Contribution of Lactobacillus plantarum and Leuconostoc mesenteroides subsp. mesenteroides to Atypical Odors of Beef Strip Loins

Sterile beef strip loin tissue was inoculated with Lactobacillus plantarum or Leuconostoc mesenteroides subsp. mesenteroides, placed in sterile sample bottles which were purged with CO₂, and stored up to 28 days at 3°C. Volatile compounds detected in the headspace of these samples included acetone, toluene, acetic acid, ethyl acetate, a C₇ hydrocarbon, and trichloromethane. The profile of volatiles in packaged sterile loin tissue stored for up to 28 days was similar. However, the inoculated samples spoiled (soured) at a faster rate.     

Influence of a malolactic starter on the quality of the cider produced on an industrial scale

The application of starter culture technologies to induce the malolactic fermentation in cidermaking are not yet established, as is already the case in winemaking. In this work, a selected indigenous cider malolactic strain was tested as a starter culture to assess its implementation and its influence on cider production on an industrial scale (10,000 l). The results showed that the culture, under the fermentation conditions tested, allowed successful achievement of the malolactic fermentation. Analysis of L-malic acid in the fermenting apple must medium revealed a highly significant difference in the rate of consumption of this acid from the moment of bacterial inoculation when compared with that of the control. The concentration of the malolactic starter culture maintained the inoculation level (10⁶ cfu/ml) during the process, the level necessary to ensure the malolactic fermentation. Thus, the cider malolactic starter culture showed good adaptation to the harsh environmental conditions found in the fermenting apple must, such as low temperature and the presence of SO₂ and ethanol. Several parameters were monitored during the process (specific gravity, temperature, pH, free SO₂ content, microbiological count, malic acid degradation rate, lactic acid formation, other major organic acids and volatile compounds) under inoculated and not inoculated conditions.     

Antioxidant enzyme activities in strawberry fruit exposed to high carbon dioxide atmospheres during cold storage

The effects of storage, in air or a 20% CO₂ in air (16.8% O₂) atmosphere for 12 d at 2 °C, on antioxidant enzymes of strawberry fruit (Fragaria x ananassa Duch. cv. ‘Jewel’) were investigated. The concentrations of acetaldehyde, ethanol and ethyl acetate associated with fermentation were measured, and the activities of peroxidase (POX), catalase (CAT) and superoxide dismutase (SOD) assayed. Ethanol, acetaldehyde and ethyl acetate concentrations increased in CO₂-treated fruit within a day of treatment, but more extensively after four days, while concentrations remained low in air-stored fruit. The total protein content extracted was not affected by CO₂ or storage time. Activities of POX were similar in air- and CO₂-treated fruit, with an increase occurring only in air-treated fruit on day-12. Neither CAT nor SOD activities were affected by CO₂ treatment. In summary, a 20% CO₂ storage treatment induced fermentation but did not significantly affect total antioxidant enzyme activities.     

Effect of added sulphur dioxide levels on the fermentation characteristics of strawberry wine

The aim of this study to evaluate the effects of sulphur dioxide (SO₂) on strawberry wine fermentation and on the quality of the final wine product. Major aroma compounds, reducing sugars, ethanol, titratable acid and microflora were analyzed during the fermentation of strawberry wine supplemented with 0–100 mg/L SO₂. As the amount of added SO₂ increased, the consumption of reducing sugars and soluble solids and ethanol production decreased during early fermentation, but increased during late fermentation. During the fermentation process, the concentrations of 2‐phenethanol, isobutanol and isopentanol significantly increased and those of n‐propanol, isoamyl acetate and ethyl lactate decreased with increasing amount of added SO₂. The production of n‐butanol, ethyl acetate and ethyl butyrate was slightly dependent on the amount of added SO₂. Yeast cells were the dominant microbe in the fermenting strawberry pulp, and indigenous bacteria and fungi populations decreased rapidly or disappeared because of their sensitivity to SO₂. It was concluded that 60–80 mg/L SO₂ should be added during strawberry wine fermentations to improve wine quality. Copyright © 2016 The Institute of Brewing & Distilling     

A Dynamic Analysis of Higher Alcohol and Ester Release During Winemaking Fermentations

Isobutanol, isoamyl acetate and ethyl hexanoate production during winemaking fermentations was precisely described. Volatile compound concentrations and their rates of change and losses in the exhausted gas were determined throughout the fermentation. Negligible amounts of isobutanol were lost, whatever the fermentation temperature. In contrast, 56 % of the ethyl hexanoate and 34 % of the isoamyl acetate were stripped by CO₂ when the temperature profile simulated red winemaking conditions. Even at a moderate temperature of 20 °C, typical of white wine fermentations, 40 % of the ethyl hexanoate and 21 % of the isoamyl acetate were lost. The effect of temperature on the production of the volatile compounds was assessed by running fermentations at different temperatures, with the same medium and strain. By taking into account the volatile compound losses in the exhausted gas, changes in volatile compound production were found to be smaller than those usually calculated from the concentrations in the wine. These findings highlight the potential importance of knowledge concerning aroma gas–liquid balances for both an understanding of yeast metabolism and the identification of innovative control strategies minimizing aroma losses.     

