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ABSTRACTOver the last three decades, the appeal for monoclonal antibodies (mAbs) as therapeutics has been steadily increasing as evident with FDA’s recent landmark approval of the 100th mAb. Unlike mAbs that bind to single targets, multispecific biologics (msAbs) have garnered particular interest owing to the advantage of engaging distinct targets. One important modular component of msAbs is the single-chain variable fragment (scFv). Despite the exquisite specificity and affinity of these scFv modules, their relatively poor thermostability often hampers their development as a potential therapeutic drug. In recent years, engineering antibody sequences to enhance their stability by mutations has gained considerable momentum. As experimental methods for antibody engineering are time-intensive, laborious and expensive, computational methods serve as a fast and inexpensive alternative to conventional routes. In this work, we show two machine learning approaches – one with pre-trained language models (PTLM) capturing functional effects of sequence variation, and second, a supervised convolutional neural network (CNN) trained with Rosetta energetic features – to better classify thermostable scFv variants from sequence. Both of these models are trained over temperature-specific data (TS50 measurements) derived from multiple libraries of scFv sequences. On out-of-distribution (refers to the fact that the out-of-distribution sequnes are blind to the algorithm) sequences, we show that a sufficiently simple CNN model performs better than general pre-trained language models trained on diverse protein sequences (average Spearman correlation coefficient, [Formula: see text], of 0.4 as opposed to 0.15). On the other hand, an antibody-specific language model performs comparatively better than the CNN model on the same task ([Formula: see text] 0.52). Further, we demonstrate that for an independent mAb with available thermal melting temperatures for 20 experimentally characterized thermostable mutations, these models trained on TS50 data could identify 18 residue positions and 5 identical amino-acid mutations showing remarkable generalizability. Our results suggest that such models can be broadly applicable for improving the biological characteristics of antibodies. Further, transferring such models for alternative physicochemical properties of scFvs can have potential applications in optimizing large-scale production and delivery of mAbs or bsAbs.

Most commercially available red wines undergo alcoholic fermentation by Saccharomyces yeasts, followed by a second fermentation with the lactic acid bacteria Oenococcus oeni once the initial process is complete. However, this traditional approach can encounter complications in specific scenarios. These situations pose risks such as stalled alcoholic fermentation or the growth of undesirable bacteria while the process remains incomplete, leaving residual sugars in the wine. To address these challenges and the issue of low acidity prevalent in warmer viticultural regions, several novel alternatives are available. The alternatives involve the combined use of Lachancea thermotolerans to increase the acidity of the musts, lactic acid bacteria (Oenococcus oeni and Lactiplantibacillus plantarum) to ensure malic acid stability during early alcoholic fermentation stages, and Saccharomyces cerevisiae to properly complete alcoholic fermentation. The study showed variations in the final chemical parameters of wines based on the microorganisms used.

‘Timorasso’ is an autochthonous, non-aromatic white grape variety cultivated mainly in the southwest of the Piedmont region (northwestern Italy). The sensory profile of wines produced from this variety evolves greatly with aging. In this study, 31 wines from 2015–2021 vintages were analyzed to investigate changes in sensory descriptors at various stages of aging and their correlation with physicochemical properties (wine basic parameters, color, and total polyphenols) and sensory-perceptual typicity. A sensory analysis was conducted by a panel of experts, who were asked to indicate the in-mouth and aroma descriptors. The aroma-related terms were analyzed as individual descriptors or grouped in “Categories”. Moreover, the panel rated the Color, In-Mouth, and Aroma typicity of these wines. ‘Timorasso’ based wines were found to have, on average, a relevant alcohol content (14.20 ± 0.56% v/v), moderate acidity (5.8 ± 0.6 g/L), and low pH (3.19 ± 0.09). In fact, Timorasso wines were sensorially identified in terms of citation frequency with the in-mouth descriptors acidity (32.9%), sapidity (25.5%), and minerality (17.4%). The aroma of younger wines (2 years of aging) was characterized by “Green”, “White flowers”, “White pulp fruit”, and “Citrus”. In general, the most cited aroma category was “Kerosene” (27.9%), distinguishing wines with 5–6 years of aging. “Kerosene” category correlated with Aroma typicity (p < 0.001), as well as with “Balsamic” (10.8%, p < 0.01) and “Empyreumatic” (5.5%, p < 0.05) aroma categories.

