The formation of volatiles in fruit wine process and its impact on wine quality

Fruit wine is one of the oldest fermented beverages made from non-grape fruits. Owing to the differences in fruit varieties, growing regions, climates, and harvesting seasons, the nutritional compositions of fruits (sugars, organic acids, etc.) are different. Therefore, the fermentation process and microorganisms involved are varied for a particular fruit selected for wine production, resulting in differences in volatile compound formation, which ultimately determine the quality of fruit wine. This article reviews the effects of various factors involved in fruit wine making, especially the particular modifications differing from the grape winemaking process and the selected strains suitable for the specific fruit wine fermentation, on the formation of volatile compounds, flavor and aroma profiles, and quality characteristics of the wine thus produced. KEY POINTS: • The volatile profile and fruit wine quality are affected by enological parameters. • The composition and content of nutrients in fruit must impact volatile profiles. • Yeast and LAB are the key determining factors of the volatile profiles of fruit wines.

Flavor assessment of a lactic fermented vinegar described in Japanese books from the Edo period (1603-1867)

Aims

Rice vinegar is a traditional fermented seasoning in Japan, and its production remained unchanged for over 800 years until the Edo period. However, based on the available information regarding rice vinegar production methods from this period and the results of reproduction experiments, we speculated that unlike the modern-day acetic fermented vinegar, rice vinegar produced during the Edo period was lactic fermented. Main methods: To verify this assumption, we analyzed the flavor components of Honcho, a lactic fermented product prepared using a method described in books, including "Honchoshokkan" from the Edo period, by capillary electrophoresis/time-of-flight mass spectrometry, high-performance liquid chromatography, gas chromatography mass spectrometry, and taste sensor analysis. Sensory evaluation was also conducted to assess validation as a seasoning.

Results

Honcho contains 2 % lactic acid, which gives it its acidity, and small amounts of other nonvolatile acids, but significantly lower levels of acetic acid (0.188 ± 0.015 g/100 mL, p < 0.01). It contains more than double the free amino acids of Kurozu, a modern rice vinegar, and more glutamic acid. Boiling to remove ethanol from yeast fermentation concentrated the free amino acids 1.5 times. Sensor taste analysis showed Honcho had weaker acidity but stronger umami taste than commercial rice vinegar. The volatile compounds related to acetic acid fermentation were significantly different between Honcho and Kurozu. Boiling increased Honcho's acidity, mainly through non-volatile acids.

Significance

These findings provide evidence to indicate that Honcho was an acidic seasoning for heat-cooking, which is uncommon in Japanese cuisine today and is mentioned in Edo period books. This seasoning contains many amino acids, implying that it adds umami flavor, not only the sourness of modern vinegar.

Targeted 1-H-NMR wine analyses revealed specific metabolomic signatures of yeast populations belonging to the Saccharomyces genus

This study aimed to explore the non-volatile metabolomic variability of a large panel of strains (44) belonging to the Saccharomyces cerevisiae and Saccharomyces uvarum species in the context of the wine alcoholic fermentation. For the S. cerevisiae strains flor, fruit and wine strains isolated from different anthropic niches were compared. This phenotypic survey was achieved with a special focus on acidity management by using natural grape juices showing opposite level of acidity. A 1H NMR based metabolomics approach was developed for quantifying fifteen wine metabolites that showed important quantitative variability within the strains. Thanks to the robustness of the assay and the low amount of sample required, this tool is relevant for the analysis of the metabolomic profile of numerous wines. The S. cerevisiae and S. uvarum species displayed significant differences for malic, succinic, and pyruvic acids, as well as for glycerol and 2,3-butanediol production. As expected, S. uvarum showed weaker fermentation fitness but interesting acidifying properties. The three groups of S. cerevisiae strains showed different metabolic profiles mostly related to their production and consumption of organic acids. More specifically, flor yeast consumed more malic acid and produced more acetic acid than the other S. cerevisiae strains which was never reported before. These features might be linked to the ability of flor yeasts to shift their metabolism during wine oxidation.

Reduced production of Ethyl Carbamate in wine by regulating the accumulation of arginine in Saccharomyces cerevisiae

Ethyl carbamate (EC), a multisite carcinogenic compound, is naturally produced from urea and ethanol in alcoholic beverages. In order to reduce the content of EC in wine, the accumulation of arginine in Saccharomyces cerevisiae was regulated by genetic modifying genes involved in arginine transport and synthesis pathways to reduce the production of urea. Knockout of genes encoding arginine permease (Can1p) and amino acid permease (Gap1p) on the cell membrane as well as argininosuccinate synthase (Arg1) respectively resulted in a maximum reduction of 66.88% (9.40 µg/L) in EC, while overexpressing the gene encoding amino acid transporter (Vba2) reduced EC by 52.94% (24.13 µg/L). Simultaneously overexpressing Vba2 and deleting Arg1 showed the lowest EC production with a decrease of 68% (7.72 µg/L). The yield of total higher alcohols of the mutants all decreased compared with that of the original strain. Comprehensive consideration of flavor compound contents and sensory evaluation results indicated that mutant YG21 obtained by deleting two allele coding Gap1p performed best in must fermentation of Cabernet Sauvignon with the EC content low to 9.40 μg/L and the contents of total higher alcohols and esters of 245.61 mg/L and 41.71 mg/L respectively. This study has provided an effective strategy for reducing the EC in wine.

The Use of Hanseniaspora opuntiae to Improve 'Sideritis' Wine Quality, a Late-Ripening Greek Grape Variety

In view of climate change and the increasingly antagonistic wine market, the exploitation of native genetic resources is revisited in relation to sustainable wine production. 'Sideritis' is a late-ripening Greek grape variety, which is quite promising for counteracting wine quality issues associated with the annual temperature rise. The aim of this study was to improve the quality and to enhance the aroma of 'Sideritis' wine through the use of native yeasts. To improve vinification, Hanseniaspora opuntiae L1 was used along with Saccharomyces cerevisiae W7 in mixed fermentations (SQ). The addition of H. οpuntiae significantly altered the chemical profile of the wine compared to the single-inoculated fermentations with W7 (IS). H. opuntiae increased all the acetate esters, except for hexyl acetate and (Z)-3-hexen-1-ol acetate. The concentration of 2-phenylethyl acetate, which imparts flowery and sweet notes, exhibited a 2.6-fold increase in SQ as compared to IS wines. SQ also showed higher levels in several ethyl esters, including ethyl butyrate, ethyl heptanoate and ethyl 7-octenoate, which are associated with fruity notes compared to IS. H. opuntiae produced citronellol, a terpene associated with rose and green notes, and increased the overall acceptance of the wine. Present results are thus quite promising for improving 'Sideritis' wine quality towards a sustainable wine production in Greece in view of global warming.