Volatile Compounds on Sterile Pork Loin Tissue Inoculated with Lactobacillus plantarum and Lactobacillus fermentum

Sterile pork loin tissue was inoculated with Lactobacillus plantarum 1 and Lactobacillus fermentum, placed in sterile sample bottles, purged with CO₂, and stored for up to 24 days at 3°C. L. plantarum grew more rapidly than L. fermentum under these conditions. Among the 15 compounds identified in the headspace of sterile and inoculated pork loin tissue were acetone, sulfur dioxide, dichloroethane, trichloromethane, benzene and toluene. Profiles of volatile compounds were similar for inoculated and sterile pork loin tissue.     

应用HS-SPME技术测定固态发酵浓香型酒醅微量成分

HS-SPME的方法是检测酒醅中微量风味物质的一种好的方法。该法简单、方便、快速。样品不需要进行预处理。检测成分完全可以用于浓香型固态发酵酒醅的发酵过程分析。从浓香型固态发酵酒醅中共检测出106种挥发性化合物,其中醇类9种,醛类6种,酮类2种,酸类10种,酯类47种,芳香族化合物12种,硫化物3种,呋喃类化合物4种,酚类化合物8种,以及其它化合物5种。重要的挥发性化合物是己酸乙酯、己酸、辛酸乙酯、丁酸、乙酸乙酯、乳酸乙酯和丁酸乙酯。     

Elevated carbon dioxide affects fruit flavor in field‐grown strawberries (Fragaria × ananassa Duch)

The effect of elevated carbon dioxide on fruit quality and aroma volatile composition in field‐grown strawberries (Fragaria × ananassa Duch) was studied. Elevating the ambient CO₂ concentration (ambient + 300, and ambient +600 µmol mol^?1 CO₂) resulted in high fruit dry matter, fructose, glucose and total sugar contents and low citric and malic acid contents. High CO₂ growing conditions significantly enhanced the fruit content of ethyl hexanoate, ethyl butanoate, methyl hexanoate, methyl butanonate, hexyl acetate, hexyl hexanoate, furaneol, linalool and methyl octanoate. Thus, the total amounts of these compounds were higher in berries grown in CO₂‐enriched conditions than those grown in ambient conditions. The highest CO₂ enrichment (600 µmol mol^?1) condition yielded fruit with the highest levels of these aroma compounds. Copyright © 2004 Society of Chemical Industry     

Volatile compounds in dry-cured Serrano ham subjected to high pressure processing. Effect of the packaging material

The effect of high pressure treatment (400 MPa, 10 min at 12 °C) on the volatile profile of Spanish dry-cured Serrano ham, packaged with or without aluminum foil in a multilayer polymeric bag, was investigated. The analysis of the volatile fraction was carried out by dynamic headspace extraction coupled to gas chromatography–mass spectrometry. Pressure treatment only had a slight effect on the volatile fraction of Serrano ham. Most compounds affected by pressurization, such as alkanes (C₉–C₁₂), 2-undecene, 2-nonanone, 1-octen-3-one, 1-heptanol, 2-hexanol, 2-heptanol, ethyl pentanoate, benzaldehyde and styrene, presumably originated from the metabolism of moulds. A significant effect of pressurization on the migration of compounds from the plastic material was found. Linear and branched chain alkanes, alkenes as well as benzene compounds, were generally less abundant in pressurized samples than in untreated samples. A scalping effect was also observed for compounds such as butanal, pentanal, ethyl esters and pyrazines.     

