The Influence of Chitosan on the Chemical Composition of Wines Fermented with Lachancea thermotolerans.

Chitosan exerts a significant influence on various chemical parameters affecting the quality of wine produced using multiple strains of Lachancea thermotolerans. The impact of chitosan on these parameters varies depending on the specific strain studied. We observed that, under the influence of chitosan, the fermentation kinetics accelerated for all examined strains. The formation of lactic acid increased by 41% to 97% across the studied L. thermotolerans strains, depending on the specific strain. This effect also influenced acidity-related parameters such as total acidity, which increased by 28% to 60%, and pH, which experienced a decrease of over 0.5 units. The consumption of malic acid increased by 9% to 20% depending on the specific strain of L. thermotolerans. Nitrogen consumption also rose, as evidenced by all L. thermotolerans strains exhibiting a residual value of Primary Amino Nitrogen (PAN) of below the detection limit, and ammonia consumption increased by 90% to 100%, depending on the strain studied. However, certain parameters such as acetic acid, succinic acid, and glycerol showed contradictory results depending on the strain under investigation. In terms of volatile composition, chitosan supplementation led to increased production of i-butanol by 32% to 65%, 3-methylbutanol by 33% to 63%, and lactic acid ethyl ester by 58% to 91% across all studied strains of L. thermotolerans. Other analyzed aroma compounds exhibited varying changes depending on the specific strain of L. thermotolerans.

A comparative study of Lachancea thermotolerans fermentative performance under standardized wine production conditions.

The study explores diverse strains of Lachancea thermotolerans in single-inoculum wine fermentation conditions using synthetic grape must. It aims to analyze the role of the species without external influences like other microorganisms or natural grape must variability. Commercial strains and selected vineyard isolates, untested together previously, are assessed. The research evaluates volatile and non-volatile chemical compounds in final wine, revealing significant strain-based variations. L. thermotolerans notably produces lactic acid and consumes malic acid, exhibiting moderate ethanol levels. The volatile profile displays strain-specific impacts, affecting higher alcohol and ester concentrations compared to S. cerevisiae. These effects vary based on the specific compounds. Using a uniform synthetic must enables direct strain comparisons, eliminating grape-related, environmental, or timing variables in the experiment, facilitating clearer insights into the behavior of L. thermotolerans in wine fermentation. The study compares for the first time all available commercial strains of L. thermotolerans.

The Influence of Pichia kluyveri Addition on the Aroma Profile of a Kombucha Tea Fermentation.

Traditional kombucha is a functional tea-based drink that has gained attention as a low or non-alcoholic beverage. The fermentation is conducted by a community of different microorganisms, collectively called SCOBY (Symbiotic Culture of Bacteria and Yeast) and typically consists of different acetic acid bacteria and fermenting yeast, and in some cases lactic acid bacteria that would convert the sugars into organic acids-mostly acetic acid. In this study, the effect of including a Pichia kluyveri starter culture in a kombucha fermentation was investigated. P. kluyveri additions led to a quicker accumulation of acetic acid along with the production of several acetate esters including isoamyl acetate and 2-phenethyl acetate. A subsequent tasting also noted a significant increase in the fruitiness of the kombucha. The significant contribution to the aroma content shows the promise of this yeast in future microbial formulations for kombucha fermentations.

Engineering a fermenting yeast able to produce the fragrant ß-ionone apocarotenoid for enhanced aroma properties in wine.

Wine is composed of multitudinous flavour components and volatile organic compounds that provide this beverage with its attractive properties of taste and aroma. The perceived quality of a wine can be attributed to the absolute and relative concentrations of favourable aroma compounds; hence, increasing the detectable levels of an attractive aroma, such as ß-ionone with its violet and berry notes, can improve the organoleptic qualities of given wine styles. We here describe the generation of a new grape-must fermenting strain of Saccharomyces cerevisiae that is capable of releasing ß-ionone through the heterologous expression of both the enzyme carotenoid cleavage dioxygenase 1 (CCD1) and its substrate, ß-carotene. Haploid laboratory strains of S. cerevisiae were constructed with and without integrated carotenogenic genes and transformed with a plasmid containing the genes of CCD1. These strains were then mated with a sporulated diploid wine industry yeast, VIN13, and four resultant crosses-designated MQ01-MQ04-which were capable of fermenting the must to dryness were compared for their ability to release ß-ionone. Analyses of their fermentation products showed that the MQ01 strain produced a high level of ß-ionone and offers a fermenting hybrid yeast with the potential to enhance the organoleptic qualities of wine.

Co-Fermentations of Kveik with Non-Conventional Yeasts for Targeted Aroma Modulation.

