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Autoxidation of tartaric acid in air-saturated aqueous solutions in the presence of Fe(II) at low pH, 2.5, shows autocatalytic behavior with distinct initiation, propagation, and termination phases. With increasing pH, the initiation phase speeds up, while the propagation phase shortens and reduces to none. We show that the propagation phase is a chain reaction that occurs via activation of oxygen in the initiation stage with the production of hydrogen peroxide. The subsequent Fenton oxidation that regenerates hydrogen peroxide with a positive feedback is typical of a self-sustained chain reaction. The conditions for such a chain reaction are shown to be similar to those of a dynamical system with critical behavior; namely, the system becomes unstable when the kinetic matrix of pseudo-first-order reaction becomes negatively defined with a negative eigenvalue giving the rate of exponential (chain) growth of the reactive species.

This work aimed to investigate the evolution of phenolic compounds and elements during the aging of Malbec red wines from different regions of Mendoza (Argentina) and California (United States). The profiles of low molecular weight polyphenols and anthocyanins were analyzed using high-performance liquid chromatography with a diode-array detector (HPLC-DAD), and the elemental composition using microwave plasma-Atomic emission spectrometry (MP-AES). Through uni- and multivariate statistical analyses, the effects of aging time and region on wine were investigated. It was observed that aging time was a significant factor that affected the phenolic compound profile in the studied Malbec wines studied and that after five years of aging, the wines could be differentiated according to region. The results of this study may impact decisions made regarding the storage of Malbec wines in the future.

The reduction-oxidation potential, or redox potential, in a fermenting juice may influence the reactions in the juice and within the yeast cells during wine fermentations. The ability to monitor and control the redox potential at a chosen value by adding air during a red wine fermentation was demonstrated in triplicate at the 100-L scale. The Brix curves and redox potential patterns in the controlled fermentations were compared to those in the un-aerated fermentations. The redox control system consisted of a commercial pH meter with a reduction-oxidation electrode and a custom-designed electronic controller. The study showed the redox potential could be controlled at 215 mV, well above its natural level throughout the fermentation. Control of the redox potential resulted in faster peak fermentation rates and earlier completion of the wine fermentations. Analysis of these fermentation curves using a mathematical model indicated that yeast cell viability and the specific maintenance rate of the viable cells were significantly increased by controlling the redox potential during the fermentation.

The self-sustainable winery was conceived in 2006 and the intention was to create a building and its related utility systems that would operate independently from the energy and water grids and to eliminate hydrocarbon fuels from its operation, capture and sequester the carbon dioxide from its fermentations and create a zero carbon footprint facility. The winery was the highest scoring LEED building at any university when it was completed and the first LEED Platinum Winery in the USA. The adjacent Jess Jackson sustainable winery building is a highly passive research and utility space that will house the advanced energy and water systems that make this off-grid performance possible. Together these buildings will operate every daily in energy and water positive modes and at capacities, which exceed the demands even during the harvest season. The data system incorporated into these buildings for one hundred and fifty research fermentors, fourteen teaching fermentors will also monitor all energy, water and building activities in a secure, cloud-based software system that supports both web and handheld access, with the potential for bidirectional date and control functions. This data network has been extended to include real time monitoring of temperature, humidity, carbon dioxide and volatile organic compounds in five production areas within two commercial winery sites and two creamery facilities, located more than 100 km from Davis. This now provides an example of a distributed dynamic network for the monitoring of the built environment in remote commercial food and wine facilities.