SYNTHESIS OF AROMA COMPOUNDS BY WORT ENTEROBACTERIA DURING THE FIRST STAGE OF LAMBIC FERMENTATION

Lambic is a special type of Belgian beer obtained by a spontaneous fermentation. The fermentation is initiated by a growth of enterobacteria and non-maltose fermenting yeasts. These organisms die off after one to two months. To gain a clear insight in the relations between the enterobacteria and the aroma compounds formed in wort during this first period, several bacterial isolates were studied with respect to their metabolites formed in a synthetic medium and in two different lambic worts, using aerobic or semi-anaerobic conditions. The results showed that enterobacteria, especially Enterobacter species, are responsible for the production of 2, 3-butanediol, acetic, lactic and succinic acid and lower amounts of ethyl acetate and higher alcohols which are the main aroma compounds found in 1 to 2 months old lambic. Ethanol production is mainly due to yeast activity. The results are in agreement with previous determinations of entero-bacterial species present in first phase lambic¹⁸ .     

Effect of sulphur dioxide concentration added at different processing stages on volatile composition of ciders

This study evaluated the effect of sulphur dioxide (SO₂) added at different steps in the process on the volatile composition contributing to the fruity aroma of cider. Potassium metabisulphite was added (150 and 300 mg/L) at three processing steps (a) crushed apple, (b) apple must and (c) final product. The SO₂ added to the crushed apple either maintained or increased the fermentation rate, whereas the addition to the apple must slowed the fermentation rate. The addition of 300 mg/L of potassium metabisulphite to Golden Delicious apple must inhibited fermentation. The losses of volatile compounds varied from 23 to 46% and from 33 to 97% in all of the treatments with 150 and 300 mg/L of potassium metabisulphite, respectively. 3‐Methyl‐1‐butanol, acetaldehyde and ethyl ethanoate corresponded to >85% of the volatile compounds in the cider; 3‐methyl‐1‐butanol was not affected by the sulphur dioxide. Acetaldehyde showed the greatest reduction (>80%) with the addition of sulphur dioxide and ethyl ethanoate was reduced when the compound was added to the crushed apple and apple must. All of the interactions between the apple variety, the stage of SO₂ addition and the concentration of SO₂ showed significant negative impact on volatile compounds. © 2018 The Institute of Brewing & Distilling     

Contribution of wild yeasts to the formation of volatile compounds in inoculated wine fermentations

The aim of this work was to study the contribution of wild yeasts to the volatile composition of wine in inoculated fermentations. To do so, Parellada must, sterilized and inoculated with Saccharomyces cerevisiae strain Na33 (pure inoculated fermentation), inoculated Parellada must (mixed inoculated fermentation) and Parellada must that fermented with its wild yeasts (control fermentation) were used. From the results obtained in the pure inoculated fermentation it can be seen that S. cerevisiae produced appreciable quantities of isoamyl acetate, ethyl hexanoate, ethyl octanoate, and ethyl decanoate. However, the wild yeasts also contributed to the synthesis of esters since the total concentration of these substances was higher in the mixed inoculated fermentation than in the pure inoculated fermentation. 2-Phenylethyl acetate was only synthesized by wild yeasts when they did not compete with S. cerevisiae. The concentration of total alcohols was similar in the three samples; the important production of isobutanol and 2-phenylethanol in the control fermentation is noteworthy. As regards the acids, the greatest concentration corresponded to the mixed inoculated fermentation. The wild yeasts contributed to the synthesis of these compounds to a significant extent and S. cerevisiae synthesized appreciable amounts of short-chain fatty acids.     

EFFECT OF DIFFERENT CA CONDITIONS ON AROMA AND QUALITY OF GOLDEN DELICIOUS APPLES

“Golden Delicious” apples were cold stored in semicommercial chambers in normal atmosphere and in different controlled atmospheres (CA) in which oxygen and carbon dioxide were held at 1%, 2% and 3% for three, five and seven months. Following storage, fruit was kept at 20C for 1, 5, and 10 days, after which volatile emission was collected and analyzed. The highest emission of volatile components was obtained after 5 months storage, in which the low CA conditions (2% O₂/CO₂) gave the highest aromatic production. Esters were the main compounds released during ripening at 20C after cold storage in all conditions. Ethyl 2-methyl butyrate, ethyl butyrate, hexyl acetate and ethyl hexanoate were the compounds that contributed most to the overall aroma of “Golden Delicious”.     

