Compositional Consequences of Ultrafiltration Treatment of White and Red Wines.

Clarification and stabilisation processes are routinely performed post-fermentation to 'finish' wines, but traditional methods are slow and energy intensive, create waste, and can affect wine volume and quality. New methods that 'finish' wine rapidly, with higher recovery rates, and reduced waste and input costs, are therefore needed. Ultrafiltration is a separation process that fractionates liquids, nominally, according to molecular weight.

Apple Pomace Compositional Data Highlighting the Proportional Contribution of Polymeric Procyanidins.

Recent years have seen an increase in research focusing on the amelioration of apple pomace waste for use in the food and nutraceutical industries. Much of this work has concentrated on the characterisation of the polyphenol composition of apple pomace materials to determine their role in conferring nutritional and health benefits. Although apples contain substantial quantities of polymeric procyanidins (condensed tannins), this class of compounds has received limited attention in apple research.

Performance of Urinary Phenyl-γ-Valerolactones as Biomarkers of Dietary Flavan-3-ol Exposure.

Background: Phenyl-γ-valerolactones (PVLs) have been identified as biomarkers of dietary flavan-3-ol exposure, although their utility requires further characterization.

Objectives: We investigated the performance of a range of PVLs as biomarkers indicative of flavan-3-ol intake.

Methods: We report the results of 2 companion studies: a 5-way randomized crossover trial (RCT) and an observational cross-sectional study.

A novel solution to tartrate instability in white wines.

Tartrate stabilization remains a necessary step in commercial wine production to avoid the precipitation of crystals in bottled wine. The conventional refrigeration method to prevent crystallization of potassium bitartrate is time-consuming, energy-intensive, and involves a filtration step to remove the sediment. Nevertheless, it is still the most used stabilization method by winemakers.

Quantification of protein by acid hydrolysis reveals higher than expected concentrations in red wines: Implications for wine tannin concentration and colloidal stability.

Protein is reportedly negligible in most red wines, due to its loss following co-precipitation with phenolic substances. A method for protein quantification in red wine was developed which overcame analytical interference from phenolic substances, based on ethanol precipitation, followed by acid-hydrolysis and amino acid quantification. Protein concentration was surveyed in a range of red wines produced from V.

Fluorescence sensing technology for the rapid detection of haze-forming proteins in white wine.

The methods currently available for determining haze proteins in wine are time-consuming, expensive, and often not sufficiently accurate. The latter may lead to bentonite over-fining of a wine, which might strip wine phenolics and aroma compounds, or wine under-fining, which increases the risk of protein instability. In this work, an efficient and rapid fluorescence-based technology to detect haze-forming proteins in white wines was developed.

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

This study investigated the color, phenolic, polysaccharide, volatile and sensory profiles of Cabernet Sauvignon wines made from flash détente (FD) treated musts fermented at different temperatures (16, 24 or 32 °C), with and without suspended grape solids. Low fermentation temperature and low solids content increased the concentration of esters, whereas the opposite conditions increased the concentration of fusel alcohols, polysaccharides and glycerol. Higher fermentation temperatures also increased linalool concentration independent of solids content.

Precipitation of Tannin-Anthocyanin Derivatives in Wine is Influenced by Acetaldehyde Concentration and Tannin Molecular Mass with Implications for the Development of Nonbleachable Pigments.

This study aimed to assess the effect of tannin molecular mass on nonbleachable pigment formation and subsequent stability under wine-like conditions. Tannin fractions of a defined molecular mass range were prepared from grape skins and seeds and reacted with malvidin-3-glucoside for 120 days in three media types: chemically defined wine media with or without acetaldehyde addition or model wine without acetaldehyde. Precipitation was observed after the reaction period and increased in response to both higher tannin molecular mass and acetaldehyde concentration.

Potential Mitigation of Smoke Taint in Wines by Post-Harvest Ozone Treatment of Grapes.

When bushfires occur near grape growing regions, vineyards can be exposed to smoke, and depending on the timing and duration of grapevine smoke exposure, fruit can become tainted. Smoke-derived volatile compounds, including volatile phenols, can impart unpleasant smoky, ashy characters to wines made from smoke-affected grapes, leading to substantial revenue losses where wines are perceivably tainted. This study investigated the potential for post-harvest ozone treatment of smoke-affected grapes to mitigate the intensity of smoke taint in wine.

Fluorescence correlation spectroscopy to unravel the interactions between macromolecules in wine.

In this work, the interaction of wine macromolecules with a bovine serum albumin (BSA) was investigated using fluorescence correlation spectroscopy (FCS). FCS offers the opportunity to study molecular and macromolecular aggregation without disturbing the wine by introducing only very small amounts of fluorescently labelled molecules to the system. It was observed that the diffusion coefficient of fluorescently labelled BSA varies with the addition of wine macromolecules, indicating changes in the protein conformation and the formation of complexes and aggregates.

Pre-Fermentation Water Addition to High-Sugar Shiraz Must: Effects on Wine Composition and Sensory Properties.

Changes to Australian regulations now allow the limited addition of water to high-sugar musts pre-fermentation. In light of these changes, this study explored how water addition affects Shiraz wine composition and sensory properties. Wines were made from grapes at ≈13.

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.

Bioavailability of red wine and grape seed proanthocyanidins in rats.

This study explored plasma levels and urinary and fecal excretion of metabolites and microbial-derived catabolites over a 24 h period following the ingestion of red wine (RWP) or grape seed (GSP) proanthocyanidin-rich extracts by rats. In total, 35 structurally-related (epi)catechin metabolites (SREMs) and 5-carbon side chain ring fission metabolites (5C-RFMs) (phenyl-γ-valerolactones and phenylvaleric acids), and 50 phenolic acid and aromatic catabolites were detected after intakes of both extracts. The consumption of the RWP extract, but not the GSP extract, led to the appearance of a ∼200 nmol L peak plasma concentration of SREMs formed from flavan-3-ol monomers.

