Concentrations Of Ethyl Esters Research Articles

Impact of yeast selection on composition of vinegar fermented from pomace of a Finnish apple cultivar

Alcoholic beverages and vinegar products were produced using the pomace of a Finnish apple cultivar, and the influence of yeast strains on the non-volatile and volatile compound contents were studied. Apple pomace mashes were fermented with Saccharomyces cerevisiae, Torulaspora delbrueckii, and sequential inoculation with Lachancea thermotolerans and S. cerevisiae to produce alcoholic beverages. Commercial non-pasteurized vinegar was used as a starter to ferment alcoholic beverages into vinegars. Ethanol, acetic acid, sugars and organic acids were determined using GC-FID. A total of 63 volatile compounds were detected in the samples using HS-SPME-GC-MS. Alcoholic beverages fermented with the sequential inoculation had the highest total content of organic acids, and pure inoculation with T. delbrueckii resulted in the highest total content of sugars. Selection of different yeast strains did not alter the content of ethanol or acetic acid, but it significantly influenced the composition of volatile compounds in alcoholic beverages and vinegars. Compared to initial apple pomace mash, significant increases in the contents of ethyl esters (up to 4810-folds), higher alcohols (up to 24-folds) and volatile acids (up to 1853-folds) were observed in fermented products depending on the yeasts used. The main volatile compounds in vinegars prepared from S. cerevisiae fermented beverage were 2-phenylethanol, octanoic acid, and decanoic acid, from T. delbrueckii beverage 2-methylpropanoic acid and 3-methylbutanoic acid, and from sequential fermentation ethyl acetate, and ethyl 2-hydroxypropanoate. In conclusion, non-Saccharomyces yeasts have potential to produce more complex aromatic profile to fermented products derived from by-products of apple juice processing.

Supernatant of plant-associated bacteria potency against biofilms formed by foodborne pathogen and food spoilage bacteria.

Food products are often contaminated by pathogens and spoilage bacteria. Most of them can form biofilms, a community of cells embedded in protective extracellular matrix layers resistant to harsh conditions, including antibiotics. Therefore, alternative antibiofilm agents are required to overcome biofilm formation. This study aims to determine and quantify the antibiofilm activity of supernatants from plant-associated bacteria against biofilms of foodborne pathogen and food spoilage bacterium, namely Bacillus cereus and Bacillus subtilis. Plant-associated bacteria (PAB) have shown promising antibiofilm activities against biofilm-forming pathogens in previous studies. Thirteen PAB isolated from Ternate, Indonesia were used in this study. Supernatants of PAB were subjected to antimicrobial activity and quorum quenching detection, both using the well diffusion method. Four supernatants inhibited the growth of B. subtilis, but none affected the growth of B. cereus. Eight supernatants were able to disrupt the quorum sensing system of an indicator bacterium, wild-type Chromobacterium violaceum. Biofilm inhibition and destruction were quantified using 96-well microplates. The highest biofilm inhibition and destruction activities of PAB supernatants against each of B. cereus and B. subtilis biofilms were > 76%, and were later confirmed by light microscope and scanning electron microscope. Brine shrimp lethality assay (BSLA) was conducted and revealed that the selected PAB supernatants were non-toxic. The 16S rRNA gene of PAB were sequenced and they showed similarities to Bacillus, Priestia, and Chryseobacterium. Compounds in the supernatants were determined by GC-MS which revealed contents of fatty acids, ethyl esters, and diketopiperazines. Therefore, PAB supernatants have potential as antibiofilm agents against biofilm formed by Bacillus cereus and Bacillus subtilis.