Kveik are consortia of yeast used for farmhouse ale production in Western Norway. Yeast strains derived from these mixtures are known, for example, for their high fermentation rate, thermotolerance, lack of phenolic off flavor production (POF-) and strong flocculation phenotype. In this study, we used five single cell yeast isolates from different Kveik yeasts, analyzed their fermentation and flavor production, and compared it with a typical yeast used in distilleries using 20 °C and 28 °C as the fermentation temperatures. One of the isolates, Kveik No 3, showed an impairment of maltotriose utilization and thus a reduced ethanol yield. Kveik fermentations for spirit production often harbor bacteria for flavor enrichment. We sought to improve Kveik fermentations with non-conventional yeasts (NCY). To this end we co-fermented Kveik isolates with Hanseniaspora uvarum, Meyerozyma guilliermondii and Pichia kudriavzevii using 5:1 ratios (Kveik vs. NCY) at 20 °C. The combinations of Kveik No 1 with P. kudriavzevii and Kveik No 1 with Hanseniaspora uvarum showed substantially increased amounts of specific volatile aroma compounds that were previously identified in the NCYs. Our results indicate that Kveik isolates appear to be suitable for co-fermentations with certain NCY to enhance beer or spirit fermentations, increasing the potential of these yeasts for beverage productions.

Biological management of acidity in wine industry: A review.

Climate change is generating several problems in wine technology. One of the main ones is lack of acidity and difficulties performing malolactic fermentation to stabilize wines before bottling. Among the different available acidity management technologies, such as direct acid addition, ion exchange resins, electro-membrane treatments, or vineyard management, the microbiological option is reliable and deeply studied. The main approach is the increase in malic acid content because of the metabolism of specific Saccharomyces strains and to increase lactic acid because of the metabolism of Lachancea genus. Other non-Saccharomyces yeasts, such as Starmerella bacillaris or Candida stellata can also acidify significantly because of the production of pyruvic or succinic acid. Wine industry needs the removal of malic acid in most red wines before bottling to achieve wine stability. Oenococus oeni performs the malolactic fermentation of red wines on most conditions because of the metabolization of malic acid into lactic acid. However, modern oenology challenges such as high ethanol concentrations, high pH or low levels of malic acid have made researchers to look for other options to reduce potential risks of deviation. Other wine-related microorganisms able to de-acidify malic acid have appeared as interesting alternatives for specific difficult scenarios. Lactiplantibacillus plantarum and Schizosaccharomyces genus make up nowadays the main studied alternatives.

The film-forming Pichia spp. in a winemaker's toolbox: A simple isolation procedure and their performance in a mixed-culture fermentation of Vitis vinifera L. cv. Gewürztraminer must.

Certain yeast species belonging to the Pichia genus are known to form a distinctive film on grape must and wine. In a mixed-culture type fermentation, Pichia spp. (P. kluyveri in particular) are known to impart beneficial oenological attributes. In this study, we report on an easy isolation method of Pichia spp. from grape must by exploiting their film-forming capacity on media containing 10% ethanol. We isolated and identified two Pichia species, namely Pichia kudriavzevii and Pichia kluyveri, and subsequently co-inoculated them with Saccharomyces cerevisiae to ferment Gewürztraminer musts. Noteworthy differences included a significant increase in the 2-phenethyl acetate levels with the P. kluyveri co-fermentation and a general increase in ethyl esters with the P. kudriavzevii co-fermentation. Both Pichia co-inoculations yielded higher levels of glycerol in the final wines. Based on all the wine parameters we tested, the P. kluyveri strain that was isolated performed similarly to a commercial P. kluyveri strain.

Synthesis of Aroma Compounds as a Function of Different Nitrogen Sources in Fermentations Using Non-Saccharomyces Wine Yeasts.

Non-Saccharomyces yeasts are prevalent at the onset of grape must fermentations and can have a significant influence on the final wine product. In contrast to Saccharomyces cerevisiae, the biosynthetic pathways leading to aroma compound formation in these non-conventional yeasts, in particular those that are derived from amino acid metabolism, remains largely unexplored. Within a synthetic must environment, we investigated the amino acid utilization of four species (Hanseniaspora uvarum, Hanseniaspora osmophila, Zygosaccharomyces rouxii, Starmerella bacillaris) and S. cerevisiae. We report on the differential uptake preferences for amino acids with H. uvarum displaying the most rapid uptake of most amino acids. To investigate the fate of amino acids and their direct contribution to aroma synthesis in H. uvarum, H. osmophila and Z. rouxii, musts were supplemented with single amino acids. Aroma profiling undertaken after three days showed the synthesis of specific aroma compounds by the respective yeast was dependent on the specific amino acid supplementation. H. osmophila showed similarities to S. cerevisiae in both amino acid uptake and the synthesis of aroma compounds depending on the nitrogen sources. This study shows how the uptake of specific amino acids contributes to the synthesis of aroma compounds in wine fermentations using different non-Saccharomyces yeasts.