The kinetics of the autoxidation reaction of tartaric acid in an air-saturated solution in the presence of Fe(II) show autocatalytic behavior with distinct initiation, propagation, and termination phases. The initiation phase, which involves activation of dissolved oxygen, decreases with increasing pH, over the test range of pH of 2.5–4.5, indicating that activation of oxygen is catalyzed by an Fe(II)–tartrate complex. The autocatalytic nature of this reaction indicates the presence of a catalytic intermediate that is produced during the initiation phase and regenerated during the propagation phase. The addition of catalase, as well as direct measurements, provided evidence of the presence and kinetic action of hydrogen peroxide as one of the intermediates. Direct addition of hydrogen peroxide resulted in shortening of the initiation stage and the propagation phase with similar rates as in the autoxidation reaction at low pH. The propagation is approximately a zero order reaction with respect to oxygen and iron. The kinetic analysis suggests that an intermediate catalytic complex(s) involving a ferryl ion (FeO2+) controls the rate of the propagation reaction. The Fe(III) formation shows autocatalytic behavior that mirrors the dissolved oxygen consumption patterns under all pH conditions studied. At pH values of 2.5 and 3.0, Fe(III) accumulated to a maximum, before it was partially consumed. This maximum coincided with the depletion of dissolved oxygen. The consumption of Fe(III), or the reduction of Fe(III) back to Fe(II), reflects the catalytic nature of Fe(II) and the essential role of tartaric acid in the initiation phase of Fenton’s original reaction.

Wood samples collected from multiple barrels during the toasting process at a commercial cooperage were analyzed for their content of several volatile compounds related to the aroma of toasted oak wood. Changes in the content of these compounds during the toasting process are presented for two different toasting protocols. Multifactor analysis (MFA) and partial least squares (PLS) regression were done to relate the volatile composition of the wood samples to the stage of the toasting process. These findings may provide objective guidance to coopers for the development of toasting protocols.

Phenolic compounds play a major role in red wine quality, affecting color, taste, mouthfeel, and aging potential. The objective of this research was to compare the phenolic composition of Malbec wines from California and Mendoza, Argentina, produced in 150 L volumes. Sixteen vineyards in California and 26 blocks in Mendoza were selected based on their uniformity and regional representativeness. Anthocyanins and low molecular weight phenolics were analyzed by HPLC at approximately six to nine months of aging. Malbec wines were compared using chemometrics on 33 phenolic components comprising individual anthocyanins, low molecular weight phenolics, and total phenolics by HPLC. The results demonstrate that Malbec wines produced in Mendoza have different phenolic profiles than those produced in California.

Malbec grapes are widely grown and studied in Argentina, whereas the smaller production in California is less well known. This study sought to define and compare Malbec wine compositions from various regions in Mendoza, Argentina and California, USA. The Malbec wines were clearly separated, based on their chemical and sensory profiles, by wine region and country. Descriptors of Malbec wines were aromas of cooked vegetal, earthy, soy and volatile acidity, as well as acidic taste and astringent mouthfeel, regardless of the region of origin. Malbec wines from Mendoza generally had more ripe fruit, sweetness, and higher alcohol levels, while the Californian Malbec wines had more artificial fruit and citrus aromas, and bitter taste. Compositional differences between the two countries were related more to altitude than precipitation and growing degree days. To our knowledge, this is the first time that an extensive regionality study has been attempted for Malbec wines.

Concealed damage (CD) is defined as a brown discoloration of the kernel interior (nutmeat) that appears only after moderate to high heat treatment (e.g., blanching, drying, roasting, etc.). Raw almonds with CD have no visible defects before heat treatment. Currently, there are no screening methods available for detecting CD in raw almonds. Herein, the feasibility of using near-infrared (NIR) spectroscopy between 1125 and 2153 nm for the detection of CD in almonds is demonstrated. Almond kernels with CD have less NIR absorbance in the region related with oil, protein, and carbohydrates. With the use of partial least squares discriminant analysis (PLS-DA) and selection of specific wavelengths, three classification models were developed. The calibration models have false-positive and false-negative error rates ranging between 12.4 and 16.1% and between 10.6 and 17.2%, respectively. The percent error rates ranged between 8.2 and 9.2%. Second-derivative preprocessing of the selected wavelength resulted in the most robust predictive model.

