andrew g reynolds managin wine quality volume 2 book

Woodhead Publishing Limited, 2010

Managing wine quality


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Woodhead Publishing Series in Food Science, Technology and Nutrition:Number 192

Managing wine qualityVolume 2: Oenology and wine quality

Edited byAndrew G. Reynolds

Oxford Cambridge Philadelphia New Delhi


Published by Woodhead Publishing Limited, Abington Hall, Granta Park,Great Abington, Cambridge CB21 6AH, UKwww.woodheadpublishing.com

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Contents

Contributor contact details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii

Woodhead Publishing Series in Food Science, Technology and Nutrition . . xvii

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxv

Part I Winemaking technologies and wine quality

1 Yeast fermentation management for improved wine quality . . . . . . . . 3G. Specht, Lallemand, USA1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.2 Yeast and fermentation management and wine quality . . . . . . . . . 41.3 Yeast rehydration and handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.4 Yeast inoculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.5 Yeast inoculation rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.6 Yeast inoculation timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.7 Sequential yeast inoculation strategies . . . . . . . . . . . . . . . . . . . . . 101.8 Yeast storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.9 Nutrient strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.10 Difficult fermentation conditions . . . . . . . . . . . . . . . . . . . . . . . . . 191.11 Sulphur compounds and their management . . . . . . . . . . . . . . . . . 211.12 Preventing stuck and sluggish fermentations . . . . . . . . . . . . . . . . 231.13 Restarting stuck and sluggish fermentations . . . . . . . . . . . . . . . . . 271.14 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291.15 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291.16 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

vi Contents


2 Metabolic engineering of wine yeast and advances in yeast selectionmethods for improved wine quality . . . . . . . . . . . . . . . . . . . . . . . . . . . 34B. Divol and F. F. Bauer, Stellenbosch University, South Africa2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342.2 Improving wine yeasts: current targets . . . . . . . . . . . . . . . . . . . . . 372.3 A systems biology approach to wine yeast studies . . . . . . . . . . . . 412.4 Biotechnology, systems biology and the generation of new

yeast strains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442.5 Molecular biology and systems biology in the identification

of wine yeasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472.6 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512.7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

3 Effects of malolactic fermentation on wine quality . . . . . . . . . . . . . . . 60A. Lonvaud-Funel, University Victor Segalen Bordeaux II, France3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603.2 Spontaneous growth of lactic acid bacteria in wine . . . . . . . . . . . 613.3 Variations in the diversity of lactic acid bacteria species

during winemaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 713.4 Lactic acid bacteria and improving wine quality . . . . . . . . . . . . . 743.5 Lactic acid bacteria and wine spoilage: undesirable lactic

acid bacteria strains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 793.6 Controlling malolactic fermentation by malolactic starters . . . . . 853.7 Conclusions and future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . 883.8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

4 Enzymes and wine quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93R.-M. Canal-Llaubres, Novozymes, France4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 934.2 Definitions and production methods . . . . . . . . . . . . . . . . . . . . . . . 944.3 Regulatory aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 984.4 Enzyme applications in winemaking . . . . . . . . . . . . . . . . . . . . . . . 994.5 Advances in enzyme discovery . . . . . . . . . . . . . . . . . . . . . . . . . . 1044.6 Enzyme use in pre-fermentation stages . . . . . . . . . . . . . . . . . . . . 1094.7 Enzyme use in post-fermentation stages . . . . . . . . . . . . . . . . . . . 1184.8 Monitoring enzyme performance . . . . . . . . . . . . . . . . . . . . . . . . 1244.9 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1264.10 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1274.11 Sources of further information . . . . . . . . . . . . . . . . . . . . . . . . . . 1284.12 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1284.13 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

Contents vii


5 Membrane and other techniques for the management of winecomposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133D. Wollan, Memstar Pty Ltd, Australia5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1335.2 Some caveats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1345.3 Some perspective convention and intervention . . . . . . . . . . . . 1345.4 Next-generation tools phase change techniques . . . . . . . . . . . 1355.5 Membrane separation techniques . . . . . . . . . . . . . . . . . . . . . . . . 1395.6 Membrane separation treatment and recombination . . . . . . . . . . 1455.7 Volatile acidity removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1465.8 The problem of excess alcohol . . . . . . . . . . . . . . . . . . . . . . . . . . 1485.9 Taint removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1545.10 Ultrafiltration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1575.11 Electrodialysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1585.12 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

6 Ageing on lees (sur lies) and the use of speciality inactive yeasts duringwine fermentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164C. Charpentier, Universit de Bourgogne, France6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1646.2 Definition and composition of lees . . . . . . . . . . . . . . . . . . . . . . . 1646.3 Yeast autolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1666.4 Ageing of white wines on lees . . . . . . . . . . . . . . . . . . . . . . . . . . 1706.5 Ageing of red wines on lees . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1726.6 Ageing of sparkling wines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1766.7 Removal of undesirable compounds from wine . . . . . . . . . . . . . 1786.8 Yeast specialities mimicking lees . . . . . . . . . . . . . . . . . . . . . . . . 1806.9 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1826.10 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

7 New directions in stabilization, clarification and fining ofwhite wines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188R. Marchal, University of Reims, France; and E. J. Waters,The Australian Wine Research Institute, Australia7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1887.2 White wines, proteins and haze . . . . . . . . . . . . . . . . . . . . . . . . . . 1897.3 The origin of wine proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1907.4 Characterization of wine proteins . . . . . . . . . . . . . . . . . . . . . . . . 1917.5 Protein levels in white wines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1937.6 Protein haze formation in wine . . . . . . . . . . . . . . . . . . . . . . . . . . 1977.7 Bentonite fining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1987.8 Use of gelatine in white wine fining . . . . . . . . . . . . . . . . . . . . . . 2067.9 Wine fining with plant proteins . . . . . . . . . . . . . . . . . . . . . . . . . . 2077.10 Must clarification using the flotation technique . . . . . . . . . . . . . 209

viii Contents


7.11 Other fining agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2147.12 Equipment for the addition of fining agents to wine . . . . . . . . . . 2167.13 Wine fining: general conclusion and practical

recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2167.14 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2177.15 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

8 Micro-oxygenation, oak alternatives and added tannins andwine quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226W. J. du Toit, Stellenbosch University, South Africa8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2268.2 Basic oxidation reactions and substrates of oxidation in wine . . 2278.3 Basic phenolic reactions in red wine involving oxygen . . . . . . . 2288.4 When does oxygen come into contact with wine? . . . . . . . . . . . 2298.5 Micro-oxygenation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2308.6 Recent micro-oxygenation research at the Department of