The Role of Keeving in Modulating Fermentation and the Flavour Profiles of Apple Brandy

Keeving is the removal of nutrients from apple musts due to their binding to pectin, resulting in a slower fermentation and spontaneous arrest. The aim of this study was to determine the effect of keeving on the chemical composition of fermented apple must and on the volatile profile and sensory analysis of apple brandies. We compared the application of keeving during spontaneous fermentation with fermentation carried out by Saccharomyces cerevisiae (SafSpirit HG-1). We evaluated the impact of adding different doses of calcium chloride on various parameters of fermented musts and distillates. Calcium chloride had a greater effect on the ethanol concentration, total extract, and fermentation efficiency than on the type of fermentation used. However, a different phenomenon was observed with respect to the volatiles. The concentration of most of the higher alcohols, acetaldehyde, dodecanal, and geranylaceton, decreased after spontaneous fermentation and increased during the fermentation carried out with Saccharomyces cerevisiae SafSpirit HG-1. In general, the application of keeving contributed to a decrease in the concentration of ethyl and methyl esters, but caused an increase in the concentration of all acetate esters and terpenoids. When the amount of nutrients in the environment is limited and starvation occurs, microorganisms use the available nutrients for basic metabolic processes that allow them to survive and limit the formation of side metabolites such as volatiles. However, most of the samples fermented after the faecal depletion achieved high scores for the floral, fruity, and “overall note” parameters in the sensory analysis. This means that this method, carried out with a properly selected yeast strain, could be feasible for the distilling industry.

Effect of Grist Particle Size Distribution and Wort Turbidity on Ester Composition of Malt Whisky New Make Spirit

The parameters used during milling of malt have considerable implications for the turbidity of wort collected during lautering, and wort turbidity has previously been demonstrated to impact ester development by yeast (during fermentation of brewer’s wort). The present research assesses the impact of milling regime and wort turbidity on congener development during production of malt whisky new make spirit. New make spirit was produced from pot still malt prepared with a disc mill under differing milling regimes (mill gap: 0.5–1.5 mm; laboratory scale). Use of increasingly coarse milling conditions positively correlated with wort turbidity and reduced concentration of acetate and ethyl esters in new-make spirit. Similar to previous research within the brewing industry, turbid wort was generally associated with reduced ester content, particularly in samples produced under the coarsest milling conditions (mill gap: 1.5 mm). Turbidity of new-make spirit (diluted to 30% ABV) was reduced in samples produced from wort of elevated turbidity, likely due to reduced content of ethyl esters and other haze-active congeners.

First Insight into Lignin Valorization as a Promising Biopolymer for the Modulation of the Physicochemical Properties of Port Wine.

Lignosulfonate (LS), kraft lignin (KL), and organosolv lignin (OL) were evaluated as potential modulating agents of the physicochemical properties of Port wine at two different concentrations for 7 and 30 days. KL and LS demonstrated the ability to remove proteins and potentiate the anthocyanin concentration. LS reduced the tannin content and the interaction of salivary acidic proline-rich proteins with wine phenolic compounds. None of the lignin promoted a perceptible color change; however, the yellowish color of KL and OL at 100 g/hL contributed to an increase in the yellow tones of wines. Lignin improved wine aroma by reducing the amount of unwanted volatiles by 30% and increasing the content of ethyl esters associated with fruity aromas by up to 60%. The results suggest that lignin, especially LS, can be employed as a modulating agent, positively impacting wine's physicochemical properties. This valorization of a byproduct opens up new opportunities for the wine industry.

The Role of Indigenous Yeasts in Shaping the Chemical and Sensory Profiles of Wine: Effects of Different Strains and Varieties.

The microbial terroir is an indispensable part of the terroir panorama, and can improve wine quality with special characteristics. In this study, eight autochthonous yeasts (Saccharomyces cerevisiae), selected in Huailai country, China, were trailed in small-scale and pilot fermentations for both white (Riesling and Sémillon) and red (Cabernet Sauvignon and Syrah) wines and evaluated by GC-MS analysis and the rate-all-that-apply (RATA) method. Compared to commercial yeast strains, the indigenous yeasts were able to produce higher concentrations of ethyl esters and fatty acid ethyl esters, and higher alcohol, resulting in higher odor activity values of fruity, floral attributes. Marked varietal effects were observed in the pilot fermentation, but yeast strains exerted a noticeable impact in modulating wine aroma and sensory profile. Overall, indigenous yeast could produce more preferred aroma compounds and sensory characteristics for both white and red wines, demonstrating the potential for improving wine quality and regional characteristics.

