Use of Winemaking Supplements To Modify the Composition and Sensory Properties of Shiraz Wine

The characteristics of polysaccharide composition of red wines in China: Effects of grape varieties, origins and winemaking techniques

In this work, the polysaccharide profile of different grapes and red wines in China was studied and the influences of two common winemaking techniques on the components of wine were analyzed. The soluble polysaccharide content in the skins of native grape species in China (non-Vitis vinifera grapes) was significantly higher than that of Vitis vinifera species, while the terroir effect on V. vinifera varieties was limited. The combination of the enzyme preparation and the addition of mannoproteins (MPs) at the beginning of alcoholic fermentation (MP1 + E) could increase the contents of MPs and acid polysaccharides (APS) compared to the control wines. Meanwhile, better color characteristics and higher level of anthocyanin derivatives were observed. However, MP1 + E treatment reduced the content of polysaccharides rich in arabinose and galactose (PRAGs) due to enzymatic hydrolysis. The study will provide useful information for winemakers to regulate the wine polysaccharide profile.

Characterization of chemical and sensory properties of Cabernet Sauvignon and Marselan wines made by flash détente technique

This study aimed to characterize the sensory profiles of wines produced using the flash détente (FD) technique and to identify the flavor compounds contributing to the sensory characteristics. The FD technique was applied to two major grape varieties, Cabernet Sauvignon and Marselan, from the Changli region of China to produce high-quality wines with aging potential. Compared to the traditional macerated wines, the FD wines showed greater color intensity, mainly due to the higher levels of anthocyanins. Regarding the aroma characteristics, FD wines were found to have a more pronounced fruitness, especially fresh fruit note, which was due to the contribution of higher concentration of esters. Concurrently, FD wines showed an increased sweet note which was associated with increased lactones and furanones. In addition, FD wines exhibited reduced green and floral notes due to lower levels of C6 alcohols and C13-norisoprenoids. With regard to mouthfeel, FD wines presented greater astringency and bitterness, which was due to the higher levels of phenolics. The total concentration of condensed tannins and condensed tannins for each degree of polymerization was considerably higher in FD wines due to the strong extraction of the FD technique. A significant increase in grape-derived polysaccharides and glycerol was also found in FD wines, contributing to a fuller body. This study contributed to an increase in the knowledge of the Changli region and demonstrated that the FD technique could be applied to the wine production in this region to address the negative impacts of rainfall in individual vintages.

Exploring fungal bioemulsifiers: insights into chemical composition, microbial sources, and cross-field applications

The demand for emulsion-based products is crucial for economic development and societal well-being, spanning diverse industries such as food, cosmetics, pharmaceuticals, and oil extraction. Formulating these products relies on emulsifiers, a distinct class of surfactants. However, many conventional emulsifiers are derived from petrochemicals or synthetic sources, posing potential environmental and human health risks. In this context, fungal bioemulsifiers emerge as a compelling and sustainable alternative, demonstrating superior performance, enhanced biodegradability, and safety for human consumption. From this perspective, the present work provides the first comprehensive review of fungal bioemulsifiers, categorizing them based on their chemical nature and microbial origin. This includes polysaccharides, proteins, glycoproteins, polymeric glycolipids, and carbohydrate-lipid-protein complexes. Examples of particular interest are scleroglucan, a polysaccharide produced by Sclerotium rolfsii, and mannoproteins present in the cell walls of various yeasts, including Saccharomyces cerevisiae. Furthermore, this study examines the feasibility of incorporating fungal bioemulsifiers in the food and oil industries and their potential role in bioremediation events for oil-polluted marine environments. Finally, this exploration encourages further research on fungal bioemulsifier bioprospecting, with far-reaching implications for advancing sustainable and eco-friendly practices across various industrial sectors.

Interaction between a Commercial Mannoprotein and Cyanidin-3-O-glucoside-4-vinylphenol and Its Stability and Antioxidative Properties as a Novel Functional Pigment

Hydroxyphenyl-pyranoanthocyanins, which are derived from anthocyanins and phenolic acids during the fermentation and aging of red wine, are prone to polymerization and precipitation, which largely limits their application and bioactivity research. In the present study, cyanidin-3-O-glucoside-4-vinylphenol (C3GVP), a hydroxyphenyl-pyranoanthocaynin, was prepared from C3G and p-coumaric acid, and mannoprotein (MP) was employed to improve its stability in various complex solvents by forming a stable anthocyanin-MP complex. We used scanning electron microscopy, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, and circular dichroism spectroscopy to observe structural changes in C3GVP and MP. The results demonstrated that the intermolecular polymerization of C3GVP was mitigated and the secondary conformation of MP was changed slightly. Fluorescence spectroscopy and molecular docking indicated that C3GVP and MP interacted via hydrogen bonds and hydrophobic interactions. Importantly, the C3GVP-MP complex exhibited better thermal stability and antioxidant capacity than C3G.

