Formation and evolution profiles of anthocyanin derivatives and tannins during fermentations and aging of red wines

Gallic acid improves color quality and stability of red wine via physico-chemical interaction and chemical transformation as revealed by thermodynamics, real wine dynamics and benchmark quantum mechanical calculations

The aim of this study was to explore the copigmentation effect of gallic acid on red wine color and to dissect its mechanism at the molecular level. Three-dimensional studies, e.g., in model wine, in real wine and in silico, and multiple indicators, e.g., color, spectrum, thermodynamics and phenolic dynamics, were employed. The results showed that gallic acid significantly enhanced the color quality and stability of red wine. Physico-chemical interactions and chemical transformations should be the most likely mechanism, and physico-chemical interactions are also a prerequisite for chemical transformations. QM calculations of the physico-chemical interactions proved that the binding between gallic acid and malvidin-3-O-glucoside is a spontaneous exothermic reaction driven by hydrogen bonding and dispersion forces. The sugar moiety of malvidin-3-O-glucoside and the phenolic hydroxyl groups of gallic acid affect the formation of hydrogen bonds, while the dispersion interaction was related to the stacking of the molecular skeleton.

Advancements in the promotion of pyranoanthocyanins formation in wine: A review of current research

Pyranoanthocyanin (PACN) is a class of anthocyanin (ACN)-derived pigments found in aged red wines, which has certain advantages over the prototype ACN in terms of stability, and biological activity. However, the efficiency and yield of PACNs in the natural fermentation system are low. This article summarizes five frequently employed physical processing techniques that can accelerate the formation of PACN. From a mechanistic standpoint, these techniques can produce large amounts of active substances, further promoting the extracellular release of phenolics and the formation of some cofactors and PACNs' pyran rings. Precursor substances and environmental factors affecting PACN yields are also pointed out. It mainly included the parent ring substitution in ACNs, the type and quantity of glycosides, the electron donating ability and concentration of cofactors, etc. Thus, this article aims to provide an overview of the advancements in processing techniques, thereby facilitating their wider utilization in the food and beverage industry.

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.

Influence of Oxygen Management during the Post-Fermentation Stage on Acetaldehyde, Color, and Phenolics of Vitis vinifera L. Cv. Cabernet Sauvignon Wine

Oxygen exposure is unavoidable and the impact of its management during the post-fermentation stage (PFS) on dry red wine is poorly investigated. This study was dedicated to the variation of acetaldehyde, color and phenolics of Cabernet Sauvignon dry red wine during five discontinuous oxidation cycles of four levels of controlled oxygen supply, which were carried out to simulate probable oxidation during the PFS. Free SO2 disappeared after the first, second and third oxidation cycles in wines with high, medium and low levels of oxygen exposure severally, but subsequent oxygen exposure below or equal to 2 mg O2/L per cycle had little effect while 3-3.9 mg O2/L per cycle dramatically facilitated acetaldehyde accumulation, which was accompanied by an enormous variation in color and pigments, especially when total oxygen consumption was above 10 mg/L. The utilization of clustered heatmap and partial least square regression demonstrated the feasibility of characterization of wine oxidation degree using the chemical parameters measured by UV-spectrophotometry. Oxygen exposure during the PFS should be emphatically controlled, and chemical indexes determined by the UV-spectrophotometric method can be used for a scientific and effective description of wine oxidation degree.

Grape Pomace Valorization by Extraction of Phenolic Polymeric Pigments: A Review

In recent years there has been a growing concern about environmental pollution linked to the generation of agroindustrial waste. The wine industry generates approximately 8.49 million tons of grape pomace per year worldwide; this residue can be used to obtain compounds with biological activity. Grape pomace is a source of anthocyanins, pigments that have antioxidant properties and help prevent cardiovascular disease. The development of sustainable extraction, purification and identification techniques constitutes an important step in adding value to this waste. Therefore, the present research has focused on presenting a review of works carried out in the last years.