The presence of mousy off-flavours in wine, attributed to the production of N-heterocycles by lactic acid bacteria or Brettanomyces bruxellensis, poses a significant challenge in the winemaking industry. This study is the first one to investigate the impact of co-cultures focusing on B. bruxellensis with two common wine microorganisms, Pediococcus parvulus and Saccharomyces cerevisiae on the formation of mousy compounds. The screening was conducted in a synthetic medium under controlled conditions. It reveals the nuanced effects of the microorganism combinations. Depending on the P. parvulus or S. cerevisiae strain co-inoculated with B. bruxellensis a synergistic effect is observed on the 2-acetyltetrahydropyridine (ATHP) production, while an inhibitory effect on 2-acetylpyrroline (APY) production by P. parvulus is highlighted when co-inoculated with B. bruxellensis. These findings shed light on the potential impact of the alcoholic fermentation yeast (S. cerevisiae) on the production of mousy off-flavours. Finally, a correlation between ATHP and 2-ethyltetrahydropyridine (ETHP) appears to be confirmed with a ratio of 1:10 between ETHP and ATHP produced in the N-heterocycles assay medium.

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.

In wines, rice cake and sausage skin aromas are generally associated with the alteration of mousy off-flavours and constitute an increasingly prevalent deviation in some wines. In the present study microorganisms present in 25 altered wines were isolated. The spoilage yeast Brettanomyces bruxellensis, and lactic acid bacteria of the species Oenococcus oeni and Lentilactobacillus hilgardii were identified, and their ability to produce the N-heterocycles responsible for the mousy off-aroma was deterimined. B. bruxellensis was found in a minority of the wines altered by the mousiness.

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.

In recent years, the frequency of occurrence of mousy off-flavours in wines has increased. This could be caused by the significant decrease in sulphur dioxide addition during processing, the increase in pH or even the trend for spontaneous fermentation in wine. This off-flavour was associated with Brettanomyces bruxellensis or lactic acid bacteria metabolisms. Three N-heterocyclic compounds (APY, ETHP, ATHP) were described as involved in mousiness perception. Thus far, no study addressed the variability in that N-heterocycles production according to microorganism strains from different species. Twenty-five wines presenting mousy off-flavour were analysed. In total, 252 bacteria with 90.5 % of Oenococcus oeni and 101 yeast strains with 53.5 % of Saccharomyces cerevisiae were isolated and identified. Their capacity to produce mousy compounds was investigated using Stir Bar Sorptive Extraction-Gas Chromatography-Mass Spectrometry (SBSE-GC-MS) and a standardised N-heterocycle assay medium. While four and three species of yeast and bacteria, respectively, were isolated from mousy wines, only three species of microorganisms were associated with N-heterocycles production: B. bruxellensis, Lentilactobacillus hilgardii and Oenococcus oeni. The screening was then extended to collection strains for these three species to improve their genetic representativity. Our results show that the levels and the ratios of the three N-heterocycles present huge variations according to the species. In addition, it has been shown that in most mousy wines, B. bruxellensis was not found. Finally, an interesting correlation between ATHP and ETHP was identified.

Despite the increasing number of publications on non-conventional yeasts (NCYs), many areas in this field remain poorly understood, making the examination of these strains important for determining their potential in wine fermentations. The amino acid metabolic pathways involved, particularly the catabolic Ehrlich pathway but also anabolic pathways such as the leucine biosynthesis pathway, are crucial for producing high-value aroma compounds that contribute to the final flavour of wine. We examined the potential use of Saccharomycopsis fermentans in wine fermentations. We selected mutant strains resistant to the toxic compound trifluoro-leucine (TFL), verified mutations in the SfLEU4 gene, and characterized the ability of the resulting strains to contribute to fermentation bouquets. Resistance to TFL relieves feedback inhibition in the leucine biosynthesis pathway and resulted in increased leucine biosynthesis. Concomitantly, the S. fermentans TFL-resistant mutants generated increased amounts of isoamyl alcohol and isovalerate during wine fermentation. Selection of TFL-resistant strains thus provides a generally applicable strategy for the improvement in NCYs and their utilization in co-fermentation processes for different grape must varieties.

