WHITE WINE ENOLOGY

OPTIMIZING SHELF LIFE AND FLAVOR STABILITY OF WHITE WINES - HOW LONG-LASTING WHITE WINES ARE PRODUCED

Volker Schneider

• Publisher: tredition
• Year: 2024
• ISBN:
  9783384016164
• Topic: Technology & Engineering
• Subtopic: Applied Sciences
• Index: Technology & Engineering

WHITE WINE ENOLOGY could also be titled as SCIENCE AND PRACTICE OF WHITE WINEMAKING. It is characterized by two particular features: Firstly, it is authored by a practitioner who has worked his whole life in decision-making technical positions in the wine industry. Secondly, it is dedicated exclusively to the enology of white wines, and focuses its attention on flavor preservation rather than strategies that seek to obtain short-lived quality benefits. In doing so, it addresses one of the most important issues of white winemaking, which is the limited shelf life and flavor stability of most such wines, and shows how different white wine enology is from red.Due to the complex chemical process of white wine aging that goes well beyond oxidative aging, this book has a strong focus on sensory analysis throughout. It specifies the flavor-active compounds responsible for aging-related faults, identifies the chemical mechanisms of their formation, and clearly defines the decisive measures to take in order to mitigate them and improve flavor stability.While this book includes a deep treatment of the scientific fundaments of the different kinds of white wine aging, it also examines typical engineering issues common to commercial winemaking. Thus, it provides numerous practical hints and technical details of hands-on winery work and a valuable insight into the inherently cross-disciplinary nature of fine white winemaking. Extensive personal experience was decisive for this purpose.Volker Schneider was founder of the international consulting firm Schneider-Oenologie, which specialized in innovative winery operations, product development, quality control, and research. He has authored more than 450 technical articles and a range of scientific papers on these topics. He was also lecturer of enological chemistry at Geisenheim University.

