Tannin Content in Vitis Species Red Wines Quantified Using Three Analytical Methods

The Staining Susceptibility and Surface Roughness of Teeth Restored by Microabrasion and Resin Infiltration: An In Vitro Study

This study assessed the susceptibility to staining and surface roughness of white-spot lesions (WSLs) treated with resin infiltration (RIT) and microabrasion (MA) under simulated aging through thermocycling in red wine. Seventy-eight extracted human premolars with artificial WSLs were divided into three groups: untreated WSLs (control), RIT-treated (ICON®, DMG), and MA-treated (Opalustre®, Ultradent). Each group was further split: one subgroup immersed in artificial saliva and the other thermocycled in red wine. The color change (∆E) and surface roughness (Ra) were measured before and after staining using a spectrophotometer and a non-contact profilometer. Thermocycling in red wine increased color change (ΔE) across all groups, with the highest values observed for MA (43.94 ± 3.57), followed by RIT (31.40 ± 4.89). Surface roughness (Ra) was highest in untreated WSLs (0.61 ± 0.18 µm) and lowest in RIT (0.15 ± 0.03 µm). While RIT and MA similarly improved WSL appearance, RIT exhibited superior smoothness. These findings suggest that RIT provides a more durable surface with reduced roughness, although staining susceptibility remains comparable to MA. Moderate positive correlation was found between ΔE and Ra, indicating that roughness is one of the factors influencing color changes.

Synergetic effect of Accentuated Cut Edges (ACE) and macerating enzymes on the phenolic composition of Marquette red wines

One of the challenges of cold-hardy grape cultivars is their typical low content of tannins, alongside the presence of anthocyanin diglucoside and high acidity, which can lead to unbalanced red wines. This study hypothesized that the combination of Accentuated Cut Edges (ACE) and macerating enzymes would improve phenolics extraction from grape skins after disruption. The effects of those two winemaking techniques, either used separately or together, on red wine quality characteristics were investigated at crushing, bottling, and after six or nine months of aging. Overall, the combination of treatments improved the concentration of monomeric phenolics (20 %) and tannins (21 %) after nine months of aging. ACE or enzyme treatment separately applied had little impact on phenolics extraction in finished wines. This study exhibited a potential strategy to modify phenolics profile through the synergistic effect of ACE and macerating enzymes by causing cellular breakdown in a cold-hardy red grape cultivar.

Influence of Grape Flesh on the Retention and Composition of Polyphenols from Skins and Seeds

This study examined the impact of grape flesh polysaccharide, protein, and amino acid contents on polyphenol retention from skins and seeds in Pinot noir (Vitis vinifera) and cold-hardy interspecific cultivars Marquette and Frontenac (Vitis spp.). After isolating grape tissues (skin, seed, and flesh), they were soaked either individually or combined with other tissues in a wine-like solution for up to 7 days. Findings revealed that flesh significantly reduces the concentration of condensed tannin, and mono- and diglucoside forms of anthocyanins in the supernatants, due to its rich content in polysaccharides and proteins. Frontenac skin and flesh tissues were the main sources of soluble proteins, amino acids, and soluble polysaccharides. Surprisingly, Marquette exhibited a higher retention of skin tannin than Pinot noir, likely due to its smaller tannin molecular mass, and a potential competitive effect with anthocyanins for the binding sites of flesh.

Tannin and Iron-Reactive Phenolics Content in Red Cold-Hardy Hybrid Grape Tissues throughout Development and Ripening

Phenolic compounds, especially tannins, are important for red wine quality. Wines made from cold-hardy hybrid grape cultivars have much lower tannin concentrations than wines from Vitis vinifera grape cultivars. This study assessed the phenolics content of berry tissues of three red cold-hardy hybrid cultivars in comparison to V. vinifera cv. 'Pinot noir' throughout development and ripening. Basic chemical properties, iron-reactive phenolics content, and tannin content were evaluated in the juice, skins, and seeds of Vitis spp. cvs. 'Crimson Pearl', 'Marquette', and 'Petite Pearl' and 'Pinot noir' at six time points from one week post-fruit set to harvest in 2021 and 2022. 'Crimson Pearl' displayed similar iron-reactive phenolics and tannin contents in juice, skins (22.6-25.4 mg/g dry skin and 8.0-12.2 mg/g dry skin, respectively), and seeds (12.8-29.8 mg/g dry seed and 4.2-22.0 mg/g dry seed, respectively) as 'Petite Pearl' and 'Marquette' at harvest in 2022. The hybrid cultivars showed a similar trend of phenolic accumulation as 'Pinot noir' but resulted in overall lower content in skins and seeds. Despite differences in developmental trends, the three hybrid grape cultivars displayed similar phenolic content at harvest ripeness. This is the first study examining the phenolic content of 'Crimson Pearl' and 'Petite Pearl' throughout berry development and ripening. This study provides important information for the wine industry to make informed decisions on making wine with these cultivars.