The composition of phenolic compounds plays an important role in food science and nutrition; thus, there is a need of a new method of analysis that is able to speed up the monitoring of product quality parameters. In this view, the amount of selected color components of 145 commercial red wines (total wine color, polymeric pigments, total anthocyanins, and copigmentation index) was investigated using Fourier transform mid-infrared spectroscopy (MIR) combined with partial least squares (PLS) regression. The feasibility of several preprocessing algorithms (first and second derivative, standard normal variate, and direct orthogonal signal correction) was compared in terms of coefficient of determination (R2) and root mean square error of prediction using an independent test set of wines. The composition of red wines showed great difference in terms of total color (5.07 ± 1.95 AU at 520 nm) compared to copigmentation index (0.66 ± 0.58 AU at 520 nm). The best prediction model was obtained using direct orthogonal signal correction (DOSC) preprocessing. In particular, the prediction of total wine color, total anthocyanins, and polymeric pigments showed a good fitting (R2 ≥ 0.82), whereas copigmentation index was more difficult to be predicted by FTIR (R2 = 0.57). This preliminary study showed the potential of MIR spectroscopy with DOSC–PLS algorithm to successfully analyze selected color components of red wine on a large number of samples in short time with almost no sample preparation and no chemical waste is created.

Multivariate statistical modeling was used to identify significant correlations between several chemical constituents and physical properties of wine and its perceived body or viscous mouthfeel. Seventeen white wines that span an anecdotal range of perceived viscous mouthfeel, including Chardonnay, Viognier, Pinot gris, Riesling and Sauvignon blanc, were assessed using a descriptive analysis technique to determine quantitative ratings of viscous mouthfeel. These wines were also submitted to a wide range of chemical constituents and physical property analyses, including viscosity, density and concentrations of ethanol, total phenolics, organic acids (lactate, citrate, tartrate, malate, succinate), glycerol, sugars (fructose and glucose), total extract, and several inorganic anions and cations. The multivariate statistical model shows that the viscous mouthfeel of these white wines is significantly correlated with physical properties, such as viscosity and osmotic potential, chemical properties, such as lactate and total extract. This work is also consistent with previously published results from other researchers indicating that ethanol and glycerol do not significantly contribute to viscous mouthfeel. PRACTICAL APPLICATIONS This research provides evidence that panelists can differentiate the mouthfeel of wines that span a relatively narrow range of viscosities. The results were also correlated with various chemical and physical properties of wine. Sensory and analytical measurements such as these could provide a link from viscous mouthfeel to viticultural and winemaking practices of wine.

The influence of cultivar, growing region and method of vinification (industrial vs. laboratory) on the protein profiles of white wines of Portuguese and Austrian origin was comparatively analysed. The profiles were obtained by fractionation of the wine samples using anion exchange HPLC, resulting in fifteen fractions. A principal component analysis (PCA) was performed by considering the percentual peak area as the input factor and the results showed that there is a relationship between the occurrence of some of the protein fractions identified. Clustering techniques indicated that cultivars and the region of production were the factors that had a significant influence on the protein profile of a given wine, the former being particularly predominant. Les proteines du vin sont une cause majeure aux problemes de stabilisation chimique des vins blancs et roses mais le profil proteique et la relation avec les problemes d'instabilite ne sont pas encore compris. L'objectif de cette etude est de tester l'hypothese que le cultivar, la region geographique et la methode de vinification pourraient influencer les profils proteiques, en utilisant la methode quantitative d'analyse des amas. Dans la derniere partie, 2 extremes sont considerees: la microvinification en laboratoire et une similaire vinification industrielle. L'analyse des relations entre l'occurence de differentes fractions proteiques est aussi realisee. Les resultats indiquent que le cultivar principalement et aussi la region de production sont les facteurs qui ont une influence significative sur le profil proteique d'un vin.