Photoselective shading is a process that modulates the radiation intensity in specific regions of the electromagnetic spectrum. It is a common practice in horticulture to manipulate specific plant physiological responses, but to date has only received minimal attention in viticulture. The potent odorant 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) is of particular relevance for aged Riesling wine, which are also known to be impacted by the magnitude of bunch zone light exposure during berry development. Hence, in this study, the effect of photoselective bunch zone shading on the formation of TDN in wine was investigated across two consecutive growing seasons. Applying red, black or green shade cloth (SC) to the bunch zone provided unique bunch zone light environments and yielded distinct differences in grape and wine composition compared with the unshaded control. Overall, bunch zone shading through shade cloth was effective in reducing overall photosynthetically active radiation compared to the control and the photoselectivity of the SC treatments differently affected a number of grape and wine measures. Fruit yield was somewhat but not significantly lower under black SC treatments, while juice pH was increased in grapes grown under green and black SC across both vintages compared to the control. Both grape sugar accumulation (P = 0.035) and ammonia nitrogen (P = 0.043) showed evidence of treatment effects, although with low F-statistics (4 and 3, respectively). Measures of hydrolytically released TDN in juice and free TDN concentrations in wine were lower in SC treatments. Unexpectedly, sensory descriptive analysis of the wines demonstrated that increased ‘kerosene-like’ aroma was not consistently associated with free TDN concentrations in wine. In summary, photoselective bunch shading was demonstrated to be an effective method for manipulating grape and wine outcomes and may aid in overcoming viticultural obstacles and quality impacts associated with climate change.

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.

Torulaspora delbrueckii is known for improving the aroma quality in wine and beer, but information for cider manufacturing is scarce. We explored the behaviour of two commercial strains of T. delbrueckii in apple juice fermentation to produce cider and sparkling cider. The influence of the strain, method, and strain–method interaction on the physicochemical parameters of cider was analysed by enzymatic and chromatographic assays. The data were subjected to an analysis of variance and a principal component analysis. Both strains also showed regular fermentation kinetics under pressure. Ethanol, lactic acid, acetic acid, and glycerol were produced with significant differences between strains and production methods. Then, 26 volatile compounds were identified, with higher alcohols being the quantitatively most abundant group. Strain A was associated with a higher production of methyl butanol, 2-phenyl ethanol, and butyric, propionic, and succinic acid esters, while strain B was associated with higher amounts of hexanoic acid, and acetate and valerate esters. In addition, 13 compounds showed significant differences between methods, and 14 were influenced by the method–strain interaction. Our findings encourage the further investigation of the application of T. delbrueckii as a solo player to produce ciders with a unique flavour.

In this study, the aroma-production profiles of seven different Hanseniaspora strains, namely H. guilliermondii, H. meyeri, H. nectarophila, H. occidentalis, H. opuntiae, H. osmophila and H. uvarum were determined in a simultaneous co-inoculation with the wine yeast Saccharomyces cerevisiae Champagne Epernay Geisenheim (Uvaferm CEG). All co-inoculated fermentations with Hanseniaspora showed a dramatic increase in ethyl acetate levels except the two (H. occidentalis and H. osmophila) that belong to the so-called slow-evolving clade, which had no meaningful difference, compared to the S. cerevisiae control. Other striking observations were the almost complete depletion of lactic acid in mixed-culture fermentations with H. osmophila, the more than 3.7 mg/L production of isoamyl acetate with H. guilliermondii, the significantly lower levels of glycerol with H. occidentalis and the increase in certain terpenols, such as citronellol with H. opuntiae. This work allows for the direct comparison of wines made with different Hanseniapora spp. showcasing their oenological potential, including two (H. meyeri and H. nectarophila) previously unexplored in winemaking experiments.

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.

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.

In this study, the impact of the apiculate yeast Hanseniaspora occidentalis as a co-partner with Saccharomyces cerevisiae was investigated in a sequential-type mixed-culture fermentation of Muscaris grape must. As with other fermentation trials using Hanseniaspora strains, a significant increase in ethyl acetate was observed, but most intriguing was the almost complete abolition of malic acid (from 2.0 g/L to 0.1 g/L) in the wine. Compared to the pure S. cerevisiae inoculum, there was also a marked increase in the concentrations of the other acetate esters. Modulation of some of the varietal elements, such as rose oxide, was also observed. This work shows the promising use of H. occidentalis in a mixed-culture must fermentation, especially in the acid modulation of fruit juice matrices.