Puree and Juice of Thai Mango and Pineapple Analyzed by High-Performance Thin-Layer Chromatography Hyphenated with Effect-Directed Assays.

The requirements for analytical tools are changing due to the global production chain, the increasing cases of adulteration, and the growing trend towards consumption of plant-based food products worldwide. The assessment of bioactivity of natural foods is currently not a quality criterion, and a paradigm shift is postulated. A non-targeted effect-directed profiling by high-performance thin-layer chromatography hyphenated with five different effect-directed assays was developed exemplarily for the puree and juice products of mango Mangifera indica L. (Anacardiaceae) and pineapple Ananas comosus (L.) Merr. (Bromeliaceae). Several bioactive compounds were detected in each sample. The additional bioactivity information obtained through effect-directed profiles improves, expands and modernizes product control. Non-target effect-directed profiling adds a new perspective to previous target analysis results that can be used not only to ensure health claims based on bioactive compounds, but also to detect unknown bioactive compounds coming from contamination or residues or changes caused by food processing.

Construction and Analysis of a Yeast for the Simultaneous Release and Esterification of the Varietal Thiol 3-Sulfanylhexan-1-ol.

Polyfunctional thiols like 3-sulfanylhexan-1-ol (3SH) and its ester 3-sulfanylhexyl acetate (3SHA) are important aroma determinants in wine with exceptionally low odor thresholds. 3SH is largely found in grape must bound to glutathione and cysteine and requires enzymatic action to be perceived sensorially. The wine yeast Saccharomyces cerevisiae is ineffective in releasing volatile thiols from their precursor configuration. For this purpose, a yeast strain was constructed that expresses the carbon-sulfur lyase encoding the tnaA gene from Escherichia coli and overexpresses its native alcohol acetyltransferase encoding genes, ATF1 and ATF2. The resulting yeast strain, which co-expresses tnaA and ATF1, showed elevated 3SH-releasing capabilities and the esterification of 3SH to its acetate ester 3SHA. Levels of over 7000 ng/L of 3SHA in Sauvignon blanc wines were achieved. Enhanced release and esterification of 3SH were also shown in the fermentation of guava and passionfruit pulp and three hop varieties. This study offers prospects for the development of flavor-enhancing yeast strains with optimized thiol-releasing and esterification capabilities in a diverse set of beverage matrices.

Wine Storage at Cellar vs. Room Conditions: Changes in the Aroma Composition of Riesling Wine.

Storage temperature is one of the most important factors affecting wine aging. Along with bottling parameters (type of stopper, SO2 level and dissolved O2 in wine), they determine how fast wine will evolve, reach its optimum and decline in sensory quality. At the same time, lowering of the SO2 level in wine has been a hot topic in recent years. In the current work, we investigated how Riesling wine evolved on the molecular level in warm (~25 °C) and cool (~15 °C) conditions depending on the SO2 level in the wine (low, medium and high), flushing of the bottle's headspace with CO2 and three types of stoppers (Diam 30, Diam 30 origin and Diam 5) with different OIR levels (0.8-1.3 mg) and OTR levels (0.3-0.4 mg/year). It was demonstrated that the evolution of primary and secondary aromas, wine color and low molecular weight sulfur compounds (LMWSCs) during the two years of aging mainly depended on the storage temperature. Variation in the SO2 level and CO2 in the headspace affected mostly certain LMWSCs (H2S, MeSH) and ß-damascenone. New aspects of C13-norisprenoids and monoterpenoids behavior in Riesling wine with different levels of SO2 and O2 were discussed. All three types of stoppers showed very close wine preservation properties during the two years of storage. The sensory analysis revealed that, after only six months, the warm stored wines with a low SO2 level were more oxidized and different from the samples with medium and high SO2 levels. A similar tendency was also observed for the cool stored samples.

Development of Genetic Modification Tools for Hanseniasporauvarum.

