Inhibition of the decrease of volatile esters and terpenes during storage of a white wine and a model wine medium by caffeic acid and gallic acid

Caffeic acid and gallic acid were tested as inhibitors of the decrease of volatile acetate esters, ethyl esters and terpenes during storage of a white wine and a model wine medium. Wine and model wine samples were analysed by SPME along with GC–MS. At t = 0, no effect on the concentration of any volatile was observed as a result of adding each phenolic acid in any of wine or model wine samples. Many esters, such as isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, and linalool decreased during storage of Debina-white wine for up to 20 months. Caffeic acid and gallic acid at 60 mg/L inhibited the decrease of these volatiles. Isoamyl acetate, ethyl hexanoate and linalool decreased during storage of the model wine medium containing 0, 20 or 40 mg/L SO₂. Caffeic acid and gallic acid inhibited the decrease of three volatiles; SO₂ inhibited the decrease of isoamyl acetate and ethyl hexanoate. In some cases, SO₂ increased the inhibitory action of two phenolic acids. The inhibitory action of caffeic acid and gallic acid was dose dependent in the range 0–60 mg/L. Caffeic acid was active at 7.5 mg/L while gallic acid at 15 mg/L.Present results indicate that caffeic acid and gallic acid may be taken into account as potent inhibitors of the disappearance of aromatic volatile esters and terpenes in wines at concentrations similar to those existing in wines.     

Manipulation of volatile compound transformation in durian wine by nitrogen supplementation

This study evaluated the impact of added diammonium phosphate (DAP) and a L‐leucine‐L‐phenylalanine mixture (Leu+Phe) on durian wine fermentation by Saccharomyces cerevisiae var. bayanus EC‐1118. Changes in yeast cell population, ^oBrix, sugars, organic acids and pH were similar in all fermentations, regardless of nitrogen supplementation at a concentration of 150 mg N L^?1. The supplementation of Leu+Phe accelerated the utilisation and reduced the formation of volatile sulphur compounds such as diethyl disulphide, ethyl thioacetate and 2‐(ethylthio)ethanol, which were 64.3%, 26.0% and 48.4% lower than the control, respectively. Nevertheless, the supplementation of Leu+Phe heightened the production of isoamyl alcohol, 2‐phenylethyl alcohol and their corresponding esters, especially isoamyl acetate was 1.6 times and 2‐phenylethyl acetate was 26.5 times higher than the control. The supplementation with DAP exerted negligible effects on the volatile composition. The results of this study suggest that the addition of specific amino acids may be a novel approach to manipulating durian wine flavour by suppressing or accentuating the formation of certain aroma compounds.     

Effects of Fermentation Temperature on Key Aroma Compounds and Sensory Properties of Apple Wine

Fermentation temperature strongly affects yeast metabolism during apple wine making and thus aromatic and quality profiles. In this study, the temperature effect during apple wine making on both the key aroma compounds and sensory properties of apple wine were investigated. The concentration of nine key aroma compounds (ethyl acetate, isobutyl acetate, isopentylacetate, ethyl caprylate, ethyl 4‐hydroxybutanoate, isobutylalcohol, isopentylalcohol, 3‐methylthio‐1‐propanol, and benzeneethanol) in apple wine significantly increased with the increase of fermentation temperature from 17 to 20 °C, and then eight out of the nine key aroma compounds with an exception of ethyl 4‐hydroxybutanoate, decreased when the temperature goes up 20 to 26 °C. Sensory analysis showed that the apple wine fermented at 20 °C had the highest acceptance for consumers. Fermentation at the temperature of 20 °C was therefore considered to be the most suitable condition using the selected yeast strain (Saccharomyces cerevisiae AP05) for apple wine making. Changes in the fermentation temperature can considerably affect the production of key aroma compounds and sensory profiles of apple wine. These results could help apple wine producers make better quality production for consumers at the optimal fermentation temperature.     

