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The Chemistry of WineFrom Blossom to Beverage and Beyond$
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David R. Dalton

Print publication date: 2018

Print ISBN-13: 9780190687199

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780190687199.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 26 October 2021

More Than Skin Deep

More Than Skin Deep

16 (p.179) More Than Skin Deep
The Chemistry of Wine

David R. Dalton

Oxford University Press

The grape berry is composed of skin, flesh (pulp) and seeds. After destemming (Chapter 13), the grapes are sent on for crushing. On crushing, the thick walls of the skin, including the waxy cuticle, are broken. Crushing the grapes (Figure 16.1) is a question of quantity. Small quantities are handled differently than large. The skins, including the contaminants thereon, as well as the majority of the materials discussed above for the individual grapes (i.e., phenols, anthocyanins, tanins, some acids, terpenes, pyrazines, and some carbohydrates including those attached to the anthocyanidins, forming anthocyanins) therein, are released. The cells of the pulp are also broken and released into the juice on crushing. This berry cell juice is mainly water (70–80% by weight) which contains the mixture of sugars (mostly glucose and fructose, but small concentrations of many other carbohydrates are also present), carboxylic acids (mostly tartaric and malic, but additional members of the tricarboxylic acid cycle, oxalic, glucuronic, etc. are also present), complex cross-linked polysaccharides from cell walls (pectins), some phenols and proteins (as well as the peptides and simple amino acids from which they are constructed), and minerals, including oxides of iron (Fe), phosphorus (P), and sulfur (S), as well as salts of potassium (K) and sodium (Na) brought up in the xylem to the growing berry. The seeds have their cellulose carbohydrate-based exterior coatings, which are also rich in complexed polyphenols (tannins). Additionally, amino acids, generally found as constituents of peptides, proteins, and enzymes, and their cofactors needed for all life, nucleic acids and their attached sugars needed for the next generation, are all present too. Thus, overall, the result of crushing the berries is a mixture consisting of skins, seeds, and fruit juice (the must = Latin vinum mustum = young wine). This mixture may, if the grapes were “white,” be cooled and the cap on the must—sometimes called the pomace (the solid portion of the must) removed early or late (usually between 12 and 24 hours) by the vintner. Most of the flavoring constituents are quickly extracted, and brightly colored phenols, tannins, anthocyanins, etc.

Keywords:   Aureusidin synthase, caftaric acid, dehydroascorbic acid, emendation, filtering, lees, minerals, nephelometer, oxidasic casse, particulate matter

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