Influence of yeast strain on binding of sulphur dioxide in wines,and on its formation during fermentation

The amounts of sulphur dioxide bound by acetaldehyde, pyruvic acid and α-ketoglutaric acid during fermentation of three grape juices by eight wine yeasts (Saccharomyces sp.) are reported. These constituents accounted for 49–83 % (mean 69) of the measured bound SO₂, depending on the yeast strain and juice. the maximum range of concentrations of the binding components for individual wines were 10–48 ppm for acetaldehyde, 9–77 ppm for pyruvic acid and 5–63 ppm for α-ketoglutaric acid, depending on yeast strain and grape juice. the validity of the calculations was verified by an experiment with SO₂ and the three binding compounds in a multicomponent model system. The acetaldehyde content was related to the total SO₂ present, which itself was determined by the strain of yeast. SOz bound in the wines after a further SO₂ addition was correlated significantly with pyruvic and α-ketoglutaric acids, but not with acetaldehyde. Certain yeasts produced SO₂ during fermentation in grape juice and in synthetic media with defined sulphur sources. More SO₂ was produced at pH 3.6 than 3.0 in the absence of added sulphate in grape juice. Sulphate was the best sulphur source for SO₂ production in synthetic media, although some yeasts were able to produce smaller amounts of SO₂ from l-cysteine and reduced glutathione.     

Formation of α-ketoglutaric acid by wine yeasts and its oenological significance

α-Ketoglutaric acid was measured enzymically in wines made in the laboratory from three grape varieties by pure cultures of 12 wine yeasts of the genus Saccharomyces. The results were confirmed with the same juices and 4 yeasts on pilot-plant scale in replicated 30 gallon lots. Mean values for the 12 yeasts ranged from 9 to 117 ppm (overall mean 53). In any one juice the yeasts differed by at least 10-fold in the amounts produced, and certain yeasts produced consistently high or low yields in all juices. The amounts of α-ketoglutaric acid produced depended somewhat on the grape juices used, even though these had comparable pH values, and a significant yeast-juice interaction occurred. The amount of α-ketoglutaric acid formed during fermentation at 15° was 60 per cent of that formed at 25°, and over twice as much was formed at pH 4.2 as at pH 3.0, using four yeast strains. Formation of α-ketoglutaric and pyruvic acids were not significantly correlated. The α-ketoglutaric acid content of 18 white table wines made under comparable conditions on pilot-plant scale from different grape varieties using the same yeast strain ranged from 38 to 152 ppm (mean 90). The significance of the results is discussed, particularly in relation to the binding of sulphur dioxide in wine, and recommendations are given on how to make wines which are low in α-ketoglutaric acid. Formation of α-ketoglutaric acid by three yeasts in a chemically defined medium was lower with increased amounts of nitrogen as ammonium sulphate and higher in the presence of L-glutamic acid, both being used separately as sole nitrogen sources. These findings are discussed in relation to the rǒle of α-ketoglutaric acid in nitrogen metabolism of yeasts.     

The influence of pre‐fermentative practices on the dominance of inoculated yeast starter under industrial conditions

The influence of pre‐fermentative practices on the growth dynamics of a ‘natural’ starter culture with specific phenotype (H₂S^?) concurrently with wild yeast populations was evaluated under winery conditions. Different clarification procedures and added SO₂ strongly influenced species and cell numbers isolable at the pre‐fermentation stage. Independent treatments of must with sulphite addition or vacuum‐filtering clarification caused a 30‐fold reduction in viable cells. Clarification procedures, enhanced by the selective effect of SO₂ addition, induced the appearance of Saccharomyces cerevisiae ‘wild’ yeasts. Correct application of the inoculum generally guarantees the dominance of fermentation by starter cultures. However, inoculated fermentations using unclarified white and red musts exhibited a consistent presence and persistence of non‐Saccharomyces and/or Saccharomyces ‘wild’ yeasts during fermentation. The extent and composition of the initial wild microflora at the start of fermentation may affect the presence and persistence of wild Saccharomyces and non‐Saccharomyces yeasts during guided fermentations under commercial conditions. The above findings confirm the results of previous works carried out at laboratory‐ or pilot‐scale level. Furthermore, they suggest a clear correlation between the modality of pre‐fermentative practices and the presence and persistence of ‘wild’ yeasts during fermentation. © 2002 Society of Chemical Industry     

Fermentation of sulphite-free white musts with added lysozyme and oenological tannins: Nitrogen consumption and biogenic amines composition of final wines