Fermentation of Soybean Meal Hydrolyzates with Saccharomyces cerevisiae and Zymomonas mobilis for Ethanol Production

Most of the ethanol currently produced by fermentation is derived from sugar cane, corn, or beets. However, it makes good ecological and economic sense to use the carbohydrates contained in by‐products and coproducts of the food processing industry for ethanol production. Soybean meal, a co‐product of the production of soybean oil, has a relatively high carbohydrate content that could be a reasonable substrate for ethanol production after fermentable sugars are released via hydrolysis. In this research, the capability of Saccharomyces cerevisiae NRRL Y‐2233 and Zymomonas mobilis subsp. mobilis NRRL B‐4286 to produce ethanol was evaluated using soybean meal hydrolyzates as substrates for the fermentation. These substrates were produced from the dilute‐acid hydrolysis of soybean meal at 135 °C for 45 min with 0, 0.5%, 1.25%, and 2% H₂SO₄ and at 120 °C for 30 min with 1.25% H₂SO₄. Kinetic parameters of the fermentation were estimated using the logistic model. Ethanol production using S. cerevisiae was highest with the substrates obtained at 135 °C, 45 min, and 0.5% H₂SO₄ and fermented for 8 h, 8 g/L (4 g ethanol/100 g fresh SBM), while Z. mobilis reached its maximum ethanol production, 9.2 g/L (4.6 g ethanol/100 g fresh SBM) in the first 20 h of fermentation with the same hydrolyzate.     

Optimization of fermentation conditions for Chinese bayberry wine by response surface methodology and its qualities

Colour and flavour are both important challenges for bayberry wine production because of a shortage of selected strains. The yeast Saccharomyces cerevisiae strain YF152, separated from a natural Chinese bayberry fermentation mash [alcohol tolerance capacity (18.0%), SO₂ (200 mg/L), sugar content (40%) and pH (2.50)] was employed to brew Chinese bayberry wine. Response surface methodology was used to simultaneously analyse the effects of the fermentation conditions on Chinese bayberry wine. The optimum conditions were found to be a temperature of 26.5 °C, an initial sugar content of 22.0°Brix, an inoculum size of 4.0% and an initial pH of 2.90. Under these conditions, the final alcohol content of the bayberry wine was 13.4%, the anthocyanin content was 77 mg/L and the residual sugar content was 1 g/L. These numbers agreed well with the predicted values. The major characteristic flavour components of the wine were 3‐methyl‐1‐butanol, 2‐phenylethanol, ethyl acetate, 2‐methylbutyl acetate and acetic acid. Copyright © 2016 The Institute of Brewing & Distilling     

草莓果酒酿造工艺的优化及其香气成分分析

以草莓为原料,采用单因素试验和Box-Behnken试验设计研究SO2添加量、酵母添加量及发酵温度对果酒发酵的影响,建立各影响因素的回归方程,并通过响应面分析法优化,得到草莓果酒的最佳工艺条件：SO2添加量为81 mg/L、酵母添加量为1 g/L、发酵温度为20 ℃。然后采用顶空固相微萃取法,利用气相色谱-质谱联用技术对草莓果酒香气成分进行分析与鉴定,结果表明：从草莓果酒中共鉴定出香气物质85 种,占总峰面积的99.55%;其主体香气物质主要是异戊醇、乙酸异戊酯、己酸乙酯及辛酸乙酯。     

Inoculated fermentation of orange juice (Citrus sinensis L.) for production of a citric fruit spirit

