Comparative study of the biochemical changes and volatile compound formations during the production of novel whey-based kefir beverages and traditional milk kefir

Cheese whey (CW) and deproteinised cheese whey (DCW) were investigated for their suitability as novel substrates for the production of kefir-like beverages. Lactose consumption, ethanol production, as well as organic acids and volatile compounds formation, were determined during CW and DCW fermentation by kefir grains and compared with values obtained during the production of traditional milk kefir. The results showed that kefir grains were able to utilise lactose from CW and DCW and produce similar amounts of ethanol (7.8–8.3 g/l), lactic acid (5.0 g/l) and acetic acid (0.7 g/l) to those obtained during milk fermentation. In addition, the concentration of higher alcohols (2-methyl-1-butanol, 3-methyl-1-butanol, 1-hexanol, 2-methyl-1-propanol, and 1-propanol), ester (ethyl acetate) and aldehyde (acetaldehyde) in cheese whey-based kefir and milk kefir beverages were also produced in similar amounts. Cheese whey and deproteinised cheese whey may therefore serve as substrates for the production of kefir-like beverages similar to milk kefir.     

Characterization of major volatile compounds in whey spirits produced by different distillation stages of fermented lactose-supplemented whey

This research aimed to advance the understanding of acceptable sensory qualities of potable whey-based spirit from nonsupplemented, mid-supplemented, and high-supplemented whey samples by analyzing major volatile compounds during different stages of distillation (head, heart, and tail). The results demonstrated that commercial Saccharomyces cerevisiae strain in lactase-hydrolyzed whey showed rapid and complete sugar hydrolysis and efficient ethanol production in 24, 30, and 36 h on average, producing up to 29.5, 42.1, and 56.4 g/L of ethanol, respectively. The variations in titratable acidity, specific gravity, pH value, residual protein, sugar content, and alcohol yield were investigated during the fermentation. The total amount of volatile compound concentrations significantly decreased from the head (2,087–2,549 mg/L) to the tail whey spirits (890–1,407 mg/L). In the whey spirit, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-1-propanol, 1-propanol, acetaldehyde, and ethyl acetate were the most prevalent dominant compounds, accounting for the largest proportion of total volatile compounds. The volatile compounds detected were far below the acceptable legal limit. The results suggest that high sensory qualities of potable whey-based spirits can be produced by fermentation of lactose-supplemented whey with S. cerevisiae cells.     

Effect of the addition of different quantities of amino acids to nitrogen-deficient must on the formation of esters, alcohols, and acids during wine alcoholic fermentation

In this work the effect of the addition of different quantities of amino acids to a nitrogen-deficient must on the formation of volatile compounds during the wine alcoholic fermentation was studied. To do so, fermentations of Mazuelo must were carried out, to which were added ammonium and 45, 120, and 250 mg/l of amino acids. The results showed that the formation of total esters, isoamyl acetate, and 2-phenylethyl acetate was directly proportional to the quantity of amino acids added to the must while the synthesis of diethyl succinate, and ethyl 3-hydroxybutyrate was inversely proportional to this addition. The alcohols, with the exception of tyrosol and 2-phenylethanol, did not show any direct correlation between their formation and the addition of amino acids. The quantity of amino acids added to the must favoured the formation of total acids but it had scant influence on the individual synthesis of the acids. So, it may be stated that, in general, the addition of amino acids in the concentrations under study to a nitrogen-deficient must, favoured the formation of volatile compounds in the wine.     

