Stem
Stem in winemaking refers to the lignified structural framework of the grape bunch, comprising the main rachis and its branching pedicels, which connect individual berries to the vine. Stems play a limited role during grape growing but can have a significant impact on wine composition, texture, and aroma when retained during fermentation, most notably in whole-bunch or partial whole-cluster fermentation.[1]
Definition and composition
Grape stems are composed primarily of cellulose, hemicellulose, lignin, water, and a range of phenolic compounds, including tannins and potassium salts. As berries ripen, stems undergo lignification, shifting from green, herbaceous tissue to woody material. The degree of stem maturity is a critical determinant of their sensory impact when included in fermentation.[2]
Compared with grape skins and seeds, stems contain relatively low concentrations of anthocyanins but can contribute substantial quantities of tannins and other phenolics, often with a different structural profile.[3]
Role in winemaking
In most modern red winemaking, grapes are destemmed prior to fermentation to avoid excessive bitterness or vegetal characters. However, deliberate stem inclusion is employed as a stylistic choice in certain regions, varieties, and wine styles.
Whole-bunch and whole-cluster fermentation
Whole-bunch fermentation refers to fermenting intact grape clusters, including berries, skins, seeds, and stems. Partial stem inclusion may also be achieved by blending destemmed berries with a proportion of whole clusters. These techniques influence fermentation kinetics, phenolic extraction, and wine texture.[4]
Stems can:
- Increase tannin content and structural firmness
- Raise must pH through potassium release
- Modify extraction by improving capillary drainage in the fermenting mass
- Introduce herbal, spicy, floral, or woody aromatic notes
The impact depends strongly on stem ripeness, proportion used, and fermentation conditions.[5]
Phenolic and textural effects
Stem-derived tannins differ from seed and skin tannins in both size and reactivity. They tend to contribute firmness and dryness rather than bitterness, potentially enhancing perceived structure and ageing capacity when used judiciously. Excessive inclusion, particularly with unripe stems, may result in harsh astringency or green flavours.[6]
Cheynier and colleagues note that stems act as both phenolic sources and adsorption surfaces, influencing the overall phenolic balance of the wine.[7]
Varietal and regional considerations
The suitability of stem inclusion varies by grape variety and growing conditions. Varieties with naturally lignified stems at harvest, such as [[Pinot Noir]] and Syrah in certain climates, are more commonly associated with whole-bunch techniques. In contrast, varieties with persistent green stems may be less suitable unless grown in warm or dry conditions that promote full stem maturity.[8]
Historically, stem inclusion was often unavoidable due to limited destemming technology, particularly in traditional European regions. Modern use is more selective and stylistically driven, often associated with producers seeking aromatic lift, structural nuance, or a perceived expression of place.[9]
Risks and limitations
Potential drawbacks of stem inclusion include:
- Green or vegetal aromas from methoxypyrazines and related compounds
- Excessive astringency from under-lignified stems
- Elevated pH and reduced colour stability
As a result, careful assessment of stem maturity and proportion is essential. Many producers adjust inclusion levels annually based on vintage conditions rather than following a fixed recipe.[10]
Contemporary trends
Interest in stem inclusion has increased in recent decades, particularly among producers influenced by Burgundian practices or seeking lower-intervention approaches. The technique is often framed as a tool for complexity rather than power, contributing to a broader discussion about texture, freshness, and balance in modern red wines.[11]
Consumer perception of stem-influenced wines varies, with some associating them with elegance and savoury complexity, while others interpret herbal notes as faults. This underscores the stylistic and cultural dimensions of stem use in winemaking.[12]
See also
References
- ↑ Jancis Robinson, Oxford Companion to Wine, Oxford University Press, 17 Sept. 2015. ISBN 9780198705383.
- ↑ PhD Jackson, Ronald S., Wine Science: Principles and Applications, Academic Press Inc, 14 April 2020. ISBN 9780128161180.
- ↑ Pascal Ribéreau-Gayon, Yves Glories, Alain Maujean, Denis Dubourdieu, & 1 more, Handbook of Enology, Volume 2: The Chemistry of Wine - Stabilization and Treatments, Wiley, 31 Mar. 2006. ISBN 9780470010372.
- ↑ Roger B. Boulton, Vernon L. Singleton, Linda F. Bisson, Ralph E. Kunkee, & 1 more, Principles and Practices of Winemaking, Springer, 31 Oct. 1998. ISBN 9780834212701.
- ↑ Peynaud, Knowing and Making Wine, Wiley, 1984, ISBN 9780471881491.
- ↑ Andrew L. Waterhouse, Understanding Wine Chemistry, Wiley, 19 Aug. 2016. ISBN 9781118627808.
- ↑ Cheynier et al., Wine Chemistry and Biochemistry, Elsevier, 2012, ISBN 9780123884381.
- ↑ Jancis Robinson, Jose Vouillamoz, Julia Harding, & 0 more, Wine Grapes: A Complete Guide to 1,368 Vine Varieties, Including Their Origins and Flavours, Ecco, 1 Nov. 2012. ISBN 9780062206367.
- ↑ Unwin, Wine and the Vine, Routledge, 1991, ISBN 9780415042698.
- ↑ PhD Jackson, Ronald S., Wine Science: Principles and Applications, Academic Press Inc, 14 April 2020. ISBN 9780128161180.
- ↑ Anderson & Pinilla, Wine Globalization, Cambridge University Press, 2018, ISBN 9781108445687.
- ↑ Charters, Wine and Society, Elsevier, 2006, ISBN 9780750669788.