Mouthfeel subqualities in wines: A current insight on sensory descriptors and physical-chemical markers

Astringency and more generally mouthfeel perception are relevant to the overall quality of the wine. However, their origin and description are still uncertain and are constantly updating. Additionally, the terminology related to mouthfeel properties is expansive and extremely diversified, characterized by common traditional terms as well as novel recently adopted descriptors. In this context, this review evaluated the mention frequency of astringent subqualities and other mouthfeel attributes in the scientific literature of the last decades (2000-August 17, 2022). One hundred and twenty-five scientific publications have been selected and classified based on wine typology, aim, and instrumental-sensorial methods adopted. Dry resulted as the most frequent astringent subquality (10% for red wines, 8.6% for white wines), while body-and related terms-is a common mouthfeel sensation for different wine types, although its concept is still vague. Alongside, promising analytical and instrumental techniques investigating and simulating the in-mouth properties are discussed in detail, such as rheology for the viscosity and tribology for the lubrication loss, as well as the different approaches for the quantitative and qualitative evaluation of the interaction between salivary proteins and astringency markers. A focus on the phenolic compounds involved in the tactile perception was conducted, with tannins being the compounds conventionally found responsible for astringency. Nevertheless, other non-tannic polyphenolic classes (i.e., flavonols, phenolic acids, anthocyanins, anthocyanin-derivative pigments) as well as chemical-physical factors and the wine matrix (i.e., polysaccharides, mannoproteins, ethanol, glycerol, and pH) can also contribute to the wine in-mouth sensory profile. An overview of mouthfeel perception, factors involved, and its vocabulary is useful for enologists and consumers.

Impact of accentuated cut edges (ACE) technique on volatile and sensory profiles of Shiraz wines

Varietal thiols are important wine aroma compounds that are generally less abundant in red wines. Accentuated cut edges (ACE), known for accelerating phenolic extraction, was applied to Shiraz winemaking and compared with conventional crushing (NOACE) to examine the effects on varietal thiol precursor extraction and thiol formation. Water addition to grape must and skin contact time (SCT) during fermentation were also assessed. Although there was no difference for precursors in the must, ACE significantly decreased 3-S-glutathionylhexan-1-ol concentration during fermentation. 3-Sulfanylhexan-1-ol and ethyl esters were significantly influenced by crushing method and/or SCT, with NOACE or shorter SCT yielding higher concentrations. Acetates, higher alcohols, fatty acids, and isoprenoids differed according to the interaction of crushing method and SCT, with ACE and shorter SCT significantly enhancing all groups except acetates. Volatiles in Sauvignon blanc and Pinot noir wines produced at commercial scale with ACE were briefly evaluated, suggesting an impact of grape variety.

Revisiting the use of pectinases in enology: A role beyond facilitating phenolic grape extraction

With the objective of improving both the extraction of phenolic compounds from grapes and their maintenance in the final wine, we compared the effect of favoring phenolic extraction with a pectolytic-based maceration enzyme with that of favoring both phenolic extraction and the partial elimination of the suspended material using a pectolytic-based clarification enzyme. The phenolic composition of the final wines and those adsorbed to the precipitated lees were analyzed. Both enzymes increased wine color intensity and phenolic content, but the best results were observed when the clarification enzyme was used. This enzyme generated the largest losses of phenolics bound to precipitated lees. However, this resulted in a positive effect, the precipitation of lees rich in phenolic compounds probably created a pronounced gradient of phenolic compounds from grapes to must/wine and better chromatic characteristics in the final wine, compared with the wine made using a traditional maceration enzyme.

Effects of Yeast Product Addition and Fermentation Temperature on Lipid Composition, Taste and Mouthfeel Characteristics of Pinot Noir Wine

Lipids have important impacts on wine sensory. By targeting the lipid sources in wine, mainly from grape tissues and yeast cell walls, it was possible to alter the wine lipid profile thus potentially changing the final product quality. This research examined the changes of wine total lipids, lipid composition and sensory characteristics of Pinot noir wines in response to the winemaking factors, fermentation temperature and yeast product addition. Pinot noir grapes were fermented at 16 °C and 27 °C. After fermentation, Oenolees® yeast product was added to the wines at three levels (0 g/L, 0.5 g/L and 1.0 g/L). The six wine treatments were subjected to chemical analyses measuring total lipids and an untargeted lipidomic approach analyzing lipid composition. High temperature fermentation wines had significantly higher total lipid content. Random forest analysis distinguished the wine groups based on the 25 main lipids, including free fatty acids, acylcarnitines, diglycerides, triglycerides and phospholipids. Taste and mouthfeel characteristics of each treatment were assessed using descriptive analysis and check-all-that-apply (CATA) techniques. Multivariate analyses showed that changing fermentation temperature significantly impacted sweetness and drying perception in Pinot noir wines. Yeast product addition had nuanced effects on wine lipid profiles and sensory perception.