The influence on amino acid consumption and biogenic amines composition of white wines obtained by replacing SO₂ during fermentation with lysozyme and tannins was studied. At the same time, the fermentative performance of two low SO₂ producing selected yeasts strains was evaluated. For this purpose, a series of laboratory-scale fermentations of fresh white must and a HPLC-DAD method for the analysis of amino acids, biogenic amines and ammonium ion were undertaken. The presence of SO₂ or lysozyme affected the consumption of nitrogen as a function of the yeast strain, while oenological tannin had no substantial influence. Strain 1042 increased the consumption of total YAN in the presence of SO₂, as a consequence of the enhanced utilization of ammonium ion and a number of amino acids. By contrast, strain 333 tended not to change the total YAN uptake, whatever the juice treatment, and reduced the consumption of aspartic and glutamic acids, GABA and other compounds in the case of samples added with SO₂. When compared with lysozyme addition, for both strains, SO₂ increased the consumption of alanine and glutamine, the latter being a major contributor to the assimilable nitrogen of the must. No influence of must treatments was found on the content of biogenic amines in the final wines.     

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     

Physiological features of Schizosaccharomyces pombe of interest in making of white wines

This work studies the physiology of Schizosaccharomyces pombe strain 938 in the production of white wine with high malic acid levels as the sole fermentative yeast, as well as in mixed and sequential fermentations with Saccharomyces cerevisiae Cru Blanc. The induction of controlled maloalcoholic fermentation through the use of Schizosaccharomyces spp. is now being viewed with much interest. The acetic, malic and pyruvic acid concentrations, relative density and pH of the musts were measured over the entire fermentation period. In all fermentations in which Schizo. pombe 938 was involved, nearly all the malic acid was consumed and moderate acetic concentrations produced. The urea content and alcohol level of these wines were notably lower than in those made with Sacch. cerevisiae Cru Blanc alone. The pyruvic acid concentration was significantly higher in Schizo. pombe fermentations. The sensorial properties of the different final wines varied widely.     

Influence of addition of ammonium and different amino acid concentrations on nitrogen metabolism in spontaneous must fermentation

The effect of the addition of different amino acid concentrations in must on yeast nitrogen metabolism during alcoholic fermentation was studied. To do this, fermentations of Mazuelo must, poor in nitrogen compounds, were carried out. Ammonium and different concentrations of amino acids (0, 45, 120, 250 and 450 mg/l) were added to the must. Addition of 45, 120 and 250 mg/l of proteic amino acids to the must increased the rate of fermentation. Proline was mainly consumed in fermentations with smaller amounts of amino nitrogen and, at the same time, this amino acid showed the highest residual concentration in the final wines. The consumption of other proteic amino acids was directly proportional to their concentration in the musts, with the exception of leucine and isoleucine that were synthesized. However, a difference in the percentages of the amino acids consumed by the yeasts was observed. The percentages of aspartic acid, alanine and arginine consumed were higher in the fermentations supplemented with amino acids than in the fermentation where only ammonium was added. The percentages of tyrosine and phenylalanine consumed gradually increased with increase of their initial concentration.     

发酵前后甜石榴汁中有机酸的变化研究

本试验利用反相液相色谱（RP-HPLC）法分离测定发酵前后甜石榴汁中有机酸种类和含量。在甜石榴汁中检测到的有机酸包括草酸、苹果酸、α-酮戊二酸、乳酸、乙酸、柠檬酸与富马酸,其中主要有机酸为乳酸（占总有机酸的51.2%）、草酸（占总有机酸的26.8%）和柠檬酸（占总有机酸的16.8%）。发酵后甜石榴汁中的草酸与乳酸含量下降,乙酸含量增加,新生成酒石酸、丙酮酸与琥珀酸;苹果酸与柠檬酸含量增加。发酵后甜石榴汁的有机酸总量下降了7.8%.     