Reactive compounds with one or more sulfane sulfur atoms can be an important source of reductive off-odors in wine. These substances contain labile sulfur, which can participate in microbiological (enzymatic) and chemical transformations (including in the post-bottling period), releasing malodorous hydrogen sulfide (H2S) and its derivatives (MeSH, EtSH, etc.). The following sulfane sulfur compounds were considered in this review as important precursors in the wine chemistry of reductive aromas: elemental sulfur (S8), persulfides (R-S-S-H), polysulfanes (R-Sn-R(′)), polythionates (−O3S-Sn-SO3−), thiosulfate (S2O32−) and derivatives of (poly)sulfane monosulfonic acids (R-Sn-SO3H). This review discusses the formation of these compounds, their reactivity and chemical transformations in wine, including reactions of nucleophilic substitution. In particular, the reactions of thiolysis, thiosulfatolysis and sulfitolysis of sulfane sulfur compounds are described, which lead in the end to reductive aroma compounds. In this way, the review attempts to shed light on some of the mysteries in the field of sulfur chemistry in wine and the reappearance of reductive off-odors after bottling.

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.

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 β-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.

The intrinsic quality of a wine is strongly linked with its volatile compound composition involved in the complexity of wine’s subtle flavor nuances. Those reminiscent of green pepper, herbaceous, blackcurrant, blackberry, figs or prunes are strongly linked with the maturity of the grapes. Nowadays it is well accepted that macroscopic effects of climate change modify the environmental conditions of grape growing at local scale in all the vineyards across the world. The expected effects on grape and wine production can be positive when they increase the maturity of the grapes, but when the conditions are too warm and too dry they induce opposite effects producing grapes and wines with a lower intrinsic quality. These effects were perceived in young wines but also in older wines kept several years in bottle. In this article, we provide some examples of effects of climate change and growing conditions on grapevine and wine quality expressed as flavors and antioxidant composition. We also report some results associated with the incidence of grape growing conditions on white and red wine aging potential and on the composition of old wines. Finally, we discuss the opportunities for vine growers and winemakers to manage the quality of their grapes and wines in this climate change context.

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. Keywords: Wine flavour, Aroma, Riesling, Hybrid yeasts, Saccharomyces cerevisiae var. bayanus, Saccharomyces kudriavzevii, Saccharomyces paradoxus, Monoterpenes

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 β-ionone as starting substances was demonstrated • Modifications of the use of reagents in the second and third steps of TDN synthesis were proposed

Aim: This research was undertaken in the context of climate change and understanding how rising temperatures may interact with viticultural practices, used to manage fruit exposure in Riesling. An experimental system was designed to passively warm the bunch zone and separate the factors, heat and indirect heat by solar radiation. Methods and results: Field experiments were conducted in 2016 and 2017 at an experimental site located near Rüdesheim in Germany. To increase bunch exposure compared to non-defoliated controls (CON), around 75% of the leaves were removed manually from the bunch zone in an early defoliation treatment at pea size (DEF_E; E-L 31) and later defoliation at véraison (DEF_L, E-L 35). An open heating system (OHS) was installed from pea size stage (E-L 31) onwards. Temperature, light penetration and canopy characterization were determined. Maturity measurements included determination of berry fresh weight, total soluble solids, available primary amino acids (N-OPA), pH, titratable acid and organic acids. For determination of the phenols, berry skin was freeze dried, extracted and analysed by HPLC-PDA. Compared to the same position in the control vine rows, the temperature was more than 10 °C warmer inside the chamber, around 5 °C warmer at the opening of the chamber and at the upper end of the bunch zone, up to 3 °C warmer on a day with high solar radiation. On overcast days there was no temperature difference between these treatments. The OHS treatment affected the ratio of malic and tartaric acid as well as the ratio of glucose and fructose, and produced smaller berries compared to both CON and DEF treatments. Phenols (flavanols, hydroxycinnamic acids, flavonols) in the berry skin were mostly affected by the defoliation. In both years, DEF_E had the highest amount of phenols, followed by the DEF_L. In 2016 OHS had nearly the same concentration of phenols compared to CON. In 2017, the concentrations of phenols were higher in OHS compared to CON. Conclusion: Under future scenarios of increasing temperature conditions, strong changes will be expected for berry maturity parameters. It was found that using an experimental setup to passively heat the bunch zone, malic acid was reduced, smaller berries were produced, and the glucose/fructose ratio changed. For the defoliation treatments, phenol concentrations in berry skin were strongly affected by defoliation and to a lesser extent by higher temperature. Basic maturity parameters were relatively unaffected by defoliation. Significance and impact of the study: Riesling is known for its fruity character and the importance of the sweetness and acidity balance for determining wine style. Under warmer temperature conditions the acidity content will decrease through faster malic acid respiration, impacting the wine´s profile. Higher phenol content could lead to an astringent taste and together with higher protein content, may provide a risk of haze in wine. Neither effect is desirable. In this study, increased bunch exposure following defoliation had a greater effect than temperature alone on phenols. Therefore, the vineyard and canopy management practice will need to be adapted.