Nonconventional yeasts and hybrids for low temperature handcrafted sparkling ciders elaboration in Patagonia

Yeasts play a crucial role in transforming apple must into cider. While Saccharomyces cerevisiae (Sc) has been traditionally associated to cider fermentations worldwide, cryotolerant species such as Saccharomyces uvarum (Su) as well as natural S. cerevisiae × S. uvarum (Sc×Su) hybrids have also been detected in ciders fermented at low temperatures. This study aimed to evaluate the ability of two Patagonian cryotolerant yeast strains (Su and Se) and their interspecific hybrids with a Sc to conduct handcrafted apple must fermentations and a second fermentation process (champenoise method). The main chemical parameters and sensory quality of the resulting sparkling beverages was also analysed. Firstly, Sc×Se and Sc×Su hybrids were evaluated in their fermentative features at laboratory scale. Hybrids were compared with their respective parental species evidencing significant differences in the physicochemical and aromatic composition of the obtained base ciders. Both Su parental strain and the hybrid Sc×Se were selected for performing pilot scale fermentations (250 L) using natural (non-sterilized) apple juice at two different temperatures: 20 °C and 13 °C. Sc parental strain was also evaluated for comparative purposes. All base ciders obtained were then subjected to a second fermentation. A high implantation capacity of both Su and the hybrid was evidenced at the lowest evaluated temperature, while commercial Sc strain was not detected at the final fermentation stage, independently from the temperature. All sparkling ciders exhibited distinct physicochemical profiles. Ciders inoculated with commercial Sc (but effectively fermented with local Sc strains) allowed the development of malolactic fermentation (MLF) in processes carried out at both temperatures. Contrarily, no MLF was observed in ciders inoculated with either Su or the hybrid. Sparkling ciders fermented with Su displayed the highest concentrations of 2-phenylethanol and 2-phenylethyl acetate, regardless of the fermentation temperature. Conversely, ciders fermented with the hybrid at 20 °C exhibited the highest concentrations of ethyl octanoate and ethyl decanoate, contributing to floral and fruity notes in the beverage. Sensory analysis conducted with untrained individuals revealed a preference for sparkling ciders produced with the hybrid strain at both 20 °C and 13 °C. The cider fermented at 20 °C exhibited floral notes, sweetness, and a full body, while ciders fermented at 13 °C displayed moderate acidity and a well-balanced profile. Conversely, a trained panel described the cider fermented at 20 °C with Su as a fruity and acidic beverage, whereas the ciders fermented at 13 °C exhibited intense bitterness and acidity. This study highlights the potential of cryotolerant Saccharomyces species and hybrids in the development of new starter cultures for producing artisanal sparkling ciders with distinctive properties.

Enhanced Expression of Alcohol Dehydrogenase I in Pichia pastoris Reduces the Content of Acetaldehyde in Wines

Acetaldehyde is an important carbonyl compound commonly detected in wines. A high concentration of acetaldehyde can affect the flavor of wines and result in adverse effects on human health. Alcohol dehydrogenase I (ADH1) in Saccharomyces cerevisiae catalyzes the reduction reaction of acetaldehyde into ethanol in the presence of cofactors, showing the potential to reduce the content of acetaldehyde in wines. In this study, ADH1 was successfully expressed in Pichia pastoris GS115 based on codon optimization. Then, the expression level of ADH1 was enhanced by replacing its promoter with optimized promoters and increasing the copy number of the expression cassette, with ADH1 being purified using nickel column affinity chromatography. The enzymatic activity of purified ADH1 reached 605.44 ± 44.30 U/mg. The results of the effect of ADH1 on the content of acetaldehyde in wine revealed that the acetaldehyde content of wine samples was reduced from 168.05 ± 0.55 to 113.17 ± 6.08 mg/L with the addition of 5 mM NADH and the catalysis of ADH1, and from 135.53 ± 4.08 to 52.89 ± 2.20 mg/L through cofactor regeneration. Our study provides a novel approach to reducing the content of acetaldehyde in wines through enzymatic catalysis.

Effect of Apple Cultivar and Selected Technological Treatments on the Quality of Apple Distillate

Apple producers are looking for new markets to dispose of their harvest surpluses. One of the solutions may be the production of apple spirits by small distilleries. This study aimed to evaluate the influence of apple cultivars and technological treatments, i.e., pasteurization, depectinization, and deacidification, on the fermentation efficiency and quality of the distillates. Samples for fermentation were prepared from Polish apple cultivars (Antonówka, Delikates, Kosztela, Kronselska). The control samples were raw pulp-based samples. After fermentation, the samples were analyzed for ethanol, residual sugars, and by-product content by the HPLC technique. The distillates were tested for volatile compounds by the GC-MS method and their sensory evaluation was performed. Raw pulp-based samples, independent of the apple cultivar, showed fermentation efficiencies between (75.77 ± 4.69)% and (81.36 ± 4.69)% of the theoretical yield. Depectinization of apple pulp prior to fermentation resulted in the highest ethanol concentration and yield up to approximately 89%. All tested apple distillates were rich in volatile aroma compounds and met the requirements of the EU regulation for hydrogen cyanide content. The obtained results indicate that the tested apple cultivars can be used for the efficient production of apple spirits, providing producers with an opportunity for brand development.

Influence of spontaneous, "pied de cuve" and commercial dry yeast fermentation strategies on wine molecular composition and sensory properties

While most producers in recent decades have relied on commercial yeasts (ADY) as their primary choice given their reliability and reproducibility, the fear of standardising the taste and properties of wine has led to the employment of alternative strategies that involve autochthonous yeasts such as pied de cuve (PdC) and spontaneous fermentation (SF). However, the impact of different fermentation strategies on wine has been a subject of debate and speculation. Consequently, this study describes, for the first time, the differences between the three kinds of fermentation at the metabolomic, chemical, and sensory levels in two wines: Chardonnay and Pinot Noir. The results showed how the yeast chosen significantly impacted the molecular composition of the wines, as revealed by metabolomic analysis that identified biomarkers with varying chemical compositions according to the fermentation modality. Notably, higher numbers of lipid markers were found for SF and PdC than ADY, which contained more peptides. Key molecules from the metabolic amino acid pathway, which are addressed in this article, showed evidence of such variations. In addition, the analysis of volatile aromatic compounds revealed an increase in groups of compounds specific to each fermentation. The sensorial analysis of Chardonnay wine showed a more qualitative sensory outcome (Higher fruit intensity) for ADY and SF compared to PdC. Our finding challenges the common speculation among wine producers that autochthonous yeast fermentations may offer greater complexity and uniqueness in comparison to commercial yeast fermentations.

Influence of metabolic guilds on a temporal scale in an experimental fermented food derived microbial community

The influence of community diversity, which can be measured at the level of metabolic guilds, on community function is a central question in ecology. Particularly, the long-term temporal dynamic between a community's function and its diversity remains unclear. We investigated the influence of metabolic guild diversity on associated community function by propagating natural microbial communities from a traditionally fermented milk beverage diluted to various levels. Specifically, we assessed the influence of less abundant microbial types, such as yeast, on community functionality and bacterial community compositions over repeated propagation cycles amounting to ∼100 generations. The starting richness of metabolic guilds had a repeatable effect on bacterial community compositions, metabolic profiles, and acidity. The influence of a single metabolic guild, yeast in our study, played a dramatic role on function, but interestingly not on long-term species sorting trajectories of the remaining bacterial community. Our results together suggest an unexpected niche division between yeast and bacterial communities and evidence ecological selection on the microbial communities in our system.