Replacement of sulfur dioxide by lysozyme and oenological tannins during fermentation: influence on volatile composition of white wines

BACKGROUND: In recent years the use of sulfur dioxide, a commonly used additive in winemaking, has been questioned because of its toxic effects on human health. Studies have been conducted to find alternatives that can effectively substitute for this additive in all its various technological functions. In previous work, lysozyme and oenological tannins were found as possible substitutes in controlling bacterial undesirable fermentations and phenolic oxidation. However, data on the volatile composition of wines obtained by that protocol are lacking. In this work, the effects on volatile composition of white wines by the substitution of SO₂ during fermentation with lysozyme and tannin were studied. At the same time, the technological performance of two strains of yeast that produce low amounts of SO₂ were evaluated. RESULTS: The results showed that both SO₂ and lysozyme prevented the development of undesirable bacterial fermentations. The study of volatile compounds shows differences in the alcohol, acid and ester contents among the final products: wines fermented with strain 1042 and lysozyme had higher total alcohol concentration, while the addition of SO₂ promoted higher production of 3‐methyl‐1‐butanol, 3‐methylthio‐1‐propanol, phenylethyl alcohol and 4‐hydroxy‐benzenethanol. Esters, as a total, were influenced by the different strain and tannins addition, while amounts of medium‐chain fatty acid ethyl esters and their corresponding fatty acids were found in higher amounts in wines coming from fermentations with lysozyme. The sensory analysis revealed a preference for wines to which lysozyme and tannins had been added. CONCLUSION: The data suggest that the addition of lysozyme and oenological tannins during alcoholic fermentation could represent a promising alternative to the use of SO₂ and for the production of wines with reduced content of SO₂. The composition of the volatiles in the final wines was affected by the different vinification protocols (mainly with regards to alcohols and ethyl esters). Copyright © 2009 Society of Chemical Industry     

完全发酵与适度发酵苹果醋主要成分的差异性分析

研究苹果醋分别采用适度发酵和完全发酵时主要成分及芳香物质种类和含量的差异性。采用福林-酚法、高效液相色谱法、固相微萃取结合气相色谱-质谱联用分别测定2种发酵方式苹果醋中总酚、有机酸含量和芳香成分。结果表明,适度发酵苹果醋总酚含量比完全发酵高21%;2种果醋的有机酸种类完全一致,但适度发酵法中的酒石酸、柠檬酸和富马酸含量更高,而丙酮酸、苹果酸、α-酮戊二酸、乳酸、乙酸和琥珀酸的含量则略低于完全发酵的醋样。适度发酵苹果醋芳香物质种类更丰富,检测到37种芳香成分,其中保留了不少原果香气,如香茅醇、橙花醇、乙酸丁酯、乙酸-4-甲基-3-己酯和乙酸二甲基丁酯等。适度发酵可减少苹果醋总酚的损失,同时保留了更多的苹果原香物质,是值得探索改善苹果醋品质的途径。     

New applications for Schizosaccharomyces pombe in the alcoholic fermentation of red wines

The fermentation of grape must using non‐Saccharomyces yeasts with particular metabolic and biochemical properties is of growing interest. In the present work, red grape must was fermented using four strains of Schizosaccharomyces pombe (935, 936, 938 and 2139), Saccharomyces cerevisiae 7VA and Saccharomyces uvarum S6U, and comparisons were made over the fermentation period in terms of must sugar (glucose + fructose), malic acid, acetic acid, ammonia, primary amino nitrogen, lactic acid, urea (a possible fermentation activator or precursor of other metabolites) and pyruvic acid (a molecule affecting vitisin formation and therefore colour stability) concentration. The colour intensity of the fermenting musts was also recorded. The Schizosaccharomyces strains consumed less primary amino nitrogen and produced less urea and more pyruvic acid than other Saccharomyces species. Further, three of the four Schizosaccharomyces strains completed the breakdown of malic acid by day 4 of fermentation. The main negative effect of the use of Schizosaccharomyces was strong acetic acid production. The Schizosaccharomyces strains that produced most pyruvic acid (938 and 936) were associated with better ‘wine’ colour than the remaining yeasts. The studied Schizosaccharomyces could therefore be of oenological interest.     

Improvement of mead fermentation by honey‐must supplementation

Through honey's fermentation, diverse beverages can be obtained, among which is mead, an alcoholic drink with 8 to 18% of ethanol (v/v). Since honey is a matrix with a low nutrient concentration and other unfavourable growth conditions, several problems are usually encountered, namely delayed or arrested fermentations, unsatisfactory quality parameters and lack of uniformity of the final product, as well as unpleasant sensory properties. In this context, the aim of this work was to optimize mead production through honey‐must supplementation with (a) salts, (b) vitamins or (c) salts + vitamins. The effects of the honey‐must formulation on the fermentation kinetics, growth profile and physicochemical characteristics of final meads were evaluated. The results showed minor differences in the fermentation profile and time between fermentations with the different formulations. The growth profile was influenced more by the yeast strain than by the supplements added to the honey‐must. In general, the honey‐must composition did not influence meads’ final characteristics, except regarding the SO₂ concentration of the meads produced using the strain QA23. In summary, the addition of salts and/or vitamins to honey‐must had no positive effects on the fermentation, growth profile or characteristics of the final products. Copyright © 2015 The Institute of Brewing & Distilling     