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.

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) 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.

Carbon dioxide (CO2) as one of the main factors driving climate change is known to increase grapevine growth and yield and could, therefore, have an impact on the fruit quality of vines. This study reports the effects of elevated CO2 (eCO2) on berry development and bunch structure of two grapevine cultivars (Vitis vinifera L. cvs. Riesling and Cabernet Sauvignon) within the VineyardFACE (Free-Air Carbon Dioxide enrichment) experiment, using must analysis and non-invasive fluorescence sensor technology. Berry development was examined on five dates over three consecutive years by analyzing total soluble solids (TSS), pH, total acidity, organic acids, nutrition status, and non-invasive Multiplex measurements. Before harvest, secondary bunches were collected to examine bunch and berry parameters. Results showed that eCO2 had little impact on berry composition of Riesling and Cabernet Sauvignon during berry development, which could be related to bunch structure or single berry weight within single seasons. Elevated CO2 (eCO2) did not result in modified TSS accumulation during ripening but was directly related to the chlorophyll index SFR_R. Higher single berry weights (SBW), higher malic acid (MA), and lower tartaric acid (TAA) were examined at some stages during development of berries under eCO2 levels. Our study provides evidence that eCO2 did alter some bunch and berry parameters without a negative impact on fruit quality.

Fungal infections are detrimental for viticulture since they may reduce harvest yield and wine quality. This study aimed to characterize the effects of bunch rot and powdery mildew on wine aroma by quantification of representative aroma compounds using Stable Isotope Dilution Analysis (SIDA). For this purpose, samples affected to a high degree by each fungus were compared with a healthy sample in each case; to this aim, the respective samples were collected and processed applying identical conditions. Thereby, the effects of bunch rot were studied in three different grape varieties: White Riesling, Red Riesling and Gewürztraminer whereas the influence of powdery mildew was studied on the hybrid Gm 8622-3. Analyses revealed that both fungal diseases caused significant changes in the concentration of most target compounds. Thereby, the greatest effects were increases in the concentration of phenylacetic acid, acetic acid and γ-decalactone for both fungi and all grape varieties. Regarding other compounds, however, inconsistent effects of bunch rot were observed for the three varieties studied.

This study was performed with the aim of characterizing the fermentative performance of three commercial strains of Torulaspora delbrueckii and their impact on the production of volatile and non-volatile compounds. Laboratory-scale single culture fermentations were performed using a commercial white grape juice. The addition of commercial nutrient products enabled us to test the yeasts under two different nutrient conditions. The addition of nutrients promoted fermentation intensity from 9% to 20 % with significant differences (p < 0.05) among the strains tested. The strain diversity together with the nutrient availability influenced the production of volatile compounds.

Anthocyanins and volatile aromas may contribute to the identity of a wine varietal. Various parameters such as terroir (including vineyard altitude), viticultural management, vinification techniques and ageing conditions can influence the physiochemical pathways of the compounds. This work evaluated the anthocyanins and volatile compounds of two monovarietal wines from indigenous varieties, Yiannoudi and Maratheftiko, grown in the island of Cyprus from the vintages 2014, 2015 and 2016. The experimental analysis comprised the determination of anthocyanin’s profile (high-performance liquid chromatography-diode array detection chromatography-electrospray ionization tandem mass spectrometry, HPLC-DAD-ESI/MS) and fermentation derived volatiles (gas chromatography-flame ionization detector, GC-FID) and a blind wine testing sensory evaluation. Both the analytical results and the blind wine tasting showed that wines, at their early stage, were easily differentiated by variety, especially in terms of anthocyanins composition, while, in aged wines, the differences among samples were influenced in time by the winemaking procedures and it was not possible to differentiate varieties in such conditions.