1H-NMR Metabolomics as a Tool for Winemaking Monitoring

The chemical composition of wine is known to be influenced by multiple factors including some viticulture practices and winemaking processes. 1H-NMR metabolomics has been successfully applied to the study of wine authenticity. In the present study, 1H-NMR metabolomics in combination with multivariate analysis was applied to investigate the effects of grape maturity and enzyme and fining treatments on Cabernet Sauvignon wines. A total of forty wine metabolites were quantified. Three different stages of maturity were studied (under-maturity, maturity and over-maturity). Enzyme treatments were carried out using two pectolytic enzymes (E1 and E2). Finally, two proteinaceous fining treatments were compared (vegetable protein, fining F1; pea protein and PVPP, fining F2). The results show a clear difference between the three stages of maturity, with an impact on different classes of metabolites including amino acids, organic acids, sugars, phenolic compounds, alcohols and esters. A clear separation between enzymes E1 and E2 was observed. Both fining agents had a significant effect on metabolite concentrations. The results demonstrate that 1H-NMR metabolomics provides a fast and robust approach to study the effect of winemaking processes on wine metabolites. These results support the interest to pursue the development of 1H-NMR metabolomics to investigate the effects of winemaking on wine quality.

Grape polysaccharides: compositional changes in grapes and wines, possible effects on wine organoleptic properties, and practical control during winemaking

Polysaccharides present in grapes interact with wine sensory-active compounds (polyphenols and volatile compounds) via different mechanisms and can affect wine organoleptic qualities such as astringency, color and aroma. Studies on the role that grape polysaccharides play in wines are reviewed in this paper. First, the composition of grape polysaccharides and their changes during grape ripening, winemaking and aging are introduced. Second, different interaction mechanisms of grape polysaccharides and wine sensory-active compounds (flavanols, anthocyanins and volatiles) are introduced, and the possible effects on wine astringency, color and aroma caused by these interactions are illustrated. Finally, the control of the grape polysaccharide content in practice is discussed, including classical winemaking methods (applying different maceration enzymes, temperature control, co-fermentation, blending), modern vinification technologies (pulsed electric field, ultrasound treatment), and the development of new grape polysaccharide products.

Anthocyanin and Phenolic Acids Contents Influence the Color Stability and Antioxidant Capacity of Wine Treated With Mannoprotein

Wine is consumed by humans worldwide, but the functional components are lost and the color changes during its production. Here, we studied the effects of mannoprotein (MP) addition (0, 0.1, and 0.3 g/L) upon crushing and storage. We measured anthocyanins, phenolic acids profiles, color characteristics, and antioxidant activities of wine. The results showed that the addition of MP before fermentation significantly increased the total phenolic content (TPC), total anthocyanin content, total tannin content (TTC), total flavonoid content, and total flavanol content in wine, whereas the addition of MP during storage had the opposite effect. The addition of MP before alcohol fermentation significantly increased the amount of individual anthocyanins and individual phenolic acids, maintained the color, and increased the antioxidant capacity of wine. In addition, the addition of 0.3 g/L MP during storage increased the content of individual phenolic acids and TPC of wine. However, the addition of 0.1 g/L MP during storage significantly reduced the TPC, TAC, TTC, and individual anthocyanin content (except for malvidin-3-glucoside and malvidin-3-acetly-glucoside); meanwhile, the treatment attenuated the color stability and antioxidant capacity of wine. The results demonstrated that the addition of MP before alcohol fermentation could increase the functional components and improve the color stability and antioxidant capacity of wine.

Exploring young consumers' attitudes and emotions to sensory and physicochemical properties of different red wines

To gain deeper understanding on young consumers' attitudes and preferences to wines is needed to connect wine industry with the youth. The aims of the present study were (i) to define 'trendy wine' for young consumers and (ii) to identify chemical drivers of liking in red wines for the youth. The study was divided in two phases: phase I explored young consumers' attitudes towards wines using an online survey, and phase II studied the relationship between hedonic and emotional responses elicited by 12 red wine samples and their physico-chemical characteristics. Consumers' responses and physico-chemical data were related using Principal Component Analysis (PCA). Results of the online survey showed that trendy wines were associated to: sparkling, soft, fresh, fruity, sweet, light, and balanced wines. Also, young consumers reported that, although flavor was considered the most important attribute, price and Protected Designation of Origin could be valuable attributes. PCA results of phase II showed that wines with a lower ratio [total polyphenol index/polysaccharides] were more liked and elicited more positive emotions than wines with higher total polyphenol index, color intensity, volatile acidity, and alcohol content. Liking and positive emotions were positively related to higher Odor Activity Values of the volatile compounds from the organic acids group. The presence of benzenoids and lactones, and the lower presence of terpenoids & norisoprenoids were associated with negative emotions. In conclusion, red wines should be soft (described as lower ratio [total polyphenol index/polysaccharides]), and have floral, and fruity aromas to better connect with young consumers.