Unlocking lager's flavour palette by metabolic engineering of Saccharomyces pastorianus for enhanced ethyl ester production

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 ScFAS1I306A and ScFAS2G1250S significantly improved ethyl hexanoate production and ScFAS1R1834K boosted the ethyl octanoate production. Combinations of ScFAS1 mutant genes with ScFAS2G1250S 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.

Hydrothermal Co-Liquefaction of Sugarcane Bagasse and Residual Cooking Soybean Oil for Bio-Crude Production

Hydrothermal co-liquefaction (co-HTL) is a process involving two sources of biomasses aiming at bio-crude production. Since there is a lack of studies performed with sugarcane bagasse and residual soybean oil, this study investigated different conditions for the co-HTL of these biomasses, with and without the presence of ethanol as a co-solvent to maximize the bio-crude yield. All co-HTL reactions were carried out in a 300 mL Parr® reactor at temperatures ranging from 200 to 300 °C. After the reaction, a vacuum filtration was performed to separate the bio-char, later washed with ethanol to extract heavy bio-crude, while the liquid-phase was mixed with dichloromethane to recover light bio-crude. Bio-crude yields of around 95 wt.% were obtained at 300 °C using ethanol and water as solvents. The highest bio-char yield (16.6 wt.%) was achieved when using only sugarcane bagasse as the substrate, without the presence of soybean oil. Bio-crude samples obtained at higher temperatures (280 °C and 300 °C) using ethanol as a hydrogen donor presented higher contents of both free fatty acids and fatty acid ethyl esters. This work presents a promising process to produce high-quality bio-crude using an abundant feedstock (sugarcane bagasse) in the presence of a lipid source which could cause environmental problems if poorly handled.

Esters and higher alcohols regulation to enhance wine fruity aroma based on oxidation-reduction potential

Fruity aroma is a crucial element in reflecting the flavor of wine, believed to be closely linked to esters and higher alcohols associated with the oxidation-reduction potential (ORP) of wine. In this work, the impact of ORP on the production of esters and higher alcohols, and consequently the fruity aroma in Cabernet Sauvignon (CS) and Ecolly wines were investigated. Results revealed that the maximum concentration of medium-chain fatty acid ethyl esters (MCFAEEs) was achieved at −80 mV, which was 48.78% and 25.10% higher than those of the CK groups (ORP without artificial control) in CS and Ecolly wines, respectively. However, the concentrations of acetates and higher alcohols in CS were not significantly different from that in CK, while those in Ecolly were elevated. Additionally, the temperate fruity aroma in CS and citrus aroma in Ecolly wines were enhanced at −80 mV. Partial least-squares regression further indicated that, higher alcohols contributed positively to these enhanced aromas of CS and Ecolly. MCFAEEs have also been suggested to have a positive impact on the fruity and floral aromas for CS and tropical fruity aroma for Ecolly wines. Our work provides an alternative for improving the aroma quality of wine through fermentation process.

The Influence of Prefermentation Skin Contact, Stabulation, and Skin Fermentation on the Aromatic Behaviour and Phenolic Compounds of Important Austrian White Wine Cultivars

