The effects of temperature and ethanol concentration on the kinetics of anthocyanin adsorption and desorption interactions with five cell wall materials (CWM) of different composition were investigated. Using temperatures of 15 °C and 30 °C and model wine with ethanol concentrations of 0% and 15% (v/v) over 120 min, the adsorption and desorption rates of five anthocyanin-glucosides were recorded in triplicate. Small-scale experiments were conducted using a benchtop incubator to mimic a single berry fermentation. Results indicate that more than 90% of the adsorption occurs within the first 60 min of the addition of anthocyanins to CWM. However, desorption appears to occur much faster, with maximum desorption being reached after 30 min. The extent of both adsorption and desorption was clearly dependent not only on temperature and ethanol concentration but also on the CWM composition.

The impact of increasing cold soak (CS) duration (0, 1, 4, 7, and 10 days at 10 °C) on the extraction of phenolic compounds during the CS period and primary fermentation as well as the final composition of Cabernet Sauvignon wine was investigated. The results showed that CS duration had no effect on hydroxycinnamate and flavonol extractions. Greater amounts of gallic acid, (+)-catechin, (−)-epicatechin, and total tannins were extracted with increasing CS duration, with differences maintained during bottle aging. Anthocyanin extraction and color density increased with longer periods of CS; however, by the end of primary fermentation, as well as three months’ bottle aging, there were no significant differences due to CS duration. The wines made with seven and 10 days of CS had higher seed tannin contributions and total tannin compared to the non-CS wine, which could potentially result in increased astringency.

Grapevine red blotch disease (GRBD) is a recently identified viral disease that affects grapevines. GRBD has been shown to impact grapevine physiology and grape composition by altering specific ripening events. However, no studies have been reported on the impact of GRBD on wine composition and its sensory attributes. This study evaluated the impact of GRBD on wine primary and secondary metabolites, in addition to its sensory properties, when making wines from Cabernet Sauvignon and Merlot grapes during two seasons. Wines made with GRBD-impacted fruit were lower in ethanol content when compared to wines made with grapes from healthy grapevines. This was attributed to the lower total soluble sugar (TSS) levels of diseased grapes due to delayed ripening at harvest. GRBD impacted wine phenolic composition by decreasing anthocyanin concentrations and increasing flavonol concentrations in some instances. Additionally, proanthocyanidin concentrations were also consistently higher in GRBD wines compared to wines made from healthy fruit. Descriptive analysis demonstrated that GRBD can impact wine style by altering aroma, flavor, and mouthfeel attributes. However, the extent of GRBD impact on wine composition and sensory properties were site and season dependent.

Grapevine red blotch virus (GRBV) is a recently identified virus. Previous research indicates primarily a substantial impact on berry ripening in all varieties studied. The current study analyzed grapes’ primary and secondary metabolism across grapevine genotypes and seasons to reveal both conserved and variable impacts to GRBV infection. Vitis vinifera cv. Cabernet Sauvignon (CS) grapevines grafted on two different rootstocks (110R and 420A) were analyzed in 2016 and 2017. Metabolite profiling revealed a considerable impact on amino acid and malate acid levels, volatile aroma compounds derived from the lipoxygenase pathway, and anthocyanins synthesized in the phenylpropanoid pathway. Conserved transcriptional responses to GRBV showed induction of auxin-mediated pathways and photosynthesis with inhibition of transcription and translation processes mainly at harvest. There was an induction of plant-pathogen interactions at pre-veraison, for all genotypes and seasons, except for CS 110R in 2017. Lastly, differential co-expression analysis revealed a transcriptional shift from metabolic synthesis and energy metabolism to transcription and translation processes associated with a virus-induced gene silencing transcript. This plant-derived defense response transcript was only significantly upregulated at veraison for all genotypes and seasons, suggesting a phenological association with disease expression and plant immune responses.

As the major byproduct of the winemaking industry, grape pomace remains an untapped source of valuable bioactive phenolic compounds. This study elucidated the optimal aqueous extraction parameters for maximizing phenolic extractability, while avoiding the use of harsh conventional solvents and limiting water usage, from Cabernet Sauvignon grape pomace in which the red grape was processed for white wine. In the single-stage aqueous extraction process (AEP), the concurrent impact of pH (2.64–9.36), solids-to-liquid ratio (SLR, g pomace/mL water) (1:50–1:5), and temperature (41.6–58.4 °C) on the total phenolic content (TPC) of Cabernet Sauvignon pomace was evaluated alongside a kinetic study (15–90 min). Optimal single-stage extraction conditions (pH 9.36, 1:50 SLR, 50 °C, 75 min) guided the development of a two-stage countercurrent extraction process (pH 9.36, 1:10 SLR, 50 °C, 75 min) to further reduce water consumption without compromising overall extractability. The countercurrent process reduced fresh water usage by 80%, increased the TPC of the extracts by 18%, and improved the in vitro antioxidant activities (ABTS and ORAC) of the extracts. Untargeted metabolomics enabled the identification of a diverse pool of phenolics, especially flavonol glycosides, associated with grape pomace, while further phenolic quantitation detected improvements in the release of commonly bound phenolics such as ferulic acid, p-coumaric acid, syringic acid, and protocatechuic acid in alkaline extracts compared to the ethanolic extract. This investigation provides an efficient, eco-friendly extraction strategy suitable for applications in functional food, beverage, nutraceutical, and cosmetic industries.

Proanthocyanidins are complex polymers of flavan-3-ol monomers and play a key sensory and health role in foods and beverages. We describe here a novel method for characterizing wine proanthocyanidins using a theoretical database comprised of the chemical formula and exact mass of 996 compounds. The database was constructed using the four primary grape and wine proanthocyanidin monomers: (epi)catechin, (epi)catechin-3-O-gallate, (epi)gallocatechin, and (epi)gallocatechin-3-O-gallate, each combined in all possible combinations up to a polymerization of 10. The database was queried against spectra collected using ultrahigh performance liquid chromatography (UHLPC) with a hydrophilic interaction liquid chromatography (HILIC) column and coupled to a high-resolution accurate mass quadrupole time-of-flight mass spectrometer (Q-TOF MS). Two wine samples produced with different post fermentation maceration were analyzed using the presented method to demonstrate application for analysis of diverse proanthocyanidins. The first sample was pressed immediately at the end of fermentation when all sugar had been utilized and the second received eight weeks of post fermentation maceration. The HILIC column combined with high resolution tandem mass spectrometry and database matching provided tentative identification of 89 compounds with excellent resolution and without the need for two-dimensional separations. The identified compounds were visualized with Kendrick mass analysis, a simple technique allowing for rapid visualization of which compounds are present in a given sample.