Exploring the potential of cellulose autofluorescence for optical detection of tannin in red wines

The growing demand for opto-electronic devices within an automated landscape has opened up new opportunities for harnessing sustainable cellulose materials for sensors technology. Cellulose, a versatile material, enables its combination with other materials, but in most of these applications, cellulose is typically employed as support or substrate, while its inherent autofluorescence remains largely underexplored for sensors. In light of this context, this study delves into the autofluorescence characteristics of pristine cellulose nanocrystals extracted from wood via enzymatic route for optical sensors tailored to detect tannins. By fine-tuning the experimental setup, photoluminescence (PL) emission bands were scrutinized across three distinct spectral regions, namely 300-400 nm, 400-500 nm and 550-700 nm. The proposed mechanism reveals the occurrence of dynamic fluorescence quenching, which enabled the selective monitoring of tannins in red wines across a dynamic range spanning from 10 to 1060 μg mL-1. This sensing platform provided a limit of detection (LoD) of 6.1 μg mL-1. Notably, the sensing platform's efficacy was validated with remarkable recovery rates of 99.7 % and 95.3 % when subjected to testing with cabernet sauvignon and tannat wines. These findings emphasize the sensing platform's potential for monitoring tannic acids in beverages and food products.

Effect of infrared drying on chemical and microbial properties of Cold-Hardy grape pomace (Edelweiss and Marquette)

This study aims to add value to a common wine industry waste by preserving bioactive compounds in cold-hardy grape pomace (GP) and preventing any microbial growth under the proper drying conditions. Effects of infrared (IR) and hot air (HA) drying on the microbial and physicochemical properties such as color, phenolic compounds, and antioxidant activity of white (Edelweiss) and red (Marquette) GP were studied. The IR heating rapidly reduced the moisture content of GP from 55% wet basis (w.b.) to less than 10%, which resulted in a drying time reduction of 71.9% to 80.2% compared to HA drying. There were no significant differences in color parameters among the IR- and HA-dried pomaces (p > .05). The phenolic content of 'Edelweiss' pomace was not significantly affected by both IR and HA drying, whereas the phenolic content of 'Marquette' pomace was substantially reduced from 274 mg/g dry extract in raw pomace to 127 mg/g dry extract after HA drying and to 141.9 mg/g dry extract after IR drying. Overall, the microbial load on the fresh pomace samples was dramatically reduced by IR heating, with a reduction of more than 99.9% when the pomaces were dried using IR at a temperature higher than 130°C. However, this high temperature of IR led to a significant reduction of DPPH antiradical scavenge activity for 'Edelweiss' pomace (p < .05). This study shows that using the IR approach, cold-hardy 'Edelweiss' and 'Marquette' grape pomaces can be efficiently dried with the antioxidant activity maintained, which could be used in a variety of food products as a functional ingredient.

Effect of Whole Cluster Fermentation on Phenolics in Cold-Hardy Hybrid Wines

Generally, red wines made from cold-hardy hybrid grapes have much lower tannin content than Vitis vinifera wines and they are often perceived as being of lower quality. This study evaluated the chemistry and sensory perception of whole-cluster (WC) fermented “Frontenac” and “Marquette” red wines from Iowa (F-ISU, M-ISU) and “Marquette” red wines from Minnesota (M-UMN). Three conditions were compared: Control 0% WC (w/w), 25% WC (w/w), and 50% WC (w/w). The 50% WC wines had significantly higher iron-reactive phenolics, tannin, and anthocyanin contents than control wines. The color intensity in 50% WC wines was maintained after 4 months of aging. A tasting evaluation was conducted with the “Marquette” wines from both states and untrained panelists preferred 50% WC “Marquette” wines over control wines. This study showed promising results on the use of 50% (w/w) whole clusters as a pre-fermentative technique to improve “Marquette” and “Frontenac” red wine quality.

What are the challenges to producing high quality red wines from interspecific grapes?