Viticulture and Oenology, Stellenbosch University . . . . . . . . . . 2358.7 A few recommendations when using micro-oxygenation . . . . . . 2438.8 Alternative oak treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2468.9 Exogenous tannins in winemaking . . . . . . . . . . . . . . . . . . . . . . . 2498.10 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2518.11 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

9 Alternatives to cork in wine bottle closures . . . . . . . . . . . . . . . . . . . . 255J. Goode, www.wineanorak.com, UK9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2559.2 The key property of closures: oxygen transmission . . . . . . . . . . 2569.3 The various closure types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2599.4 Conclusions and future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . 2699.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

10 Current issues in organic winemaking: consumer expectations,producer attitudes and oenological innovation . . . . . . . . . . . . . . . . . 271D. Rauhut, Forschungsanstalt Geisenheim (Geisenheim ResearchCenter (GRC)), Germany; and C. Micheloni, AIAB ItalianAssociation for Organic Agriculture, Italy10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27110.2 Organic wine: a synthesis attempt . . . . . . . . . . . . . . . . . . . . . . . . 27610.3 Harmonisation process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28610.4 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28710.5 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28810.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288

Contents ix


Part II Managing sensory quality

11 Yeast selection for wine flavour modulation . . . . . . . . . . . . . . . . . . . 293P. Marullo, SARCO Laffort Inc., France; and D. Dubourdieu, INRA-Universit Bordeaux, France11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29311.2 Key issues in efficient wine yeast selection . . . . . . . . . . . . . . . . 29411.3 Selection of natural yeast isolates: methods and limits . . . . . . . . 29511.4 Metabolic engineering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29611.5 Conventional genetic strategies . . . . . . . . . . . . . . . . . . . . . . . . . . 29811.6 Mixed cultures as an alternative strategy . . . . . . . . . . . . . . . . . . 30311.7 Yeast by-products affecting wine aromas: glycerol . . . . . . . . . . 30411.8 Yeast by-products affecting wine aromas: acetic acid . . . . . . . . 30711.9 Yeast by-products affecting wine aromas: hydrogen sulphide . . 30911.10 Yeast by-products affecting wine aromas: higher alcohols . . . . 31311.11 Yeast by-products affecting wine aromas: esters . . . . . . . . . . . . 31811.12 Varietal aromas resulting from grape precursor

biotransformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32311.13 Conclusions and future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . 33311.14 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

12 Brettanomyces/Dekkera off-flavours and other wine faultsassociated with microbial spoilage . . . . . . . . . . . . . . . . . . . . . . . . . . . 346L. Conterno, Fondazione E. Mach IASMA Research andInnovation Centre, Italy; and T. Henick-Kling, Washington StateUniversity, USA12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34612.2 Brettanomyces/Dekkera off-flavours and their related

metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34912.3 Brettanomyces/Dekkera taxonomy and phylogenetic

relationships with other wine yeasts . . . . . . . . . . . . . . . . . . . . . . 35212.4 Brettanomyces/Dekkera physiology . . . . . . . . . . . . . . . . . . . . . . 35512.5 Other defects associated with the presence of

Brettanomyces/Dekkera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35812.6 Other faults associated with microbial spoilage . . . . . . . . . . . . . 36112.7 Detection and methods to prevent and defeat microbial

spoilage faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36712.8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37212.9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

13 Reducing cork taint in wine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388R. Jung and V. Schaefer, Forschungsanstalt Geisenheim(Geisenheim Research Center (GRC)), Germany13.1 Introduction: cork taint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38813.2 Compounds causing mustymouldy off-flavours . . . . . . . . . . . . 389

x Contents


13.3 Quality management and control methods for wine corks:introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394

13.4 Test procedures to evaluate the quality of cork stoppers . . . . . . 39613.5 Standard test procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39713.6 Additional test procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40113.7 Handling and processing of corks and bottles during bottling

and storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40213.8 Prevention of mustymouldy off-flavours in the cellar

environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40513.9 Methods to reduce musty off-flavours in contaminated wines . . 41013.10 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414

14 Ladybug (Coccinellidae) taint in wine . . . . . . . . . . . . . . . . . . . . . . . . 418A. Botezatu and G. Pickering, Brock University, Canada14.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41814.2 Quality implications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41914.3 Causal compound(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42114.4 Threshold and tolerances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42414.5 Other Coccinellidae species . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42414.6 Post-harvest prevention and remediation . . . . . . . . . . . . . . . . . . 42514.7 Conclusions and future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . 42814.8 Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42814.9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429

15 Understanding and controlling non-enzymatic wine oxidation . . . . 432P. A. Kilmartin, The University of Auckland, New Zealand15.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43215.2 Oxygen in wine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43315.3 Polyphenol oxidation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43415.4 Oxidation of aroma compounds . . . . . . . . . . . . . . . . . . . . . . . . . 43815.5 Measures of wine oxidation status . . . . . . . . . . . . . . . . . . . . . . . 44015.6 White wine oxidation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44215.7 Red wine oxidation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44415.8 Influence of wine antioxidants . . . . . . . . . . . . . . . . . . . . . . . . . . 44615.9 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45015.10 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451

16 Ageing and flavour deterioration in wine . . . . . . . . . . . . . . . . . . . . . 459A. W. Linsenmeier, D. Rauhut and W. R. Sponholz, Forschungs-anstalt Geisenheim (Geisenheim Research Center (GRC)), Germany16.1 Introduction: ageing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45916.2 Sensory changes during storage/ageing . . . . . . . . . . . . . . . . . . . 46016.3 Aromatic compounds related to flavour deterioration . . . . . . . . 461

Contents xi


16.4 Chemical reactions of ageing . . . . . . . . . . . . . . . . . . . . . . . . . . . 46916.5 Factors influencing the ageing process and future trends

in research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47316.6 Untypical ageing (UTA) off-flavour . . . . . . . . . . . . . . . . . . . . . . 47616.7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486

17 Biogenic amines and the winemaking process . . . . . . . . . . . . . . . . . . 494M. V. Moreno-Arribas, Institute of Industrial Fermentations (CSIC),Spain; and A. Y. Smit and M. du Toit, Stellenbosch University, SouthAfrica17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49417.2 Incidence of biogenic amines in wines and health effects . . . . . 49517.3 Formation of biogenic amines during the winemaking process . 50217.4 Methods of detection and quantification of biogenic

amines in wines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51117.5 Methods and tools to prevent the presence of biogenic amines

in wines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51317.6 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51417.7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515