The yeast Saccharomyces cerevisiae UFLA CA1174 was evaluated for its potential to produce an orange spirit, as a possible alternative to reduce waste and increase income to citrus farmers. The sugar concentration of the orange juice was adjusted to 16ºBrix and the pH to 4.5. The orange juice was inoculated at approximately 7 log CFU/mL, and the fermentation was performed at room temperature until ºBrix stabilization. The yeast used showed high values for the conversion factors of the substrates into ethanol (Y_p/s 0.50 g/g), the volumetric productivity of ethanol (Q_p 1.78 g/L/h), the biomass productivity (P_x 58.47 g/g) and the fermentation efficiency (E_f 97.83%). The sugars were converted quickly, and a high ethanol concentration (58.13 g/L) was achieved after 24 h of fermentation. The orange wine was distilled in a copper alembic, and the head, heart and tail fractions were collected. The orange spirit produced (heart fraction) had high concentrations of acetaldehyde, ethyl acetate, isoamyl alcohol and 2‐phenylethanol. The results showed that orange juice could be a good substrate for fermentation and distillation, and the sensory analysis performed revealed that the produced beverage had good acceptance by the tasters. Copyright © 2013 The Institute of Brewing & Distilling     

The Influence of Inoculum Level on Fermentation and Flavour Compounds of White Wines Made from cv. Emir

In this study, the influence of the addition of a commercial wine yeast (Saccharomyces cerevisiae) at inocula of 1 × 10⁴ to 1 × 10⁷ cells/ml in Emir must was investigated with a focus on yeast growth, fermentation rate, ethyl alcohol and flavour compound formation. Spontaneous fermentation without inoculation was also performed. Higher peak counts were observed with higher amounts of S. cerevisiae yeast. Addition of various amounts of yeast led to the earlier disappearance of non‐Saccharomyces yeasts. The fermentation rate was improved with higher amounts of yeast, but ethanol production was not affected. Concentrations of higher alcohols increased with increasing inoculum levels, especially inoculum sizes of 1 × 10⁶ cells/ml and 1 × 10⁷ cells/ml. The amount of ethyl acetate was reduced with increased inoculum levels.     

The Effect of Proanthocyanidins on Growth and Alcoholic Fermentation of Wine Yeast under Copper Stress

Proanthocyanidins (PAs) derived from the grape skin, as well as from grape seeds, grape stems, are an important group of polyphenols in wine. The aim of this study was to understand the effect of PAs (0.1, 1.0 g/L) on growth and alcoholic fermentation of 2 strains of Saccharomyces cerevisiae (commercial strain FREDDO and newly selected strain BH8) during copper‐stress fermentation, using a simple model fermentation system. Our results showed that both PAs and Cu²⁺ could pose significant inhibition effects on the growth of yeast cells, CO₂ release, sugar consumption, and ethanol production during the initial phase of the fermentation. Compared to PAs, Cu²⁺ performed more obvious inhibition on the yeast growth and fermentation. However, adding 1.0 g/L PAs increased in the vitality and metabolism activity of yeast cells at the mid‐exponential phase of fermentation in the mediums with no copper and 0.1 mM Cu²⁺ added, shortened the period of wine fermentation, and decreased the copper residues. It indicated that PAs could improve the ability of wine yeast to resist detrimental effects under copper‐stress fermentation condition, maintaining cells metabolic activity, and fermentation could be controlled by manipulating PAs supplementation.     

Effect of storage conditions on the volatile composition of wines obtained from must stabilized by PEF during ageing without SO2

The aim of this work was to study the effect of the storage conditions on the evolution of volatile composition of white wines aged in bottles without the addition of SO₂. Therefore Parellada must was stabilized by pulsed electric fields (PEF) and fermented without the employment of SO₂ and later on the wine was aged in bottles, without addition of this preservative, at low and controlled temperature and at room temperature. The obtained results showed that the concentration of some important compounds for wine aroma such as isoamyl acetate, and ethyl esters of fatty acids was higher in the wines stored at low and controlled temperature than in those aged at room temperature. However, the temperature favoured the formation of total alcohols during the aging of wines in the bottles. Consequently, from the point of view of the aromatic quality, the conservation of white wines obtained from fermentation of must processed by PEF and aged in bottles without the addition of SO₂ was improved under controlled storage conditions than at room temperature.