Yeast cell vacuum infusion into fungal pellets as a novel cell encapsulation methodology

Immobilized yeast cells are used industrially in winemaking processes such as sparkling wine and Sherry wine production. Here, a novel approach has been explored for the infusion and immobilization of yeast cells into filamentous fungal pellets, which serve as a porous natural material. This was accomplished through vacuum application to force the yeast cells towards the core of the fungal pellets followed by culture in YPD medium to promote their growth from the interior. This method represents an improved variation of a previous approach for the assembly of "yeast biocapsules," which entailed the co-culture of both fungal and yeast cells in the same medium. A comparison was made between both techniques in terms of biocapsule productivity, cell retention capacity, and cell biological activity through an alcoholic fermentation of a grape must. The results indicated a substantial increase in biocapsule productivity (37.40-fold), higher cell retention within the biocapsules (threefold), and reduction in cell leakage during fermentation (twofold). Although the majority of the chemical and sensory variables measured in the produced wine did not exhibit notable differences from those produced utilizing suspended yeast cells (conventional method), some differences (such as herbaceous and toasted smells, acidity, bitterness, and persistence) were perceived and wines positively evaluated by the sensory panel. As the immobilized cells remain functional and the encapsulation technique can be expanded to other microorganisms, it creates potential for additional industrial uses like biofuel, health applications, microbe encapsulation and delivery, bioremediation, and pharmacy. KEY POINTS: • New approach improves biocapsule productivity and cell retention. • Immobilized yeast remains functional in fermentation. • Wine made with immobilized yeast had positive sensory differences.

Comparison of microbial communities and volatile profiles of wines made from mulberry and grape

In this study, three kinds of wines separately made from mulberry (MW), grape (GW), or mulberry/grape (MGW) were developed and their enological parameters, sensory scores, volatile components, and microbiota were investigated and compared. Contrary to the order of residual sugar and acidity of the three kinds of wines, the order of alcohol content from high to low is GW, MW, and MGW. A total of 60 volatile components (VCs), including esters (17), alcohols (12), acids (6), aldehydes (7), ketones (3), alkenes (3), amines (3), alkanes (4), pyrazines (2), benzene (1), sulfide (1), and thiazole (1), were identified by gas chromatography-ion mobility spectrometer (GC-IMS). The fingerprint of VCs and principal component analysis revealed that the volatile profiles of MGW and GW were more similar in comparison to that of MW and were significantly correlated with the mass ratio of mulberry to grape. Lactobacillus, Weissella, Pantoea, Leuconostoc, Lactococcus, Paenibacillus, Pediococcus, and Saccharomyces were identified as the main microflora at the genus level shared by the MW, MGW, and GW, suggesting that the heterolactic bacteria may contribute more to the high content of volatile acids in MW and MGW. The heatmap of core microbiota and main VCs of MW, MGW, and GW suggested the complicated and significant correlation between them. The above data implied that the volatile profiles were more closely related to the raw materials of winemaking and markedly affected by the fermentation microorganisms. This study provides references for evaluation and characterization of MGW and MW and improvement of MGW and MW winemaking process. KEY POINTS: • Fruit wine enological parameters, volatile profile, and microbiota were compared. • Sixty volatile compounds were identified by GC-IMS in three types of fruit wines. • Winemaking materials and microbiota affect volatile profiles of the fruit wines.

Development of Distillation Sensors for Spirit Beverages Production Monitoring Based on Impedance Spectroscopy Measurement and Partial Least-Squares Regression

During spirit beverages production, the distillate is divided into three parts: the head, the heart, and the tail. Acetaldehyde and ethanol are two key markers which allow the correct separation of distillate. Being toxic, the elimination of the head part, which contains a high concentration of acetaldehyde, is crucial to guarantee the consumer's health and security. Plus, the tail should be separated from the heart based on ethanol concentration. Nowadays, online or in-line sensors for acetaldehyde monitoring during distillation do not exist, and the online sensors for alcohol monitoring, based on density measurement, remain expensive for producers. In this work, we demonstrate the development of distillation monitoring sensors based on electrical impedance spectroscopy (EIS) measurements, combined with PLS-R (partial least-squares regression) modeling. Four types of sensors are proposed and tested with wine-based distillates. Using PLS-R, the best correlations were found for one electrode, named "SpotsSym". With an R ² up to 89.9% for acetaldehyde concentration prediction and an R ² up to 86.8% for ethanol, the obtained results indicate the promising potential of the proposed approach. To our knowledge, this is the first report of sensors capable of simultaneously measuring ethanol and acetaldehyde concentrations. Furthermore, these sensors offer the advantages of being low cost and nondestructive. Based on these results, the development of an in-line distillation monitoring system is possible in the near future, providing a promising tool for spirit beverages producers.

A comparative study of the effect of bacteria and yeasts communities on inoculated and spontaneously fermented apple cider

Understanding bacteria and yeasts communities can reduce unpredictable changes of apple cider. In this study, apple juice inoculated with Saccharomyces cerevisiae WET 136 and fermented spontaneously were compared, the relationships of bacteria, yeasts, organic acids, and volatiles were analyzed. Results showed that microbial diversity affected the fermentation, organic acids and volatiles in apple ciders. In the first four spontaneous fermentation days, LAB (lactic acid bacteria) multiplied and reached 7.89 lg CFU/mL, and then triggered malolactic fermentation (MLF), leading to malic acid decreased by 3880.52 mg/L and lactic acid increased by 4787.55 mg/L. The citric, succinic and fumaric acids content was 2171.14, 701.51 and 8.06 mg/L lower than that in inoculated cider, respectively. Although the yeasts multiplied during spontaneous fermentation, it did not reach 7.50 lg CFU/mL until the 5th day, which led to a long lag period, as well as later and lower production of acetaldehyde and higher alcohols. The inoculated yeast inhibited LAB, acetic acid bacteria, Rahnella, and non-Saccharomyces. Yeasts were the key to produce citric acid, acetaldehyde and 3-methyl-1-butanol in apple cider; while bacteria were closely related to the formation of lactic acid, acetic acid and ethyl acetate. It suggested that low higher alcohols and acetaldehyde can be realized by selecting yeasts, and Leuconostoc pseudomesenteroides can work as candidate to reduce L-malic and citric acids in apple cider.