THE EFFECT OF PITCHING YEAST AERATION ON THE PRODUCTION OF ACETIC ACID DURING FERMENTATIONS WITH BREWERS' YEAST: AN ENZYMATIC APPROACH

Aeration of pitching yeast signicantly increases the metabolism of acetate. This increase is particularly noticed at an enzymatic level, with special reference to the specific activity of the Fe⁺⁺⁺ linked pyruvate de-carboxylase which has been shown to be involved in the production of acetic acid. At the beginning of fermentations carried out with aerobic and anaerobic pitching yeasts, an increase in acetic acid production is observed, this is followed by reabsorption. Stabilisation in the concentration of acetic acid is observed until the end of fermentation. Initial and final concentrations of acetic acid obtained during fermentations were significantly higher in fermentations carried out with aerobic pitching yeasts than in fermentations carried out with anaerobic pitching yeasts.     

Dynamics of indigenous yeast populations during spontaneous fermentation of wines from Mendoza, Argentina

Fermentation of wine is a complex microbial reaction, which involves the sequential development of various species of yeasts and lactic acid bacteria. Of these, yeasts are the main group responsible for alcoholic fermentation. The aim of this work was to study, under industrial conditions, the evolution of yeast populations and to describe the individual evolution of the most important yeasts during three spontaneous fermentations of Malbec musts from Argentina. This work shows the significant participation of non-Saccharomyces yeasts during spontaneous fermentation of musts, with the ubiquitous presence of three main species: Kloeckera apiculata, Candida stellata and Metschnikowia pulcherrima.     

Multifactorial analysis of acetaldehyde kinetics during alcoholic fermentation by Saccharomyces cerevisiae

Acetaldehyde is the terminal electron acceptor in the alcoholic fermentation by Saccharomyces cerevisiae. Quantitatively the most important carbonyl by-product, it has relevance for ethanol production yields as well as product stabilization and toxicology. The aim of this study was to investigate the effect of various enological parameters on acetaldehyde kinetics during alcoholic fermentations. Two commercial yeast strains were tested in two grape musts and the pH, temperature, SO₂ and nutrient addition were varied. All incubations had uniform kinetics where acetaldehyde reached an initial peak value followed by partial reutilization. Peak acetaldehyde concentrations and residual concentrations after 15 days of fermentations ranged from 62 to 119 mg l^− 1 and 22 to 49 mg l^− 1, respectively. A positive linear relationship was found between peak and final acetaldehyde levels in Gewürztraminer, but not Sauvignon Blanc fermentations, where sluggish fermentations were observed. Several factors had a significant effect on peak and/or final acetaldehyde levels. SO₂ addition, grape cultivar and fermentation nutrition were important regulators of peak acetaldehyde production, while final acetaldehyde concentrations were correlated with SO₂ addition, grape cultivar and temperature. The results allowed to estimate the acetaldehyde increase caused by SO₂ addition to 366 ??g of acetaldehyde per mg of SO₂ added to the must. The course of the final fermentation phase was shown to determine acetaldehyde residues. Comparison of acetaldehyde and hexose kinetics revealed a possible relationship between the time of occurrence of peak acetaldehyde concentrations and the divergence of glucose and fructose degradation rates.     

Liquid sourdough fermentation: industrial application perspectives

Sourdough fermentation is considered to play a key role to get improved flavour, texture, nutritional and shelf-life properties of bakery products. Since few years Barilla R&D has been focusing on liquid sourdough fermentation which may deserve several advantages with respect to traditional processes. The results showed that the micro-biota of sourdough markedly influences flavour and texture of bakery products. Particular attention has been paid to lactic acid bacteria and yeasts. Selected lactic acid bacteria and yeasts were tested in sourdough liquid fermentation as single strain or in association. The parameters of fermentations were optimized and standardized to set up a laboratory plant liquid fermentation. Only a few strains of lactic acid bacteria were found to be suitable for liquid fermentation alone or in association with yeasts. Fermentations were carried out at pilot plant and an industrial technology was developed. This work describes the results found for the organoleptic profile of an industrial bread started with liquid sourdough with respect to bakers' yeast bread without sourdough addition.     

