) aroma compounds were detected in all samples, of which 17 esters, 3 alcohols, 4 ketones, and 2 acids. Low molecular weight ethyl esters, ethyl hexanoate, ethyl 2‐methyl propanoate, ethyl octanoate, ethyl benzoate, ethyl butanoate, and ethyl cinnamate, were the most abundant. Carob pod maceration in 50% v/v hydroalcoholic base (1:5 solid to liquid ratio) in darkness at room temperature during 8 weeks can be recommended as optimal maceration conditions for production of the aromatic carob macerate with functional properties. [ABSTRACT FROM AUTHOR]

Biofortification of Baijiu fermentation using exogenous functional strains can change the microbial community structure of the fermentation ecosystem and flavor metabolism, which can impact Baijiu flavor. In this work, a high ethyl hexanoate-producing Saccharomyces cerevisiae Y285 strain was added for biofortification to investigate microbial communities' succession and flavor compounds throughout the fermentation of strong-flavor Baijiu. The microbial community composition of the fermentation samples was analyzed using the Illumina MiSeq platform, and the results showed that Pediococcus , Lactobacillus , Weissella and Saccharomyces were the dominant genera. A total of 111 flavor compounds, consisting of esters (50), alcohols (14), acids (3), aldehydes (9), phenols (9), pyrazines (3), ketones (8), and others (15), were detected in all samples, and the content of total esters of the fortified Daqu increased dramatically. Among them, the content of ethyl acetate decreased while that of ethyl hexanoate increased significantly, and the content of other compounds such as ethyl palmitate, ethanol, phenethyl alcohol and tetramethylpyrazine also increased. Redundancy analysis and Spearman's correlation analysis revealed that Saccharomyces , Pediococcus , Lactobacillus , and Weissella were significantly positively correlated with esters and alcohols. To summarize, biofortification with S. cerevisiae during Baijiu fermentation modifies microbial community composition, as well as the content of ethyl hexanoate in Baijiu, and induces changes in the content of other flavor compounds. These findings imply that modifying the microorganisms throughout the Baijiu fermentation process can alter the flavor of Baijiu and further enhance it. [Display omitted] • The biofortification with high yield ethyl hexanoate-producing yeast. • Ethyl hexanoate content was associated with Saccharomyces , Pediococcus , Lactobacillus and Weissella. • Biofortification can alter the microbial community structure and flavor metabolism during Baijiu fermentation. [ABSTRACT FROM AUTHOR]

The popularity of texiang aroma type baijiu (liquor), known for its unique production technology and multilayered flavor, has been steadily increasing among consumers. So far, no research has determined its key aroma compounds for characterizing the unique flavor, which is the purpose of this paper. Using gas chromatography-olfactometry (GC-O) coupled with the GC-mass spectrometry (GC-MS) method, 87 aroma-active compounds were identified and screened out with intensity values ≥2.0. 1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) was first confirmed by GC-O in Chinese liquor. According to a quantitative study and odor activity values (OAVs), 42 odorants were determined as important aroma compounds. These odorants were recombined based on quantitative concentrations, successfully simulating the overall aroma profile. Omission experiments verified ethyl hexanoate, β-damascenone, and 2-furfuryl ethyl ether as the key aroma compounds and revealed that ethyl acetate, furfural, and ethyl 2-phenylacetate were important aroma compounds to the overall flavor of texiang aroma and flavor type liquor.

BACKGROUND: Strawberries are perishable fruits that decay quickly after harvest, but are valued for their distinctive taste and aroma. Melatonin is involved in plant resistance against stress, plant senescence and fruit ripening, and was shown to delay post-harvest spoilage of strawberries. OBJECTIVE: The effects of melatonin postharvest treatment on shelf-life and volatile organic compound profile were assessed in strawberry fruits cv "Luca". METHODS: Strawberry fruit were treated with 100 μM melatonin and stored at 4°C for 12 days to assess whether melatonin treatment could delay spoilage without adversely affecting aroma. RESULTS: Melatonin treatment delayed fruit deterioration by reducing weight loss and incidence of decay as well as maintaining total soluble solids, titratable acidity, anthocyanin, and taste. Melatonin treatment also significantly reduced CO2 production compared to control fruits. The relative abundance of the majority of volatile organic compounds (VOCs) was not affected, however abundance of two VOCs that are important components of strawberry aroma were affected by melatonin treatment. CONCLUSIONS: Post-harvest treatment of strawberries with 100 μM melatonin improved strawberry quality and conserved bioactive compounds after 12 d of storage. However, components of the aroma profile were altered in a way which may affect consumer perception of quality. [ABSTRACT FROM AUTHOR]

Copyright of China Brewing is the property of China Brewing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The use of interspecific hybrids during the industrial fermentation process has been well established, positioning the frontier of advancement in brewing to capitalize on the potential of Saccharomyces hybridization. Interspecific yeast hybrids used in modern monoculture inoculations benefit from a wide range of volatile metabolites that broaden the organoleptic complexity. This is the first report of sake brewing by Saccharomyces arboricola and its hybrids. S. arboricola x S. cerevisiae direct-mating generated cryotolerant interspecific hybrids which increased yields of ethanol and ethyl hexanoate compared to parental strains, important flavor attributes of fine Japanese ginjo sake rice wine. Hierarchical clustering heatmapping with principal component analysis for metabolic profiling was used in finding low levels of endogenous amino/organic acids clustered S. arboricola apart from the S. cerevisiae industrial strains. In sake fermentations, hybrid strains showed a mosaic profile of parental strains, while metabolic analysis suggested S. arboricola had a lower amino acid net uptake than S. cerevisiae. Additionally, this research found an increase in ethanolic fermentation from pyruvate and increased sulfur metabolism. Together, these results suggest S. arboricola is poised for in-depth metabolomic exploration in sake fermentation.