Apiculate yeasts belonging to the genus Hanseniaspora are commonly isolated from viticultural settings and often dominate the initial stages of grape must fermentations. Although considered spoilage yeasts, they are now increasingly becoming the focus of research, with several whole-genome sequencing studies published in recent years. However, tools for their molecular genetic manipulation are still lacking. Here, we report the development of a tool for the genetic modification of Hanseniaspora uvarum. This was employed for the disruption of the HuATF1 gene, which encodes a putative alcohol acetyltransferase involved in acetate ester formation. We generated a synthetic marker gene consisting of the HuTEF1 promoter controlling a hygromycin resistance open reading frame (ORF). This new marker gene was used in disruption cassettes containing long-flanking (1000 bp) homology regions to the target locus. By increasing the antibiotic concentration, transformants were obtained in which both alleles of the putative HuATF1 gene were deleted in a diploid H. uvarum strain. Phenotypic characterisation including fermentation in Müller-Thurgau must showed that the null mutant produced significantly less acetate ester, particularly ethyl acetate. This study marks the first steps in the development of gene modification tools and paves the road for functional gene analyses of this yeast.

Responses on Must and Wine Composition of Vitis vinifera L. cvs. Riesling and Cabernet Sauvignon under a Free Air CO2 Enrichment (FACE).

Challenges of climate change on the future grape and wine production are widely discussed in science and in the wine industry with the goal to maintain a consistent must and wine quality in the future. Therefore, the effect of elevated CO2 (eCO2)-as one of the relevant greenhouse gases jointly responsible for a changing climate-was investigated concerning the composition of must and wine made of two grapevine cultivars V. vinifera L. cvs. Riesling and Cabernet Sauvignon within the established VineyardFACE (Free-Air Carbon dioxide Enrichment) experiment. Must and wine analysis were conducted in three consecutive years (2014-2016) by analyzing standard must and wine parameters, e.g., total soluble solids (TSS), pH, total acidity (TA), organic acids (e.g., tartaric acid, malic acid, shikimic acid, citric acid, volatile acid and gluconic acid) or total phenolics (TP). Also, for both cultivars CIELab coordinates (L* for lightness, a* as green/red and b* as blue/yellow components) were used to test colour in young white and red wines. Additionally, total anthocyanins and monomeric indices were analyzed for young wines of the red cultivar Cabernet Sauvignon. With marginal differences between CO2 treatments, the composition of must and young wines was not found to be negatively influenced by an eCO2 concentration.

Phenotypic and transcriptional analysis of Saccharomyces cerevisiae during wine fermentation in response to nitrogen nutrition and co-inoculation with Torulaspora delbrueckii.

Nitrogen content of grape musts strongly impacts on fermentation performance and wine metabolite production. As nitrogen is a limiting nutrient in most grape musts, nitrogen supplementation is a common practice that ensures yeast growth during fermentation. However, preferred nitrogen sources -as ammonium- repress the genes related to alternative nitrogen sources consumption, usually involved in aromatic compounds production. Here, we describe the effect of high ammonium doses in Saccharomyces cerevisiae fermentation performance and wine properties, and how it is affected by yeast co-inoculation in mixed (S. cerevisiae + Torulaspora delbrueckii) fermentations. In addition, an RNA-seq analysis allowed us to study the S. cerevisiae transcriptional response to ammonium nutrition and yeast interaction, demonstrating that T. delbrueckii presence affects the global S. cerevisiae transcriptional response, reducing ammonium effects at both phenotypic -fermentation kinetics and metabolite production- and transcriptional levels, under experimental conditions.

The Impact of Chitosan on the Chemical Composition of Wines Fermented with Schizosaccharomyces pombe and Saccharomyces cerevisiae.

This study investigates the influence of the antimicrobial agent chitosan on a selected Schizosaccharomyces pombe strain during the alcoholic fermentation of ultra-pasteurized grape juice with a high concentration of malic acid. It also studies a selected Saccharomyces cerevisiae strain as a control. The study examines several parameters relating to wine quality, including volatile and non-volatile compounds. The principal aim of the study is to test the influence of chitosan on the final chemical composition of the wine during alcoholic fermentation, and to compare the two studied fermentative yeasts between them. The results show that chitosan influences the final concentration of acetic acid, ethanol, glycerol, acetaldehyde, pyruvic acid, α-ketoglutarate, higher alcohols, acetate esters, ethyl esters, and fatty acids, depending on the yeast species.

1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) Sensory Thresholds in Riesling Wine.

1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) is an aroma compound responsible for the kerosene/petrol notes in Riesling wines. In the current article, three sensory thresholds for TDN were determined in young Riesling wine: detection threshold (about 4 µg/L), recognition threshold (10-12 µg/L), and rejection threshold (71-82 µg/L). It was demonstrated that an elevated content of free SO2 in wine may have a certain masking effect on the TDN aroma perception. In addition, the influence of wine serving temperature on the recognition of kerosene/petrol notes was studied. It was found, that a lower wine serving temperature (about 11 °C) facilitated identification of the TDN aroma compared to the same wine samples at room temperature.