Influence of SO2 on the consumption of nitrogen compounds through alcoholic fermentation of must sterilized by pulsed electric fields

The aim of this work was to study the influence of SO₂ on the use of nitrogenous compounds by yeast during wine alcoholic fermentation. Thus Parellada must was sterilized by a pulsed electric field treatment and inoculated with Saccharomyces cerevisiae Na33 strain. The fermentations were carried out with SO₂ (20 mg/l) and without SO₂. Results showed that yeast better consumed the amino acids in the first half of fermentation in the presence of SO₂. The final concentration of amino acids in the obtained wine was greater when the must was fermented without SO₂ than when the latter compound was present. Therefore, the presence of SO₂ facilitated the consumption of amino acids and, hence, such wine should have more complex flavour and better microbiological stability than that obtained from fermentation without SO₂.     

Permanence of yeast inocula in the winery ecosystem and presence in spontaneous fermentations

The oenological practice of systematic inoculation with active dried yeasts is commonly used by many wineries around the world. However, the use of these yeasts is not free from controversy, since this practice has occasionally been described as having a negative effect on the biodiversity of natural yeast present in the wineries. The purpose of this study is to analyse the presence of commercial yeasts used as inocula in the ecosystem of three D.O.Ca. (“Qualified” Designation of Origin) Rioja wineries. It studies the permanence of these yeasts in winery equipment and their participation in spontaneous fermentations where they have not been used for inoculation. The results indicate that the presence of the active dry yeasts used in the wineries was scarce or non-existent, both in the ecosystem of each winery and in the spontaneous fermentations where they had not been added. So, repeated inoculation with active dry yeasts allowed a high presence and development of autochthonous (Saccharomyces and non-Saccharomyces) yeasts, both in equipment and in the spontaneous fermentations carried out.     

Microbiological and physicochemical changes of naturally black olives fermented at different temperatures and NaCl levels in the brines

The effect of different temperatures (25°C, 18°C and ambient temperature) and NaCl levels in brines (4%, 6% and 8%) on the microbiological and physicochemical characteristics of naturally black olives of Conservolea variety was studied for up to 190 days. Fermentation was carried out according to the traditional anaerobic method. The initial microflora consisted of Gram-negative bacteria, lactic acid bacteria and yeasts. Inhibition of Gram-negative bacteria was evident in all fermentations. The prevailing micro-organisms were lactic acid bacteria and yeasts, the association of which was dependent on the conditions of fermentation. At 25°C and 18°C in brines containing 4% and 6% NaCl, the growth of lactic acid bacteria was favoured resulting in a lactic acid fermentation, as indicated by the high free acidity levels and low pH values in the brines. On the contrary, 8% NaCl concentration affected the growth of lactic acid bacteria and enhanced the activity of fermentative yeasts, producing a final product with lower free acidity and higher pH value. At ambient temperature, the counts of lactic acid bacteria followed the fluctuation of temperature regardless of salt concentration, while yeasts did not seem to be affected. The lactic acid bacteria identified belonged to the species Lactobacillus mesenteroides, Lactobacillus brevis, Lactobacillus plantarum and Lactobacillus pentosus. The best conditions for fermentation were at 25°C and 6% NaCl, developing free acidity of 142 mM (1·28% w/v) lactic acid and pH value of 3·8. After 5 months of brining, olives fermented at 25°C were judged by panelists as being debittered and ready to eat. No off-odour development was detected in any case due to anomalous fermentation. The HPLC analysis revealed that citric, malic, tartaric, succinic, lactic and acetic were among the end products of fermentation.     

梯度洗脱高效液相色谱法快速测定1,3-丙二醇发酵液中有机酸

提出了一种快速分析发酵液中9种有机酸的高效液相色谱方法。该方法利用RSpakKC-811色谱柱(300mm×8mmi.d.),采用超纯水-4mmol/L高氯酸为流动相进行梯度洗脱。流动相流速1.0mL/min,紫外检测波长210nm,柱温60℃时,能够快速、准确地分离测定发酵液中的丙酮酸、柠檬酸、苹果酸、延胡索酸、琥珀酸、乳酸、甲酸、乙酸等8种有机酸,分析时间只需15min。各种有机酸的线性相关系数R2≥0.9992,精密度的相对标准偏差为0.97%-2.72%,样品回收率为96.8%-102.5%,具有较高的精密度和准确度,可以用于1,3-丙二醇发酵液中有机酸的分析。