Solid-phase microextraction for headspace analysis of key volatile compounds in orange beverage emulsion

Headspace solid-phase microextraction (HS-SPME) gas chromatography was used to analyze target flavor compounds in orange beverage emulsion. The effects of SPME fiber (PDMS 100 μm, CAR/PDMS 75 μm, PDMS/DVB 65 μm and DVB/CAR/PDMS 50/30 μm), adsorption temperature (25–45 °C), adsorption time (5–25 min), sample concentration (1–100%), sample amount (5–12.5 g), pH (2.5–9.5), salt type (K₂CO₃, Na₂CO₃, NaCl and Na₂SO₄), salt amounts (0–30%) and stirring mode were studied to develop HS-SPME condition for obtaining the highest extraction efficiency and aroma recovery. For the head space volatile extraction, the optimum conditions were: CAR/PDMS fiber, adsorption at 45 °C for 15 min, 5 g of diluted beverage emulsion (1:100), 15% (w/w) of NaCl with stirring and original pH 4. The main volatile flavor compounds were: limonene, 94.9%; myrcene, 1.2%; ethyl butyrate, 1.1%; γ-terpinene, 0.41%; linalool, 0.36%; 3-carene, 0.16%; decanal, 0.12%; ethyl acetate, 0.1%; 1-octanol, 0.06%; geranial, 0.05%; β-pinene, 0.04%; octanal, 0.03%; α-pinene, 0.03%; and neral, 0.03%. The linearity was very good in the considered concentration ranges (R² ? 0.97). Average recoveries ranged from 88.3% to 121.7% and showed good accuracy for the proposed analytical method. Average relative standard deviation (RSD) for five replicate analyses was found to be less than 14%. The limit of detection (LOD) ranged from 0.06 to 2.27 mg/l for all volatile flavor compounds and confirmed the feasibility of the HS-SPME technique for headspace analysis of orange beverage emulsion. The method was successfully applied for headspace analysis of five commercial orange beverage emulsions.     

气质联用分析青梅发酵酒和浸泡酒的香气成分

采用气相色谱-质谱联用对青梅发酵酒和浸泡酒的香气成分进行分析，鉴定出青梅发酵酒中的64个香气成分，除苯甲醇（8．119％）外，其他主要成分均由酵母发酵产生。青梅酒中还有4-羟基苯乙醇、4-羟基丁酸乙酯。从青梅浸泡酒中鉴定出48种挥发性化合物，其中以棕榈酸乙酯（14．493％）、亚油酸乙酯（11．652％）、油酸乙酯（9．244％）等高级脂肪酸酯、笨甲醛（10．870％）等成分为主。青梅的典型香气成分苯甲醛含量较高。     

Fermentative capacity of Kluyveromyces marxianus and Saccharomyces cerevisiae after oxidative stress

Volatile compound production during alcoholic fermentation has been studied in the production of many beverages. Temperature, yeast strain, nutrients and pH have been identified as important factors in the production of volatile compounds. In addition, other factors could influence this production during the fermentation process as well. Oxidative stress could occur during yeast biomass production because oxygen is an essential nutrient that is added to the growth medium. The fermentation parameters and the volatile compound production of one Saccharomyces cerevisiae strain (MC4) and two Kluyveromyces marxianus strains (OFF1 and SLP1) were evaluated in relation to fermentation parameters after oxidative stress induced by hydrogen peroxide or menadione. These yeasts were compared with S. cerevisiae W303–1A and showed significant differences in ethanol production, ethanol yield and maximum ethanol production rate. K. marxianus (OFF1) showed better fermentative capacity after oxidative stress. The higher alcohol production decreased after oxidative stress by >35% after 72 h fermentation time, and the amyl alcohol decreased at a higher level (>60%); however, the isobutanol production increased after oxidative stress between 1.5 and 4 times. The yeasts produced significant concentrations of esters however ethyl lactate, ethyl caprylate and the ethyl caproate were not detected in the control fermentation, while in the stress fermentation they accounted for up to 3 mg/L. These results demonstrate that oxidative stress can play an important role in the final aroma profile; but it is necessary to guarantee adequate yeast growth to obtain the volatile compounds desired. Copyright © 2017 The Institute of Brewing & Distilling     

Monitoring of chemical parameters of oxygen-treated musts during alcoholic fermentation and subsequent bottle storage of the resulting wines

The effect of hyper-oxygenation of Airén white wines on color characteristics, phenolic composition, and volatile profile has been evaluated in different processing steps, not previously reported in conjunction: musts, musts during the alcoholic fermentation, resulting young wines and after 1 year of bottle storage. Hyper-oxygenation treatment achieved a positive effect on color stabilization by means of significantly lower contents of most important phenolic compound families (hydroxycinnamic acid derivatives, benzoic acids, flavonols, and flavan-3-ols) in oxygen-treated musts in fermentation, young wines, and one-year-stored white wines. Therefore, browning was avoided in wines elaborated from hyper-oxygenated musts and their values of a* (green–red component of color) were maintained, in contrast to what occurred in control wines. With regard to volatile profile, the concentration of the majority of individual volatile compounds was significantly higher in wines derived from hyper-oxygenated musts, even after 1 year of bottle storage, especially those derived from alcoholic fermentation (alcohols: 2-methyl-1-butanol and 3-methyl-1-butanol, polar esters: ethyl lactate and ethyl glutarate, C₆ alcohols: 3-methyl-1-pentanol, and acetates: 2-phenylethyl acetate). This study enhances knowledge regarding the effects of hyper-oxygenation process during and after alcoholic fermentation and 1 year of bottle aging, especially as there is scarce literature available on the subject.     