Effect of dilution rate and nutrients addition on the fermentative capability and synthesis of aromatic compounds of two indigenous strains of Saccharomyces cerevisiae in continuous cultures fed with Agave tequilana juice

Knowledge of physiological behavior of indigenous tequila yeast used in fermentation process is still limited. Yeasts have significant impact on the productivity fermentation process as well as the sensorial characteristics of the alcoholic beverage. For these reasons a better knowledge of the physiological and metabolic features of these yeasts is required. The effects of dilution rate, nitrogen and phosphorus source addition and micro-aeration on growth, fermentation and synthesis of volatile compounds of two native Saccharomyces cerevisiae strains, cultured in continuous fed with Agave tequilana juice were studied. For S1 and S2 strains, maximal concentrations of biomass, ethanol, consumed sugars, alcohols and esters were obtained at 0.04 h⁻¹. Those concentrations quickly decreased as D increased. For S. cerevisiae S1 cultures (at D = 0.08 h⁻¹) supplemented with ammonium phosphate (AP) from 1 to 4 g/L, concentrations of residual sugars decreased from 29.42 to 17.60 g/L and ethanol increased from 29.63 to 40.08 g/L, respectively. The S1 culture supplemented with AP was then micro-aerated from 0 to 0.02 vvm, improving all the kinetics parameters: biomass, ethanol and glycerol concentrations increased from 5.66, 40.08 and 3.11 g/L to 8.04, 45.91 and 4.88 g/L; residual sugars decreased from 17.67 g/L to 4.48 g/L; and rates of productions of biomass and ethanol, and consumption of sugars increased from 0.45, 3.21 and 7.33 g/L·h to 0.64, 3.67 and 8.38 g/L·h, respectively. Concentrations of volatile compounds were also influenced by the micro-aeration rate. Ester and alcohol concentrations were higher, in none aerated and in aerated cultures respectively.     

Enhanced production of isoamyl acetate from beet molasses with addition of fusel oil by Williopsis saturnus var. saturnus

Fusel oil which contains high level of amyl alcohols (approximately 45–55%) is a by-product obtained from the distillation of alcohol made by fermentation of molasses. Williopsis saturnus is a yeast which is able to convert isoamyl alcohol into isoamyl acetate. The aim of this study was to increase the formation of isoamyl acetate by the addition of fusel oil at the ratios of 1%, 2% and 3% (v/v) to molasses based fermentation medium using W. saturnus. It was found out that bioconversion of added fusel oil into isoamyl acetate was possible and an addition of 1% fusel oil led to an increase in isoamyl acetate concentration from 118 to 354 mg/L.     

黑枸杞乳清酒发酵工艺优化及挥发性风味物质分析

采用单因素及正交试验对以乳清粉和黑枸杞为原料的黑枸杞乳清酒发酵工艺进行优化,并利用顶空固相微萃取-气相色谱-质谱联用技术（HS-SPME-GC-MS）分析黑枸杞乳清酒的挥发性风味成分。结果表明,黑枸杞乳清酒最佳发酵工艺为黑枸杞汁∶乳清液1∶3（V/V）、酵母接种量1.1%、发酵温度28 ℃、发酵时间115 h,此条件下所得黑枸杞乳清酒的感官评分为90.2分。在检测到的挥发性风味物质中,以酯类物质为主,占全部挥发性风味物质的72.42%,主要成分是癸酸乙酯和辛酸乙酯,其次是醇类物质,占检出总量的24.76%,主要成分是异戊醇和2-甲基丁醇,其他成分如酸类、醛类、烃类和酚类物质等检出含量很少,总占比只有2.82%。     

静态顶空气质联用法测定霞多丽在酒精发酵过程中香气的变化

运用静态顶空-气相色谱质谱联用法,从霞多丽葡萄汁到酒精发酵结束,每隔12h对其香气成分进行检测。检测得到的香气成分通过质谱谱库进行定性,色谱峰面积归一化法进行定量。测定结果显示:霞多丽在酒精发酵过程中共检测出31中香气物质,其中醇类物质有11种,酯类物质有13种,其他物质(酸、醛、酮)有7种。发酵前后香气成分的种类和相对含量变化显著。其中酯类和醇类物质的种类和相对含量随着发酵的进行有所增加,而其他类(酸、醛、酮)物质的种类和相对含量随着发酵的进行急剧下降。发酵结束后,发酵液的主要香气成分为:乙醇、2-甲基丙醇、3-甲基丁醇、2,3-丁二醇、苯乙醇、正丙醇、己醇、乙酸己酯、辛酸乙酯、壬酸乙酯、2-苯基乙酸乙酯、十二酸乙酯、乙酸乙酯、2-甲基乙酸丙酯、3-甲基乙酸丁酯、己酸乙酯、乙酸。     