Industrial relevance

SO₂ is used as a preservative agent in wine due to its multi-action in the wine conservation. Although neither carcinogenicity nor mutagenic effects have been found in SO₂, this compound has an influence on human health. For that reason, several competent international organizations (WHO, FAO, OIV) have set down maximum limits for wines as well as promote a reduction of its concentration in wines. Therefore, potential industrial applications of this work include the possibility to produce and store wines without SO₂. This has been achieved by stabilizing the musts with PEF. The wines produced under these conditions can be conserved without this additive when used under controlled conditions of storage.     

EFFECTS OF PROTEOLYTIC ACTIVITY ON THE CHARACTERISTICS OF AROMATIC RED RICE WINE

The quality of rice wine made from uncooked, unpolished aromatic red rice grain was improved by use of a commercial preparation of acid protease from Aspergillus niger during ethanol fermentation. The fermentation rate of the mash which contained the acid protease was much higher than that of mash that did not contain the preparation of acid protease. The rice wine made from uncooked, polished aromatic red rice, which usually had a less acceptable aroma, was improved by use of the preparation of acid protease, and large amounts of isobutyl alcohol, n-propyl alcohol and ethyl acetate were detected in the resultant rice wine. By contrast, the quality of rice wine made from the bran fraction of aromatic red rice was not improved by the preparation of acid protease. The polished rice fraction of aromatic red rice was affected by the acid protease and the aromatic quality of the rice wine was improved. The aromatic characteristics of red rice wine made from cooked, unpolished aromatic red rice grains, which was rather inferior in terms of both aroma and color, were also improved by the addition of the preparation of acid protease during ethanol fermentation. Thus acid protease has beneficial effects on the production of aromatic red rice wine.     

Production of Garcinia wine: changes in biochemical parameters,organic acids and free sugars during fermentation of Garcinia must

Garcinia wine was prepared by fermentation of ameliorated must of Garcinia xanthochymus using Saccharomyces cerevisiae. The present studies focused on changes in biochemical parameters (brix, pH, aldehydes, esters and alcohols), organic acids (reduction of oxalic acid), free sugars and antioxidant activities on fermentation of Garcinia must. The wine had higher amount of residual sugars contributing to the calorific value. The aldehydes and esters content in the final wine were 0.034% and 0.26%, respectively. There was reduction of citric acid and oxalic acid (antinutritional factor) and synthesis of aspartic acid and glutamic acid. Garcinia beverage was accepted on sensory analysis with high score for desirable attributes and overall quality with alcohol content of 6.1%. There was increase in total phenolics (0.039% gallic acid equivalent) and reducing power on fermentation but decrease in 2,2‐diphenyl‐1‐picrylhydrazyl radical scavenging activity.     

Oenococcus oeni,a species born and moulded in wine: a critical review of the stress impacts of wine and the physiological responses

Oenococcus oeni is a lactic acid bacterium highly adapted to the stressful environment of wine, and is widely used as an industrial starter culture to conduct malolactic fermentation (MLF), the conversion of L‐malate to L‐lactate. Some cold‐climate wine regions still produce wines which prove too stressful for the application of a starter culture, resulting in sluggish or stuck MLFs which compromise the quality and stability of the wine. The literature on the three primary stress factors, low pH, ethanol and SO₂, is reviewed as well as their toxic mechanisms; possible interactions between the stress factors are also discussed. In particular, the toxic mechanisms of SO₂, an extremely inhibitory compound, are poorly understood. in vitro studies as well as in vivo studies in other prokaryotes point to numerous mechanisms which could have widespread impacts on the cell envelope, proteins and DNA in O. oeni. We also review the responses of O. oeni to these stress factors and offer a simplified model of events which cultures inoculated into particularly stressful wines may experience. Although significant advances have been made in our understanding of the stress responses in recent years, many fundamental aspects still require study.     