Regeneration of Magnetic Nanoparticles Used in the Removal of Pathogenesis-Related Proteins from White Wines.

Protein haze remains a serious problem for the wine industry and requires costly bentonite treatment, leading to significant wine volume loss. Recently developed magnetic separation technology that allows a fast and efficient separation of haze proteins from wine shows promise for the development of an alternative method for white wine fining. The key purpose of this study was to understand the potential of the nanoparticles to be reused in multiple fining and regeneration cycles.

Potato Protein Fining of Phenolic Compounds in Red Wine: A Study of the Kinetics and the Impact of Wine Matrix Components and Physical Factors.

Producing wines within an acceptable range of astringency is important for quality and consumer acceptance. Astringency can be modified by fining during the winemaking process and the use of vegetable proteins (especially potato proteins) as fining agents has gained increasing interest due to consumers' requirements. The research presented was the first to investigate the effect of a potato protein dose on the kinetics of tannin and phenolic removal compared to gelatin for two unfined Cabernet Sauvignon wines.

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

To gain knowledge on the role of 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.

Pectolytic enzyme reduces the concentration of colloidal particles in wine due to changes in polysaccharide structure and aggregation properties.

To explore the effect of pectolytic enzyme application on polysaccharide size and colloidal interactions, rosé wines were prepared from pressed Shiraz grape juice, and red wines were made from the same juice by the addition of skins and seeds from fresh pressings. A pectolytic enzyme preparation containing primarily polygalacturonase and side-activities of arabinase and pectin lyase was used. Enzyme treatment enhanced the contribution of high molecular weight (≈ 200 kDa) polysaccharides rich in mannose and glucose (mannoproteins) and removed arabinose-rich polysaccharides of intermediate (≈ 40 kDa) size.

Effect of Grape Seed and Skin Tannin Molecular Mass and Composition on the Rate of Reaction with Anthocyanin and Subsequent Formation of Polymeric Pigments in the Presence of Acetaldehyde.

Polymeric pigments formed via ethyl linkages between grape tannins and anthocyanins are important to the development of stable red wine color. To determine the effect of tannin structure on the stability and color properties of ethyl-linked polymeric pigments, tannin fractions with average polymerization between 4 and 43 units were prepared from grape skins and seeds and combined with malvidin-3-glucoside (M3G) in model wine containing acetaldehyde. As tannin molecular mass increased, the reaction rate with M3G increased.

Oxygen exposure during red wine fermentation modifies tannin reactivity with poly-l-proline.

Red wines injected with nitrogen or oxygen during fermentation were used to identify the effect of gas exposure on tannin structure and reactivity with poly-l-proline. Tannin was purified from wine after fermentation and after three years of bottle storage. Tannin from nitrogen-treated wine had a lower percentage of galloylation and were less pigmented than tannin from oxygen-exposed wine.

Applying Nanoparticle Tracking Analysis to Characterize the Polydispersity of Aggregates Resulting from Tannin-Polysaccharide Interactions in Wine-Like Media.

Interactions between grape seed tannin and either a mannoprotein or an arabinogalactan in model wine solutions of different ethanol concentrations were characterized with nanoparticle tracking analysis (NTA), UV-visible spectroscopy and dynamic light scattering (DLS). NTA results reflected a shift in particle size distribution due to aggregation. Furthermore, the light scattering intensity of each tracked particle measured by NTA demonstrated the presence of aggregates, even when a shift in particle size was not apparent.

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.

Development and validation of an UHPLC-HRMS protocol for the analysis of flavan-3-ol metabolites and catabolites in urine, plasma and feces of rats fed a red wine proanthocyanidin extract.

This study developed, optimized and validated an ultra-high-performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS) method to identify and quantify metabolites and microbial-derived catabolites in urine, plasma and feces of rats following ingestion of 50 mg of a red wine proanthocyanidin-rich extract. The method was validated for specificity, linearity, limit of detection (LD) and quantification (LQ), intra-day and inter-day precision, recovery and matrix effects, which were determined for 34 compounds in the three biological matrices. After method validation, three parent flavan-3-ols, four 5-carbon side chain ring fission metabolites, and 27 phenolic acid and aromatic catabolites were quantified in plasma, urine and feces after red wine proanthocyanidin intake.

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.

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

Wine quality can be significantly affected by tannin and polysaccharide composition, which can in turn be influenced by grape maturity and winemaking practices. This study explored the impact of three commercial wine additives, a maceration enzyme, an enotannin, and a mannoprotein, on the composition and sensory properties of red wine, in particular, in mimicking the mouthfeel associated with wines made from riper grapes. Shiraz grapes were harvested at 24 and 28 °Brix and the former vinified with commercial additives introduced either individually or in combination.

Retention of Proanthocyanidin in Wine-like Solution Is Conferred by a Dynamic Interaction between Soluble and Insoluble Grape Cell Wall Components.

For better understanding of the factors that impact proanthocyanidin (PA) adsorption by insoluble cell walls or interaction with soluble cell wall-derived components, application of a commercial polygalacturonase enzyme preparation was investigated to modify grape cell wall structure. Soluble and insoluble cell wall material was isolated from the skin and mesocarp components of Vitis vinifera Shiraz grapes. It was observed that significant depolymerization of the insoluble grape cell wall occurred following enzyme application to both grape cell wall fractions, with increased solubilization of rhamnogalacturonan-enriched, low molecular weight polysaccharides.