Many varietal aromas of wine are located in the berry skin. In the present study, we evaluated four important Austrian grape varieties: Grüner Veltliner, Sauvignon Blanc, Traminer, and Pinot Blanc. We assessed whether prefermentation skin contact, fermentation with the skin (only for Grüner Veltliner), and stabulation (lees stirring; only for Sauvignon Blanc, Traminer, and Pinot Blanc) could enhance the varietal aromas of the different grape cultivars. The aim was to intensify the varietal aromas without extracting the undesirable phenols. We performed a detailed analytical characterisation of approximately 100 volatile and phenolic compounds as well as a sensory characterisation. Although mash fermentation significantly increased the spicy aromas of Grüner Veltliner, which are affected by climate change (especially the sesquiterpene rotundone), it markedly decreased the fruitiness and increased the bitterness; therefore, it cannot be recommended for this cultivar. For Sauvignon Blanc, stabulation is a possible option; the varietal aromas (thiols and methoxypyrazines) were increased in the final wines of these variants. For Pinot Blanc and Traminer, prefermentation skin contact yielded the best results: for Traminer, it produced the highest content of monoterpenes (especially z-rose oxide), and for Pinot Blanc, it produced the highest content of ethyl esters. To summarise, stabulation will not completely replace classic skin contact, and mash fermentation is certainly not an alternative for the production of standard Grüner Veltliner wine. However, additional investigations are necessary with regard to other grape varieties, terroirs, and vintages before we can make final recommendations.

Влияние винных и виноградных спиртов на качество напитков из виноградного сырья

Table grapes that have lost their marketable appearance are considered waste products. However, such grapes still possess some technological properties that make it possible to use them as a raw material for wine and grape spirits. This research featured the effect of the composition and technology of table grape alcohols on the volatile compounds and sensory profile 
 of grape beverages.
 The study involved six white and six red grape beverages. In the test samples, the fermentation process was stopped by adding wine spirits and grape spirits obtained by rectification of distillates from table grapes. In the control samples, the procedure involved rectified grain alcohol. The physicochemical parameters of drinks and spirits were defined by standard methods. The highly volatile compounds were determined by gas chromatography. The sensory assessment was conducted by panelists from the Winemaking Research Center of the North-Caucasian Federal Scientific Center of Horticulture, Viticulture, and Winemaking.
 In this study, the wine spirits and the grape spirits obtained from table grapes had no effect on the standard indicators, e.g., volatile acids and acetoin. However, they increased the mass concentrations of highly volatile compounds in the following manner: drinks with grain alcohol ˂ drinks with wine alcohol ˂ drinks with grape alcohol. The content of acetaldehyde increased by 10–14% while the contents of ethyl acetate, esters, and higher alcohols increased by 25–35, 4.5–8.5, and 15%, respectively. The furfural content increased by 0.4–1.4 mg/L in the samples with grape alcohol. The samples with white grape varieties acquired a more prominent floral-honey flavor whereas those with black grapes acquired hints of hazelnut and honey.
 As a result of the study, it was found that wine alcohol and grape alcohol moderately increased the content of volatile compounds in drinks and had a positive effect on their sensory perception, which proves the expediency of their use in beverage technology.

Screening and characterization of indigenous non-Saccharomyces cerevisiae with high enzyme activity for kiwifruit wine production

To explore the diversity and fermentation potential of non-Saccharomyces cerevisiae associated with kiwifruit, indigenous yeasts isolated from kiwifruit and natural fermentation were comprehensively analyzed. A total of 166 indigenous yeasts were isolated, of which 54 representative strains were used for subsequent enzyme activity characterization. Different colorimetric methods were used to verify the ability of these strains to secrete hydrolytic enzymes, and then six strains were selected for sequential fermentation by specific activity assay. The performance of indigenous yeasts in improving organic acids, polyphenols, volatile compounds and sensory characteristics of wines was evaluated holistically. Results indicated that most sequential fermentations exhibited significant improvements in vitamin C and polyphenols. Remarkably, the involvement of Zygosaccharomyces rouxii, Meyerozyma guilliermondii, and Pichia kudriavzevii increased the concentrations of ethyl esters, acetates and alcohols, enhancing floral and tropical fruit odors and ultimately achieving the highest overall sensory acceptability, thereby highlighting their potential in kiwifruit wine fermentation.