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     

Effectiveness of dimethyldicarbonate to stop alcoholic fermentation in wine

The alcoholic fermentation of Botrytis-affected wines is stopped by the addition of high concentrations of sulfur dioxide (SO₂). The natural microbial unstability of these wines and the binding phenomena forces winemakers to periodically add sulfur dioxide during maturation, leading to a high concentration of a maximum of 400 mg/l in the bottled wine. Dimethyldicarbonate (DMDC) is now considered as a reliable fungicide which could be partially used instead of SO₂, especially just before bottling. This study investigated the use of DMDC to stop alcoholic fermentation. The experiment was carried out on pure cultures of three yeast species present in this type of wine (Saccharomyces cerevisiae, Candida stellata and Zygosaccharomyces bailii). The results were very promising and suggested that DMDC was more effective than SO₂. The yeast cells died after the addition of DMDC whereas they partially entered into a viable but non-culturable (VBNC) state with SO₂. However, the same experiment carried out on botrytized must, whose fermentation was carried out using indigenous microflora, was less conclusive. It pointed out that DMDC, used in a concentration of 200 mg/l, was more effective than SO₂ but leading to the same results: the entering of a part of the cells into a VBNC state. DMDC could be used to stop alcoholic fermentation, but could not replace SO₂. Nevertheless, the concentrations of SO₂ added in this type of wine could be reduced in this way.     

Fermentation Characteristics and Aromatic Profile of Plum Wines Produced with Indigenous Microbiota and Pure Cultures of Selected Yeast

The aim of this study was to assess and compare fermentation characteristics and aromatic profile of plum wines produced with indigenous microbiota and pure cultures of different selected yeast. Experiments were carried out with plum (Prunus domestica L.) varieties of different fruit ripening times (?a?anska rana, ?a?anska lepotica, and Po?ega?a). Wine fermentations were conducted by the activity of indigenous microbiota, commercially available Saccharomyces cerevisiae and Saccharomyces bayanus yeast strains and joint activity of Schizosaccharomyces pombe and S. cerevisiae (sequential inoculation). Statistically significant differences in fermentative characteristics and the content of certain volatile compounds were observed as a result of metabolic activity of various indigenous and/or selected yeasts during fermentation of plum pomace. Minimal duration of fermentation (4 to 5 d) and fastest ethanol production rate (from 12.3 to 15.5 g/L/d) were the characteristics of the studied S. cerevisiae strains. Isobutanol, 3‐methyl‐1‐butanol, 1‐heptanol, and 1‐octanol were the most prevalent higher alcohols in the tested plum wine samples. The predominant ester in plum wines was ethyl acetate, ethyl lactate, amyl acetate, isoamyl acetate, and ethyl palmitate, esters responsible for the floral and fruity olfactory tones, were also present in large amounts. Also, the use of S. cerevisiae strains resulted in the production of plum wines with better sensory characteristics than ones produced with other investigated yeasts. Obtained results are significant since there is limited data on the compounds responsible for the unique flavor of plum wine, as well as on the impact of different yeast starter cultures application on the overall quality of fruit wines.     

Inhibition of the decrease of volatile esters and terpenes during storage of a white wine and a model wine medium by glutathione and N-acetylcysteine

Glutathione and N‐acetylcysteine, each at 20 mg L^?1, were tested as inhibitors of the decrease of volatile esters and terpenes during storage of Debina white wine. Moreover, the inhibition of the decrease of isoamyl acetate, ethyl hexanoate and linalool in a model wine medium by glutathione and N‐acetylcysteine, each at 0–20 mg L^?1, was also tested. Several volatiles, such as isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate and linalool, decreased during wine storage. Glutathione or N‐acetylcysteine significantly restricted the decrease of these volatiles. In the model medium, each thiol inhibited the decrease of the three volatiles in a dose‐dependent manner. N‐acetylcysteine inhibited the decrease of all three volatiles at 2.5 mg L^?1 while glutathione at 2.5 or 5.0 mg L^?1. The present results indicate that glutathione and N‐acetylcysteine may be taken into account as potent inhibitors of the disappearance of aromatic esters and terpenes in wines.     