18 Managing the quality of icewines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523A. J. Bowen, Brock University, Canada18.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52318.2 Definitions of icewine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52418.3 Viticulture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52618.4 Harvest considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53118.5 Oenology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53418.6 Chemical analysis of icewines . . . . . . . . . . . . . . . . . . . . . . . . . . 54018.7 Sensory properties of icewine . . . . . . . . . . . . . . . . . . . . . . . . . . . 54518.8 Authentication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54818.9 Future trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54918.10 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550

19 Managing the quality of sparkling wines . . . . . . . . . . . . . . . . . . . . . . 553S. Buxaderas and E. Lpez-Tamames, University of Barcelona,Spain19.1 Types of sparkling wines: definitions and characteristics . . . . . . 55319.2 Description of the organoleptic characteristics of sparkling

wines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55419.3 Factors affecting sensory quality . . . . . . . . . . . . . . . . . . . . . . . . . 57019.4 Quality control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57819.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58019.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582

xii Contents


20 Extraction technologies and wine quality . . . . . . . . . . . . . . . . . . . . . 589A. Razungles, Montpellier SupAgro, France20.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58920.2 Extraction factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59220.3 Techniques applied to white wine vinification . . . . . . . . . . . . . . 59620.4 Techniques applied to ros wine vinification . . . . . . . . . . . . . . . 59820.5 Techniques applied to traditional red wine vinification . . . . . . . 59920.6 Very hot, short maceration applied to red wine vinification . . . . 60920.7 Vinification of red wines by carbonic maceration . . . . . . . . . . . 61720.8 Traditional vinification of red wines with whole berries . . . . . . 62020.9 Draining and pressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62120.10 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62520.11 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 631


Contributor contact details(* = main contact)

EditorDr Andrew G. Reynolds500 Glenridge AvenueBrock UniversitySt CatharinesOntarioLS2 3A1Canada

Email: [email protected]

Chapter 1G. SpechtLallemandP.O. Box 5512PetalumaCalifornia 94955USA


Chapter 2B. Divol* and F. F. BauerInstitute for Wine BiotechnologyStellenbosch UniversityPrivate Bag X1

Matieland 7602South Africa


Chapter 3A. Lonvaud-Funel,UMR Oenologie- ISVVUniversity Victor Segalen

Bordeaux 2.CS 50008.33882 Villenave DOrnon CedexFrance


Chapter 4Dr R.-M. Canal-LlaubresGlobal Application Manager WineNovozymes France S.A. (Bordeaux

Cedex)23, Parvis des Chartrons33074 Bordeaux CedexFrance


xiv Contributor contact details


Chapter 5D. WollanMemstar Pty Ltd29 Dalgety StreetOakleighVictoria 3166Australia


Chapter 6C. CharpentierUMR Sant de la Vigne et Qualit du

VinUniversity of BurgundyCampus universitaireBP 2787721078 Dijon CedexFrance


Chapter 7R. Marchal*Laboratory of Enology and Applied

ChemistryUniversity of ReimsBP 103951687 Reims Cedex 02France


E. J. WatersThe Australian Wine Research

InstituteP.O. Box 197Glen OsmondSouth Australia 5064Australia

Chapter 8W. J. du ToitDepartment of Viticulture and

OenologyStellenbosch UniversityPrivate Bag X1Matieland 7602South Africa


Chapter 9Jamie Goode6 The GreenHigh StreetFelthamTW13 4AFUK


Chapter 10D. Rauhut*Forschungsanstalt Geisenheim

(Geisenheim Research Center(GRC))

Section of Microbiology and Bio-chemistry

Von-Lade Strae 1D-65366 GeisenheimGermany


C. MicheloniAIAB Italian Association for

Organic Agriculturevia Piave 14I-00187 RomeItaly


Contributor contact details xv


Chapter 11P. Marullo*LAFFORTBP 40F-33 072 BordeauxFranceEmail: philippe.marullo@

u-bordeaux2.fr

D. DubourdieuInstitut des Sciences de la Vigne et du

VinUMR Oenologie; INRA-Universit

Bordeaux 2,210 Chemin de Leysotte CS 50008F-33 882 Villenave dOrnonFrance

Chapter 12L. Conterno*Fondazione E. MachIASMA Research and Innovation

CentreFood Quality and NutritionVia E. Mach 138010 San Michele a/Adige (TN)Italy


T. Henick-KlingViticulture and Enology ProgramWashington State University2710 University DriveRichlandWA 99354USAEmail: [email protected]

Chapter 13R. Jung and V. Schaefer*Forschungsanstalt Geisenheim


Section of Oenology and WineTechnology

Blaubachstrae 19D-65366 GeisenheimGermany

Email: [email protected];[email protected]

Chapter 14A. Botezatu and G. Pickering*Brock University500 Glenridge AvenueSt CatharinesOntarioLS2 3A1Canada


Chapter 15P. A. KilmartinWine Science ProgrammeThe University of AucklandPrivate Bag 92019AucklandNew Zealand


xvi Contributor contact details


Chapter 16A. W. Linsenmeier*Section of Soil Science and Plant

NutritionForschungsanstalt Geisenheim


Von-Lade Strae 1D-65366 GeisenheimGermany


D. Rauhut and W. R. SponholzSection of Microbiology and Bio-

chemistryForschungsanstalt GeisenheimVon-Lade Strae 1D-65366 GeisenheimGermany

Chapter 17M. V. Moreno-Arribas*Institute of Industrial Fermentations

(CSIC)Juan de la Cierva 328006 MadridSpain


A. Y. Smit and M. du ToitInstitute for Wine BiotechnologyStellenbosch UniversityPrivate Bag X1Matieland 7602South Africa


Chapter 18A. J. BowenCool Climate Oenology and Viticul-

ture InstituteBrock University500 Glenridge AvenueSt CatharinesOntarioLS2 3A1Canada


Chapter 19S. Buxaderas* and E. Lpez-

TamamesDepartment of Nutrition and Food

ScienceUniversity of BarcelonaFaculty of PharmacyAv. Joan XXIII, s/n08028 BarcelonaSpain


Chapter 20A. RazunglesMontpellier SupAgroInstitut des Hautes Etudes de la Vigne

et du VinUMR Sciences pour lOenologie2 Place Pierre Viala34060 Montpellier Cdex 1France



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Edited by D. Kilcast192 Managing wine quality Volume 2: oenology and wine quality Edited by A. G.

