Pulp
Pulp refers to the soft, juicy interior of the grape berry, constituting the largest proportion of the fruit and forming the primary source of grape must used in winemaking. Enclosed by the skin and surrounding the seeds, the pulp is central to wine composition, supplying water, sugars, organic acids and numerous soluble compounds essential to fermentation and finished wine balance.[1]
Anatomical role
In grape berry anatomy, the pulp (also referred to as the mesocarp) develops from the ovary wall following flowering and expands rapidly during berry growth. It typically accounts for 75–85% of total berry weight, depending on variety, growing conditions and ripeness.[2]
The pulp consists primarily of thin-walled parenchyma cells filled with juice, which rupture easily during crushing or pressing, releasing must while leaving skins and seeds initially intact.[3]
Chemical composition
The pulp is the principal reservoir of water and fermentable sugars in the grape, with glucose and fructose accumulating during ripening as a result of photosynthesis and translocation from the vine.[4] It also contains organic acids, notably tartaric and malic acid, which define the basic acid structure of the must.
In contrast to skins and seeds, the pulp contains relatively low levels of phenolic compounds and colour pigments, making it especially significant in the production of white wine and lightly extracted styles.[5]
Contribution to must
During crushing and pressing, the pulp releases juice that forms the liquid phase of must. The composition of this juice largely determines potential alcohol, acidity, pH and fermentation kinetics.[6]
Nitrogenous compounds present in the pulp, including amino acids and ammonium ions, are essential nutrients for yeast metabolism and influence fermentation completeness and aroma development.[7]
Viticultural influences
Pulp composition is shaped by grape variety, yield level, water availability and climatic conditions during the growing season. Water stress, for example, can reduce pulp volume relative to skin mass, increasing the skin-to-juice ratio and altering extraction dynamics.[8]
Ripeness at harvest is particularly critical, as sugar accumulation and acid degradation in the pulp directly affect wine balance and style.[9]
Winemaking considerations
In white winemaking, rapid separation of pulp juice from skins is often employed to minimise phenolic extraction, while in red winemaking the pulp serves primarily as the fermentation medium through which compounds from skins and seeds are extracted.[10]
Pressing regimes, juice handling and clarification practices all influence how pulp-derived components are preserved or modified prior to fermentation.[11]
See also
References
- ↑ Robinson (ed.), The Oxford Companion to Wine, Oxford University Press, 2015, ISBN 978-0198705383.
- ↑ Keller, The Science of Grapevines, 2nd ed., Academic Press, 2015, ISBN 978-0124199873.
- ↑ Coombe & Dry, Viticulture Volume 1: Resources, Winetitles, 1992, ISBN 978-1875130095.
- ↑ Jackson, Wine Science, Academic Press, 2020, ISBN 978-0128161180.
- ↑ Ribéreau-Gayon et al., Handbook of Enology, Vol. 2, Wiley, 2006, ISBN 978-0470010396.
- ↑ Boulton et al., Principles and Practices of Winemaking, Springer, 1999, ISBN 978-0834217011.
- ↑ Waterhouse, Sacks & Jeffery, Understanding Wine Chemistry, Wiley, 2016, ISBN 978-1118627808.
- ↑ Keller, The Science of Grapevines, Academic Press, 2015, ISBN 978-0124199873.
- ↑ OIV, “Grape morphology and must”.
- ↑ Ribéreau-Gayon et al., Handbook of Enology, Vol. 2, Wiley, 2006, ISBN 978-0470010396.
- ↑ Amerine & Ough, Methods for Analysis of Musts and Wines, Wiley, 1980, ISBN 978-0471036732.