explore wine chemistry.
The goal of these two works was not to create an exhaustive bibliography of each subject. The authors strove to choose only the most relevant and significant publications to their particular field of research. A large number of references to French enological research have been included in these works in order to make this information available to a larger non‐French‐speaking audience.
In addition, the authors have tried to convey a French and more particularly a Bordeaux perspective of enology and the art of winemaking. The objective of this perspective is to maximize the potential quality of grape crops based on the specific natural conditions that constitute their “terroir.” The role of enology is to express the characteristics of the grape specific not only to variety and vineyard practices but also maturation conditions, which are dictated by soil and climate.
It would, however, be an error to think that the world's greatest wines are exclusively a result of tradition, established by exceptional natural conditions, and that only the most ordinary wines, produced in giant processing facilities, can benefit from scientific and technological progress. Certainly, these facilities do benefit the most from high‐performance installations and automation of operations. Yet history has unequivocally shown that the most important enological developments in wine quality (for example, malolactic fermentation) have been discovered in ultra‐premium wines. The corresponding techniques were then applied to less prestigious products.
High‐performance technology is indispensable for the production of great wines, since a lack of control of winemaking parameters can easily compromise their quality, which would be less of a problem with lower quality wines.
The word “vinification” has been used in this work and is part of the technical language of the French tradition of winemaking. Vinification describes the first phase of winemaking. It comprises all technical aspects from grape maturity and harvest to the end of alcoholic and sometimes malolactic fermentation. The second phase of winemaking “wine maturation, stabilization, and treatments” is completed when the wine is bottled. Aging specifically refers to the transformation of bottled wine.
This distinction of two phases is certainly the result of commercial practices. Traditionally, in France, a vine grower farmed the vineyard and transformed grapes into an unfinished wine. The wine merchant transferred the bulk wine to his cellars, finished the wine, and marketed the product, preferentially before bottling. Even though most wines are now bottled at the winery, these long‐standing practices have maintained a distinction between “wine grower enology” and “wine merchant enology.” In countries with a more recent viticultural history, generally English speaking, the vine grower is responsible for winemaking and wine sales. For this reason, the Anglo‐Saxon tradition speaks of winemaking, which covers all operations from harvest reception to bottling.
In these works, the distinction between “vinification” and “stabilization and treatments” has been maintained, since the first phase primarily concerns microbiology and the second, chemistry. In this manner, the individual operations could be linked to their particular sciences. There are of course limits to this approach. Chemical phenomena occur during vinification; the stabilization of wines during storage includes the prevention of microbial contamination.
Consequently, the description of the different steps of enology does not always obey logic as precise as the titles of these works may lead to believe. For example, microbial contamination during aging and storage is covered in Volume 1. The antiseptic properties of SO2 incited the description of its use in the same volume. This line of reasoning led to the description of the antioxidant‐related chemical properties of this compound in the same chapter as well as an explanation of adjuvants to sulfur dioxide: sorbic acid (antiseptic) and ascorbic acid (antioxidant). In addition, the on lees aging of white wines and the resulting chemical transformations cannot be separated from vinification and are therefore also covered in Volume 1. Finally, our understanding of phenolic compounds in red wine is based on complex chemistry. All aspects related to the nature of the corresponding substances, their properties, and their evolution during grape maturation, vinification, and aging are therefore covered in Volume 2.
These works only discuss the principles of equipment used for various enological operations and their effect on product quality. For example, temperature control systems, destemmers, crushers, and presses, as well as filters, inverse osmosis, machines, and ion exchangers are not described in detail. Bottling is not addressed at all. An in‐depth description of enological equipment would merit a detailed work dedicated to the subject.
Wine tasting, another essential role of the winemaker, is not addressed in these works. Many related publications are, however, readily available. Finally, wine analysis is an essential tool that a winemaker should master. It is, however, not covered in these works except in a few particular cases, i.e. phenolic compounds, whose different families are often defined by analytical criteria.
The authors thank the following people who have contributed to the creation of this work:
J.F. Casas Lucas, Chapter 14, Sherry; A. Brugirard, Chapter 14, Sweet Wines; J.N. de Almeida, Chapter 14, Port Wines; A. Maujean, Chapter 14, Champagne; C. Poupot for the preparation of material in Chapters 1, 2, and 13; Miss F. Luye‐Tanet for her help with typing.
They also thank Madame B. Masclef in particular for her important part in the typing, preparation, and revision of the final manuscript.
Pascal Ribéreau‐Gayon
Bordeaux
REMARKS CONCERNING THE EXPRESSION OF CERTAIN PARAMETERS OF MUST AND WINE COMPOSITION
Units
Metric system units of length (m), volume (l), and weight (g) are exclusively used. The conversion of metric units into Imperial units (inches, feet, gallons, pounds, etc.) can be found in the following enological work: Principles and Practices of Winemaking, R.B. Boulton, V.L. Singleton, L.F. Bisson, and R.E. Kunkee, 1995, The Chapman & Hall Enology Library, New York.
Expression of Total Acidity and Volatile Acidity
Although EU regulations recommend the expression of total acidity in the equivalent weight of tartaric acid, the French custom is to give this expression in the equivalent weight of sulfuric acid. The more correct expression in milliequivalents per liter has not come into widespread use. In this work, we have generally expressed acid levels as sulfuric acid, but in certain cases, the corresponding weight in tartaric acid, often used in other countries, has been given.
Using the weight of the milliequivalent of various acids, the table below can be used to convert from one expression to another.
| Coefficients of conversion from one expression of total or volatile acidity to another | |||||
| Desired expression | |||||
| Known expression | mEq/l | g/l H2SO4 | g/l tartaric acid |
| |