The aromatic profile of wine distillates from Ugni blanc grape musts is influenced by the nitrogen nutrition (organic vs. inorganic) of Saccharomyces cerevisiae

Although the impact of nitrogen nutrition on the production of fermentative aromas in oenological fermentation is well known today, one may wonder whether the effects studied are the same when winemaking takes place at high turbidities, specifically for the production of wines intended for cognac distillation. To that effect, a fermentation robot was used to analyze 30 different fermentation conditions at two turbidity levels with several factors tested: (i) initial addition of nitrogen either organic (with a mixture of amino acids - MixAA) or inorganic with di-ammonium phosphate (DAP) at different concentrations, (ii) variation of the ratio of inorganic/organic nitrogen (MixAA and DAP) and (iii) addition of different single amino acids (alanine, arginine, aspartic acid and glutamic acid). A metabolomic analysis was carried out on all resulting wines to have a global vision of the impact of nitrogen on more than sixty aromatic molecules of various families. Then, at the end of the alcoholic fermentation, the wines were micro-distilled. A first interesting observation was that the aroma profiles of both wines and distillates were close, indicating that the concentration factor is rather similar for the different aromas studied. Secondly, the fermentation kinetics and aroma results have shown that the nitrogen concentration effect prevailed over the nature of nitrogen. Although the lipid concentration was in excess, an interaction between the assimilable nitrogen and lipid contents was still observed in wines or in micro-distillates. Alanine is involved in the synthesis of acetaldehyde, isobutanol, isoamyl alcohol and isoamyl acetate. Finally, it was demonstrated that modifying the ratio of assimilable nitrogen in musts is not an interesting technological response to improve the aromatic profile of wines and brandies. Indeed, unbalance the physiological ratio of the must by adding a single source of assimilable nitrogen (organic or inorganic) has been shown to deregulate the synthesis of most of the fermentation aromas produced by the yeast. Wine metabolomic analysis confirmed the results that had been observed in micro-distillates but also in the other aromatic families, especially on terpenes. The contribution of solid particles, but also yeast biosynthesis (via sterol management in must) to wine terpenes is discussed. Indeed, the synthesis of terpenes in this oenological context seems to be favored, especially since the concentration of assimilable nitrogen (in addition to the lipid content) favor their accumulation in the medium. A non-negligible vintage effect on the terpene profile was also demonstrated with variations in their distribution depending on the years. Thus, the present study focuses on the metabolism of wine yeasts under different environmental conditions (nitrogen and lipid content) and on the impact of distillation on the fate of flavor compounds. The results highlight once again the complexity of metabolic fluxes and of the impact of nitrogen source (nature and amount) and of lipids. Furthermore, this study demonstrates that beyond the varietal origin of terpenes, the part resulting from the de novo synthesis by the yeast during the fermentation cannot be neglected in the context of cognac winemaking with high levels of turbidity.

Sulphate Uptake Plays a Major Role in the Production of Sulphur Dioxide by Yeast Cells during Oenological Fermentations

Sulphur dioxide (SO2) is mostly used as an antioxidant additive in winemaking, but excessive levels may be harmful to both wine quality and consumers health. During fermentation, yeast Saccharomyces cerevisiae contributes significantly to final SO2 levels, and low-producing strains become especially interesting for the wine industry. Recent evidence implicating the impairment of sulphate transport in the SO2 decrease prompted us to further investigate the sulphate/sulphite metabolic connection in multiple winery yeast strains. Here, we inactivated by CRISPR/Cas9 the high-affinity sulphate permeases (Sul1p and Sul2p) in four strains normally used in winemaking, selected by their different abilities to produce SO2. Mutant strains were then used to perform fermentation assays in different types of natural must, and the final levels of SO2 and other secondary metabolites, crucial for wine organoleptic properties, were further determined for all fermentation products. Overall, data demonstrated the double ΔSUL1/ΔSUL2 inactivation in winery strains significantly decreases the levels of SO2 produced by mutant cells, without however altering both yeast fermentative properties and the ability to release relevant metabolites. Since similar effects were observed in diverse must types for strains with different features, the data strongly support that sulphate assimilation is the determining factor in SO2 production during oenological fermentations.

Contribution of Starmerella bacillaris and Oak Chips to Trebbiano d'Abruzzo Wine Volatile and Sensory Diversity

In this study, six fermentation trials were carried out: co-inoculation and sequential inoculation of Saccharomyces cerevisiae and Starmerella bacillaris in the presence and absence of oak chips. Moreover, Starm. bacillaris strain was attached to the oak chips and co-inoculated or sequentially inoculated with S. cerevisiae. Wines fermented with Starm. bacillaris adhered to oak chips showed a higher concentration of glycerol (more than 6 g/L) than the others (about 5 g/L). These wines also showed a higher content of polyphenols (more than 300 g/L) than the others (about 200 g/L). The addition of oak chips induced an increase of yellow color (b* value of about 3). Oak-treated wines were characterized by a higher concentration of higher alcohols, esters and terpenes. Aldehydes, phenols and lactones were detected only in these wines, independently from the inoculation strategy. Significant differences (p < 0.05) were also observed in the sensory profiles. The fruity, toasty, astringency, and vanilla sensations were perceived as more intense in wines treated with oak chips. The white flower descriptor showed a higher score in wines fermented without chips. Oak surface-adhered Starm. bacillaris cells could be a good strategy to improve the volatile and sensory profile of Trebbiano d'Abruzzo wines.

Influence of the use of sulfur dioxide, the distillation method, the oak wood type and the aging time on the production of brandies

Brandies are spirits produced from wine spirit and wine distillates. The original wines selected to be distilled to produce the wine spirits as well as the distillation method used determine, to a large extent, the organoleptic characteristics of the final products. The young wine spirits evolve during their aging in oak casks, this being another key stage that affects the chemical and sensorial characteristics of the final brandy. In this work, seven different brandies have been studied. They were obtained from wine produced with and without the addition of sulfur dioxide, during their fermentation, using different distillation methods (single, double or serial distillation using pot stills and continuous column distillation) and aged for 14 or 28 months in three different types of oak wood (Quercus alba, Quercus robur and Quercus petraea) previously toasted to two different grades (medium or light). The use of unsupervised pattern recognition methods (HCA and FA) determined that the addition of sulfur dioxide during the fermentation of the base wine has a major influence on the aromatic and phenolic profile of the aged distillates. On the other hand, by means of supervised pattern recognition methods such as LDA and ANNs, the most significant variables that would allow to discriminate between the classes of brandies identified in the study were evaluated. Thus, the results obtained should cast some light on the most significant variables to be taken into account regarding Brandy production processes if a better control over these production processes is to be achieved, so that more exclusive and better quality products are obtained.

Volatile aroma compounds of distilled “tsipouro” spirits: effect of distillation technique

The main objective of the present study was to determine the effect of the distillation technique: (i) fractional column distillation (FCD), (ii) copper alembic distillation (CAD), and (iii) home distillation (HD) on the aroma profile of the distilled spirit “tsipouro”. Volatile compounds were identified and semi-quantified in all above fractions for comparison purposes using Solid Phase Micro-extraction–Gas chromatography/Mass Spectrometry (SPME–GC/MS). Τhe richest (p < 0.05) distillate in volatile compounds was that of the FCD, with a total concentration of 768.38 mg/L followed by the HD (577.79 mg/L) and CAD (315.30 mg/L). The concentrations of the volatiles determined (alcohols, aldehydes, ketones, acetals, esters, organic acids, terpenes, hydrocarbons, and heterocyclic compounds) were found to be similar to those of other Greek and European distilled marc spirits. Ethanol and total volatile compound content were within limits set by Greek and EU legislation. Methanol, a toxic compound of grape marc distillates, was determined only in the entire product of CAD 1st distillation (19.35 mg/L) and the “head + tail” fraction of the CAD 2nd distillation (12.82 mg/L) in amounts well below the EU legal limit of 1000 g/hL of absolute alcohol. A general reducing trend was noted in most volatile compound concentration proceeding from the 1st to the 2nd CAD distillation refining the flavor of tsipouro.

