Enology II Winery Technology & Operations Yair Margalit

Enology II Winery operation flow charts (pgs x-xii)

Enology II Grape Ripening: The maturity definition of the grapes (or more specifically the time to harvest) is not a simple and clean-cut decision; it depends on many factors, such as the variety of the grapes, the appellation (soil and climate), the weather during the last days or weeks before the prospective time of harvest, the bunch health (mold infection), the vineyard disease state, and the style of wine to be made.

Enology II Sugar: the main sugars in grapes are D-glucose and L-fructose, generally in a 1:1 ratio, with fluctuations of plus or minus 30 percent, depending on the variety and maturity of the grapes.

Enology II In grapes infected with Botrytis Cinerea mold, the ratio is in favor of fructose, which is twice as sweet as glucose.

Enology II During fermentation with most yeast strains, the consumption of glucose is faster than that of fructose, and toward the end of fermentation, most of the residual sugar is fructose.

Enology II Units which are used to measure the solid concentration are: Brix (or Balling) – percentage of soluble solids in 100 grams of solution (grams of solid/100 grams of solution) Baume – percentage of potential alcohol, or more specifically, the potential alcohol in grams/100mlof wine. Oechsle – the density difference between the sample and water.

Enology II Brix (measured by density) includes all solid materials in the must (sugar, acids, salts, proteins, pigments, etc.) the approximate percentage of pure sugar content can be estimated. % Sugar (w/v) = (Brix-2.1) x density

Enology II The sugar is converted by the fermentation, mostly to ethyl alcohol and carbon dioxide: C 6 H 12 O  2 C 2 H 5 OH + 2CO gram 92 gram 88 gram

Enology II By the molar ratio of the products to the substrate (sugar) 51% of the sugar would be transformed into ethyl alcohol. In practice, part of the sugar is utilized by the yeast itself, and part is converted to other products (higher alcohols, aldehydes, esters, acids, etc.)

Enology II The final ethanol content is also dependent on the temperature of fermentation due to evaporation losses.

Enology II Acids: the main acids in must are L(+) tartaric acid and L(-) malic acid. The tartaric acid is almost unique to vines, while malic acid is quite common in many fruits.

Enology II During the advanced maturing process, toward the end of stage III, the concentration of malic acid decreases gradually by respiration, while that of tartaric acid remains practically constant.

Enology II Another acid which exists in the must in a comparable amount is L-citric acid with concentration range between gram/L.

Enology II The most important parameter reflecting the acidity in the must is the pH. The pH of grape juice at maturity runs from pH – 2.9 to 3.8

Enology II Example: This means that tartaric acid releases H+ at this pH, almost three times more than the malic acid does. It is clear that tartaric acid is the strongest organic acid in the must and, being at the highest concentrations is the main source of proton ions.

Enology II During the ripening period, as the malic acid concentration decreases, the potassium ion concentration increases up to gram/L, the net result of these changes is that the pH gradually increases.

Enology II As for the acidic taste, it has been found that at the same pH, the acidic taste increases in the following order: tartaric< citirc< malic. This order is obvious, because it requires reduced acid concentration (less tartaric than malic) to produce a certain pH number, according to the order of the PKa’s values.

Enology II The total concentration of acids in must or wine is determined by titration with sodium hydroxide solution. The common expression for the total titratable acidity (TA) value, is as tartaric acid (molecular weight M = 150), or as sulfuric acid (M=98).

Enology II In any method used to determine maturity, there is practically no need to start the observations before the grapes have reached Brix. Te ration Brix/total acidity is a parameter that increases with time, because the sugar is gradually accumulated while the malic acid decreases.

Enology II Another method takes into account only the sugar development and the loss of water per berry. It is bases on the product of PxS where: P = weight of a certain and constant number of berries, 200 to 500 (at any weight unit), and S = the average Brix of those berries. Fig A.3 (pg 8)

Enology II Another method emphasizes the varietal character development of the grapes. In this method, the most important parameter is the varietal aroma and flavor, and the Brix limits are a general recommended range.

Enology II The full varietal flavor of the grape is most important in order to achieve the maximum varietal character in that wine. This method needs the experience and the ability to project the grapes’ flavor and taste into the finished wine.

Enology II There are some more complicated methods which reflect the ripening development, such as measuring the tartaric/malic acids ration, the polyphenolic compounds development, or the potassium development, but none of these methods include a conclusive precise assessment of the maturity timing.

Enology II In cold growing regions where grape ripening is a well known problem the major wine quality parameter is the Brix content of the grapes at harvest.