Biotransformation of durian pulp by mono- and mixed-cultures of Saccharomyces cerevisiae and Williopsis saturnus

Durian is a seasonal tropical fruit widely grown and highly prized in Southeast Asia. This is a first study to assess the transformation of durian constituents during fermentation with mono- and mixed-cultures of Saccharomyces cerevisiae and Williopsis saturnus with a view to developing a novel alcoholic beverage. A diversity of volatiles was produced especially alcohols and esters, while those volatiles initially present in durian, particularly the character-impact sulphur-containing odorants, were transformed. Most of the sulphur-containing compounds decreased with fermentation. 3-(Ethylthio)-1-propanol was produced initially then remained relatively stable, whereas ethyl thioacetate was formed initially then decreased in all culture types. The kinetic changes and concentrations of volatile compounds were similar in both the mixed-culture and the S. cerevisiae monoculture, except for higher amounts of alcohols in the mixed-culture. The W. saturnus monoculture, on the other hand, was the main producer of acetate esters. Sensory evaluation revealed a strong sulphury note retained in all fermentations but less unfavourable metallic and yeasty notes in the mixed-culture. The study suggests that biotransformation by yeasts can be effective in modifying the constituents and modulating the organoleptic properties of durian.     

Effect of ammonium nitrogen supplementation of grape juice on wine volatiles and non-volatiles composition of the aromatic grape variety Albariño

Vitis vinifera cv. Albariño is an aromatic variety characterised by terpenes present largely as glycosidic flavour precursor compounds, which depends on fermentation to reveal its aromatic varietal potential. Clarified Albariño must containing 250 mg N/L (control) was supplemented with diammonium phosphate to 350 and 450 mg N/L before fermentation with a high-nitrogen-demand wine strain of Saccharomyces cerevisiae (M05). Ammonium supplementation had a significant effect on the chemical composition (titratable acidity and ethanol) and volatile profile of Albariño wines. Varietal compounds in the free fraction (limonene, linalool, α-terpineol, α-ionone and β-damascenone) and bound (limonene, linalool and α-terpineol), as well as most yeast-derived fermentation products (including esters, higher alcohols and volatile acids) were associated with moderate nitrogen concentrations. Free β-ionone, bound geraniol, bound α-ionone, bound β-damascenone and 1-hexanol were associated with high nitrogen concentrations. OAV wines made with moderate nitrogen exhibited a higher total odorant activity, driven by ethyl esters, terpenes and C₁₃-norisoprenoids, resulting in fruity and floral aroma attributes.     

Effect of fusel oil addition on volatile compounds in papaya wine fermented with Williopsis saturnus var. mrakii NCYC 2251

The impact of fusel oil addition on volatile compounds formation in papaya wine fermented with yeast Williopsis saturnus var. mrakii NCYC2251 was studied with a view to enhancing papaya wine aroma production. Time-course papaya juice fermentations were carried out using W. saturnus var. mrakii NCYC2251 with fusel oil added (0, 0.1 and 0.5% v/v). Fermentation characteristics in terms of yeast growth, Brix and pH changes were similar for all fermentations except for those added with 0.5% (v/v) fusel oil. The addition of 0.5% (v/v) fusel oil inhibited yeast growth. A wide range of volatile compounds were produced during fermentation including acids, alcohols, esters and aldehydes with esters being the most abundant volatile compounds produced. The addition of 0.1% (v/v) fusel oil reduced the production of undesirable volatiles such as ethyl acetate and acetic acid, while increasing the desirable volatiles production such as ethanol and acetate esters. This study suggests that papaya juice fermentation with W. saturnus var mrakii NCYC 2251 together with a low concentration of added fusel oil can be another means of modulating papaya wine aroma compound formation.     