Reynolds193 Winemaking problems solved Edited by C. E. Butzke194 Environmental assessment and management in the food industry Edited by U.

Sonesson, J. Berlin and F. Ziegler195 Consumer-driven innovation in food and personal care products Edited by

S.R. Jaeger and H. MacFie196 Tracing pathogens in the food chain Edited by S. Brul, P.M. Fratamico and T.A.

McMeekin197 Case studies in novel food processing technologies: innovations in processing,

packaging, and predictive modelling Edited by C. J. Doona, K Kustin and F. E.Feeherry

198 Freeze-drying of pharmaceutical and food products T-C Hua, B-L Liu and HZhang

199 Oxidation in foods and beverages and antioxidant applications: Volume 1Understanding mechanisms of oxidation and antioxidant activity Edited by E.A. Decker, R. J. Elias and D. J. McClements

200 Oxidation in foods and beverages and antioxidant applications: Volume 2Management in different industry sectors Edited by E. A. Decker, R. J. Eliasand D. J. McClements

201 Protective cultures, antimicrobial metabolites and bacteriophages for foodand beverage biopreservation Edited by C. Lacroix

202 Separation, extraction and concentration processes in the food, beverage andnutraceutical industries Edited by S. S. H. Rizvi

203 Determining mycotoxins and mycotoxigenic fungi in food and feed Edited byS. De Saeger

204 Developing childrens food products Edited by D. Kilcast and F. Angus205 Functional foods: concept to profit Second edition Edited by M. Saarela206 Postharvest biology and technology of tropical and subtropical fruits Volume 1

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Edited by E. M. Yahia

Woodhead Publishing Series in Food Science, Technology and Nutrition xxiii


208 Postharvest biology and technology of tropical and subtropical fruits Volume 3Edited by E. M. Yahia

209 Postharvest biology and technology of tropical and subtropical fruits Volume 4Edited by E. M. Yahia

210 Food and beverage stability and shelf-life Edited by D. Kilcast and P.Subramaniam

211 Processed Meats: improving safety, nutrition and quality Edited by J. P. Kerryand J. F. Kerry

212 Food chain integrity: a holistic approach to food traceability, authenticity,safety and bioterrorism prevention Edited by J. Hoorfar, K. Jordan, F. Butlerand R. Prugger

213 Improving the safety and quality of eggs and egg products Volume 1 Edited byY. Nys, M. Bain and F. Van Immerseel

214 Improving the safety and quality of eggs and egg products Volume 2 Edited byY. Nys, M. Bain and F. Van Immerseel

215 Feed and fodder contamination: effects on livestock and food safety Edited byJ. Fink-Gremmels

216 Hygiene in the design, construction and renovation of food processingfactories Edited by H. L. M. Lelieveld and J. Holah

217 Technology of biscuits, crackers and cookies Fourth edition Edited by D.Manley

218 Nanotechnology in the food, beverage and nutraceutical industries Edited byQ. Huang

219 Rice quality K. R. Bhattacharya220 Meat, poultry and seafood packaging Edited by J. P. Kerry221 Reducing saturated fats in foods Edited by G. Talbot222 Handbook of food proteins Edited by G. O. Phillips and P. A. Williams223 Lifetime nutrional influences on cognition, behaviour and psychiatric illness

Edited by D. Benton


Preface

Our current knowledge of the chemistry, microbiology and technology ofwinemaking is astounding. Volume 2 of Managing wine quality provides 20chapters on the science of winemaking from leading experts around the world. Weanticipate that this book, and its companion volume dealing with viticulturaltechnologies, will provide a valuable resource for students, scholars and membersof the wine industry. It is our opinion that these two volumes could form the basisfor a senior level undergraduate or graduate level course in wine science. Volume2 is divided into two sections: Part I, Winemaking technologies and wine quality;and Part II, Managing sensory quality. Part I contains microbiological topics suchas yeast and fermentation management (Specht), metabolic engineering of wineyeasts (Divol and Bauer), and malolactic fermentation (Lonvaud-Funel). Generalwine technology subjects range from the use of oenological enzymes (Canal-Llaubres), membrane separation and recombination (Wollan), ageing on lees(Charpentier), stabilisation and clarification (Marchal and Waters), and the use ofmicro-oxygenation and oak alternatives (du Toit). Specialty topics such as alterna-tive wine closures (Goode) and low input (e.g. organic) approaches to winemaking(Rauhut and Micheloni) are included. Part II of this volume, dealing with manag-ing wine sensory quality, includes some exciting new information on the impact ofvarious oenological practices on aroma and flavour. Some examples are yeastselection for wine flavour modulation (Marullo and Dubourdieu), Brettanomyces/Dekkera off-flavours (Conterno and Henick-Kling), reduction of cork taints (Jungand Schaefer), ladybug taint (Botezatu and Pickering), non-enzymatic wine oxida-tion (Kilmartin), atypical ageing (Linsenmeier, Rauhut and Sponholz), and theavoidance of biogenic amine production during winemaking (Moreno-Arribas,Smit and du Toit) are also included. The reader will additionally find two chapterson specialty wine products icewines (Bowen) and sparkling wines (Buxaderasand Lpez-Tamames). The final chapter discusses the impact of specific technolo-gies on wine aroma and flavour such as extraction processes (Razungles). Volume2 and its companion volume represent the state of the art on winemaking science

xxvi Preface


and technology from the vineyard to the glass. I hope that the reader findsManaging wine quality both edifying and enjoyable, and that it will be considereda valuable resource for years to come.

Andrew G. ReynoldsEditor


Part I

Winemaking technologies and winequality


1

Yeast fermentation management forimproved wine qualityG. Specht, Lallemand, USA

Abstract: The yeast and alcohol fermentation management practices reviewed in thischapter are applicable for most alcohol fermentations that winemakers will encounter.The way the yeast is prepared at the yeast production facility and managed duringrehydration and throughout the early phases of alcohol fermentation by the winemakerwill have a substantial influence on the yeasts ability to conduct a problem-free fermen-tation and the resulting wine quality. In spite of improved winemaking technology, thereis still much to learn about properly managing yeasts and conducting healthy stress-freefermentations as sluggish and stuck fermentations are still a universal problem.

Key words: yeast, stuck fermentations, yeast nutrition, alcohol fermentation, yeastinoculation.