Fermentative behavior of Saccharomyces strains during microvinification of raspberry juice (Rubus idaeus L.)

Sixteen different strains of Saccharomyces cerevisiae and Saccharomyces bayanus were evaluated in the production of raspberry fruit wine. Raspberry juice sugar concentrations were adjusted to 16°Brix with a sucrose solution, and batch fermentations were performed at 22 °C. Various kinetic parameters, such as the conversion factors of the substrates into ethanol (Y_p/s), biomass (Y_x/s), glycerol (Y_g/s) and acetic acid (Y_ac/s), the volumetric productivity of ethanol (Q_p), the biomass productivity (P_x), and the fermentation efficiency (E_f) were calculated. Volatile compounds (alcohols, ethyl esters, acetates of higher alcohols and volatile fatty acids) were determined by gas chromatography (GC-FID). The highest values for the E_f, Y_p/s, Y_g/s, and Y_x/s parameters were obtained when strains commonly used in the fuel ethanol industry (S. cerevisiae PE-2, BG, SA, CAT-1, and VR-1) were used to ferment raspberry juice. S. cerevisiae strain UFLA FW 15, isolated from fruit, displayed similar results. Twenty-one volatile compounds were identified in raspberry wines. The highest concentrations of total volatile compounds were found in wines produced with S. cerevisiae strains UFLA FW 15 (87,435 μg/L), CAT-1 (80,317.01 μg/L), VR-1 (67,573.99 μg/L) and S. bayanus CBS 1505 (71,660.32 μg/L). The highest concentrations of ethyl esters were 454.33 μg/L, 440.33 μg/L and 438 μg/L for S. cerevisiae strains UFLA FW 15, VR-1 and BG, respectively. Similar to concentrations of ethyl esters, the highest concentrations of acetates (1927.67 μg/L) and higher alcohols (83,996.33 μg/L) were produced in raspberry wine from S. cerevisiae UFLA FW 15. The maximum concentration of volatile fatty acids was found in raspberry wine produced by S. cerevisiae strain VR-1. We conclude that S. cerevisiae strain UFLA FW 15 fermented raspberry juice and produced a fruit wine with low concentrations of acids and high concentrations of acetates, higher alcohols and ethyl esters.     

Characterisation of volatile compounds in Maotai flavour liquor during fermentation and distillation

Volatile constituents in raw liquor and zaopei during fermentation and distillation were investigated by gas chromatography. Zaopei (steamed grains mixed with Daqu [FG1], stacking fermented grains [FG2], anaerobic fermented grains [FG3] and steamed grains [FG4]) presented changes in physicochemical properties. In all, 72 volatile compounds were identified in zaopei and raw liquor with similarity across 12 zaopei preparations. Principal component analysis and partial least squares discriminant analysis differentiated FG3 from other samples based on content of aroma compounds. FG3 had the highest level of aroma compounds, which increased from the fourth to sixth batches, and was characterised by the presence of 1, 2‐propanediol, acetic acid and linoleic acid, while the others were portrayed by phenylpropionate, ethyl laurate and 4‐ethyl guaiacol. The volatile compounds of raw liquor were dominated by ethyl acetate and ethyl lactate. Correlation analysis illustrated a lack of correlation of volatile compound content between the raw liquors and the zaopei distillation variants. © 2019 The Institute of Brewing & Distilling     

Intracellular gas bubbles deform organelles in fermenting brewing yeasts

We reported previously the presence of large numbers of gas bubbles inside fermenting brewing yeasts. Here we report that these bubbles deform organelles. The mechanical effects on metabolism and coding functions of yeasts, when organelles including the nucleus are deformed and severely contorted, should now be addressed. The implications of this finding on practical brewing conditions require consideration during optimization of fermentation parameters to prevent CO₂ toxicity effects on fermentation performance and flavour formation. Copyright © 2013 The Institute of Brewing & Distilling