Enology- General Enology

Thomas Giagou | Kanwaljit Bajwa | Hui Chong | Nick Dokoozlian

Anthocyanin Composition: A Closer Look at Mono- and Di-glucosides

Thomas Giagou,* Kanwaljit Bajwa, Hui Chong, and Nick Dokoozlian
*E & J Gallo Winery, 600 Yosemite Blvd., Modesto, CA, 95354
(thomas.giagou@ejgallo.com)

Anthocyanins are water-soluble compounds belonging to the flavonoid family, synthesized via secondary metabolic pathways in plants. In addition to their role in red wine color and color density, there is strong evidence that anthocyanins have important antimicrobial, anti-inflammatory, and antioxidant properties. Anthocyanin stability is influenced by many factors, including pH, temperature, ultraviolet light, oxygen, enzymes, and co-pigmentation. Sugar molecules can reduce degradation of unstable anthocyanin intermediates into phenol and aldehyde acid molecules. The presence of two sugar molecules in anthocyanin structures (di-glucosides) increases their stability more than having only one sugar molecule (mono-glucosides). Anthocyanin stability is further enhanced by increased methylation and decreases as more hydroxyl groups are added to the B-ring of anthocyanidins. Therefore, it is imperative to monitor the composition of anthocyanins to better understand color stability and its contribution to wine quality. The present analytical method, implemented on an Agilent high-performance liquid chromatography instrument with diode-array detection, provides an opportunity to quantitatively measure five mono-glucosides (delphinidin 3-O-glucoside, cyanidin 3-O-glucoside, petunidin 3-O-glucoside, peonidin 3-O-glucoside, and malvidin 3-O-glucoside) and five di-glucosides (delphinidin 3,5-di-O-glucoside; pelargonidin 3,5-di-O-glucoside; peonidin 3,5-di-O-glucoside; malvidin 3,5-di-O-glucoside; and cyanidin 3,5-di-O-glucoside) of anthocyanins in grape and wine. Analysis of seven Vitis vinifera varieties (Cabernet Sauvignon, Merlot, Petit Verdot, Petite Sirah, Teroldego, Pinot noir, and Zinfandel) established the dominance of mono-glucoside anthocyanins in all varieties. However, Napa Valley Cabernet Sauvignon contained elevated amounts of cyanidin 3,5-di-O-glucoside (up to 94.5 mg/L) and peonidin 3,5-di-O-glucoside (up to 78.9 mg/L). These results provide the potential to produce wine with improved color stability.

Funding Support: E & J Gallo Winery

A Second Look at What We “Know” about Tannins in Wine and How They Are Perceived

Misha Kwasniewski,* Ryan J. Elias, Alex J. Fredrickson, Helene Hopfer, Yanxin Lin, Cynthia Loi, and Ezekiel Warren
*Penn State, 326 Rodney A. Erickson Food Science Building
University Park, PA, 16802 (mtk5407@psu.edu)

Despite significant advances in tannin research, we cannot consistently predict tannin sensory characteristics (e.g., roughness, drying, silkiness) in all wines or predict their extraction, retention, and elongation during vinification with any certainty or reproducibility. Some of these issues result from oversimplification of a complex system. From both a perceptual and a winemaking perspective, tannin interactions are often explained using the protein precipitation model, where all proteins (and tannins) are assumed to behave similarly, with any protein equally precipitating any tannin. However, protein and tannin structures do greatly matter. While specific proteins like F6HAU0 (a vascular invertase protein) and A0A438IRV9 (ß-fructofuranosidase) are reduced in wine by tannin additions, other prevalent proteins, such as those involved in Vitis lipid transfer, correlate poorly with tannin retention. Similarly, human saliva interacts with a different profile of tannins than common reagents used in precipitation assays (e.g., bovine serum albumin). This explains why, while these assays correlate with astringency, they often cannot explain sensory differences. Studying astringency in another high-phenolic product, cocoa, we found that test subjects perceived astringency differently and the interaction of specific salivary proteins with phenolics varied greatly by individual. These findings reinforce the idea that the complex structural differences within the tannin and protein categories contribute to their functionality. To better characterize tannin structure diversity, we have developed liquid chromatography with tandem mass spectrometry methods that can measure intact fragments of complex procyanidins post-chromatographic separation as well as elongation products caused by ethylene bridging. This comprehensive phenolic fingerprint allows us to differentiate wines and other high-phenolic foods with similar total phenolic concentrations. In the future, we expect to resolve the uncertainties in tannin evolution during winemaking and tannin perception by characterizing the diversity within tannins, proteins, and polysaccharides.

Funding Support: PA Wine Marketing and Research Program- Pennsylvania Liquor Control Board

Mark Bartz | Renee Threlfall

Effect of Alternative Packaging on Vignoles (Vitis Hybrid) White Wine Quality during Storage

Mark Bartz and Renee Threlfall*
*University of Arkansas, 2650 N. Young Avenue, Fayetteville, AR, 72704
(rthrelf@uark.edu)

The sustainability of grape (Vitis species) wine production is affected by cost and supply-chain issues with glass packaging. Although ideal as a moisture and oxygen barrier, glass wine packaging contributes one-third of the total carbon footprint for wine production. Other packaging materials, like aluminum and plastics, are used as alternatives to glass, but consumers may view them as lower quality. The effect of wine packaging on color and total phenolics of Vignoles (Vitis hybrid) white wine was evaluated at 0-, 6-, and 12-months storage at 15°C. Grapes were harvested in 2022, produced into wine, and bottled in January 2023. Eight wine packaging treatments were evaluated: three of glass (250, 375, and 750 mL) and five 250-mL alternatives made of aluminum, polyethylene terephthalate (PET), high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP). The packaging × storage interaction was significant for L*, hue, chroma, brown color, and total phenolics. For wine at 0-month compared to 12-months storage, all packaging treatments except glass (375 and 750 mL) had decreased L* and hue and increased chroma and brown color. All packaging treatments had decreased total phenolics. From 0- to 6-months storage, wine in LDPE, HDPE, and PP had >100% more brown color, while wine in aluminum and PET had 28 and 45%, respectively. From 0 to 12-months storage, wine in LDPE, HDPE, and PP had >200% more brown color; wine in aluminum and PET had 176 and 149% more brown color, respectively; and wine in glass 250, glass 375, and glass 750 mL had 68, 0, and 1% more brown color, respectively. Wine in traditional glass bottles (375 mL and 750 mL), 250 mL glass, aluminum, and PET had the most potential for further investigation of the effect of packaging on wine quality.

Funding Support: Southern Region Small Fruit Consortium

10:15 am – 10:35 am	Anthocyanin Composition: A Closer Look at Mono- & Di-glucosides Thomas Giagou, E & J Gallo Winery, California
10:35 am – 10:55 am	A Second Look at What We “Know” about Tannins in Wine and How They Are Perceived Misha Kwasniewski, The Pennsylvania State University, University Park
10:55 am – 11:15 am	Effect of Alternative Packaging on Vignoles (Vitis Hybrid) White Wine Quality during Storage Mark Bartz, University of Arkansas, Fayetteville

Enology- General Enology

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Thomas Giagou

Misha Kwasniewski

Mark Bartz

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Kristen Barnhisel