The influence of different yeast strains and yeast nutrients on the aroma of Krstač and Žižak wines

Krstač and Žižak are autochthonous grape varieties grown in Montenegro. Although international varieties are more popular, the autochthonous varieties are very important, especially for countries developing tourism. The fermentation aromas produced during alcoholic fermentation contribute significantly to wine quality. The effects of yeasts (Saccharomyces cerevisiae and Saccharomyces bayanus) and yeast nutrients (Fermaid E and Fermaid O) on aromatic compounds in wines were investigated. Using GC/FID-MS analysis, aroma compounds in Krstač and Žižak wines were characterized and quantified. Wines produced with the addition of yeast and yeast nutrients had mostly lower total alcohol content than wines obtained by spontaneous fermentation of Krstač and Žižak varieties. The results of this study showed that the concentration of compounds depends on the yeast strains. The yeast S. cerevisiae (ICV) provided a higher content of higher alcohols, while S. bayanus produced a higher concentration of esters and (medium chain) fatty acids. Total ester content ranged from 3.34 to 11.97 mg/l for Krstač wines and 8.51 to 13.68 mg/l for Žižak wines. Among all wines, Krstač and Žižak wines produced with S. bayanus and Fermaid E addition had the highest concentration of total esters. The yeast nutrients Fermaid E and O emphasized different characteristics of the yeasts. They had a statistically significant effect on the content of ethyl and acetate esters. The highest overall scores were obtained for ICVE and BayE Krstač wines (18.1 out of 20 points) and Žižak ICVE wine (18.2 out of 20 points).

Inoculation of Yarrowia lipolytica promotes the growth of lactic acid bacteria, Debaryomyces udenii and the formation of ethyl esters in sour meat

Yarrowia lipolytica N12 and A13 with high lipase activity obtained by mutagenesis were inoculated into sour meat, and their effects on physicochemical properties, microbial community succession, free amino acids, and volatile compounds of sour meat were investigated. Inoculation fermentation increased the contents of free amino acids observably, rapidly reduced pH, promoted the accumulation of total acids, decreased 2-thiobarbituric acid reactive substances (TBARS) values. In addition, the addition of Y. lipolytica might contribute to the growth of lactic acid bacteria, Candida spp., and Debaryomyces udenii, which play an important role in production of volatile compounds. It was shown that inoculation promoted the production of esters, aldehydes, and alcohols, especially ethyl esters, giving sour meat a better meat flavor. Besides, it was found that Y. lipolytica A13 had better fermenting property. Sample of A13 group had higher contents of ethyl esters, free amino acids and dominant microorganisms. The results may help to provide new strains for sour meat fermentation.

Wine aroma modification by Hanseniaspora uvarum: A multiple-step strategy for screening potential mixed starters

Hanseniaspora uvarum is a prevalent yeast species in vineyards. However, its application in grape wine fermentation remains limited. This study used culture-dependent and -independent approaches to investigate the dynamics of H. uvarum during the spontaneous fermentation of Cabernet Sauvignon grapes. The results revealed that H. uvarum constituted 77.49 % of the non-Saccharomyces yeast population during fermentation. An indigenous strain, QTX-C10, was isolated from the 148 H. uvarum strains using a multistep screening strategy. The 1:1 co-inoculation of QTX-C10 with Saccharomyces cerevisiae proved to be an optimal strategy for mixed fermentation, resulting in a 48.54 %–59.55 % increase in ethyl esters in Cabernet Sauvignon wine and a 96.94 %–110.92 % increase in Chardonnay wine. Furthermore, this approach reduced the acetic acid levels by 12.50 %–17.07 % for Cabernet Sauvignon wine and 10.81 %–17.78 % for Chardonnay wine. Additionally, increased ethyl ester content may enhance the tropical fruit flavor of Cabernet Sauvignon wines.