1.1 IntroductionKilgore Trout once wrote a short story which was a dialogue between twopieces of yeast. They were discussing the possible purposes of life as theyate sugar and suffocated in their own excrement. Because of their limitedintelligence, they never came close to guessing that they were makingChampagne.

(Kurt Vonnegut, Breakfast of Champions)Alcoholic fermentation is the process by which a microorganism (yeast) convertssugar into alcohol and carbon dioxide gas. Most winemakers can appreciate that

4 Managing wine quality


yeast is not just some unnecessary ingredient but that it is a living organism whoserole is so critical that without yeast there is no wine. These diverse single-celledorganisms can be divided into 60 broad genera such as Saccharomyces and over700 more tightly defined groups called species such as cerevisiae. Meaningfulselection of yeast was begun about a century and a half ago by Louis Pasteur whodemonstrated the role of live yeast in the fermentation process.

The first Saccharomyces yeasts were selected for winemaking roughly 80 yearsago; the main criteria for selection were their ability to perform reliably andcomplete the fermentation. It was through the persistence of the wine institutes thatthe starter culture technique was refined and liquid yeast starter cultures wereaccepted by winemakers. In the mid-1960s, active dried oenological yeast startercultures were developed (Degr, 1993), and these have gained mainstream accept-ance for use by winemakers in the majority of wine made today. Since the 1980s,universities and oenological research institutes have based their selection strategyof naturally-occurring wine yeast on their research focus and available resources.Some notable examples of these yeast selection strategies would include thecompetitive factor (Barre and Vzinhet, 1984), ecological origin (Delteil andLozano, 1995), varietal volatile compounds (Tominaga et al., 1998), breedingtechniques and genetic engineering of the yeast, as covered in Chapter 2.

1.2 Yeast and fermentation management and wine qualityAmong the selected Saccharomyces available as active dried yeast, there aresubstantial differences in their kinetics and aptitude to achieve a complete fermen-tation. These differences come from the yeasts nitrogen and oxygen needs, someof which have been characterized (Sablayrolles et al., 2000), and their ability totolerate juice conditions. Another important influence on the yeast fermentationkinetics is the individual yeasts ability to compete against the microbial soup ofindigenous yeast present in the juice or must. Under winery conditions, competi-tion between yeast for the uptake of nutrients and the influence of the competitivefactor is a practical key point in the choice of yeast. The method of yeast biomasspropagation prior to dehydration has also been demonstrated in winery scalefermentations to have a direct impact on the performance of the yeast duringfermentation and on the resulting wine quality (Bohlscheid et al., 2007b). Moredetails on this will be shown in a later section of this chapter.

Oenological yeasts offer winemakers an additional tool for differentiating theirwines (Eglinton et al., 2003). Determining which yeast to use, and using them ina controlled manner, can help to achieve the subtle aroma and flavour diversity thatmany winemakers seek (Henschke, 1997b; Heard, 1999; Lambrechts and Pretorius,2000; Howell et al., 2005).

The secondary metabolism of the specific yeast produces compounds that havegreat importance in the wine analytical and sensory profiles. There are substantialdifferences among strains of Saccharomyces in terms of their production of esters,sulphur compounds, varietal compounds such as -damascenone, and

Yeast fermentation management for improved wine quality 5


polysaccharides, as well as the impact of their mannoproteins on the volatility ofcertain compounds and on the stability of pigments and polyphenols (Delteil andJarry, 1992).

With such large possible analytical differences among yeasts, it is logical thatcorrespondingly large sensory differences have been demonstrated as early as themid-1980s. Sensory differences due to the yeasts may come from their interactionwith grape flavour precursors or be due to the yeast metabolites (Pretorius et al.,2008). Yeast mannoproteins released in the fermentation also have a sensoryimpact on the aromatic expression of varietal volatile compound (Wolz, 2005). Inmultivariate sensory studies with principal component analysis (PCA) of sensoryanalysis results, different yeast strains in red wines gave sensory differences withmagnitudes as great as those obtained from grapes at different stages of ripeness,or varying maceration lengths; techniques generally recognized as having a bigimpact on the wine style (Delteil, 2001). These sensory differences may becomeeven more apparent with ageing (Dumont et al., 1994).

It is critical for the winemaker to consider using suitably selected yeast that cangrow and express its metabolic activity under the given juice or must conditions.For example, a yeast showing good tolerances to low temperatures and highlyclarified juices for making a lower alcohol aromatic white wine would probablynot ferment very well under higher temperature and higher alcohol potentialconditions in a concentrated red must and vice versa.

The yeasts impact on wine quality can also be associated with its production ofoff-flavours such as volatile acidity, acetaldehyde, ethyl acetate and negativesulphur compounds. The prevention of off-flavour formation will be addressed inlater sections of this chapter that will cover proper yeast handling, feeding andother good fermentation practices that contribute to yeast health and vitality.

1.3 Yeast rehydration and handlingProper rehydration is perhaps the most critical phase in using active dried yeast.When selected yeasts are produced in an active dried form, the goal is to get a veryhigh and viable cell population prior to a series of water removal steps until 58%moisture remains in the yeast powder. This low moisture level is necessary toensure a good shelf life in order to conserve the yeasts potential activity for morethan 36 months. These drying stages remove not only extracellular water, but alsomost of the water within the cell and bound to the cells organelles, causing theyeast cells to shrink and desiccate. With extremely low water activity, there isalmost no metabolic activity. To be functional again, the dried yeast cells mustreabsorb all of their water. When the dried yeast comes into contact with water (orany other liquid), the cells literally act like dried sponges and suck up the neededwater in seconds.

In winemaking, the grape juice is a very hostile medium for Saccharomyces:high osmotic pressure, low pH and often high SO2. Most selected yeasts resist theseconditions when their membrane and their intracellular components are in good



physiological conditions. Therefore, before inoculating a grape juice, it is abso-lutely necessary to bring back vital water at the right temperature to the active driedyeast cells in order for their membrane and intracellular components to reorganizeproperly. Not only will yeast cells not disperse very well if not properly rehydrated,they can lose a large amount of cellular components, reducing the efficiency ofoxygen and nutrient transfer to the cells (Henick-Kling, 1988). This impedes yeastgrowth and activity leading to sluggish and stuck fermentations. The use of cleanpotable water at the right temperature for the right length of time would appear tobe the most simple and effective yeast rehydration protocol.