In search for flavonoid and colorimetric varietal markers of Vitis vinifera L. cv Rufete wines

The better adaptation of autochthonous grape varieties to environmental changes is increasing the interest on them. Previous studies on Vitis vinifera L. cv Rufete, the flagship of DOP "Sierra de Salamanca", demonstrated its phenolic potential to produce quality wines. The present study aims at discovering flavonoid (HPLC-DAD-MSⁿ) and colorimetric (CIELAB) varietal markers in commercial Rufete wines (RW) that could be employed to discriminate them from those made with other varieties or mixtures. Compared to Tempranillo wines (TW), RW showed lower phenolic contents, with lower proportions of anthocyanins and flavonols but greater of flavanols. Principal Component Analysis applied to flavonoid and chromatic variables allowed varietal separation of the samples along PC2, which was mostly driven by %total prodelphinidins, %oligomeric procyanidins and C _ab * (greater in TW) and by %monomeric procyanindins and L* (greater in RW) and, additionally, by the proportions of A-type vitisins, acetaldehyde-related pigments, quercetin 3-O-glucuronide and Quercetin/Myricetin ratio (all greater in RW). The results of the present study show that the typicity of Rufete grapes is quite preserved in the wines made with up to 95% of Rufete and 5% of Tempranillo grapes or wines and independently of the enological practices of the different wineries.

Spectroelectrochemical Enzyme Sensor System for Acetaldehyde Detection in Wine

A new spectroelectrochemical two-enzyme sensor system has been developed for the detection of acetaldehyde in wine. A combination of spectroscopy and electrochemistry improves the analytical features of the electrochemical sensor because the optical information collected with this system is only associated with acetaldehyde and avoids the interferents also present in wines as polyphenols. Spectroelectrochemical detection is achieved by the analysis of the optical properties of the K₃[Fe(CN)₆]/K₄[Fe(CN)₆] redox couple involved in the enzymatic process: aldehyde dehydrogenase catalyzes the aldehyde oxidation using β-nicotinamide adenine dinucleotide hydrate (NAD⁺) as a cofactor and, simultaneously, diaphorase reoxidizes the NADH formed in the first enzymatic process due to the presence of K₃[Fe(CN)₆]. An analysis of the characteristic UV-vis bands of K₃[Fe(CN)₆] at 310 and 420 nm allows the detection of acetaldehyde, since absorption bands are only related to the oxidation of this substrate, and avoids the contribution of other interferents.

A Study on the Influence of the Use of Sulphur Dioxide, the Distillation System and the Aging Conditions on the Final Sensory Characteristics of Brandy

Brandy is a unique alcoholic beverage obtained from wine distillates. Numerous studies have been published on its physicochemical traits and the effect of certain elaboration variables on them, but not many studies have been carried out from a sensory point of view or that have followed standardized methods applicable to this discipline. This study intends to determine the effect that certain production variables have on the sensory characteristics of brandy. These variables are the following: The use of sulphur dioxide during the fermentation of the base wine, the subsequent distillation system, the alcohol content during aging, the botanical origin of the aging casks, and their toasting degree. For this purpose, the guidelines provided by the ISO standards for sensory analysis have been followed, and chromatic parameters have also been determined. Heavy extractions from Quercus petraea casks resulted in brandies with widely varying colors, although these were hard to distinguish using the olfactory and gustatory properties associated with the factors under study. Conversely, those brandies aged in Quercus alba casks presented very consistent greenish shades that are not traditionally associated with aged brandy. This lower extraction could explain why the aromatic traits that are found in the fresh spirit are better preserved when this type of oak is used. The spirit obtained through the distillation of SO2-free wines aged in Quercus robur presented average sensory characteristics: Good color, smooth in the mouth, and medium-intensity oak notes. The distillates that were aged at 55% ABV were later perceived as more aromatically intense with a greater oak note on the palate. On the other hand, the brandies obtained from wines without SO2 added were perceived as less alcoholic, sweeter, and more balanced, with a softer oak note.

Effects of Probiotic Fermented Fruit Juice-Based Biotransformation by Lactic Acid Bacteria and Saccharomyces boulardii CNCM I-745 on Anti-Salmonella and Antioxidative Properties

Fermentation is an effective process for providing various beneficial effects in functional beverages. Lactic acid bacteria and yeast fermentation-based biotransformation contribute to enhancement of nutritional value and digestibility, including lactose intolerance reduction and control of infections. In this study, the probiotic fermented fruit juice (PFJ) was produced by Lactobacillus plantarum TISTR 1465, Lactobacillus salivarius TISTR 1112, and Saccharomyces boulardii CNCM I-745 while mixed fruit juice (MFJ) was used as the basic medium for microorganism growth. The potential function, the anti-salmonella activity of PFJ, was found to be effective at 250 mg/ml of MIC and 500 mg/ml of MBC. Biofilm inhibition was performed using the PFJ samples and showed at least 70% reduction in cell attachment at the MIC concentration of Salmonella Typhi DMST 22842. The antioxidant activities of PFJ were determined and the results revealed that FSB.25 exhibited 78.40 ± 0.51 mM TE/ml by FRAP assay, while FPSB.25 exhibited 3.44 ± 0.10 mM TE/ml by DPPH assay. The volatile compounds of PFJ were characterized by GC-MS, which identified alcohol, aldehyde, acid, ester, ketone, phenol, and terpene. The most abundant organic acid and alcohol detected in PFJ were acetic acid and 2-phenylethanol, and the most represented terpene was β-damascenone. The sensory attributes showed scores higher than 7 on a 9-point hedonic scale for the FPB.25, illustrating that it was well accepted by panelists. Taken together, our results showed that PFJ could meet current consumer demand regarding natural and functional, fruit-based fermented beverages.

Preliminary Studies on Endotherapy Based Application of Ozonated Water to Bobal Grapevines: Effect on Wine Quality

The application of ozonated water in the vineyard is an increasingly popular tool for disease management, but the quality of grapes and resulting wines is likely to be affected. Endotherapy, or trunk injection, is a particularly useful method to apply phytosanitary products since many fungal pathogens colonize the grapevine woody tissues. Thus, the present study aimed to evaluate the effect on wine quality of the ozonated water applied to Bobal grapevines, one of the most cultivated red varieties in Spain, through endotherapy (E) or its combination with spraying (E + S). Endotherapy was carried out four times before harvest for both E and E + S treatments, and spraying was performed 2 days before and after each endotherapy application. Grapes were harvested, vinified, and the quality of the finished wines was evaluated through several enological parameters and the phenolic and volatile composition. Both treatments resulted in less alcoholic and more acidic wines. The E treatment, although it reduced the content of phenolic acids, stilbenes and flavanols, significantly increased anthocyanins, whereas E + S decreased the overall amount of phenolics, which had different implications for wine colour. In terms of aroma, both treatments, but E to a greater extent, reduced the content of glycosylated precursors and differentially affected free volatiles, both varietal and fermentative. Thus, the dose of ozonated water, frequency and/or method of application are determining factors in the effect of these treatments on wine quality and must be carefully considered by winegrowers to establish the optimum treatment conditions so as not to impair the quality of wines.