The monomeric and polymeric pigments of 20 young red wines were analysed using most recent of the approaches available for phenolics measurements in wine, including: (i) HPLC with silica-based reversed-phase, (ii) HPLC with polymeric-based reversed-phase columns, (iii) the spectrophotometric Adams’ tannin and polymeric pigments assay, (iv) the Boulton’s copigmentation assay, and (v) the Somers’ unbleached polymeric color assay. Moreover, a modification of an existing HPLC method, i.e. the addition of SO2 to the mobile phases, allowed the unbleached polymeric pigments to be analysed by HPLC for the first time. The wines displayed a variation in their color density at 520 nm that ranged by 10-fold, and included wines made from Pinot noir, Merlot, Cabernet sauvignon, Cabernet franc, Sangiovese, Cagnulari and Cannonau grapes. The total color of wines was an aggregate number of three components: copigmentation (8–30%), total free anthocyanins (24–35%), and polymeric pigment (35–63%). Cross-comparison between the selected method was performed and discussed. In particular, the polymeric pigments estimated by HPLC with polymeric-based reversed-phase column were in good agreement with the result of the reversed-phase C18 column (R2 = 0.9703) and the sum of small and large polymeric pigments estimated by the Adams’ assay (R2 = 0.9511). The level of copigmentation can be almost completely described by the levels of monomeric pigments (R2 = 0.9464) and not by the tannin content as has often been suggested (copigmentation vs tannin: R2 = 0.4827).

Headspace solid-phase microextraction (SPME) and GC-MS were used to analyze 17 commercial French Cognac brandies (9 young and 8 well-aged, ranging in age from 3 to 55 years). Sixty-four volatiles were chosen on the basis of chromatographic separation and/or known odor importance. Chromatographic peaks were manually integrated and the peak area data analyzed using partial least-squares (PLS) regression to study relationships between volatile composition (X variables) and age (Y variable). When only those compounds with the highest significance were included and from these selected the variables (a total of 33) with the highest correlation loadings on the first two principal components, principal component 1 explained 82% of the variance of the measured compounds and 85% of the variance in age. These were considered the most important volatiles to distinguish products of different ages because young and old samples were separated along principal component 1. Norisoprenoids, terpenes, and acetate esters had weaker positive and negative loadings and were therefore left out. The PLS model could predict sample age accurately with the optimum 33 volatiles as well as with a smaller subset consisting of ethyl esters and methyl ketones.

The copigmentation effect of prefermentation additions of different doses of caffeic acid was investigated during the 1997 harvest. Microfermentation with the major red grape cultivars Listán negro and Negramoll, grown in the Canary Islands, was carried out with the same protocol. Visible and UV spectra were registered periodically. HPLC chromatograms were carried out. The color enhancement of cv. Negramoll wine varied between 13 and 75% (AU at 520 nm), and that of cv. Listán negro wine between 25 and 45% at the end of fermentation. During aging these values were enhanced to reach even100% in some cases. An initial complex of the 1:1 type, where one molecule of caffeic acid associates with one molecule of anthocyanin, has been identified using the mathematical procedure of Brouillard et al. (J. Am. Chem. Soc. 1989, 111, 2604-2610). Caffeic acid seems to contribute to color stability and protection against oxidation. The importance of nonpigment composition in pigment extraction and color retention during and after fermentation is demonstrated.

The protein profiles of two different wines of Austrian and Portuguese origin, characterized by HPLC fractionation, were compared before and after ion-exchange adsorption of the wine proteins. Conventionally used sodium bentonite and three alternative nonswelling commercial resins were used. Profile similarity was assessed in terms of the Euclidean distance of all protein peak areas for two samples, and of the average of the differences between each protein peak percentile area between two samples. In general, the differences between profiles for the same material increased with the amount of wine adsorbed, showing that some protein fractions were more easily adsorbed than others. Differences between the adsorption with bentonite or with the alternative adsorbents were not statistically significant, with the exception of one adsorbent in one of the wines, where protein removal was more extensive.