Proper yeast rehydration gets them off to a good start and helps to ensure that theyeast will stay healthy throughout the fermentation. Degr (1993) proposed ageneral recommendation procedure for active dried yeast rehydration which is asfollows:

sprinkle 500 g of dry yeast into 5 L of warm water (3540 C); stir the suspension after 5 minutes to re-suspend the yeast cells; leave the suspended yeast cells no more than 30 minutes; add yeast to 2025 hL must to be fermented, which would correspond to a yeast

inoculation level of dosage 2530 g/hL ca. 25 106 cfu/mL.

Recent studies have investigated the effects of rehydration protocols on therecovery of fermentative activity of different yeasts. Some differences wereobserved among yeasts using different rehydration protocols; however, these

Fig. 1.1 Atomic force microscopy photograph of rehydrated active dried yeast after20 minutes; taken at The University of Abertay Dundee, Scotland.



Fig. 1.2 Atomic force microscopy photograph of rehydrated active dried yeast after 20minutes in the presence of supplemented micronutrients and sterols; taken at The University

of Abertay Dundee, Scotland.

differences were not large enough, suggesting that the best advice is to follow theyeast producers rehydration instructions (Sablayrolles et al., 2006). Other recentstudies have shown the influence on yeast viability and vitality of rehydratingactive dried yeast in the presence of micronutrient and or sterol and unsaturatedfatty acid-enriched inactivated yeast suspension during rehydration (Soubeyrandet al., 2005). Yeast rehydration photographs taken at The University of AbertayDundee using atomic force microscopy show rehydrated active dried yeasts after20 minutes (Fig. 1.1) and under the same rehydration conditions with supple-mented micronutrients and sterols (Fig. 1.2). Higher maximum yeast cell densityand shorter overall fermentation lengths were observed when using these types ofrehydration nutrients, especially under high sugar concentrations such as in icewine musts (Kontkanen et al., 2004).

Using grape juice or must in the initial yeast rehydration media may lead to theyeasts being directly exposed to residual agrochemicals, sulphur dioxide or otherinhibitors. The addition of grape juice or must was found, however, to be beneficialif the total rehydration length exceeded 30 minutes (Radler et al., 1985). Inpractice, grape juice or must should be added 15 to 30 minutes after the initial yeastrehydration in water. This will also help to adapt the rehydrated yeast suspensionto the cooler juice or must temperature and avoid cold shocking the yeast starterculture.



1.4 Yeast inoculationOnce you have properly prepared the yeast starter culture, there are a few common-sense guidelines to keep in mind in order to help the yeast you want to dominate thefermentation and lower the possibility of problem fermentations. When inoculat-ing the fermentor, there is a high probability that the inoculated S. cerevisiae willdominate the fermentation (Schtz and Gafner, 1993). However, inoculating withspecific yeast will not guarantee the dominance of that yeast or their contributionto the fermentation. Significant factors that affect this outcome will be how thefermentation is managed and the population of the indigenous yeasts alreadyacclimated to that juice or must.

Winery fermentation trials were made in many regions in the late 1980s andearly 1990s using a selective plating technique in order to determine the influenceof winemaking practices on the inoculated yeast implantation success. The results(Delteil and Aizac, 1998) showed that in the early part of the harvest the percentageof successful inoculated yeast implantation declined over the duration of theharvest. This is most likely the result of the indigenous flora becoming moreestablished over the course of the harvest as cellar cleaning practices become lesseffective. Longer juice settling times also resulted in lower yeast implantation . Thepractice of juice centrifugation resulted in high implantation levels which supportsthe impact of the acclimated indigenous yeasts on the ability of the inoculated yeastto implant (Querol et al., 1992).

1.5 Yeast inoculation rateThe juice or must sugar content and the hygienic conditions of the must arefundamental when choosing the inoculation rate; if indigenous yeasts or bacteriaare present in high numbers, the more precarious the hygienic conditions and,therefore, a relatively large inoculation rate of the oenological yeast should beused. For potential alcohol wines around 14%, the number of healthy yeast cellsshould be around 5 106 cells/mL which is generally obtained by the addition of25 g/hL of active dried yeast. The suggested rate of yeast inoculation is based onthe fact that a proper initial cell density is required for the onset and completion offermentation. Before the onset of fermentation, during the lag phase, it is ideal tokeep this lag phase as short as possible to avoid potential microbial spoilage andproduction of undesirable compounds. This situation is directly correlated to theinitial yeast cell density or inoculation rate. Increasing the inoculum density willresult in a decreased lag time, up to certain point where the effect is not significantdue to the crowding effect. During wine fermentation, the inoculated yeast cellpopulation will usually undergo roughly five cell divisions or a doubling of theyeast population with every cell division until the juice is colonized. One of themost important factors in obtaining a steady and complete fermentation is thepresence of an adequate cell population when the yeast has finished growing,which is normally when 3050% of the sugars remain to be fermented. In order to



Table 1.1 Yeast inoculation rate comparison trial made at INRA Research InstitutePech Rouge, France

10 g/hL 25 g/hL

Lag phase (hours) 50 32Fermentation length (hours) 778 505Residual sugar (g/L) 1.6 0.8Volatile acidity (g/L H2SO4) 0.54 0.46

complete fermentation at that stage where problems usually start occurring,approximately 120150 106 cells/mL is needed. This population is more easilyachieved when the yeast cell inoculum is approximately 5 106 cells/mL, which isobtained when the inoculation rate is 25 g/hL (Monk, 1997). It is important to notethat some yeasts will require higher cell density to complete fermentation becausetheir metabolism is different compared to others.

Table 1.1 shows the importance of an inoculum of 25 g/hL versus 10 g/hL. Ayeast inoculation level trial done by Lallemand in collaboration with the INRAPech Rouge, clearly showed the benefit of inoculating a Chardonnay must with 25g/hL since it resulted in a substantial reduction of lag phase time, fermentationlength, residual sugars and a reduction of volatile acidity.

1.6 Yeast inoculation timingIt is essential to inoculate the must as soon as possible to help ensure the dominanceof the oenological yeast. In large fermentors that take a long time to fill, it isnecessary to inoculate the yeast starter to the bottom of the fermentor (or as soonas possible during filling) to allow them to go through their lag phase and competeright away with the indigenous microbial population. Also, it is important to try toinoculate the must when the temperature is >12 C, since lower temperatures maybe stressful for most yeast and result in sluggish or stuck fermentations.