The impact of hybrid yeasts on the aroma profile of cool climate Riesling wines.

The current study highlights the effects of intra- and interspecific hybrid yeasts of the genus Saccharomyces (S.) on the alcoholic fermentation and formation of aroma compounds in cool climate Riesling wines. Three different hybrid yeasts: S. cerevisiae × S. paradoxus (SC × SP), S. cerevisiae × S. kudriavzevii (SC × SK) and S. cerevisiae var. cerevisiae × S. cerevisiae var. bayanus (SC × SB) were investigated. The species S. cerevisiae var. bayanus (SB) was chosen as control variant. It has been demonstrated that the hybrid yeasts have the ability to preserve positive properties while, suppressing undesired properties from the parental yeast species. The hybrid SC × SK showed an increase of desired acetate esters and monoterpenes. The concentrations of higher alcohols were higher in wines fermented by SC × SP, compared to the other variants. SC × SP fermentations resulted in decreased concentrations of l-malate and sulphites.

An optimized method for synthesis and purification of 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN).

1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN), an aroma compound present in wine, is used for sensory and physicochemical analyses. Therefore, synthesis of TDN of high purity is required for these purposes. Optimization of TDN synthesis in order to facilitate its subsequent purification was described. As a result, ≥99.5 % of TDN purity was reached. •The possibility of using both α-ionone and ß-ionone as starting substances was demonstrated•Modifications of the use of reagents in the second and third steps of TDN synthesis were proposed.

Plant architecture and phytochemical composition of basil (Ocimum basilicum L.) under the influence of light from microwave plasma and high-pressure sodium lamps.

Potted herbs such as basil are in high year-round demand in Central Europe. To ensure good quality in winter, artificial light is required. Many horticulturists, who want to replace their high-pressure­sodium (HPS) lamps with light-emitting diodes (LEDs) to save electricity energy, struggle with high investment costs. In addition, switching to LEDs can overwhelm many smaller horticultural enterprises since there is a requirement of adjusting individual light recipes and furthermore cultivation problems can occur due to the lack of infrared radiation. In this study, the influence of light from microwave plasma lamps (MPL), acting as alternative light sources, on secondary metabolites and morphology of basil plants (Ocimum basilicum L.) was tested. Basil plants were grown in a climate chamber with MPL with two different light bulbs emitting either artificial sunlight (AS) or broad white light with increased blue and green light content (sulfur plasma light; SPL). The effect of these new lamp types was compared to standard commercial HPS lamps. In addition to morphological parameters such as height, internode length and fresh weight, plant secondary metabolites were examined. Essential oils and monoterpenes were quantified by GC-MS analysis, whereby phenolic compounds were analyzed calorimetrically. Elongation growth and biomass production was increased under the AS spectrum in comparison to HPS-grown plants. Increased stem elongation was attributed to a higher content of far-red light in the AS spectrum. Furthermore, basil plants grown under the AS spectrum contained the highest total phenolic and total flavonoid content compared to plants grown under the SPL and HPS lamps, probably due to the higher content of UV-A radiation. The lowest content of phenolic compounds was observed when HPS light was used, which was assumed to be caused by a low blue light content in the emission spectrum. An impact of the different light spectra on essential oil composition was determined. A significantly increased content of linalool was found in basil leaves developed under both tested MPL spectra compared to HPS-grown plants. The total yield of the four major essential oils was lowest under HPS treatment.

Effects on varietal aromas during wine making: a review of the impact of varietal aromas on the flavor of wine.

Although there are many chemical compounds present in wines, only a few of these compounds contribute to the sensory perception of wine flavor. This review focuses on the knowledge regarding varietal aroma compounds, which are among the compounds that are the greatest contributors to the overall aroma. These aroma compounds are found in grapes in the form of nonodorant precursors that, due to the metabolic activity of yeasts during fermentation, are transformed to aromas that are of great relevance in the sensory perception of wines. Due to the multiple interactions of varietal aromas with other types of aromas and other nonodorant components of the complex wine matrix, knowledge regarding the varietal aroma composition alone cannot adequately explain the contribution of these compounds to the overall wine flavor. These interactions and the associated effects on aroma volatility are currently being investigated. This review also provides an overview of recent developments in analytical techniques for varietal aroma identification, including methods used to identify the precursor compounds of varietal aromas, which are the greatest contributors to the overall aroma after the aforementioned yeast-mediated odor release.