Influence of Temperature during Pre-Fermentative Maceration and Alcoholic Fermentation on the Phenolic Composition of 'Cabernet Sauvignon' Wines

This study presents the effects of different working temperatures on the transfer of compounds during the pre-fermentative and fermentative stages of the wine making process with ‘Cabernet Sauvignon’ grapes. Two different procedures have been evaluated. Firstly, the pre-fermentative maceration of the crushed grapes at two different temperatures (20 °C and 10 °C). Then, the alcoholic fermentation under two different sets of conditions, the fermentation at a constant temperature of 20 °C and the fermentation under a positive temperature gradient from 10 to 20 °C. According to the experimental results, the phenolic contents (total phenolics, total anthocyanins, and total tannins) were mainly conditioned by the fermentation temperature, however the pre-fermentative conditions also affected the content levels of these compounds. Furthermore, the use of a fermentation temperature gradient improved the organoleptic characteristics of the wines. However, the color was not as stable as that of wines produced through fermentation at a higher constant temperature. Consequently, the implementation of a temperature gradient during the alcoholic fermentation process is recommended and a longer period at high temperature over the last phase of the process would be desirable to obtain aromatic wines with the desirable color stability.

HPLC-MS/MS-based targeted metabolomic method for profiling of malvidin derivatives in dry red wines

Anthocyanin derivatives are critical components that impart color to aging red wine. In this study, we developed a targeted metabolomic method for the simultaneously profiling of the primary thirty-seven malvidin-derived anthocyanin derivatives in red wine, including various pyranoanthocyanins and flavanols-related condensation products. First, high-performance liquid chromatography (HPLC) tandem ion trap and triple-quadrupole (QqQ) mass spectrometry were used to construct the mass spectral and chromatographic database of the anthocyanin derivatives that were formed in a model wine solution. Next, the targeted profiling analysis of these compounds was achieved on a QqQ mass spectrometer in the multiple reaction monitoring mode (MRM). The method displayed excellent linearity (R² 0.9391-0.9998), sensitivity (0.221-0.604 μg/L of limit of detection (LOD) and 0.274-1.157 μg/L of limit of quantification (LOQ) equivalent to malvidin-3-O-glucoside (Mv-glc)), and repeatability (less than 10% and 15% for intra-day and inter-day relative standard deviation (RSD) respectively). Partial least squares discriminant analysis (PLS-DA) based on this method showed great discrimination over different vintage wines, thereby promising to be an effective tool in wine anthocyanin and aging related study.

Chemistry and Reactivity of Tannins in Vitis spp.: A Review

Tannins are a group of polyphenols found in fruits, leaves, trees, etc., well known in the leather industry and in apples, persimmons and grapes, because of their capacity to interact with other polyphenols or other components either from the food product or from saliva. Prior to being able to interact with other compounds, tannins have to be extracted from the food matrix, which depends on their chemistry, as well as the chemical structure of other components, such as cell wall material and proteins. Vitis vinifera grapes are commonly grown around the world and are used in winemaking, providing good quality wines with different levels of tannins responsible for the final wine’s astringency. Many studies have focused on tannins extractability and retention with cell wall material, and the reactivity of tannins with proteins in Vitis vinifera grapes and wine, but there are very few reports for other Vitis species. However, depending on the environmental characteristics of certain regions, Vitis hybrid grapes are grown and used to produce wines more and more. This review focuses on the comparison of the chemistry of tannins, and their reactivity with other macromolecules in Vitis species.

Pulsed Electric Field Processing of Red Grapes (cv. Rondinella): Modifications of Phenolic Fraction and Effects on Wine Evolution

Pulsed electric field (PEF) is a non-thermal technology able to promote color and polyphenols extraction from grape skins. Most of the publications about PEF in winemaking report data concerning international varieties, poorly considering minor cultivars and the medium/long-term effects of the treatment on wine composition during storage. PEF was applied at different specific energies (2, 10, and 20 kJ kg-1) on grapes of the low-color red cv. Rondinella, after crushing-destemming. Pressing yield, the evolution of color, and total phenolic index (TPI) were measured during skin maceration. Moreover, the wines were characterized for basic compositional parameters, color, anthocyanin profile, phenolic composition (glories indices), metal content (Fe, Cr, and Ni), and sensory characters, two and twelve months after the processing, in comparison with untreated samples and pectolytic enzymes (PE). PEF did not affect fermentation evolution, nor did it modify wine basic composition or metal content. Treatments at 10 and 20 kJ kg-1 led to higher color and TPI in wines, in comparison to PE, because of increased content of anthocyanins and tannins. The sensory evaluation confirmed these findings. Modifications remained stable in wines after twelve months. Glories indices and vitisin A content highlighted greater potential stability of wine color in PEF-treated wines.