There are exceptions when winemakers may want to inoculate at lower tem-peratures. Cold soaking, also known as pre-fermentative cold maceration,populations of apiculated yeasts such as Kloekera apiculata or Hanseniasporauvarum can develop in substantial amounts and produce high amounts of ethylacetate, which has a very pungent ascescent aroma. At low concentrations, ethylacetate can emphasize dryness and burning sensations in the mouth during tasting.When the grapes are immediately inoculated with yeast at about 5 106 live cells/mL, the yeast will begin its lag phase and develop slowly. Even at cold soaktemperatures of around 10 C, the selected Saccharomyces population will beginto use the nutrients in the must, making them unavailable to the indigenousapiculate yeast population. Because the juice is very cold for the recently-rehydrated Saccharomyces, it is recommended to rehydrate the yeast withinactivated yeast-based micronutrients, sterols and unsaturated fatty acids in orderto help it support the low temperature and limit lag phase duration. In addition, the



yeast to be inoculated should be adapted to the cold must temperature by combin-ing the rehydration suspension with the colder must. This will help the yeast adjustto the colder must temperature and avoid cold shocking the yeast. The adaptationstep may need repeating in very-low-temperature musts.

1.7 Sequential yeast inoculation strategiesThere are two scenarios where sequential yeast inoculation strategies might beconsidered by winemakers. The first situation would be addressing potentialproblems with fermentations at very high initial soluble solids concentrations[28 Brix or density (specific gravity) of 1.110] for which the goal is to finish thealcoholic fermentation with very low residual sugar. This method is already in useby winemakers dealing with extremely mature grapes. The Saccharomyces yeastis inoculated in two stages: the first at the beginning of fermentation and the secondonce the density has reached a certain point but before symptoms of a stuck orsluggish fermentation are apparent. At first, 25 g/hL of the yeast is rehydrated inwater supplemented with high yeast sterol-based inactivated yeast to help protectthe yeast from osmotic shock, and then this protected yeast is inoculated. At adensity of around 1.020 (~5 Brix), another 25 g/hL is inoculated (also rehydratedin the same manner).

This sequential inoculation strategy is also well adapted for yeasts with particu-lar qualities that winemakers would like to take advantage of but cannot due to thesensitivity of that yeast to very high potential alcohol situations. The proper way tocarry out this method is to first inoculate the must with the type of this yeast inquestion and then during the alcoholic fermentation, sequentially inoculate withalcohol-tolerant yeast.

A second considered sequential inoculation strategy is the use of non-Saccha-romyces yeast followed by a Saccharomyces. More knowledge is available on thenon-Saccharomyces impact on the sensory profiles of the wines (Ciani andFerraro, 1998). Some of these yeasts like Pichia fermentans, Candida stellata orTorulaspora delbrueckii have been studied for their interesting organolepticcontributions (Moreno et al., 1991; Ferraro et al., 2000; Clemente-Jimenez et al.,2005). Although some of these yeasts will contribute aromatic compounds ofinterest in some styles of wines, most of them are not very reliable alcoholicfermentors. A recent project by Ortiz-Julien et al. (2005) evaluating sequentialinoculation of first a non-Saccharomyces followed by a good fermenting Saccha-romyces during a late stage of alcoholic fermentation have shown promise forsome styles of wine; however, further investigation is needed.

1.8 Yeast storageIn the dry state, active dried yeasts contain



viability for several years depending on the yeast and how it was produced. Whenpreserved in their original vacuum-sealed packaging, active dried yeast may loseup to 10% of their viability per year when stored at an average ambient temperatureof 20 C. From a microbiological point of view, the loss of 10% of the yeasts cellswould have a slight effect on the inoculum and could easily be compensated for byincreasing the inoculation rate by 10%. For this reason, if they are still in theiroriginal packaging they can be used up to 2 to 4 years after their date of productionwithout much loss in activity. Nevertheless, specific and simple methods exist toverify yeast activity, and these can be obtained upon request from the active driedyeast producer.

1.9 Nutrient strategiesIn order to conduct a complete alcoholic fermentation with reliable kinetics, it isnecessary for the grape must to have adequate nutrition in a tolerable environmentfor the development of healthy yeast. This will ensure an optimum production ofyeast biomass and consequently reduces the risk of sluggish or stuck fermentations.Compared to 20 years ago, we now have a better understanding of the complex andoften frustrating interactions in grape must and their influence on yeast growth andsurvival during alcoholic fermentation. However, it is still difficult to predict whenthere is a nutrient deficiency in a must so many winemakers now routinely addsupplements using the initial musts yeast assimilable nitrogen (YAN) concentra-tion, as a guideline. In addition to the YAN concentration the alcohol potential ina must should also be a guideline when making nutrient supplement decisions.

1.9.1 NitrogenNitrogen is an important factor in oenology, playing a vital role in the kinetics ofalcoholic fermentation. Yeast assimilable nitrogen, made up of ammonia nitrogenand -amino nitrogen (free amino acids minus the proline that is not assimilated bythe yeast), is the nutrient with the greatest effect on the rate and outcome ofalcoholic fermentation (Bezenger and Navarro, 1987). During fermentation, theyeasts transport ammonium (NH4+) and amino acids from the must into the yeastcells, where they are kept for later use. These sources of nitrogen are used in thesynthesis of the yeast membrane during cell multiplication and for production ofthe enzymes necessary for glycolysis, i.e., for the conversion of glucose andfructose to ethanol. In addition, NH4+ and amino acids are used to biosynthesizepermease enzymes situated in the yeast membranes. These permeases are respon-sible for the transport of such components as other amino acids and sugars into thecell.

A YAN deficiency in the must limits the growth of yeast and the fermentationrate (Bely, 1990). During alcoholic fermentation, sugars are consumed during thestationary phase when the nitrogen gradually becomes less available. Since YANis an essential nutrient involved in the transport of sugars into the cell via protein



synthesis, this partially explains why both the yeast metabolism and the fermenta-tion activity slow down (Salmon, 1996). Thus, the lower the concentration of YANin a must, the greater the risk of sluggish fermentation (Kunkee, 1991). Most mustscontain between 80 and 400 mg/L of YAN; the threshold for YAN deficiency isabout 150 mg/L for a must with an initial sugar concentration of about 200 g/L(Henschke and Jiranek, 1993). A nitrogen deficiency in the must is also responsi-ble for stopping the protein synthesis in the yeast. The consequence of thisinactivation will be a substantial decrease in the sugar transport activity, therebyincreasing the risk of a stuck fermentation (Basturia and Lagunas, 1986).