Table of contents

• Titelbild
• WHITE
• Preface to the 1st Edition
• Preface to the 2nd Edition
• 1. Introduction
• 2. Typical and oxidative aging
• Figure 4: General structures of benzoic acids and cinnamic acids.
• Flavonoid phenols
• Figure 7 depicts the browning rate of young filtered white wines kept under air without any SO2 additions. Browning was measured as the absorbance at 420 nm (A 420
• Measurement of flavonoid phenols in white wines using the DAC-reagent
• 2.3. Influence of grape processing
• 2.4.6. Reductive vs. oxidative must processing in a nutshell
• Practical considerations on lowering phenols by finings
• 2.4.8. Importance, practice, and evaluation of juice clarification
• Bentonites are essential for protein stability, but differ among themselves
• Effect of pH
• 2.5.3. Effect of ascorbic acid
• Sensory risks and drawbacks
• 2.5.5. Effect of sulfur-containing amino acids and active dry yeasts
• 2.5.6. Oxygen consumption by post-fermentation yeast lees
• Effect of storage and age of yeast lees
• Delayed filtration protects against oxidative aging
• The special case of wooden barrels
• 2.6.2. Oxygen uptake through wine surface and headspace inertization
• 2.6.4. Measures of gentle white wine treatment
• 3. Reductive aging
• 3.3. Identification and removal of reduction flavor
• 3.3.3. The importance of depth filtration after copper fining
• Removal of excess copper by fining with PVI/PVP
• Interpreting results
• Copper in Cu-organic acid complexes, for example Cu(II)-tartrate or Cu(II)-malate (fraction I),
• 3.4.3. Measurement of total and free copper
• Qualitative, toxicological, and ethical considerations of copper fining
• 3.5. Effect of bottle closures on reductive aging
• - In comparison with the well-known tin-Saran liner, closure-related oxygen uptake and the resulting decrease in SO2 are identical and negligible.
• 4. Atypical aging
• The sensory role of 2-aminoacetophenone
• 4.2. Limited significance of microbial formation
• 4.5. Enological measures against atypical aging
• 4.6. Assessing the wines' proneness to ATA
• Figure 84: Implementation of the test to assess ATA potential.
• 5. Petrol flavor
• atypical aging (mothballs, naphthalene, damp towel, washing machine
• 6. Epilog
• Finally, there is also petrol flavor, which is another long-known kind of aging, largely limited to Riesling wines, and not considered by all to be a flaw. However, it can become unpleasantly strong w...
• 7. Literature
• I N D E X
• 1,1,6-trimethyl-1,2-dihydronaphthalene
• Anmerkungen
• [←2] Thiols are sulfur-containing organic molecules with one or more -SH functional groups. Most of them display strong odors, which can be pleasant or repulsive. Refer to section 3.1.1 for details.
• [←3] anoxic = in the absence of oxygen
• [←4]
• [←5] Higher aldehydes have more than one carbonyl (-C=O) group or a branched hydrocarbon chain, in contrast to simple aldehydes with only one carbonyl group and a linear hydrocarbon chain.
• [←6] As will be outlined in section 2.2.1, quinones are the oxidation products of phenols.
• [←7] Dicarbonyls = molecules with two carbonyl (‒C=O) groups.
• [←8] Decarboxylation = removal of a carboxyl (-COOH) group typical for carboxylic acids.
• [←9] Diamination = removal of an amino (-NH2) typical for amino acids.
• [←10]
• [←11] Lactones are cyclic carboxylic esters containing a -C(=O)-O- structure formed by intramolecular esterification of carboxylic acids.
• [←12] A benzene ring is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each.
• [←13] Phenolates are anions and salts of phenols.
• [←14]
• [←15] Dimerization is the process of joining two molecules by bonds.
• [←16] Enols are alkenes with a hydroxyl (-OH) group attached to one end of the alkene double bond, so: -C=C-OH.
• [←17]
• [←18] The degree of unsaturation of phenols refers to their number of C=C double bonds and the number of hydrogens the molecule needs to be fully saturated under loss of the double bonds.
• [←19]
• [←20]
• [←21]
• [←22] PVPP = polyvinylpyrrolidone, a synthetic and insoluble fining agent used in the beverage industry to remove undesirable phenolic compounds.
• [←23] FTIR = Fourier-transformation infrared spectroscopy, a technique used to obtain an infrared spectrum of a sample that allows an indirect measurement of certain compounds.
• [←24] VIS = visible
• [←25] CE = catechin equivalents
• [←26] Refer to section 2.4.8 for details on turbidity measurements and interpretation of NTU data.
• [←27]
• [←28]
• [←29]
• [←30] Pectins are complex polysaccharides with high molecular weight contained in all plant cell walls. Their presence in the must increases its viscosity and hampers the settling of insoluble solids.
• [←31]
• [←32]
• [←33]
• [←34] See section 2.6.6 for details on DO measurements.
• [←35]
• [←36]
• [←37] For the impact of pH on molecular SO2, refer to figure 36 (page 122).
• [←38] In this context, the term "balance" is used in the accounting sense.
• [←39]
• [←40] Lactones are cyclic intramolecular esters of hydroxycarboxylic acids.
• [←41]
• [←42] Sublimation is the direct transition of a substance from the solid to the gaseous state without first becoming a liquid.
• [←43]
• [←44] abiotic = characterized by the absence of living organisms.
• [←45]
• [←46]
• [←47]
• [←48] EDTA is ethylenediaminetetraacetic acid and widely used to bind copper, iron and calcium ions in the form of soluble complexes.
• [←49] There is a large offering of usable second-hand devices in many countries.
• [←50]
• [←51] It is a great advantage if the spectrophotometer used for this purpose can also accommodate a 40- or 50-mm cuvette in order to facilitate accurate readings in the lower Cu concentration range.
• [←52] Refer to section 3.4.2 for definition and enological implications of copper fractions.
• [←53] LD50 is the median lethal dose required to kill half of the members of a tested population under specified test conditions. LD50 figures are easily accessible online for almost all substances.
• [←54]
• [←55] Temperature and time are sometimes slightly modified. A test over six days at 40° C was also suggested for this purpose (Nardin et al. 2022).