Effects of pH,sulphur dioxide,alcohol content,temperature and storage time on colour composition of a young Portuguese red table wine

In a young Portuguese red table wine (Douro Valley) a significant relationship between the colour composition (anthocyanins, polymeric pigment, colour density) and five parameters (pH, SO₂, alcohol, temperature, time of storage) were found. Higher temperature increased the loss of individual and total anthocyanins (as measured fay HPLC) during the ageing, while the wines with higher SO₂ content contained a greater amount of anthocyanins. Malvidin 3-glucoside acetate was the only anthocyanin not affected by the SO₂ content, but its concentration was related with the interaction term (time of storage × SO₂ content). Peonidin and malvidin 3-glucoside-p-coumarate were the two anthocyanins affected by the quadratic term of temperature. Three different groups of equations corresponding to the three different states of the glucoside moiety were found. The polymeric pigment absorbance increases daring conservation and with higher temperature, while the pH and SO₂ content decreased the polymeric pigment formation. The colour density of the experimental wine was related significantly to the changes of the coloured anthocyanins and to the polymeric pigment content.     

Effect of sulphur dioxide and must extraction on colour,phenolic composition and sensory quality of red table wine

Red wines were made during 1992 from Vitis vinifera var Roriz grapes using a high and a low level of extraction and three levels of total sulphur dioxide (0, 75 and 150 mg SO₂ kg⁻¹). From this single experiment, the effects of total SO₂ and extraction on anthocyanin composition and colour were observed by HPLC, spectrophotometry and tristimulus colorimetry. High extraction produced a wine with more total pigments and total phenols than low extraction and increased the amount of organic acids extracted during fermentation. More anthocyanins were extracted with increasing SO₂ levels. On maturation, all wines lost colour and increased in brownness. Wines made without SO₂ browned more than the wines made with SO₂. The anthocyanins normally present in wines were all rapidly lost to trace levels at 24 months. Vitisin A, a more stable and highly coloured anthocyanin than malvidin 3-glucoside, showed a slower decrease in concentration than malvidin 3-glucoside and contributed significantly to the wine colour during aging. At the first analysis, the wines made without SO₂ had a higher percentage colour due to polymers than the wines made with SO₂. Polymerisation progressed during maturation, although the initial differences were maintained. Sensory analysis after 6 and 18 months storage by expert tasters revealed differences mainly related to the colour attributes, indicating that when wines are made using modern hygienic techniques, total SO₂ has a negligible effect on aroma and flavour attributes. © 1998 Society of Chemical Industry.     

The yeast enzyme Eht1 is an octanoyl‐CoA:ethanol acyltransferase that also functions as a thioesterase

Fatty acid ethyl esters are secondary metabolites that are produced during microbial fermentation, in fruiting plants and in higher organisms during ethanol stress. In particular, volatile medium‐chain fatty acid ethyl esters are important flavour compounds that impart desirable fruit aromas to fermented beverages, including beer and wine. The biochemical synthesis of medium‐chain fatty acid ethyl esters is poorly understood but likely involves acyl‐CoA:ethanol O‐acyltransferases. Here, we characterize the enzyme ethanol hexanoyl transferase 1 (Eht1) from the brewer's yeast Saccharomyces cerevisiae. Full‐length Eht1 was successfully overexpressed from a recombinant yeast plasmid and purified at the milligram scale after detergent solubilization of sedimenting membranes. Recombinant Eht1 was functional as an acyltransferase and, unexpectedly, was optimally active toward octanoyl‐CoA, with k_cat = 0.28 ± 0.02/s and K_M = 1.9 ± 0.6 μm . Eht1 was also revealed to be active as a thioesterase but was not able to hydrolyse p‐nitrophenyl acyl esters, in contrast to the findings of a previous study. Low‐resolution structural data and site‐directed mutagenesis provide experimental support for a predicted α/β‐hydrolase domain featuring a Ser–Asp–His catalytic triad. The S. cerevisiae gene YBR177C/EHT1 should thus be reannotated as coding for an octanoyl‐CoA:ethanol acyltransferase that can also function as a thioesterase. © 2014 The Authors. Yeast published by John Wiley & Sons, Ltd.