Adaptive Laboratory Evolution of Yeasts for Aroma Compound Production

Aroma compounds are important in the food and beverage industry, as they contribute to the quality of fermented products. Yeasts produce several aroma compounds during fermentation. In recent decades, production of many aroma compounds by yeasts obtained through adaptive laboratory evolution has become prevalent, due to consumer demand for yeast strains in the industry. This review presents general aspects of yeast, aroma production and adaptive laboratory evolution and focuses on the recent advances of yeast strains obtained by adaptive laboratory evolution to enhance the production of aroma compounds.

Role of Yeasts on the Sensory Component of Wines

The aromatic complexity of a wine is mainly influenced by the interaction between grapes and fermentation agents. This interaction is very complex and affected by numerous factors, such as cultivars, degree of grape ripeness, climate, mashing techniques, must chemical−physical characteristics, yeasts used in the fermentation process and their interactions with the grape endogenous microbiota, process parameters (including new non-thermal technologies), malolactic fermentation (when desired), and phenomena occurring during aging. However, the role of yeasts in the formation of aroma compounds has been universally recognized. In fact, yeasts (as starters or naturally occurring microbiota) can contribute both with the formation of compounds deriving from the primary metabolism, with the synthesis of specific metabolites, and with the modification of molecules present in the must. Among secondary metabolites, key roles are recognized for esters, higher alcohols, volatile phenols, sulfur molecules, and carbonyl compounds. Moreover, some specific enzymatic activities of yeasts, linked above all to non-Saccharomyces species, can contribute to increasing the sensory profile of the wine thanks to the release of volatile terpenes or other molecules. Therefore, this review will highlight the main aroma compounds produced by Saccharomyces cerevisiae and other yeasts of oenological interest in relation to process conditions, new non-thermal technologies, and microbial interactions.

Impact of Acetaldehyde Addition on the Sensory Perception of Syrah Red Wines

Two experimental Syrah red wines with different polyphenol contents were used to study the impact of acetaldehyde addition on olfactory perception. Free acetaldehyde levels were measured in red wine by Head Space-Gas Chromatography-Mass Spectrometry (HS-GC-MS) to determine the acetaldehyde combination levels for those wines. Significant differences were observed for both sensory threshold and acetaldehyde combination for the wines. A descriptive sensory analysis of the wines was then performed by using a trained panel and a Hierarchical-Check-All-That-Apply (HCATA) analysis of the wines with or without acetaldehyde addition. The results show that classical cited sensory descriptors for acetaldehyde (overripe apple and oxidized apple) varied significantly between the control wines and those with acetaldehyde addition. Non-acetaldehyde related descriptors (fresh vegetable, fresh flowers, cocoa, and meat juice) were also significantly impacted in the samples with increasing acetaldehyde additions. This suggests possible interactions between acetaldehyde and other volatile compounds that can create antagonistic or synergistic effects between the molecules or at the olfactory receptor level.

Direct NMR evidence for the dissociation of sulfur-dioxide-bound acetaldehyde under acidic conditions: Impact on wines oxidative stability

SO₂ reaction with electrophilic species present in wine, including in particular carbonyl compounds, is responsible for the reduction of its protective effect during wine aging. In the present study, direct ¹H NMR profiling was used to monitor the reactivity of SO₂ with acetaldehyde under wine-like oxidation conditions. The dissociation of acetaldehyde bound SO₂ was evidenced suggesting that released free SO₂ can further act as an antioxidant. EPR and DPPH assays showed an increasing antioxidant capacity of wine with the increase in the concentration of acetaldehyde sulfonate. The presence of acetaldehyde sulfonate in wines was correlated with the overall antioxidant activity of wines. The first evidence of acetaldehyde bound SO₂ dissociation provides a completely new representation of the long-term protection efficiency of SO₂ during bottle aging.

Digital Assessment and Classification of Wine Faults Using a Low-Cost Electronic Nose, Near-Infrared Spectroscopy and Machine Learning Modelling

The winemaking industry can benefit greatly by implementing digital technologies to avoid guesswork and the development of off-flavors and aromas in the final wines. This research presents results on the implementation of near-infrared spectroscopy (NIR) and a low-cost electronic nose (e-nose) coupled with machine learning to detect and assess wine faults. For this purpose, red and white base wines were used, and treatments consisted of spiked samples with 12 faults that are traditionally formed in wines. Results showed high accuracy in the classification models using NIR and e-nose for red wines (94–96%; 92–97%, respectively) and white wines (96–97%; 90–97%, respectively). Implementing new and emerging digital technologies could be a turning point for the winemaking industry to become more predictive in terms of decision-making and maintaining and increasing wine quality traits in a changing and challenging climate.

Cabernet Sauvignon Red Must Processing by UHPH to Produce Wine Without SO2: the Colloidal Structure, Microbial and Oxidation Control, Colour Protection and Sensory Quality of the Wine

A cryo-macerated must of V. vinifera L. cabernet sauvignon was processed by ultra-high-pressure homogenisation (UHPH) sterilisation without the use of SO2. The UHPH treatment of the must was carried out continuously at a pressure of 300 MPa and reaching a maximum temperature of 77 °C for less than 0.2 s. The colloidal structure of the UHPH must was evaluated by atomic force microscopy (AFM) measuring an average particle size of 457 nm. The initial microbial load was 4-log CFU/mL (yeast), 3-log CFU/mL (bacteria). No yeast and non-sporulating bacteria were detected in 1 mL and 10 mL of the UHPH-treated must, respectively. Furthermore, no fermentative activity was detected in the non-inoculated UHPH-treated musts for more than 50 days. A strong inactivation of the oxidative enzymes was observed, with lower oxidation (≈ × 3) than controls. The antioxidant activity of the UHPH-treated must was much higher (106%) than that of the control must. UHPH had a protective effect in total anthocyanins, and especially in acylated anthocyanins (+ 9.3%); furthermore, the fermentation produces fewer higher alcohol (-44,3%) and more 2-phenylethyl acetate (+ 63%).

Impact of fermentation temperature and grape solids content on the chemical composition and sensory profiles of Cabernet Sauvignon wines made from flash détente treated must fermented off-skins

This study investigated the color, phenolic, polysaccharide, volatile and sensory profiles of Cabernet Sauvignon wines made from flash détente (FD) treated musts fermented at different temperatures (16, 24 or 32 °C), with and without suspended grape solids. Low fermentation temperature and low solids content increased the concentration of esters, whereas the opposite conditions increased the concentration of fusel alcohols, polysaccharides and glycerol. Higher fermentation temperatures also increased linalool concentration independent of solids content. Traditional maceration fermentation conditions gave the highest concentration of fusel alcohols and 1-hexanol relative to FD treatments. Pre-fermentation removal of grape solids from FD juice created wines with increased red fruit and confectionery attributes, whereas inclusion of 3.5% grape solids increased dark fruit notes. In comparison, control wines had significantly higher green and savory attributes compared to wines from FD treatments. Research findings demonstrated the potential for FD to be used to create differentiated red wine styles.