The nitrogen supply, either from the grape or from the addition of nitrogensupplements, can influence yeast growth, fermentation time and the sensoryproperties of a wine. Different yeasts under similar conditions have differentgrowth rates, nutrient requirements and abilities to produce and excrete esters andfusel alcohols. The interaction between yeast and grape must composition caninfluence wine quality and style (Pretorius et al., 2008). When nitrogen is limitingin fermentation, the yeast which needs more to continue building protein forsugar transport will degrade its intracellular pool of amino acids and assimilatethe nitrogen part. So, when sulphur-containing amino acids are degraded, the resultis an accumulation of the SH fraction that will be released by the yeast as H2S(Jiranek et al., 1995; Erasmus et al., 2003). Hydrogen sulphide, when present inconcentrations >10 g/L, adversely affects the sensory quality of wine. WhenYAN is coupled with an imbalance of pantothenic acid and/or biotin, it can alsoresult in an increase in H2S production (Wang et al., 2003; Bohlscheid et al.,2007a). When H2S is produced in the early stage of fermentation, it can react withother compounds to produce sulphides, disulphides, thiols and mercaptans. Thosesulphur compounds can develop during ageing or after bottling and also negativelyaffect wine quality (Rauhut et al., 1993). Occurrence of H2S can also be caused byimproper application of agrochemicals containing elemental sulphur.

1.9.2 Organic nitrogenThe amino acids contained in grapes are predominantly proline, arginine andglutamine. Vineyard practices and climatic conditions influence the concentrationof amino acids.

The amino acids and peptides coming from inactivated yeasts are the principalsource of supplemented organic nitrogen. The importance of organic nitrogenfrom yeasts is well known as a highly efficient nutrient source for wine yeasts,especially when compared to inorganic nitrogen from diammonium phosphate(DAP) (Fig. 1.3). In addition, organic nitrogen helps avoid over-production ofundesirable sulphur compounds, compared with use of DAP as a nitrogen source.Inactivated yeast-based supplements containing a high level of organic nitrogencan also help winemakers achieve steady fermentations while limiting temperaturepeaks.

The inactivated yeast-based supplements not only provide organic nitrogen, butthey are also composed of yeast cell walls that are beneficial to the yeast during



Fig. 1.3 Comparison of the effects of organic versus inorganic nitrogen on fermentationkinetics measured by CO2 release at the INRA Research Institute Montpellier, France in 2002.

fermentation. Their cell wall fraction also supplies sterols and lipids which aresurvival factors helping to maintain the membrane fluidity and avoiding alcoholtoxicity. Additionally, cell walls can be useful, as they can be rich in polysaccharideshaving a large surface area with sorption capacity to remove residual agrochemicalsand other potential inhibitory substances resulting from yeast metabolism, such asoctanoic (caprylic) and decanoic (lauric) fatty acids (Lafon-Lafourcade et al.,1984). These compounds can adhere to the yeast cell wall and inhibit yeast activityin the last phase of the fermentation process, because they alter the permeability ofthe cell. Finally, yeast cell walls can act as elements of support, helping to keep theyeast in suspension during fermentation and avoiding their settling on the bottomof the fermentor.

1.9.3 Inorganic nitrogenInorganic nitrogen in the form of ammonia salts such as DAP or ammonia sulphateis used in winemaking to supplement the nitrogen availability, especially in mustshigh in potential alcohol and low in YAN. However, inorganic nitrogen supple-mented on its own will not obtain the best fermentation results, and over-treatmentcan lead to the development of harsh characters in wine. Under nitrogen-limiting

0 50 100 150 200

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

Time (h)

46 h fermentation time difference

8 slope

40 slope

5 mg N/L-amino N

(organic YAN)

20 mg N/Lammonium

(inorganic YAN)

Ferm

enta

tion

spee

d (g

/L h

)Chardonnay 220 g/L, fermented with EC 1118 (20 g/hL)



conditions, the goal is to balance the level of inorganic nitrogen with organicnitrogen from -amino acids to achieve optimal nitrogen concentrations. Theresult of a good balance of these products will be fermentation security and the bestexpression of fermentation and varietal characters.

1.9.4 How much nitrogen is needed?The minimal quantity of YAN needed for yeasts is reported to be 150200 mg/L,depending upon the must soluble solids concentration. The higher the initialsoluble solids concentration, the more nitrogen will be required by the yeast. Theamount of YAN needed will also vary according to the yeast used as they havedifferent relative nitrogen demands (Sablayrolles et al., 2000). The bioavailabilityof key vitamins that allow an optimal use of nitrogen also has an influence on theamount of YAN (Wang et al., 2003).

1.9.5 When should you add nitrogen?There are two optimal times to consider adding YAN to the fermenting must(Sablayrolles et al., 1996). The first time for YAN addition is during the beginningof yeast cell growth as soon as the fermentation is active, to provide YAN for yeastgrowth when it is deficient in the must. If YAN concentrations are adequate,however, this first addition is unnecessary. A second optimum time for a YANaddition is at the end of yeast cell growth, which helps to maintain the yeastsvitality to ensure a satisfactory fermentation finish. This corresponds to theconsumption of about one third of the sugar, which is at the end of the growth phaseentering into the yeasts stationary phase or at maximum cell yeast density. Table1.2 summarizes a good yeast inoculation and nutrient strategy based on must YANand initial Brix level to help avoid fermentation problems.

1.9.6 OxygenDuring the early stages of alcoholic fermentation, Saccharomyces is able to useoxygen for the synthesis of sterols. These sterols help in keeping the yeastmembrane fluid and in resisting osmotic shock and ethanol toxicity. The practicalconsequences are minimal acetic acid production during yeast growth and ahealthier yeast population resulting in a more reliable fermentation finish. Eventhough there is an important variation among the different oenological yeasts intheir response to oxygen addition, yeasts scavenge oxygen very quickly. There areno risks of juice oxidation when aerating or adding oxygen at the recommendedtimes and quantities, even in very fragile, readily-oxidized juice from varietiessuch as Sauvignon blanc or Viognier.

There are two optimal times to aerate or add oxygen (46 mg/L) to the ferment-ing must (Sablayrolles et al., 1996). First, during the beginning of yeast cell growthas soon as the fermentation is active to help the yeast resist the osmotic shock andlimit acetic acid production. In practice, this corresponds to the consumption of



Table 1.2 Yeast inoculation and nutrient strategy summary under different mustconditions

Must Brix Yeast Yeast stimulant or Nutrient strategy depending oninoculation protector during must YAN content during

rate yeast rehydration fermentation

200 mg/L: no addition30 g/hL stimulant YAN 1

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managing wine qualityvolume

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