Optimised Extraction and Preliminary Characterisation of Mannoproteins from Non-Saccharomyces Wine Yeasts

The exogenous application of yeast-derived mannoproteins presents many opportunities for the improvement of wine technological and oenological properties. Their isolation from the cell wall of Saccharomycescerevisiae has been well studied. However, investigations into the efficiency of extraction methods from non-Saccharomyces yeasts are necessary to explore the heterogeneity in structure and composition that varies between yeast species, which may influence wine properties such as clarity and mouthfeel. In this study, nine yeast strains were screened for cell wall mannoprotein content using fluorescence microscopy techniques. Four species were subsequently exposed to a combination of mechanical and enzymatic extraction methods to optimize mannoprotein yield. Yeast cells subjected to 4 min of ultrasound treatment applied at 80% of the maximum possible amplitude with a 50% duty cycle, followed by an enzymatic treatment of 4000 U lyticase per g dry cells weight, showed the highest mannoprotein-rich yield from all species. Furthermore, preliminary evaluation of the obtained extracts revealed differences in carbohydrate/protein ratios between species and with increased enzyme incubation time. The results obtained in this study form an important step towards further characterization of extraction treatment impact and yeast species effect on the isolated mannoproteins, and their subsequent influence on wine properties.

Effect of different yeast mannoproteins on the interaction between wine flavanols and salivary proteins

Unbalanced wine astringency, caused by a gap between phenolic and technological grape maturities, is one of the consequences of the global climate change in the vitiviniculture. To resolve it, potential strategies are being currently used, like the addition of commercial yeast mannoproteins (MPs) to wines. In this work, the main interactions responsible for the wine astringent sensation, namely, interactions between human salivary proteins and wine flavanols have been studied by Dynamic Light Scattering (DLS) and liquid chromatography coupled to DAD and MS detectors (HPLC-DAD-MS), in presence or absence of two MPs with different saccharide/protein ratio. The results indicate that there are differences on the substrate specificity for each mannoprotein and that its action mechanism could change not only depending on the mannoprotein composition but also on the flavanol structure. MPs with elevated carbohydrate content could act thought the stabilization of soluble aggregates with human salivary proteins and flavanols, mainly non-galloylated flavanol oligomers, whereas MPs with higher protein percentage mostly could precipitate flavanols (mainly non-galloylated ones with low degree of polymerization) which partially prevents the formation of insoluble flavanol-salivary protein aggregates.

Cell Wall Mannoproteins from Yeast Affect Salivary Protein-Flavanol Interactions through Different Molecular Mechanisms

It is known that interactions between wine flavanols and salivary proline-rich proteins (PRPs) are one of the main factors responsible for wine astringency. The addition of commercial yeast mannoproteins (MPs) to wines has been pointed to as a possible tool to modulate the excessive astringency due to a lack of phenolic maturity at harvest time that might occur as a consequence of global climate change. The aim of this work was to study by isothermal titration calorimetry and molecular dynamics simulation the molecular mechanisms by which mannoproteins could modulate astringency elicited by tannins and if it can be influenced by mannoprotein composition. Results obtained indicate that the MPs assayed had an important impact on astringency through the formation of ternary aggregates with different solubilities or by preventing the flavanol-PRP interaction by a competitive mechanism, although in a different strength, depending on the size and the compositional characteristic of the mannoprotein.

Improved Phenolic Compositions and Sensory Attributes of Red Wines by Saccharomyces cerevisiae Mutant CM8 Overproducing Cell-Wall Mannoproteins

The objective of this study was to improve the quality attributes of red wines by Saccharomyces cerevisiae (BCRC 21685) mutant CM8 with overexpression of high-mannose mannoproteins, with respective to phenolic compositions, colorimetric parameters, and consumer sensory attributes. The CM8 was mutated by ethyl methane sulfonate and showed the ability of overproducing cell wall mannoproteins selected by killer-9 toxin-containing YPD plates. Kyoho grapes were used as raw materials. It is interesting to find that the cell wall mannoproteins isolated from CM8 mutant possessed a significantly higher mannose content in the polysaccharide fraction (81% w/w) than that did from parent strain (66% w/w). The red wines made of winter grapes and CM8 (CM8-WIN) showed significantly greater total tannins, flavonols, and anthocyanins levels, as well as higher color, higher flavor, and higher consumer preference than those by its SC counterpart (SC-WIN). The characteristics of the red wines studied were further elucidated by principal component analysis. Conclusively, using CM8 starter could effectively endow the red wine with high-quality attributes via the interactions of high-mannose mannoproteins with wine compounds.