The Impact of Must Nutrients and Yeast Strain on the Aromatic Quality of Wines for Cognac Distillation

In order to understand the influence of nitrogen and lipid nutrition on the aromatic quality of wines for cognac distillation, we developed a transdisciplinary approach that combined statistical modeling (experimental central composite design and response surface modeling) with metabolomic analysis. Three Saccharomyces cerevisiae strains that met the requirements of cognac appellation were tested at a laboratory scale (1 L) and a statistical analysis of covariance was performed to highlight the organoleptic profile (fermentative aromas, terpenes, alcohols and aldehydes) of each strain. The results showed that nitrogen and lipid nutrients had an impact on the aromatic quality of cognac wines: high lipid concentrations favored the production of organic acids, 1-octen-3-ol and terpenes and inhibited the synthesis of esters. Beyond this trend, each yeast strain displayed its own organoleptic characteristics but had identical responses to different nutritional conditions.

Discovering the Influence of Microorganisms on Wine Color

Flavor, composition and quality of wine are influenced by microorganisms present on the grapevine surface which are transferred to the must during vinification. The microbiota is highly variable with a prevalence of non-Saccharomyces yeasts, whereas Saccharomyces cerevisiae is present at low number. For wine production an essential step is the fermentation carried out by different starter cultures of S. cerevisiae alone or in mixed fermentation with non-Saccharomyces species that produce wines with significant differences in chemical composition. During vinification wine color can be influenced by yeasts interacting with anthocyanin. Yeasts can influence wine phenolic composition in different manners: direct interactions—cell wall adsorption or enzyme activities—and/or indirectly—production of primary and secondary metabolites and fermentation products. Some of these characteristics are heritable trait in yeast and/or can be strain dependent. For this reason, the stability, aroma, and color of wines depend on strain/strains used during must fermentation. Saccharomyces cerevisiae or non-Saccharomyces can produce metabolites reacting with anthocyanins and favor the formation of vitisin A and B type pyranoanthocyanins, contributing to color stability. In addition, yeasts affect the intensity and tonality of wine color by the action of β-glycosidase on anthocyanins or anthocyanidase enzymes or by the pigments adsorption on the yeast cell wall. These activities are strain dependent and are characterized by a great inter-species variability. Therefore, they should be considered a target for yeast strain selection and considered during the development of tailored mixed fermentations to improve wine production. In addition, some lactic acid bacteria seem to influence the color of red wines affecting anthocyanins’ profile. In fact, the increase of the pH or the ability to degrade pyruvic acid and acetaldehyde, as well as anthocyanin adsorption by bacterial cells are responsible for color loss during malolactic fermentation. Lactic acid bacteria show different adsorption capacity probably because of the variable composition of the cell walls. The aim of this review is to offer a critical overview of the roles played by wine microorganisms in the definition of intensity and tonality of wines’ color.

Roles of free radical on the formation of acetaldehyde in model wine solutions under different ultrasound parameters: A key bridge-link compound for red wine coloration during ageing

In order to explore the effects of ultrasound on the formation of acetaldehyde and its mechanism in model wine solutions, ultrasound conditions and free radicals were investigated by response surface methodology and electron paramagnetic resonance spectroscopy (EPR), respectively. The results indicate that ultrasound does induce the production of acetaldehyde with the maximum amount under the conditions of ultrasound power density 0.2 W/cm², 48 min and 32 °C. The hydroxyl radicals and the 1-hydroxyethyl free radicals are the main initiator and precursor for acetaldehyde, respectively. Furthermore, the stronger the 1-hydroxyethyl free radicals captured by EPR, the lower the formation of acetaldehyde. In addition, the content of Fe²⁺and ethanol also exerted a certain influence on the acetaldehyde formation. In conclusion, ultrasound does promote the production of acetaldehyde in the model wine solutions, which is beneficial for well understanding the mechanism of ultrasound in modifying the wine color and accelerating ageing.

Profiling modifications in physicochemical, chemical and antioxidant properties of wild blackberry (Rubus sp.) during fermentation with EC 1118 yeast

Mexico is an extensively diverse country with a wide variety of wild species of blackberries (Rubus spp.), which are rich in bioactive compounds, however, these fruits are underutilized. Fermentation is a process that transforms the chemical compounds of fruits and increases nutraceutical properties. This study aimed to determine the physicochemical changes and the bioactive compounds profile that take place during the fermentation of wild blackberries using yeast EC 1118 and to evaluate its relationship with antioxidant activity (AOx). The results indicated that after 96 h of fermentation the content of carbohydrates (56%), total phenolic compounds (37%), and anthocyanins (22%), decreased, respectively. The physicochemical parameters showed statistic differences (p ≤ 0.05) at the endpoint of fermentation. The diversity of fatty acids was increased (55%), compared with unfermented blackberries. The modification of carbohydrates, anthocyanins, catechin, gallic and ellagic acid profiles were also monitored performing chromatographic techniques. The AOx, determined by ORAC and DPPH assays, showed the highest results for ORAC at 96 h increased a 140.2%, while DPPH values enhanced a 36.6% at 48 h of bioprocessing. Strong positive correlations were found between fermentation time and DPPH values (r = 0.8131), between ORAC and gallic acid content (r = 0.8688), and between anthocyanin content and pH (r = 0.9126). The fermentation of wild blackberries with EC 1118 yeast represents an alternative for development and formulation of potential ingredients for functional foods.

Supplementary information

The online version contains supplementary material available at (10.1007/s13197-020-04953-x).

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 ruling 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.

Production, Characterization, and Sensory Profiling of Novel Pepper Distilled Spirit

This study described the production method of novel whiskey using black pepper berries as raw material including the determination of chemical composition and sensory profile of this distillate. The production process consisted of production of fermentation medium via hydrothermal treatment, followed by fermentation and distillation. The incorporation of hydrothermal extraction process makes this whiskey production process differ from the existing commercial spirit production protocol. Chemical composition analysis showed that there were 12 main volatile compounds that contribute to the aroma profile of this pepper whiskey which consisted of 1 aldehyde group, 3 ester groups, 2 phenolic compounds, and 6 alcohol groups. All of these compounds are presented at different concentrations that are able to give pleasant and signature aroma to this spirit. A 10-member descriptive analysis panel conducted showed that 7 descriptors can be used to define the organoleptic quality of this whiskey, namely, clarity and brilliance (visual), fruity and flora (aroma), spiciness and sweetness (taste), and fruity mouthfeels. In conclusion, pepper berries can be used as raw material for pepper whiskey production and having organoleptic quality acceptable for human consumption.