Major constituents of fusel oils distilled from Australian grape wines

Fusel oils from Australian grape wines (Vine sp. Vitis vinifera) have been found to consist substantially of ethanol, n-propanol, isobutanol (2-methyl-1-propanol), isoamyl alcohol (3-methyl-1-butanol) and active amyl alcohol (2-methyl-1-butanol). In addition there are present large numbers of aliphatic esters, believed to be of considerable importance to grape brandy and spirit flavour and quality. The quantities and occurrence of these esters have been found to follow a systematic pattern. The major esterified alcohols are related to the free alcohols present and the major esterified acids occur as a series of acids of even carbon number with a maximum concentration at the n-decanoic acid. These relationships provide a basis for calculating the approximate ester composition of fusel oil.     

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.     

Pre-fermentative replacement of sulphur dioxide by lysozyme and oenological tannins: Effect on the formation and evolution of volatile compounds during the bottle storage of white wines

In this work, the effects on the volatile profile of the pre-fermentative substitution of SO₂ with lysozyme and oenological tannins were studied in white wines. At the same time, in order to understand the changes of volatile compounds in SO₂-free wines, the evolution of volatiles was evaluated over 1 year of storage in bottles. For this purpose, a number of laboratory scale fermentations of SauvignonBlanc musts were carried out and the effects of three variables (SO₂, lysozyme and oenological tannins) were investigated by means of GC–MS analysis. Results showed that the replacement of SO₂ with lysozyme and oenological tannins influenced the volatile composition of wines at the end of the alcoholic fermentation. Wines fermented with SO₂ showed higher total alcohol amounts, while the presence of oenological tannins augmented the level of esters. The presence of SO₂ influenced also the alcohols and esters profiles of wines during bottle storage. Moreover, the presence of oenological tannins displayed a positive role in maintaining the amounts of esters over certain levels in wine stored for 1 year, likely due to their oxygen scavenging ability. By contrast, acids were less affected by the investigated adjuvants both at the end of the alcoholic fermentation and during the storage time.     

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.     

不同浓度SO2处理对低度番茄酒中挥发性物质的影响

以发酵前添加0×10-6、10×10-6、20×10-6SO2所生产的低度番茄酒为样品,采用气相色谱-质谱联用技术直接进样,分析番茄酒中的挥发性成分,研究添加不同浓度SO2对低度番茄酒中挥发性成分的影响。结果表明番茄酒中主要的挥发性成分为酯类香气物质、挥发酸和醇,主要包括3-甲基-1-丁醇、辛酸、己酸、乙酸-3-甲基丁酯、乙酸乙酯、苯乙醇、己酸乙酯、辛酸乙酯、异丁醇、乙酸-3-己烯酯、1-己醇、乙酸苯乙酯、乙酸酐、丁酸乙酯等。这3份不同浓度SO2发酵处理的酒样分别检测出49、55、54种挥发性成分,各占总峰面积的94.87%、96.18%、97.41%,相对含量存在明显差异。感官评价的结果表明以发酵前添加10×10-6SO2处理的番茄酒香气和口感品质最佳。     

Production of an Alcoholic Beverage by Fermentation of Whey Permeate with Kluyveromyces fragilis II: Aroma Composition

Whey permeate was used for an alcoholic fermentation with Kluyveromyces fragilis (CECT 1123). The aim of the present study was the production of an alcoholic beverage of low alcoholic proof with acceptable concentrations of fusel alcohols. The effects of temperature and agitation on the concentration of volatile compounds was assayed in batch cultures. In addition, the production of acetaldehyde, ethyl acetate and fusel alcohols was studied in continuous culture because of interest in a continuous industrial process. Final concentrations of fusel alcohol were slightly lower at higher temperatures, while the specific production rate increased with temperature. Concentrations were suitable, in all cases, for a beverage. When agitation was assayed, an important increase in fusel alcohol concentrations was found at higher agitations. In continuous culture, the acetaldehyde, ethyl acetate and fusel alcohol concentrations were normal for an alcoholic beverage.     