Evolution and Correlation of cis-2-Methyl-4-propyl-1,3-oxathiane, Varietal Thiols, and Acetaldehyde during Fermentation of Sauvignon blanc Juice

cis-2-Methyl-4-propyl-1,3-oxathiane (cis-2-MPO) was recently identified in wine and proposed to arise from the reaction of 3-sulfanylhexan-1-ol (3-SH) and acetaldehyde. However, the evolution profile of cis-2-MPO during alcoholic fermentation (AF) and storage and its relationship with varietal thiols and acetaldehyde production were unknown. These aspects were investigated by fermenting Sauvignon blanc juice with J7 and/or VIN13 yeast strains and assessing the stability of cis-2-MPO during wine storage. Moderate to strong Pearson correlations verified similar evolution trends between acetaldehyde, 3-sulfanylhexyl acetate, and cis-2-MPO, with initial increases and a peak during the early to middle stages of AF before consecutive decreases until the end. Contrarily, 3-SH correlated moderately only at the end of AF. A consistent decrease observed for cis-2-MPO when spiked into Sauvignon blanc wine and assessed during 1-year storage revealed its general instability, but acetaldehyde addition (100 mg/L), pH 3.0, and storage at 4 °C all appeared to retain cis-2-MPO. These results have implications for wine aroma and the potential for cis-2-MPO to act as a sink (or source) for 3-SH in wine over time.

Chemical and Sensory Impacts of Accentuated Cut Edges (ACE) Grape Must Polyphenol Extraction Technique on Shiraz Wines

Accentuated Cut Edges (ACE) is a recently developed grape must extraction technique, which mechanically breaks grape skins into small fragments but maintains seed integrity. This study was the first to elucidate the effect of ACE on Shiraz wine’s basic chemical composition, colour, phenolic compounds, polysaccharides and sensory profiles. A further aim was to investigate any potential influence provided by ACE on the pre-fermentation water addition to must. ACE did not visually affect Shiraz wine colour, but significantly enhanced the concentration of tannin and total phenolics. Wine polysaccharide concentration was mainly increased in response to the maceration time rather than the ACE technique. ACE appeared to increase the earthy/dusty flavour, possibly due to the different precursors released by the greater skin breakage. The pre-fermentation addition of the water diluted the wine aromas, flavours and astringency profiles. However, combining the ACE technique with water addition enhanced the wine textural quality by increasing the intensities of the crucial astringent wine quality sub-qualities, adhesive and graininess. Furthermore, insights into the chemical factors influencing the astringency sensations were provided in this study. This research indicates that wine producers may use ACE with pre-fermentation water dilution to reduce the wine alcohol level but maintain important textural components.

Grape skins as supplements for color development in Pinot noir wine

A particular challenge to making wine from Pinot noir grapes is the delicate flavor, light color and poor ageing potential of the wine. Conventional Pinot noir must preparations were compared with those made using a skin-based supplement to assess the impact on non-bleachable (sulfur resistant) pigments in the wine. When supplemented with either fresh grape pomace of Pinot noir, Pinot gris or Chardonnay grapes; Pinot noir grape marc or a commercial liquid grape skin extract, the additional seeds and pulp from the supplements were shown to compromise the development of stable pigments in the wine. To compare the relative merits of tannin derived from grape skins and seeds, the supplements used in a parallel experiment were the skins alone of the same three grape varieties and at six months bottle age, the stable pigment concentration was found to exceed the amount attributable to the supplement. A third experiment used fermented grape skins as the supplement, with 85% of the supplementary anthocyanin recovered as stable pigment complexes in the wine. Notably, this series of experiments showed that supplements containing grape seeds appeared to compromise non-bleachable pigment formation in the wine while skin only supplements stimulated their development.

Current and future strategies for wine yeast lees valorization

Wine lees is a sludge material mainly composed of dead yeast precipitated at the bottom of wine tanks. Along with grape pomace and grape stalks, it is one of the main by-products of the winemaking industry. Given that wine lees are considered a soil pollutant, their disposal represents a cost for wineries. Numerous wine lees recovery and valorization strategies have been proposed, with a particularly steep increase in published research in recent years. This attention is strictly linked to the concepts of circular economy and environmental sustainability that are attracting the interest of the scientific community. In this review, an overview on the available wine lees recovery and valorization strategies is reported. Additionally, the methods for the extraction and valorization of yeast's cell wall polysaccharides (β-glucans and mannoproteins) are discussed. Finally, current and future innovative applications in different sectors of yeast β-glucans and mannoproteins are described and critically discussed.