The effects of pre-fermentation additions of catechin and caffeic acid to musts were investigated. The cultivar Listan negro, a major red grape grown in the Canary Islands, was used for these studies. The addition of catechin at 120 mg/l resulted in only 10% enhancement in wine colour (AU at 520 nm) after fermentation, while caffeic acid, at the same level, enhanced the wine colour by 60%. These results appear to be the first report of such a significant increase in wine colour achieved by pre-fermentation treatments with natural grape constituents, supporting the view that red wine colour is generally limited by the levels of cofactors for copigmentation rather than by the level of anthocyanins alone. This demonstrates the importance of non-pigment composition in establishing red wine colour and the influence of initial must composition.

The influence of intrinsic factors on the results of ethanol, tannin and heat tests, routinely used to assess wine protein stability, was studied. Experiments were performed on 23 Portuguese and Austrian wines. The factors considered were total protein content, pH, ethanol content and the amount of several relevant cations (calcium, iron, copper, sodium and potassium). The protein profiles were analysed by HPLC fractionation. The heat test was a good indicator of total protein content while the ethanol and the tannin tests showed significant interference by the other factors. A factorial design at two levels in selected samples was also performed to assess the influence of pH, storage temperature, tannin concentration and ethanol concentration on the development of turbidity. Results indicated that ethanol content had no significant influence, and that pH and storage temperature had a significant influence, though only when tannin was added.

An easy and sensitive method for the analysis of glutathione (GSH) and other thiol-containing compounds in grape juice and wine has been developed and optimized. Following a pre-column derivatization of thiols with o-phthalaldehyde (OPA) and 2 aminoethanol, isoindole derivatives are separated on reversed-phase HPLC column and quantified by a fluorescence detector. The minimum detection limits for thiols are: GSH, 3.3 nmol/l (1 μg/l); cysteine, 22 μmol/l (2.7 mg/L); methanethiol, 0.27 μmol/l (12.8 μg/l); ethanethiol, 0.65 μmol/l (11 μg/l). The method yields linear responses up to 40 and 21 mg/l for GSH and cysteine, respectively. GSH levels in two varietal grape juices during fermentation varied from 0 (starting juice) to 2.1 mg/l (wine) in Sauvignon blanc, while the GSH in a Palomino sample with 1.28 mg/l in the juice increased to 5.1 mg/l in the wine. This automated pre-column derivatization of thiols followed by an automatic injection procedure is sensitive, reproducible and rapid, with a run time of 35 min.

A general mathematical model for the temporal intensity response to a transient sweet stimulus was developed. The model is a set of nonlinear ordinary differential equations, expressing the rates of diffusion across a saliva boundary layer and adsorption and desorption to receptor site proteins on the taste bud cells. In this model, the perceived intensity is considered to be the product of a scaling factor and the amount of stimulus bound to receptor sites at any given time. A parameter estimation routine was used to fit the differential equations to the time–intensity (TI) curves for five equisweet stimuli (sucrose, aspartame, thaumatin, monellin, and brazzein). Model parameters were computed for each of 19 trained judges. The predicted TI curves were close to the observed time-intensity responses for all judges and sweeteners. TI parameters varied significantly across both judges and compounds, while model predicted parameters, such as adsorption and desorption coefficients, varied significantly only across compounds. Except for one model parameter (predicted plateau time), there were no significant differences across judges for the model-predicted parameters, indicating that all judges responded similarly to each compound.

Adsorption of wine proteins is an essential step in the production of white and rose wines. In order to develop environmentally friendly adsorption processes, non-swelling adsorbents are required. The performance of selected non-swelling ion-exchange resins (Macro-Prep™ 50S and Streamline® SP) was studied by describing the process kinetics of the adsorption of BSA in a model wine solution. The process was assumed to be diffusion controlled and a shrinking core model was applied. Experiments were performed in the 5–35°C temperature range and with different equilibrium partition coefficients. The results obtained with the shrinking core model were theoretically consistent and the apparent diffusivity values correlated very well with theoretically estimated effective diffusivities combined with a linear dependence of porosity with temperature. Separating the temperature effect on porosity, the apparent diffusivity followed an Arrhenius type dependency with temperature with 16.9 kJ/mole activation energy.