All laboratories dealing with microbes have to develop a strain maintenance regime. While lyophilization based on freeze-drying may be feasible for large stock centers, laboratories around the world rely on cryopreservation and freezing of stocks at −80 °C. Keeping stocks at these low temperatures requires investments of several thousand kW/h per year. We have kept yeast stocks for several decades at room temperature on agar slants in glass reagent tubes covered with vaspar and sealed with cotton plugs. They were part of the Geisenheim Yeast Breeding Center stock collection that was started in the 19th century, well before −80 °C refrigeration technology was invented. Of these stocks, 60 tubes were analyzed and around one-third of them could be regrown. The strains were typed by sequencing of rDNA PCR fragments. Based on BlastN analyses, twelve of the strains could be assigned to Saccharomyces cerevisiae, two to S. kudriavzevii, and the others to Meyerozyma and Candida. The strains were used in white wine fermentations and compared to standard wine yeasts Uvaferm/GHM (Geisenheim) and Lalvin EC1118. Even with added nitrogen, the strains exhibited diverse fermentation curves. Post-fermentation aroma analyses and the determination of residual sugar and organic acid concentrations indicated that some strains harbor interesting flavor characteristics, surpassing current standard yeast strains. Thus, old strain collections bear treasures for direct use either in wine fermentations or for incorporation in yeast breeding programs aimed at improving modern wine yeasts. Furthermore, this provides evidence that low-cost/long-term culture maintenance at zero-emission levels is feasible.

In recent years, studies have reported the positive influence of non-Saccharomyces yeast on wine quality. Many grape varieties under mixed or sequential inoculation show an overall positive effect on aroma enhancement. A potential impact by non-Saccharomyces yeast on volatile and non-volatile compounds should benefit the flavor of Riesling wines. Following this trend, four separate sequential fermentations (using the non-Saccharomyces yeasts Torulaspora delbrueckii, Metschnikowia pulcherrima, Pichia kluyveri, and Lachancea thermotolerans with Saccharomyces cerevisiae) were carried out on Riesling must and compared to a pure culture of S. cerevisiae. Sequential fermentations influenced the final wine aroma. Significant differences were found in esters, acetates, higher alcohols, fatty acids, and low volatile sulfur compounds between the different trials. Other parameters, including the production of non-volatile compounds, showed significant differences. This fermentation process not only allows the modulation of wine aroma but also chemical parameters such as glycerol, ethanol, alcohol, acidity, or fermentation by-products. These potential benefits of wine diversity should be beneficial to the wine industry.

Reductive sulfurous off-odors are still one of the main reasons for rejecting wines by consumers. In 2008 at the International Wine Challenge in London, approximately 6% of the more than 10,000 wines presented were described as faulty. Twenty-eight percent were described as faulty because they presented “reduced characters” similar to those presented by “cork taint” and in nearly the same portion. Reductive off-odors are caused by low volatile sulfurous compounds. Their origin may be traced back to the metabolism of the microorganisms (yeasts and lactic acid bacteria) involved in the fermentation steps during wine making, often followed by chemical conversions. The main source of volatile sulfur compounds (VSCs) are precursors from the sulfate assimilation pathway (SAP, sometimes named as the “sulfate reduction pathway” SRP), used by yeast to assimilate sulfur from the environment and incorporate it into the essential sulfur-containing amino acids methionine and cysteine. Reductive off-odors became of increasing interest within the last few years, and the method to remove them by treatment with copper (II) salts (sulfate or citrate) is more and more questioned: The effectiveness is doubted, and after prolonged bottle storage, they reappear quite often. Numerous reports within the last few years and an ongoing flood of publications dealing with this matter reflect the importance of this problem. In a recent detailed review, almost all relevant aspects were discussed on a scientific data basis, and a “decision tree” was formulated to support winemakers handling this problem. Since we are dealing with a very complicated matter with a multitude of black spots still remaining, these advices can only be realized using specific equipment and special chemicals, not necessarily found in small wineries. The main problem in dealing with sulfurous compounds arises from the high variability of their reactivities. Sulfur is a metalloid with a large valence span across eight electron transformations from S (−II) up to S (+VI). This allows it to participate in an array of oxidation, reduction and disproportionation reactions, both abiotic and linked to microbial metabolism. In addition, sulfur is the element with the most allotropes and a high tendency to form chains and rings, with different stabilities of defined species and a high interconvertibility among each other. We suppose, there is simply a lack of knowledge of what is transferred during filling into bottles after fermentation and fining procedures. The treatment with copper (II) salts to remove sulfurous off-odors before filling rather increases instead of solving the problem. This paper picks up the abundant knowledge from recent literature and tries to add some aspects and observations, based on the assumption that the formation of polythionates, hitherto not taken into consideration, may explain some of the mystery of the re-appearance of reductive off-odors.