Simultaneously deleting ADH2 and THI3 genes of Saccharomyces cerevisiae for reducing the yield of acetaldehyde and fusel alcohols

The reduced yields of acetaldehyde and fusel alcohols through fermentation by Saccharomyces cerevisiae is of significance for the improvement of the flavor and health of alcoholic beverages. In this study, the ADH2 (encode alcohol dehydrogenase) and THI3 (encode decarboxylase) genes of the industrial diploid strain S. cerevisiae XF1 were deleted. Results showed that single-gene-deletion mutants by separate gene deletion of ADH2 or THI3 led to a reduced production of the acetaldehyde or fusel alcohols, respectively. In the meantime, the double-gene-deletion mutant S. cerevisiae XF1-AT was constructed by deleting the ADH2 and THI3 simultaneously. An equivalent level of the ethanol production by the S. cerevisiae XF1-AT could be achieved but with the yields of acetaldehyde, isoamyl alcohol and iso-butanol reduced by 42.09%, 15.65% and 20.16%, respectively. In addition, there was no interaction between the ADH2 deletion and THI3 deletion in reducing the production of acetaldehyde and fusel alcohols. The engineered S. cerevisiae XF1-AT provided a new strategy to alcoholic beverages brewing industry for reducing the production of acetaldehyde as well as the fusel alcohols.

Lebanon's Native Oenological Saccharomyces cerevisiae Flora: Assessment of Different Aspects of Genetic Diversity and Evaluation of Winemaking Potential

A total of 296 isolates of Saccharomyces cerevisiae sampled from naturally fermenting grape musts from various locations in Lebanon were typed by interdelta fingerprinting. Of these, 88 isolates were compared with oenological strains originating from various countries, using microsatellite characterization at six polymorphic loci. These approaches evidenced a large diversity of the natural oenological Lebanese flora over the territory as well as in individual spontaneous fermentations. Several cases of dominance and perenniality of isolates were observed in the same wineries, where fermentations appeared to involve lineages of sibling isolates. Our work thus evidenced a “winery effect” on strains’ relatedness. Similarly, related or identical strains were also detected in vicinal wineries, suggesting strain circulation within small geographical areas and a further “vicinity effect”. Moreover, and despite its diversity, the Lebanese flora seemed interrelated, on the basis of microsatellite loci analysis, in comparison to worldwide communities. We finally tested the ability of 21 indigenous strains to act as potential starters for winemaking. Seven of them passed our pre-selection scheme and two of them at least may be good candidates for use provided pilot-scale assays confirm their suitability.

Non-Saccharomyces as Biotools to Control the Production of Off-Flavors in Wines

Off-flavors produced by undesirable microbial spoilage are a major concern in wineries, as they affect wine quality. This situation is worse in warm areas affected by global warming because of the resulting higher pHs in wines. Natural biotechnologies can aid in effectively controlling these processes, while reducing the use of chemical preservatives such as SO₂. Bioacidification reduces the development of spoilage yeasts and bacteria, but also increases the amount of molecular SO₂, which allows for lower total levels. The use of non-Saccharomyces yeasts, such as Lachancea thermotolerans, results in effective acidification through the production of lactic acid from sugars. Furthermore, high lactic acid contents (>4 g/L) inhibit lactic acid bacteria and have some effect on Brettanomyces. Additionally, the use of yeasts with hydroxycinnamate decarboxylase (HCDC) activity can be useful to promote the fermentative formation of stable vinylphenolic pyranoanthocyanins, reducing the amount of ethylphenol precursors. This biotechnology increases the amount of stable pigments and simultaneously prevents the formation of high contents of ethylphenols, even when the wine is contaminated by Brettanomyces.

Changes in acetaldehyde and formaldehyde contents in foods depending on the typical home cooking methods

Analytical methods were validated for the evaluation of acetaldehyde and formaldehyde, which are harmful chemicals, using solid-phase microextraction-gas chromatography/mass spectrometry in four different matrices. Typical home-cooking methods including boiling, pan-frying, and stir-frying, were applied to beef, rapeseed oil, canned pork ham, egg, and rice wine. In addition, monosaccharides, disaccharides, alanine, and glycine were heated for the formation of both aldehydes. All validation parameters, including accuracy, precision, limit of detection, limit of quantification, and uncertainty, for four different matrices were within recommended ranges, confirming the validity of the current method. Acetaldehyde contents ranged from undetectable to 17.92 μg/g and formaldehyde contents ranged from undetectable to 0.27 μg/g. Generally, boiling decreased both aldehydes except acetaldehyde in egg. Pan- and stir-frying increased both aldehyde content substantially in rapeseed oil whereas pan-frying increased acetaldehyde content in canned pork ham and egg. Fructose and sucrose produced higher content of both aldehydes than maltose and glucose when heated. Depending on food type, the cooking process had slightly different effects on the contents of acetaldehyde and formaldehyde.

Anthocyanins from purple passion fruit (Passiflora edulia Sims) rind-An innovative source for nonbleachable pigment production

Passion fruit rind is a waste product from the beverage industry that is rich in anthocyanins that can be potentially applied as a natural colorant. However, the inherent instability of anthocyanins causes rapid discoloration. In this study, the cyanidin-3-glucoside (C-3-G) in passion fruit rind was extracted using 50% ethanol and converted into nonbleachable pigments by reaction with Oolong tea extracts and acetaldehyde. Reactions over 70 days formed high concentrations of stable nonbleachable pigments (3.07-6.68 absorbance unit [A.U.], in total) such as pyranoanthocyanins, as well as oligomeric and polymeric pigments with ethyl-linked bridges. In C-3-G and acetaldehyde reaction, positive relations were found among acetaldehyde concentration, color density, and nonbleachable pigment concentrations. As for reactions with C-3-G and Oolong tea extract combined with acetaldehyde, greater color density and greater concentrations of nonbleachable pigments (10.80-12.34, 4.25-4.40 A.U., respectively) were formed compared with acetaldehyde alone. In addition, the antioxidant capabilities of the extracts were enhanced after reaction with Oolong tea extracts. The results of this study show a useful method to enhance the stability of anthocyanins from passion fruit rind and also provide greater economic value to this waste product. PRACTICAL APPLICATION: Ripened passion fruits contain a high concentration of anthocyanins in their rind. These anthocyanins can be optimally extracted by ultrasonic assisted solvent extraction to provide stable pigments by inducing acetaldehyde (a volatile compound often found in foods and beverages) into the anthocyanins. These stable pigments have a greater reddish hue in solution than the anthocyanin extracted from the rind and are more stable over a greater pH range. In addition, these stable pigments can be potentially used as colorant throughout the food and cosmetic industry to provide high economical values.

Canadian policy changes for alcohol-based hand rubs during the COVID-19 pandemic and unintended risks

The COVID-19 pandemic led to major changes in public policies to address supply chain disruption and escalated the price of consumer disinfectant products. To address market demands on alcohol-based hand rubs and disinfectants, Health Canada implemented major changes to the regulations regarding composition, handling, transportation, and packaging to insure product availability. Furthermore, accelerated licensing of ingredients and packaging did not meet standard medical quality guidelines yet were authorized for manufacturing and packaging of alcohol-based hand rubs and disinfectants. The accountability associated with these policy changes were reactive, including industry self-reporting, consumer reporting, and Health Canada advisories and recalls that were responsive to products after they were available in the market. Nonetheless, Canadian public health policy increased hand sanitizers availability. However, some of the interim policies have raised major public health concerns associated with ethanol quality, packaging, and labeling, and enforcement of regulations. In this paper, we review the changes in the Canadian regulations amid the current pandemic and we evaluate the unintended health risks that might arise from these changes.