In the U.S. Midwest region, interspecific cold hardy grape cultivars have been developed to be resistant to the harsh cold winter, late spring frosts, and hot and humid summer. However, interspecific grape red wines tend to have higher acidity and lower tannins content than Vitis vinifera wines. This leads to unbalanced wines and an increase of the risk of oxidation and therefore impact the overall quality over time. The content and type of phenolic compounds differ in interspecific grapes and wines, depending on the cultivars, the viticultural practices, the environmental conditions and the wine making process. Because the chemical properties of red wines produced from interspecific grapes compared to Vitis vinifera is not well known, it is a challenge to determine the best wine making practices to produce a high quality wine that remains stable over time. This study focuses on evaluating phenolic compounds, oxidation-related compounds, and sulfur dioxide content in Marquette and Frontenac wines aged in bottles for up to 9 years. The goal is to help improve quality of red wines made from interspecific cold-hardy grape cultivars to increase consumer acceptance and develop optimal wine making practices.

Comparative Evaluation of Physicochemical, Antioxidant, and Sensory Properties of Red Wine as Markers of Its Quality and Authenticity

The consumption of red wine by most wine drinkers has increased significantly because of the perceived health benefits which are linked to its inherent quality characteristics. In the quest to determine the conformity of Nigeria's domestic red wine quality with their international counterparts, the quality characteristics of domestic red wines produced in Nigeria were evaluated using foreign red wines as markers of wine quality and authenticity. Foreign and domestic red wines obtained in Nigeria were analyzed for physicochemical, antioxidant, and sensory properties using standard methods. Results showed that the domestic wines had significantly (p < 0.05) higher pH (4.03-4.16) and total sugar content (8.60-9.27%) while the foreign wines had significantly (p < 0.05) higher total titratable acidity (0.76-0.83%), Brix (6.98-8.04 g/100 g), alcohol (14.44-15.21% ABV), and polyphenol content (385.13-412.75 mg/L). Additionally, the domestic wines exhibited significantly (p < 0.05) lower antioxidant capacity compared to the foreign wines. Although the wines' hue angle (27.68°-41.46°) indicated a red colour spectrum in the visible region of the opponent colour chart, the total colour difference (ΔE) between foreign and domestic wines was significant. The sensory characteristics of the wines differed significantly as the panelist rating for overall acceptance ranged from 5.58 to 7.33. This research has provided valuable insight that the domestic wines studied showed a considerable level of authenticity and different levels of quality according to their varying concentration of organic acids, residual sugars, and phenolic compounds.

Optimization of the ultrasound-assisted extraction of polyphenols from Aronia and grapes

The extraction of phenolics and tannins from cold-hardy grapes is not maximized with the current methods, which lead to unbalanced wines. This study aims to investigate high-power sonication to improve polyphenolic content in cold-hardy grape juice in comparison with chokeberry juice. Three solid to solvent ratios and times were applied on chokeberry and 'Marquette' grape berries using 50% ethanol or 13% acidified ethanol and compared to a conventional extraction technique. Iron-reactive phenolic compounds, tannins content, and color were analyzed during the extractions using UV-Visible spectrophotometry, and anthocyanin content was analyzed using HPLC-DAD. At the 1:2 solid to solvent ratio, the color intensity, phenolics, and tannins content were improved using the ultrasound-assisted extraction on chokeberries. However, the tannin content of 'Marquette' berries remained the same with both techniques and solvents, suggesting that the plant cell wall structure may have a strong impact on the retention of tannins from cold-hardy grapes.

Effects of Saignée and Bentonite Treatment on Phenolic Compounds of Marquette Red Wines

To improve the phenolic extraction and color stability of red wine made from cold-hardy grapes, two winemaking practices, saignée and bentonite, were applied separately and in combination on Marquette grapes at crushing. The effects of these winemaking strategies on Marquette wine’s basic chemical properties, monomeric and polymeric phenolic compounds were studied, as well as the development of color characteristics from crushing to 5 months of aging. The saignée (9% juice run-off) treatment showed little impact on the phenolic content of the finished wine, but showed an increase in color intensity. A hue shift towards an orange-yellow tone was observed in the bentonite-treated wines, which was associated with a loss of monomeric anthocyanins. The combination of saignée and bentonite showed less impact on removing anthocyanins and wine color, and increased phenolics content, therefore improving the extraction of non-anthocyanins monomeric phenolics. Although this combination treatment led to the highest concentration of tannin content after pressing, this difference between the control and other treatments disappeared over time. These results suggested that the interactions between tannins and other wine compounds still occur after removing proteins in Marquette wines.