Stimulation by oral manipulation or ingestion of stimuli causes the salivary flow rate to increase. Not only do gustatory stimuli affect salivary response, but saliva in turn can affect perception of taste by titration, dilution, or precipitation of stimuli. Average bitterness and astringency time-intensity (TI) curves and individual TI parameters generated in response to wines varying in ethanol, pH and phenolic composition revealed differences in temporal perception among the salivary flow groups. For both attributes, low-flow (LF) subjects took a longer time to reach maximum intensity and had a longer duration than high-flow (HF) subjects. For wines with tannic acid at pH 3·0 and pH 3·6, LF subjects recorded a higher intensity at maximum of bitterness and astringency than HF subjects. This perceptual difference was more pronounced at pH 3·6, where a greater difference in salivary flow rate was also elicited between flow groups. The log intensity decay curves for bitterness and astringency were linear, suggesting that a first-order decay process governed the perception function. Desorption is thus considered to be the primary phenomenon, rather than diffusion through a boundary layer. For all flow groups, the decay constants for bitterness were higher than those for astringency. However, the decay constants within one modality were similar for all flow groups, indicating similar desorption rates. Reciprocal plots of salivary flow rate were linear, suggesting that a second-order process governed salivary flow.

The feasibility of utilizing infrared spectroscopy for the prediction of haze formation in white wines resulting from heat and colloidal stability tests was investigated. One-hundred eleven white wines, representing multiple regions and varieties from the 2008 California vintage, were collected and analyzed. The near and mid-infrared spectra were measured and heat and colloidal (ethanol addition) stability tests were performed on the same wines. Partial-least squares regression analysis was then used to construct models predictive of the resulting nepholometric turbidity to the acquired spectra. Preliminary models obtained following application of spectral pretreatments today considered as “classical” (e.g., derivatives, standard normal variate, vector normalization, constant offset elimination) lacked robustness; two alternative algorithms designed to remove spectral information unrelated to the turbidity were then employed (orthogonal signal correction; direct orthogonal signal correction). While OSC pretreatment did not result in more robust models, DOSC considerably enhanced the goodness of the PLS model constructed to predict the ethanol test turbidity. Predictive modeling of the short-NIR spectra, following DOSC preprocessing, allowed the prediction of colloidal stability on an unknown test set with an R 2 = 0.80 and a RMSEP = 10.12 using three latent variables. When the data set was restricted to Chardonnay wines alone, the predictive ability improved, with R 2 = 0.85 and RMSEP = 8.90.

Summary The protein adsorption capacity of different materials was evaluated to assess their potential efficacy as alternative adsorbents for the removal of proteins from wines, with the purpose of finding suitable low-swelling materials that could be used in a percolated bed. The adsorbents tested were thermally treated sodium bentonite, low-swelling adsorbing clays, ion exchange resins and other protein adsorbents (silica gel, hydroxyapatite and alumina). The materials were evaluated by analysing both the capacity to stabilize untreated white wines, according to a heat test, and by characterizing the adsorption isotherms of bovine serum albumin (BSA) in a model wine (water, ethanol and K-bitartrate). Breakthrough curves in a packed bed were determined experimentally for some materials, showing the influence of the adsorption isotherm shape. Some ion-exchange resins showed a favourable behaviour and have good potential as alternative adsorbents.

The bottling of wines is arguably the most important of all winemaking operations since it determines the condition in which the wine is delivered to the market. It is the culmination of the sequence that began long before, starting with grape development, harvesting, fermentation, and aging. Mistakes are costly to rectify and quality control is of primary importance.