Lower-alcohol wines produced by Metschnikowia pulcherrima and Saccharomyces cerevisiae co-fermentations: The effect of sequential inoculation timing

In Latin, 'pulcherrima' is a superlative form of an adjective that translates as beautiful. Apart from being 'the most beautiful' yeast, Metschnikowia pulcherrima has a remarkable potential in production of wines with lower ethanol content. The oenological performance of six M. pulcherrima strains was hereby tested in sequential cultures with Saccharomyces cerevisiae. The best-performing strain MP2 was further characterised in fermentations with different S. cerevisiae inoculation delays in both white grape juice and Chemically Defined Grape Juice Medium (CDGJM). The analysis of main metabolites, undertaken prior to sequential inoculations and upon fermentation completion, highlighted metabolic interactions and carbon sinks other than ethanol in MP2 treatments. Depending on the inoculation delay, MP2 white wines contained between 0.6% and 1.2% (v/v) less ethanol than the S. cerevisiae monoculture, with even larger decreases detected in the CDGJM. The MP2 treatments also contained higher concentrations of TCA cycle by-products (i.e. fumarate and succinate) and glycerol, and lower concentrations of acetic acid. The analysis of volatile compounds showed increased production of acetate esters and higher alcohols in all MP2 wines, alongside other compositional alterations arising from the S. cerevisiae inoculation delay.

Substitution or Dilution? Assessing Pre-fermentative Water Implementation to Produce Lower Alcohol Shiraz Wines

Changes to regulations by Food Standards Australia New Zealand have permitted the adjustment of must sugar levels with the addition of water in order to ensure a sound fermentation progress as well as mitigating excessive wine-alcohol levels. This study assessed the implications for Shiraz wine quality following a pre-fermentative must dilution (changing liquid-to-solid ratios), in comparison to juice substitution with water (constant liquid-to-solid ratios) that has previously been deemed a promising way to adjust wine-alcohol levels. While working within the legal limit of water addition to grape must, the effects of both approaches on wine quality parameters and sensory characteristics were rather similar, and of negligible nature. However, different implications between substitution and dilution appeared to be driven by grape maturity, and dilution was found to have a greater impact than substitution on some parameters at higher water implementation rates. In line with previous observations, longer hang-time followed by alcohol adjustments via pre-fermentation water addition were of limited merit compared to simply picking grapes earlier. This work provided further knowledge that supports informed decision making regarding the recently permitted approach of using water during winemaking.

Pre-fermentation approaches to producing lower alcohol wines from Cabernet Sauvignon and Shiraz: Implications for wine quality based on chemical and sensory analysis

Pre-fermentative juice substitution with water or early harvest wine has the potential to produce lower alcohol wines without critically modifying colour or tannin properties and only marginally changing volatile and sensory profiles. Whether this approach is suited to producing lower alcohol wines in the absence of excessive grape ripeness remained to be determined. The current study extends on pre-fermentative approaches to alcohol management under milder grape ripening conditions and builds on an existing study with McLaren Vale Cabernet Sauvignon fruit, allowing for a direct comparison under two distinct vintage conditions. Given its importance to Australia, Shiraz was also included and underwent the same consecutive harvest and juice substitution treatments. Cultivar-dependent implications on wine chemical properties were apparent and declines in wine colour and tannin were particularly evident in Shiraz wines, although impacts on overall wine quality and sensory parameters were minor when adjusting musts within the limit of 13.5 °Baumé.

Commercial Saccharomyces cerevisiae Yeast Strains Significantly Impact Shiraz Tannin and Polysaccharide Composition with Implications for Wine Colour and Astringency

To gain knowledge on the role of Saccharomyces cerevisiae yeast strains (and their hybrids) on wine sensory properties, 10 commercially available yeast strains were selected on the basis of their widespread usage and/or novel properties and used to produce Shiraz wines. Significant differences were evident post-alcoholic fermentation and after 24 months of ageing with regards to the number of wine compositional variables, in particular the concentration of tannin and polysaccharide. Strain L2323 is known for its pectinolytic activity and yielded the highest concentration of both yeast- and grape-derived polysaccharides. Wines made with the mannoprotein-producing strain Uvaferm HPS (high levels of polysaccharides) did not have elevated concentrations of yeast-derived polysaccharides, despite this observation being made for corresponding model fermentations, suggesting that mannoprotein production or retention might be limited by the wine matrix. Wine tannin concentration showed a high level of variability between strains, with L2323 having the highest, and AWRI1503 the lowest concentration. Sensory analysis of the wines after 24 months ageing revealed significant differences between the yeast strains, but only the attributes opacity (visual colour) and astringency could be predicted by partial least squares regression using the wine compositional data. Notably, the astringency attribute was associated with higher concentrations of both tannin and polysaccharide, contrary to reports in the literature which suggested that polysaccharide exerts a moderating effect on astringency. The results confirm previous reports demonstrating that the choice of yeast strain represents an opportunity to shape wine style outcomes.