Identification of volatile organic compounds extracted by headspace solid‐phase microextraction in specialty beers produced in Brazil

Beer is a very complex mixture, being an alcoholic beverage obtained by fermentation processes. The consumption and production of specialty beers in Brazil have increased in the past years; however, most Brazilian brewers still depend on imported commercial starter yeast strains and raw materials. Our data also indicate that volatile profile of Brazilian beers is more influenced by raw materials. The analysis of volatile compounds in beer is important for its quality control, and the presence of aromatic substances is related to the beverage acceptance and quality. In this study, headspace solid phase microextraction in combination with gas chromatography coupled to mass spectrometric detection was used for the identification of the volatile organic compounds in 30 samples of Brazilian Pilsen and ale beers. Ninety‐nine volatile compounds were identified and grouped into ketones, terpenes, esters, higher alcohols, aldehydes, fatty acids, hydrocarbon and other minority compounds. Analysis of the principal components showed that the majority of specialty beers have similar chemical characteristics, their volatile profile being characterized mainly by esters and higher alcohols. Additional studies are necessary to better characterize Brazilian specialty beers; however, our results open perspectives for future research of possible indicators and markers that may serve for the purposes of certification, as well as quality control of the beverage. Copyright © 2017 The Institute of Brewing & Distilling     

Assessment of the aroma profiles of low-alcohol beers using HS-SPME–GC-MS

The volatile profile of low-alcohol and alcohol-free beers was compared with that of alcoholic ones. Qualitative and quantitative differences were analyzed by headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME–GC-MS). Fermentation compounds as esters (isoamyl acetate, ethyl hexanoate, ethyl octanoate), alcohols (1-octanol, decanol, isobutanol, isoamyl alcohol) and fatty acids (hexanoic and octanoic acid) were present in higher quantities in alcoholic beers. The low-alcohol beers were characterized by compounds derived from malt and the roasting process, including pyrazines and furanes, and volatile compounds such as linalool, β-humulene and α-terpineol derived from the essential oil of hops. Benzaldehyde, acetylpyrrole, furfural and 2-furanmethanol were characteristics of free-alcohol beers.     

High-cell-density fermentation of Saccharomyces cerevisiae for the optimisation of mead production

Mead is a traditional drink that contains 8%–18% (v/v) of ethanol, resulting from the alcoholic fermentation of diluted honey by yeasts. Mead fermentation is a time-consuming process and the quality of the final product is highly variable. Therefore, the present investigation had two main objectives: first, to determine the adequate inoculum size of two commercial wine-making strains of Saccharomyces cerevisiae for the optimisation of mead fermentation; and second, to determine if an increase in yeast pitching rates in batch fermentations altered the resulting aroma profiles. Minor differences were detected in the growth kinetics between the two strains at the lowest pitching rate. With increasing pitching rates net growth of the strain ICV D47 progressively decreased, whereas for the QA23 the increasing inoculum size had no influence on its net growth. The time required to reach the same stage of fermentation ranged from 24 to 96 h depending on the inoculum size. The final aroma composition was dependent on the yeast strain and inoculum size. Fourteen of the twenty-seven volatile compounds quantified could contribute to mead aroma and flavour because their concentrations rose above their respective thresholds. The formation of these compounds was particularly pronounced at low pitching rates, except in mead fermented by strain ICV D47, at 10⁶ CFUs/mL. The esters isoamyl acetate, ethyl octanoate and ethyl hexanoate were the major powerful odourants found in the meads. The results obtained in this study demonstrate that yeast strain and inoculum size can favourably impact mead's flavour and aroma profiles.