Enology II Brix(TA)pH ranges (pg. 10)

Enology II In certain places and certain years, weather conditions (cool summer, cloudy skies) may cause a delay in the ripening, and if the delay is accompanied by rain and high humidity, the grapes will probably be infected with mold, which might get worse as the harvest is delayed. Under such conditions there is no alternative but to harvest before the full development of the sugar and flavor.

Enology II Sampling: the technique of sampling is very crucial in order to get a real representation of the grapes’ degree of ripeness. First, the distribution of the major components in the cluster is not even. The top berries on the cluster are higher in sugar than the bottom ones. The clusters themselves are not even in their development, depending on their location on the vine, the amount of light they are exposed to, and the location of the vine in the vineyard.

Enology II Usually the sugar concentration is higher closer to the skin and drops down toward the center of the berry. The acids’ concentration follows the opposite trend.

Enology II The sampling technique which might give quite a good picture on the grapes maturity is to collect berries, each one from different cluster locations on the vine, lighted and shadowed, from both sides of the rows, and from different vines in the area.

Enology II The number of berries collected as a sample will reflect the range of error in that sample. Two hundred and fifty berries will set the Brix measurement within plus/minus 1 Brix range at 95% confidence, while 500 berries will set it to plus/minus.5 Brix

Enology II Composition and yield: The overall weight composition of the grape clusters is: Stems2-6 % Seeds0-5% Skins10-20 % Must70-80%

Enology II Must composition: Water75-85% Sugar17-25% Organic acids.4-1.2% Other dry extract.3-1.0%

Enology II Every ton of grapes red or white, one should get about cases of quality wine filled in 750ml. Bottles, at 12 bottles per case.

Enology II The winery policy for the coming season would be set up before planning the major aspects of the winery operation. This should include the following points: Types of wines to be produced Quantities of each type Grapes source (quantities, quality and prices) Marketing prospects; Availability of manpower for the crush season.

Enology II From the veraison tie up through the harvest, vineyard management has a close relation with the wine quality and wine production and should come to the winemaker’s attention.

Enology II Chemicals used against different kinds of insects, fungus, and bacteria: When sulfur dust is carried by the grapes into the wine, it may cause production of hydrogen sulfide, which has a very unpleasant odor.

Enology II Bordeaux Soup (Mix) will carry copper into the must, and may later cause copper hase in the wine.

Enology II In order to prevent all these chemicals from being carried onto the grapes and into the wine, their use should be terminated around the time of veraison.

Enology II Irrigation: if irrigation is continued up to harvest, it may dilute the dry extract of the berries and reduce the grape quality; very careful inspection should be carried out with regard to the irrigation regime.

Enology II From the time of veraison it is important that the clusters are not over-shadowed. Light exposed berries develop better flavor and higher-sugar level than the shaded berries.

Enology II It is good practice to prune long shoots, clearing the way in the vineyard and also decreasing some of the shadow areas on the vine. It is recommended that this pruning be done about 2 to 4 weeks before harvesting, depending on the vigor growth of the vines.

Enology II Harvest: the main disadvantage of mechanical harvesting is that the major portion (80-90%) of the berries’ skins are broken, releasing the juice into the container. Only when the crop yield is large enough is it economical to mechanically harvest. The break-even point is around four tons per acre.

Enology II It is also recommended when hand harvesting, to harvest from very early in the morning until noon to pick the grapes at cooler temperatures.

Enology II Preparing the winery for harvest: (pg 16-17) Tanks Cooling system Barrels Machines Chemicals Lab Equipment

Enology II The purpose of destemming is to separate the stems from the must, because they contain very high levels of tannins, and may contribute a hard “vegy” or “green” flavor to the wine, if fermented with the must.

Enology II The purpose of crushing is to break the berries’ skins allowing the release of the juice either by pressing (in white must) or by fermentation (in red).

Enology II During the mechanical treatment of the must, the absorption of oxygen is very intensive because of the large surface area that the must is exposed to air by the mechanical operation. The oxidation and hence browning of white must is very fast, especially if the must temperature is not low enough (10 C) and is considered detrimental to the quality of the wine.

Enology II If skin contact is desired, the must can be transferred through heat exchanges in order to lower the temperature to about 10 C and then to a drainer or to a storage tank.

Enology II If “blush wine” is to be made from red grapes, the must is transferred from the destemmer/crusher through the heat exchanger to the press. The red skins of the blush juice, coming out of the press, can be added to the must of a red wine (in fermentation stage), to enhance color, tannin and body, if it is desired.

Enology II In certain cases it may be considered to use the stems to enhance the tannin level and to add complexity to the wine. The must containing the stems is blended later with the rest of the destemmed win.