Introduction

The winemaking community worldwide continues to be a study of philosophical contrasts. On the one hand, there are those winemakers and wineries that emphasize the "scientific" segment of winemaking through adoption of new research findings and technologies. On the other hand, others prefer to embrace Old World traditions and thereby accentuate the "artistic" aspects associated with wine production. In writing this book, the objective was not to debate the relative merits and deficiencies of either philosophy but, rather, to create a reference that was useful to enologists as well as to researchers and students globally.

Since publication of the first edition of Wine Microbiology in 1997, the volume of new information and concepts has dramatically increased. Perhaps one of the most intriguing developments in the past decade has been application of "real-time" molecular methods. Based on similarities at the gene level, these methods have evolved beyond esoteric laboratory exercises to the point where real-world problems can be solved through rapid identification of microorganisms. Another relatively new application has been the use of starter cultures of non-Saccharomyces yeasts, which yield wines that differ not only in flavor and aroma profiles but also in structure.

Winemakers are also increasingly facing spoilage issues associated with Brettanomyces, Lactobacillus, Pediococcus, and Zygosaccharomyces, some of these being consequences of changes in viticultural practices (e.g., increased so-called hang-time).

Even with the tremendous increase in available information, a comprehensive understanding regarding the role of individual microorganisms toward wine quality as well as the impact of complicated interactions between microorganisms and processing techniques is lacking. A good example would be Brettanomyces, probably the most enigmatic and controversial microorganism in the wine industry. Although initially thought of as a major threat, some winemakers are beginning to view Brettanomyces as a potential ally in the vintages of the new millennium. Hopefully, additional research and experience will provide winemakers with better microbiological control during vinification, which, in turn, will lead to a continued increase in wine quality.

We sincerely hope that you find the second edition of Wine Microbiology informative and useful in your winery, laboratory, or classroom. If you have any feedback for the authors (potential errors, ideas for the third edition, and the like), please feel free to write or e-mail us. Cheers!

Kenneth C. Fugelsang and Charles G. Edwards

February 14, 2006

Preface to the Second Edition

Organization of the large volume of material that needed to be included in Wine Microbiology was a difficult task as evidenced by the number of approaches attempted. The second edition is divided into three parts; Grape and Wine Microorganisms (Chapters 1 to 4), Vinification and Winery Processing (Chapters 5 to 11), and Laboratory Procedures and Protocols (Chapters 12 to 19). As subject areas frequently cross section or chapter boundaries, every effort was made to cross-reference related topics as a means to reduce difficulties in finding information.

Section I, Grape and Wine Microorganisms, describes those microorganisms found in grape must, juice, and wines; namely yeasts, lactic and acetic acid bacteria, and molds. Here, taxonomy, metabolism, nutritional requirements, and potential impacts on wine quality are areas of focus.

Section II, Vinification and Winery Processing, addresses on those microbiological issues of practical importance to the winemaker. Included here is a general discussion of microbial management followed by in-depth examination of microbial ecology. This section also describes general principles of sanitation (Chapter 9), implementation of a quality control program (Chapter 10), and specific wine spoilage issues (Chapter 11).

Section III, Laboratory Procedures and Protocols, begins with an introduction to the use of the microscope (Chapter 12) and follows with methodologies used to enumerate and identify wine microorganisms (Chapters 13 through 16). Because organic and inorganic precipitates found in wine are often confused with microorganisms, methods of identification as well as photomicrographs of typical precipitates are included in Chapter 17. Chapters 18 and 19 provide insight into designing a wine microbiological laboratory and related safety issues. The section ends with a glossary of terms commonly used by microbiologists.