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

Copper (II) Level in Musts Affects Acetaldehyde Concentration, Phenolic Composition, and Chromatic Characteristics of Red and White Wines

Copper (II), a vital fungicide in organic viticulture, also acts as a wine oxidation catalyst. However, limited data are currently available on the impact that maximum allowed copper (II) ion doses in wine grapes at harvest can have on aged wine quality. This was the focus of the present study. We investigated the copper (II) effects by producing both white and red wines from musts containing three initial metal concentrations according to the limits set for organic farming. In detail, the influence of copper (II) on fermentation evolution, chromatic characteristics, and phenolic compounds was evaluated. Interestingly, the white wine obtained with the highest permitted copper (II) dose initially exceeded the concentration of 1.0 mg/L at fermentation completion. However, after one year of storage, the copper (II) content fell below 0.2 ± 0.01 mg/L. Conversely, red wines showed copper (II) levels below 1.0 mg/L at the end of fermentation, but the initial copper (II) level in musts significantly affected total native anthocyanins, color intensity, hue, and acetaldehyde concentration. After 12-month aging, significant differences were observed in polymeric pigments, thus suggesting a potential long-term effect of copper (II) on red wine color stability.

Structure-dependent detection of polyphenols using crown ether-immobilized gold nanoparticles

Gold nanoparticles functionalized with 18-crown 6-ether (18C6-AuNPs) can be used for detection of tannic acid, epigallocatechin gallate, and epicatechin gallate by color change in the μg mL-1 range. 18C6-AuNPs were insensitive to l-ascorbic acid and l-tyrosine unlike conventional detection methods, such as Folin & Ciocalteu assay, whose principle is based on the redox reaction of polyphenols. Although 18C6-AuNPs did not respond to some polyphenols, such as gallic acid and epicatechin, if the polyphenols of interest are responsive to this approach, these are expected to be effective nanomaterial for simple sensing of polyphenols.

Leaching and evolution of anthocyanins and aroma compounds during Cabernet Sauvignon wine fermentation with whole-process skin-seed contact

This study explores the leaching and evolution of anthocyanins and aroma compounds during wine-making, using an industrial-scale vinification of Cabernet Sauvignon with whole-process skin-seed contact. The results indicated that compounds within the same class displayed similar evolutionary patterns during fermentation. The extraction of anthocyanins, C6 aldehydes, and β-damascenes occurred continuously during cold soak, accompanied by the conversion of C6 aldehydes into alcohols and hydrolytic release of glycosidic β-damascenone. During alcoholic fermentation, pyranoanthocyanins, polymeric pigments, esters, benzene compounds, higher alcohols, and acids were generated. The concurrent occurrence of malolactic fermentation and prolonged maceration led to aromas associated with lactic acid bacteria metabolism. Finally, a comparison between free-run wine and pressed wine revealed high concentrations of C6 compounds and polymeric pigments with flavanol dimers in the pressed wine. These results can be used as a reference to optimize the vinification process to enhance the red due and fruity aromas of the wine.

A High-Performance Food Package Material Prepared by the Synergistic Crosslinking of Gelatin with Polyphenol-Titanium Complexes

This study aims to enhance gelatin film performance in the food industry by incorporating polyphenol-titanium complexes (PTCs) as crosslinkers. PTCs introduce multiple linkages with gelatin, including coordination and hydrogen bonds, resulting in synergistic crosslinking effects. This leads to an increased hydrodynamic volume, particle size, and thermal stability of the gelatin films. Compared to films crosslinked solely by polyphenols or titanium, PTC-crosslinked gelatin films exhibit significant improvements. They show enhanced mechanical properties with a tensile strength that is 1.7 to 2.6 times higher than neat gelatin films. Moreover, these films effectively shield UV light (from 82% to 99%), providing better protection for light-sensitive food ingredients and preserving lutein content (from 74.2% to 78.1%) under light exposure. The incorporation of PTCs also improves film hydrophobicity, as indicated by water contact angles ranging from 115.3° to 131.9° and a water solubility ranging from 31.5% to 33.6%. Additionally, PTC-enhanced films demonstrate a superior antioxidant ability, with a prolonged polyphenol release (up to 18 days in immersed water) and a higher free radical scavenging ability (from 22% to 25.2%). Overall, the improved characteristics of gelatin films enabled by PTCs enhance their performance, making them suitable for various food packaging applications.