Monitoring the effects and side-effects on wine colour and flavonoid composition of the combined post-fermentative additions of seeds and mannoproteins

One of the main consequences of the advancement of harvest date associated to global climate change is that the phenolic maturity of grapes can be delayed in relation to their technological maturity. As a consequence, wines made from these grapes can be poor in phenolic compounds or possess an unbalanced phenolic composition, affecting their global quality. The combined post-fermentative addition of seeds and an astringency-modulator mannoprotein (MP) might be a potential strategy to solve this problem, since seeds might supply flavanols and improve wine chemical stability and the mannoprotein might modulate the changes induced in astringency by the addition of seeds and improve wine colloidal stability. The present study aimed at monitoring at different moments of winemaking and ageing the effects and side-effects of this combined strategy on the detailed flavanol, flavonol and anthocyanin compositions and on colour of wines made from Syrah grapes. Seeds were obtained from Pedro Ximénez overripe grapes. Flavanol composition and flavonol and anthocyanin compositions were determined by HPLC-MSⁿ-MRM and HPLC-DAD-MSⁿ analyses, respectively. Colour changes caused by these additions were studied from CIELAB parameters as well as the ability of these techniques to protect colour from bleaching agents, such as SO₂. In general, the addition of seeds initially increased the levels of flavanols and anthocyanins. However, during bottle ageing a reduction in the levels of flavanols, flavonols and anthocyanins could be observed in seed treated wines, which might be related to the greater formation of flavanol aggregates associated with greater levels of flavanols. This effect was partially solved for most of the flavonoids studied with the additional MP treatment. Treated and control wines showed colour differences that were visible to human eye, although they were reduced over time. At the end of the study, treated wines showed colour parameters corresponding to younger wines than those observed in control wines. A greater resistance against SO₂ bleaching was also observed in treated wines, which can be mainly associated to the greater percentages of polymeric pigments caused by seed treatment and to the improvement of the colloidal stability of SO₂-resistant pigments caused by the addition of the MP.

Evaluation of Yeast Derivative Products Developed as an Alternative to Lees: The Effect on the Polysaccharide, Phenolic and Volatile Content, and Colour and Astringency of Red Wines

Due to the increase of the use of yeast derivatives (YDs) in winemaking to improve the technological and sensory properties in wines, in this work we evaluated the effect of the post-fermentation application of different yeast derivative products on the physical and chemical properties and astringency of red wines during two consecutive harvests. A commercial and two experimental new yeast derivatives were applied at a medium‒high dosage (30 g/hL). The addition of different yeast derivatives in red wine increased the concentration of different polysaccharide fractions and, therefore, the total polysaccharide content, producing a decrease in the duration of the wine astringency perception over time. The use of yeast derivatives could produce an adsorption/clarification and/or protective effect on the phenolic compounds. However, it did not produce an important modification of the colour parameters. An intensification or a lower decrease of the most volatile compound groups was produced, but it depended on the YDs and yeast strain used in fermentation and post-fermentation processes.

From Flavanols Biosynthesis to Wine Tannins: What Place for Grape Seeds?

Phenolic compounds are among the most important quality factors of wines. They contribute to the organoleptic characteristics of wine such as color, astringency, and bitterness. Although tannins found in wine can come from microbial and oak sources, the main sources of polyphenols are grape skins and seeds. Since the 1960s, this subject has been widely studied by a large number of researchers covering different types of wine, climate conditions, growing practices, and grape varieties. As these works have been conducted under different conditions, the data collected can be conflicting. Moreover, even though the biosynthesis of the major proanthocyanidins units (+)-catechin and (-)-epicatechin is well-known, the mechanism of their polymerization remains unexplained. This is why the question remains: what factors influence the biosynthesis, the quantity, and the distribution of tannins in grape seeds and how can winemaking processes impact the extractability of seed tannins in wine?

Impact of Commercial Oenotannin and Mannoprotein Products on the Chemical and Sensory Properties of Shiraz Wines Made from Sequentially Harvested Fruit

The tannin and polysaccharide profiles and therefore sensory properties of wine are influenced by fruit maturity at harvest, and practices employed during winemaking. This study investigated the extent to which commercial winemaking supplements (skin and seed tannins, and mannoprotein (MP)) can enhance the mouthfeel properties of red wine, in particular, wine made from grapes harvested before commercial ripeness (early-harvest). Supplements were added to wines made from Shiraz grapes harvested at 20.8 and 24.5 °Brix. The chemical composition and mouthfeel properties of wines were then determined by high performance liquid chromatography and descriptive analysis (DA), respectively. Wines made from riper grapes had higher levels of tannin than wines made from early-harvest grapes, but similar polysaccharide levels were observed. The addition of seed oenotannin yielded higher tannin levels than addition of skin oenotannin, particularly for wines made from early-harvest grapes. The DA panel perceived sensory differences between H1 and H2 wines, but could not perceive any effect of supplementation on wine mouthfeel properties, with the exception of a minor increase in sweetness, attributed to mannoprotein addition to H1 wines, even when MP was added to wines at 2.5 times the level recommended for use in Australia.