Strong flavor baijiu (SFB), also called Luzhou-flavor liquor, is the most popular Chinese baijiu. It is manufactured via solid fermentation, with daqu as the starter. Microbial diversity of the SFB ecosystem and the synergistic effects of the enzymes and compounds produced by them are responsible for the special flavor and mouthfeel of SFB. The present review covers research studies focused on microbial community analysis of the SFB ecosystem, including the culturable microorganisms, their metabolic functions, microbial community diversity and their interactions. The review specifically emphasizes on the most recently conducted culture-independent analysis of SFB microbial community diversity. Furthermore, the possible application of systems biology approaches for elucidating the molecular mechanisms of SFB production were also reviewed and prospected.

This study was conducted to extract scarce natural liquor flavorings desired by many liquor factories from yellow water. Five straight-chain saturated fatty acids were firstly extracted from 15 fractions of yeHow water, forming 1 fraction of the ethanol solution composed of the mixture of the five straight-chain saturated fatty acids. Then, 100 fractions of the ethanol solution could produce 94. 857 6 fractions of esterification liquid through catalytic esterification at 80 m. The esterification liquid contains five esters: ethyl acetate, ethyl propionate, ethyl butyrate, ethyl valerate and ethyl caproate, with contents of 17. 68V, 2. 58V, 6. 32%, 0.06V and 19.40V, respectively. The esterification liquid prepared from 1 fraction of yeHow water could blend 10. 54 fractions of white liquor into top-grade Luzhou-flavor liquor after esterification. It indicates that yeHow water has very good recycling and utilization value. [ABSTRACT FROM AUTHOR]

Strong flavor baijiu (SFB), also called Luzhou-flavor liquor, is the most popular Chinese baijiu. It is manufactured via solid fermentation, with daqu as the starter. Microbial diversity of the SFB ecosystem and the synergistic effects of the enzymes and compounds produced by them are responsible for the special flavor and mouthfeel of SFB. The present review covers research studies focused on microbial community analysis of the SFB ecosystem, including the culturable microorganisms, their metabolic functions, microbial community diversity and their interactions. The review specifically emphasizes on the most recently conducted culture-independent analysis of SFB microbial community diversity. Furthermore, the possible application of systems biology approaches for elucidating the molecular mechanisms of SFB production were also reviewed and prospected. [ABSTRACT FROM AUTHOR]

Yeast cells ( Saccharomyces cerevisiae ), from which β-glucans have been partially extracted, were used to encapsulate flavor inside the lipid bilayer membrane as natural encapsulant. The focus of this study was to investigate the release and stability of flavors ( d -limonene and ethyl hexanoate) encapsulated in yeast cells and maltodextrin (MD) (DE = 19) by spray drying. The release behavior of encapsulated flavors from yeast cells was measured at 40, 60, 80, and 105 °C with different moisture content (0, 50, 100, and 200% of powder). Water affected flavor release from the yeast cells. The release rate constants were correlated using Gaussian distribution of the activation energy of the release rate constants. The release of d -limonene from the spray-dried MD powder showed a different trend than that of yeast cells at various temperatures. The activation energies of the release rate constant for ethyl hexanoate and d -limonene from yeast were 55 and 49 kJ/mol, respectively, under a wet condition. The formation rates of limonene oxide and carvone were slower in yeast than that of MD powder at 30 °C after 2 months. [ABSTRACT FROM AUTHOR]

Flavor encapsulation was investigated by spray drying with dried Saccharomyces cerevisiae cells. The yeast cells, Saccharomyces cerevisiae , which were by-products in the production of β-glucan, were used in the encapsulation of d -limonene and ethyl hexanoate. Effects of incubation time, temperature, and spray drying conditions on the encapsulated flavor content after spray drying were investigated. The encapsulation rate constant was 0.69 h −1 for d- limonene and ethyl hexanoate. High contents of both flavors were obtained at an incubation temperature of 40 °C for 4 h and an inlet air temperature of 200 °C for spray drying. Inlet air temperature did not significantly affect encapsulation of flavor content for ethyl hexanoate. Flavor content obtained was 37 wt% for d -limonene and 49 wt% for ethyl hexanoate at an inlet air temperature 200 °C. Thus, yeast could be used as a successful flavor-encapsulant by spray drying. [ABSTRACT FROM AUTHOR]

This study aimed at isolating and culturing Bacilli from the omagari, pit mud, and fermented grains used in Luzhou-flavor liquor in an effort to produce better flavor and quality. After an enrichment culture of Bacillus in the omagari, pit mud, and fermented grains of Luzhou-flavor liquor, 52 total strains were obtained. Based on the standard of producing high-yield ethyl hexanoate and low-yield propanol, one strain named YB-1 was screened out. It was shown that YB-1 produced ethyl hexanoate at 214.7 mg/100 mL and propanol at 0 mg/100 mL. Based on strain morphology, and physiological and biochemical characteristics, YB-1 was identified as Bacillus. According to DNA sequencing and the constructed phylogenetic tree, YB-1 and Bacillus cereus strain CCM 2010 clustered into a branch and were each other's closest relatives. Thus, YB-1 was identified as Bacillus cereus. Through this research, it is expected that the application of Bacillus cereus strain YB-1 to the traditional brewing process of Luzhou-flavor liquor could improve the flavor and quality, and enrich microbial resources for Luzhou-flavor liquor fermentation. [ABSTRACT FROM AUTHOR]