Identification of volatile organic compounds as markers to detect Monilinia fructicola infection in fresh peaches

Monilinia spp. are among the main fungal pathogen affecting peaches, and they can cause severe pre- and postharvest losses. Development of smart packaging technologies (e.g., volatile indicators), facilitating infection detection and preventing other fruit from being contaminated, is still limited. In this study, we compared for the first time the aroma profile of whole healthy fresh peaches to Monilinia fructicola-artificially inoculated peaches, identifying discriminant volatile organic compounds (VOCs). More than one hundred VOCs were detected by applying head space solid-phase microextraction followed by GC-MS analysis. The level of methyl esters, hydrocarbons, lactones, and acids decreased in infected peaches indicating fruit aroma deterioration, while the concentration of ethyl esters and alcohols increased. In particular, the amount of ethanol and derived ethyl acetate reached a maximum of 24- and 20-fold increase in the infected peaches, respectively. Isobutanol, propyl acetate, and ethyl isovalerate were specifically emitted by M. fructicola-infected peaches. These compounds might serve as markers for the development of smart sensors allowing the detection of fungal infection.

The regulatory effects of microbial community on the formation of higher alcohols and volatile flavor components in Hongqu rice wine brewing

The contents of higher alcohols (HAs) and volatile components produced by microbial metabolism largely determine the drinking comfort and flavor quality of Hongqu rice wine. The purpose of this study was to compare the differences of volatile flavor profile and microbial community in the brewing process of Hongqu rice wines with low and high HAs content (LHA and HHA). The results showed that the main HAs in Hongqu rice wine were isobututyl alcohol, isoamyl alcohol, phenylethyl alcohol, and the total content of HAs in HHA (749.07 ± 20.47 mg/L) was much higher than that in LHA (407.61 ± 20.80 mg/L). Multivariate statistical analysis and visualization showed that the volatile flavor characteristics of HHA and LHA were significantly different, and the contents of ethyl esters, medium- and long-chain fatty acids in HHA were higher than those in LHA. Microbiome analysis based on metagenomic sequencing indicated that fermentation starter has significant effect on the composition of microbial community during Hongqu rice wine brewing. Microbial species such as Cronobacter sakazakii, Weissella paramesenteroides, Klebsiella pneumoniae, Aspergillus niger, Millerozyma farinosa and Rhizopus delemar were significantly enriched in HHA brewing, while Pediococcus pentosaceus, Lactobacillus curvatus, Leuconostoc pseudomesenteroides and Leuconostoc mesenteroides were significantly enriched in LHA brewing. Furthermore, the potential relationships between the key microbial species and characteristic volatile components were revealed through correlation heatmap analysis. Bioinformatical analysis revealed that the abundances of microbial genes encoding enzymes involved in HAs metabolism were higher in HHA than LHA, but the gene abundance of phenylacetaldehyde dehydrogenase in LHA was significantly higher than that in HHA, which could limit the formation of HAs during Hongqu rice wine brewing. Collectively, this study provides important scientific data for enhancing the flavor quality of Hongqu rice wine, and lays a solid foundation for the healthy development of Hongqu rice wine industry.

Non-Saccharomyces Yeast Strains, Aromatic Compounds and Sensory Analysis of Italy and Negra Criolla Pisco from the Moquegua Region of Peru

In this study, we aimed to isolate and phenotypically characterize non-Saccharomyces yeast strains (NSYSs) from the skin of aromatic (Italy) and non-aromatic (Negra Criolla) grapes from vineyards in Moquegua, Peru, typically used for the production of pisco. Our second objective was to characterize the volatile compounds and sensory attributes of pisco made from these grapes. Pichia terricola (56%), Metschnikowia pulcherrima (31%), and Naganishia vaughanmartiniae (13%) were the main NSYSs isolated from the skin of aromatic Italy grapes and identified; meanwhile, Vishniacozyma carnescens (50%), Vishniacozyma heimaeyensis (30%), and Aureobasidium pullulans (20%) were identified on the skin of the non-aromatic Negra Criolla grapes. These NSYSs showed different capacities in terms of carbohydrate fermentation, polygalacturonase activity, ethanol tolerance, sulphite production, and nitrogen consumption. Moreover, the pisco resulting from these varieties of grape had different volatile profiles. Terpene alcohols such as citronellol, geraniol, linalool, and nerol were found in pisco made from Italy grapes, while higher contents of 2-phenylacetate and ethyl esters were found in Negra Criolla Pisco. Intermediate levels of both 1-hexanol and bencyl alcohol were also found in all the pisco. Sensory analysis performed by a trained pisco tasting panel showed that citric, floral, alcohol, and syrup descriptors were more marked in Italy Pisco, while nuts, syrup, alcohol, and floral were the most intense attributes of Negra Criolla Pisco. These results will contribute to determining the potential of indigenous grape yeasts from the Moquegua region as fermentation starters to improve the typical sensory qualities of the pisco produced in this region, which deserves further study.