This chapter includes the descriptions and origins of various kinds of microbiological spoilage organisms—and the prevention of their presence and the control of their growth if present. It is important for the winemaker to know which spoilage has occurred in any given instance and to understand potential spoilage problems, but obviously it is better to forestall spoilage than to diagnose it. The taxonomic identifications of the yeasts are given in Chapter 4, and the lactic acid bacteria in Chapter 6. For the aerobic bacteria, the taxonomies are given at the end of this chapter.

Viticulture is a science and technology separate from enology and winemaking per se. It has its own extensive literature. References that give more detail than possible here as well as additional perspectives include fairly recent examples in English from several different countries (Coombe and Dry 1988; Jackson and Schuster 1987; Pongracz 1978; Wagner 1976; Weaver 1976; Winkler et al. 1974). Examples in other languages from major wine-producing countries can also be useful (Champagnol 1984; Galet 1988; Huglin 1986; Reynier 1989; Altman 1987; Currle et al. 1983; Kadisch 1986; Ferraro-Olmos 1983; Larrea-Redondo 1981; Fregoni 1985; Saracco 1984). Although wine-makers should know as much as possible about viticulture, the professions are so demanding that it is difficult to be fully expert in both.

In total, wine aging can be considered to be all the reactions and changes that occur after the first racking that lead to improvement at some stage rather than spoilage. Aging, like all groups of reactions, takes more or less time depending upon temperature and other conditions. In early times malolactic fermentation, final clarification, and tartrate stabilization come about during the postfermentation period and were part of “aging.” As the details of such reactions became understood they were separated from aging and considered in their own right. This process continues today as separate reactions of the overall process are dissected apart. A great deal has been learned by studying various component reactions, conditions, and procedures. By such study, wine aging is easily seen to be not an entity but a family of changes. Wine aging should not be thought of as a single procedure nor even a single result.

The acidity of a juice or wine, in particular the pH, plays an important role in many aspects of winemaking and wine stability (see also Chapters 3, 8, and 12). The ability of most bacteria to grow, the solubility of the tartrate salts, the effectiveness of sulfur dioxide, ascorbic acid, and enzyme additions, the solubility of proteins and effectiveness of bentonite, the polymerization of the color pigments, as well as oxidative and browning reactions are all influenced by the juice or wine pH. The titratable acidity is an important parameter in the sensory evaluation of finished wines. It and the pH are also important in aging reactions.

The transformation of grape juice into wine is essentially a microbial process. As such, it is important for the enologist to have an understanding of yeast and fermentation biochemistry as the fundamental basis of the winemaking profession. The alcoholic fermentation, the conversion of the principal grape sugars glucose and fructose to ethanol and carbon dioxide, is conducted by yeasts of the genus Saccharomyces, generally by S. cerevisiae and S. bayanus. The current use of the old term bayanus for the yeast closely related to S. cerevisiae is controversial (see Section A3c); but we expect bayanus to become once more an accepted appellation (Vaughn-Martini and Kurtzman 1985).

This chapter deals with the transfer of musts, juices, and wines by the energy imparted by mechanical pumps and by pressure differences. The various pumps that can be used are described, as well as the manner in which they are used. The calculation procedures for the sizing of pumps and of estimating flow rates are presented, together with typical examples.

The purposes of clarification and fining during wine processing include removal of excessive levels of certain wine components, achieving clarity, and making that clarity stable especially from a physicochemical viewpoint. The noun fining is used in winemaking to describe the deliberate addition of an adsorptive compound that is followed by the settling or precipitation of partially soluble components from the wine. The materials used for these reasons are collectively referred to as fining agents, even though the solutes that they address and the mechanism of their removal vary considerably. The need to employ such treatments is often determined not only by compositional aspects of the musts but also by the winemaking practices that have been employed.

There are several aspects of wine fermentations that are of general interest and these will be considered in detail before consideration is given to the major wine types. The addresses of equipment companies mentioned in this chapter can be found in Appendix I.