Kluyveromyces marxianus Secretes a Pectinase in Shiraz Grape Must That Impacts Technological Properties and Aroma Profile of Wine

Since Saccharomyces cerevisiae strains display no to weak pectinase activity, the utilization of external pectinase is a common practice in winemaking to enhance the extraction of compounds located in the grape berry skins during maceration. In this study, the activity of the native endopolygalacturonase of a Kluyveromyces marxianus strain, isolated from grape juice, was characterized in Shiraz grape must during alcoholic fermentation with or without prefermentative cold maceration. The wines made with K. marxianus had a higher methanol concentration, more free-run wine, an altered volatile compound profile, and displayed pectinase activity in cell-free wine samples. Moreover, the results strongly suggest that K. marxianus' pectinase released polygalacturonic acid soluble fragments, unlike fungal pectinases, which mostly release monomers. Overall, this study shows that K. marxianus is an effective pectinase producer in wine with potential benefits for wine properties.

Chemical and Sensory Evaluation of Magnetic Polymers as a Remedial Treatment for Elevated Concentrations of 3-Isobutyl-2-methoxypyrazine in Cabernet Sauvignon Grape Must and Wine

3-Isobutyl-2-methoxypyrazine (IBMP) is a potent odorant present in grapes and wines that is reminiscent of green capsicum. Suprathreshold concentrations can lead to obvious vegetative characters and suppress desirable fruity aroma nuances in wines, but options to manage IBMP concentrations are limited. This work investigated pre- and postfermentation addition of a putative imprinted magnetic polymer (PIMP) as a remedial treatment for elevated concentrations of IBMP in Cabernet Sauvignon grape must in comparison to nonimprinted magnetic polymer (NIMP) and to a commercially available polylactic acid (PLA) based film added postfermentation. Chemical and sensory analyses of wines showed that PIMP treatments were more effective than PLA film for decreasing "fresh green" aroma nuances without negatively impacting overall aroma profiles and that postfermentation addition of a magnetic polymer removed up to 74% of the initial IBMP concentration compared to 18% for PLA. Prefermentation addition of magnetic polymers removed 20-30% less IBMP compared to that of postfermentation addition but also had less of an effect on other wine volatiles and color parameters.

Volatile and sensory profiling of Shiraz wine in response to alcohol management: comparison of harvest timing versus technological approaches

The aim of this study was to compare the volatile and sensory profiles of Australian Shiraz red wines produced by several methods to achieve alcohol concentrations of 10.5 and 13.5% v/v. These levels were considerably lower contents than the commercial wine (16-17% v/v) that was produced from this vineyard site. Wines were produced by: (i) harvest timing (19.3, 24 and 29.3 Brix); (ii) blending equal proportions of early harvest (19.3 Brix) and late harvest wines (29.3 Brix); and (iii) dealcoholization using reverse osmosis followed by a membrane contactor. Dealcoholization caused a significant loss of volatile compounds, particularly esters, while the blending treatment had an averaging effect on most analytes. Sensory descriptive analysis of treatments with 10.5% v/v alcohol showed that the perception of the herbaceous attribute was more intense in the early harvest wines in comparison to the dealcoholized wines, while those of dark fruit, raisin/prune, astringency and alcohol were lower. No sensory differences were found amongst the 13.5% v/v wines, except for alcohol. Sensory and compositional data were modelled by means of Common Dimension (ComDim) multi-block analysis and indicated which chemical components are important to the perceived wine sensory properties. Insights from this study will provide knowledge that may be applied to control or moderate both unripe sensory attributes in addition to a deficiency of ripe fruit aromas or mouthfeel characteristics in reduced-alcohol red wines.

Comparison of consecutive harvests versus blending treatments to produce lower alcohol wines from Cabernet Sauvignon grapes: Impact on polysaccharide and tannin content and composition

A changing climate has led to winegrapes being harvested with increased sugar levels and at greater risk of berry shrivel. A suggested easy-to-adopt strategy to manage the associated rising wine alcohol levels is the pre-fermentative substitution of juice with either "green harvest wine" or water. Our study investigates the effects of this approach on Vitis vinifera L. cv. Cabernet Sauvignon wine quality attributes. Wines were also made from fruit collected at consecutive earlier harvest time points to produce wines comparable in alcohol to the substituted wines. Tannin concentrations and colour did not change significantly in the wines with modified alcohol content even at higher juice substitution rates. Differences in polysaccharide and tannin composition indicated variability in extraction dynamics according to substitution rate and type of blending component. In scenarios where berry shrivel is inevitable, the incorporation of water in particular offers much promise as part of a strategy to manage wine alcohol content.