Sequential fermentation with indigenous non-Saccharomyces yeasts and Saccharomyces cerevisiae for flavor and quality enhancement of Longyan dry white wine

In this study, we investigated the effect of the sequential fermentation of four selected indigenous non-Saccharomyces yeasts (Candida stellimalicola HL-S-5, Rhodotorula mucilaginosa HL-S-8, Hanseniaspora uvarum HL-S-9, and Pichia kluyveri XL-48-6) and Saccharomyces cerevisiae VL2 on the oenological parameters, volatile compositions, organic acids, and sensory characteristics of Longyan dry white wine. Results showed that the ethanol concentration of pure fermentation (11.12 ± 0.04%, v/v) was the highest among all fermentations. Furthermore, the aroma concentrations produced by the fermentation of R. mucilaginosa HL-S-8/VL2 (9929.35 ± 96.87 μg/L) and P. kluyveri XL-48-6/VL2 (9017.67 ± 85.91 μg/L) were significantly higher than that of VL2 (7654.64 ± 397.07 μg/L). In particular, the treatment of R. mucilaginosa HL-S-8/VL2 increased the content of acetic esters (512.11 ± 12.92 μg/L) and fatty acid ethyl esters (6893.64 ± 56.67 μg/L), which enhanced fruity and floral characteristics. The sequential fermentation of R. mucilaginosa HL-S-8/VL2 led to significantly higher organic acid content (3843.32 ± 73.93 mg/L) than the other samples. Moreover, the sequential fermentation of R. mucilaginosa HL-S-8/VL2 wine samples resulted in the highest scores in sensory evaluation. Therefore, the sequential fermentation of R. mucilaginosa HL-S-8/VL2 was an effective way to improve wine flavor and quality. This work will provide a useful reference for improving the flavor and quality of Longyan wine through non-Saccharomyces cerevisiae.

Effect of Different Vinification Techniques on the Concentration of Volatile Aroma Compounds and Sensory Profile of Malvazija Istarska Wines

The majority of chemical compounds that contribute to varietal aroma originate from grape skin. To investigate the differences between volatile aroma compounds when different maceration conditions are applied, a total of six vinification treatments were carried out on Malvazija istarska (Vitis vinifera L.) variety, non-maceration control treatment (C), pre-fermentative two days cryomaceration treatment at 8 °C (CRYO), seven days maceration treatment at 16 °C (M7), 14 days maceration treatment at 16 °C (M14), and prolonged post-fermentative maceration treatments at 16 °C for 21 day (M21) and 42 days (M42). Wines were subjected to GC/MS and sensory analysis. Obtained results showed that prolonged post-fermentative maceration treatments contained the highest concentration of total volatile aroma compounds, precisely monoterpenes, alcohols, and other esters. Contrary, C and CRYO wines resulted in highest concentration of ethyl and acetate esters, and fatty acids. In addition, sensory analysis showed that longer maceration treatment wines (M14, M21, M42) were characterized by more aroma complexity, varietal flowery typicity, pronounced fruitiness, with accentuated dried fruit, moderate honey, and herbal notes. Obtained results can provide valuable information to producers when choosing an appropriate vinification technique based on the desired wine style which may lead to a further diversification of white wine market.