Polyphenols from persimmon fruit attenuate acetaldehyde-induced DNA double-strand breaks by scavenging acetaldehyde

Acetaldehyde, a metabolic product of ethanol, induces DNA damage and genome instability. Accumulation of acetaldehyde due to alcohol consumption or aldehyde dehydrogenase (ALDH2) deficiency increases the risks of various types of cancers, including esophageal cancer. Although acetaldehyde chemically induces DNA adducts, the repair process of the lesions remains unclear. To investigate the mechanism of repair of acetaldehyde-induced DNA damage, we determined the repair pathway using siRNA knockdown and immunofluorescence assays of repair factors. Herein, we report that acetaldehyde induces DNA double-strand breaks (DSBs) in human U2OS cells and that both DSB repair pathways, non-homologous end-joining (NHEJ) and homology-directed repair (HDR), are required for the repair of acetaldehyde-induced DNA damage. Our findings suggest that acetaldehyde-induced DNA adducts are converted into DSBs and repaired via NHEJ or HDR in human cells. To reduce the risk of acetaldehyde-associated carcinogenesis, we investigated potential strategies of reducing acetaldehyde-induced DNA damage. We report that polyphenols extracted from persimmon fruits and epigallocatechin, a major component of persimmon polyphenols, attenuate acetaldehyde-induced DNA damage without affecting the repair kinetics. The data suggest that persimmon polyphenols suppress DSB formation by scavenging acetaldehyde. Persimmon polyphenols can potentially inhibit carcinogenesis following alcohol consumption.

Impact of the Acetaldehyde-Mediated Condensation on the Phenolic Composition and Antioxidant Activity of Vitis vinifera L. Cv. Merlot Wine

Acetaldehyde is a critical reactant on modifying the phenolic profile during red wine aging, suggesting that the acetaldehyde-mediated condensation can be responsible for the variation of antioxidant activity during the aging of this beverage. The present study employs exogenous acetaldehyde at six levels of treatment (7.86 ± 0.10–259.02 ± 4.95 mg/L) before the bottle aging of Merlot wines to encourage phenolic modification. Acetaldehyde and antioxidant activity of wine were evaluated at 0, 15, 30, 45, 60 and 75 days of storage, while monomeric and polymeric phenolics were analyzed at 0, 30 and 75 days of storage. The loss of acetaldehyde was fitted to a first-order reaction model, the rate constant (k) demonstrated that different chemical reaction happened in wines containing a different initial acetaldehyde. The disappearance of monomeric phenolics and the formation of polymeric phenolics induced by acetaldehyde could be divided into two phases, the antioxidant activity of wine did not alter significantly in the first phase, although most monomeric phenolics vanished, but the second phase would dramatically reduce the antioxidant activity of wine. Furthermore, a higher level of acetaldehyde could shorten the reaction time of the first phase. These results indicate that careful vinification handling aiming at controlling the acetaldehyde allows one to maintain prolonged biological activity during wine aging.

Hop Tannins as Multifunctional Tyrosinase Inhibitor: Structure Characterization, Inhibition Activity, and Mechanism

The application of hops could be extended to obtain higher commercial values. Tannins from hops were assessed for their tyrosinase inhibition ability, and the associated mechanisms were explored. Nuclear magnetic resonance (NMR) and high-performance liquid chromatography–electrospray ionization–tandem mass spectrometry (HPLC–ESI–MS/MS) revealed that the hop tannins were characterized as condensed tannins with (epi)catechin and (epi)gallocatechin as subunits and an average polymerization degree of 10.32. Tyrosinase inhibition assay indicated that hop tannins had an IC₅₀ = 76.52 ± 6.56 μM. Kinetic studies of the inhibition processes indicated the tannins provided inhibition through competitive–uncompetitive mixed reactions. In silico molecule docking showed that tannins were bound to the active site of tyrosinase via hydrogen and electrovalent bonds. Circular dichroism (CD) observed the structural variation in the tyrosinase after reacting with the tannins. Fluorescence quenching analysis and free radical scavenging assays indicated that the tannins had copper ion chelating and antioxidant activities, which may also contribute to inhibition. The intracellular inhibition assay revealed that the melanin was reduced by 34.50% in B16F10 cells. These results indicate that these tannins can be applied as whitening agents in the cosmetics industry.

Reactivity comparison of three malvidin-type anthocyanins forming derived pigments in model wine solutions

Malvidin-3-O-glucoside (MvG), malvidin-3-O-(6-O-acetyl)-glucoside (MvAG), and malvidin-3,5-O-diglucoside (MvDG) are three representative malvidin-type anthocyanins in red wine. In this study, the influence of structural differences on the formation efficiency of two types of derived pigments ((-)-epicatechin-ethyl-anthocyanins and pyranoanthocyanins) was investigated in model solutions using UHPLC-MS. The results showed that the yields of MvAG were higher than those of MvG to form both types of derived pigments, and the formation rate of pyranoanthocyanin was also relatively higher. In contrast, acetylation slowed the formation of (-)-epicatechin-ethyl-anthocyanins, indicating that the rate of covalent reactions may be linked to the affinity of (-)-epicatechin to copigment with anthocyanins. The condensation rate of MvDG with (-)-epicatechin, mediated by acetaldehyde, was much lower than that of the two monoglucosidic anthocyanins and also exhibited lower yields. In addition, pyranoanthocyanin was not generated from MvDG due to the absence of a free hydroxyl group at the C5 position.