by Charles Nagel and Joseph Powers,
Despite the claims of some that good wine can be made only by experts, the amateur can produce high quality wines at home. In fact, thousands of people have found that satisfactory wine can be prepared at home with easily obtainable materials.
Wine in the simplest terms is the product of the fermentation of fruit juice by yeast. During fermentation, yeast converts sugar into roughly equal amounts of alcohol (ethanol) and carbon dioxide (CO2) along with numerous minor by-products. This bulletin tells you about some common problems in home winemaking, what materials you'll need to get started, and how to go about making red, white, and fruit and berry wines.
A very important factor, often overlooked by home winemakers, is good sanitation. The point of good sanitation is to ensure that a clean fermentation occurs without contamination of the juice with wild yeast or other microorganisms that can spoil the wine by causing off-odors or flavors.
Consistent winemaking success depends on making sure all of the equipment coming into contact with the juice and/or wine is properly sanitized. Clean the equipment with a warm, nonodorous detergent solution, then scrub, if necessary, and finally, rinse several times, preferably with hot water. A rinse with a dilute bleach (hypochlorite) or sulfur dioxide (SO2) can also be used as a final sanitizing step. (Keep in mind that hypochlorite tends to corrode stainless steel. Fresh, clean water should be used as a rinse.) See Sulfur Dioxide section for more information about SO2 page 4.
Sanitize bottles with a final rinse with a 200 parts per million (ppm) SO2 solution. Drain the bottles thoroughly. Sanitize corks by soaking them in a 200 ppm SO2 solution or by boiling them in water. Afterward, handle the corks only with sanitized tongs.
Avoid touching sanitized equipment surfaces or the juice, since the hands are an abundant source of microorganisms, particularly of lactic acid bacteria which can spoil the wine. Don't use your mouth to start the siphoning action during the final stages of winemaking. Instead, use a sanitary suction bulb or an uncontaminated hose.
Also be on the alert for Drosophyla melanogaster, the fruit fly, a common source of wine infection. This source of contamination can be controlled to a great degree by simple good housekeeping. During fermentation of red wines, cover the vessels with a clean sheet or other cloth to keep the flies away. Clean up all spills immediately. Finally, and perhaps most importantly, remove pomace, skins, seeds, etc., from the winemaking area immediately after pressing.
A second pitfall often encountered by the home winemaker is oxidation. After the primary fermentation, in which large amounts of protective carbon dioxide gas (CO2) are produced, you must take precautions to minimize exposure of wine to air. In the finishing vessel, this is done by filling the containers as full as possible and using air traps.
There are several types of air traps. Most depend on water as the air lock. The trap allows carbon dioxide to escape while preventing air from entering the vessel. You can easily make a water-type air trap from glass or plastic, or purchase one from a wine shop.
A second type of air trap, which does not use water, can be made by using thick-walled surgical tubing. First slit the tubing longitudinally for 1/2 to 1 inch with a razor. Then plug the tubing at one end with a short length of glass rod or other clean dowel or plug. Attach the other end to a glass tube inserted into a rubber stopper of a size to fit the container being used (Fig. 1). If the rubber tubing is thick enough and slit properly, it will allow expulsion of gases from the container, but will not allow air to enter.
During the finishing of the wine-racking (siphoning), addition of fining agents, etc.take care to minimize aeration. For example, when racking, the siphon hose in the receiving vessel should be below the surface of the wine (Figures 2 and 3). However, when hydrogen sulfide (H2S, "rotten egg smell") is detected, deliberately aerate the vessel to remove the odor.
The main determinant of the quality of any wine is the fruit used in its production. Always use high quality, sound fruit. This is not to say that overripe fruit cannot be used. However, avoid fruit that shows excessive browning or contains obvious rot or mold. Cut out diseased portions of the fruit prior to crushing and extracting the juice.
Often, fruit used for winemaking does not contain enough sugar to produce the desired 10% to 12% alcohol. Table 1 shows the amount of sugar addition and the resulting volume required to adjust the sugar content to 23° Balling, which should ensure at least 12% alcohol if the mixture is fermented to dryness. If a lower alcohol content is desired, adjust the fermentation process roughly on the basis of a 2-to-1 ratio of sugar-to-alcohol yield.
Among the most common problems with home wines is the juice has not been properly adjusted for acid content. For "light" wines, the acid content should range between 0.65% and 0.8% (expressed as tartaric acid, weight/volume basis). In sweet wines, acid contents of 1.2% or more are acceptable. In highly pigmented wines, which usually contain a large amount of tannin compounds, the acidity can be considerably less, since the tannins seem to compensate for the lack of acidity. Therefore, in "heavy" red wines, an acidity of 0.5 % to 0.7% is generally acceptable. Again, higher acidities are tolerated in sweeter wines. In fact, sugar will aid considerably in making a harsh acid wine taste less harsh and more rounded.
Table 2 shows the average sugar and acid contents of a number of fruits used in winemaking in the Pacific Northwest. Excluded from the table are grapes. Generally, if the grapes are produced in central Washington, little adjustment will be necessary. If the grapes are grown in western Washington, however, they usually do not reach full maturity and often require sugar addition as well as acid reduction.
The values in Table 2 are average values and can vary considerably depending upon the variety of fruit used. For example, Bing cherries are generally low in acid and may require acid addition, while Royal Ann cherries are relatively high in acid and often require both sugar addition and acid reduction. Apple varieties are similar. Red Delicious are quite low in acid and may require acid addition, whereas MacIntosh or Winesap tend to have enough acidity.
Other fruits not listed in the table are peaches, apricots, and pears. Peaches and pears tend to have sugar and acid contents similar to apples. When overripe, however, these fruits often require acid addition.
While wild yeasts are found on most fruit, and they may be used in a "natural" fermentation, they are not a reliable source. A more controlled, predictable fermentation is usually attained with purchased wine yeast. You can buy wine yeasts of several types from wine supply houses, usually in a dry granular form.
Certain wine yeasts are propagated as pure strains and are often named after the region from which they were originally isolated. However, do not presume that by using a certain wine yeast strain (such as Montrachet), a wine will result characteristic of the region name. Wines for which a region may be famous are a result of many factorsonly one of which may be the yeast.
Sulfur dioxide is discussed here separately since it is most important in the preparation and preservation of wines. SO2 is used in wines because it prevents oxidation. It is also a selective antiseptic that prevents the growth of undesirable microorganisms, including wild yeast, while allowing wine yeast to grow.
If you obtain Campden tablets from a wine supply shop as a sulfur dioxide source, instructions are usually supplied to indicate the amount necessary to obtain a certain concentration of SO2. If you buy sodium bisulfite (NaHSO3), sodium metabisulfite (Na2S2O5), or potassium metabisulfite (K2S2O5), a simple calculation is necessary to determine the amount necessary to generate a given amount of SO2. These sulfite salts are 61.5%, 67.4%, and 57.6% SO2, respectively.
For example, a 100 ppm (0.01%) SO2 solution from K2S2O5 is equivalent to 0.1 gram SO2 per liter. Hence, 0.1 gram divided by 0.576 equals 0.1736 gram K2S2O5 to make 1 liter of a 100 ppm SO2 solution. In gallons (1 gallon = 3.78 liters) 3.78 multiplied by 0.1736 equals 0.66 gram per gallon. For addition of small amounts of SO2, it is convenient to prepare a concentrated solution which can then be transferred through a pipette (a narrow glass tube) according to the volume and amount of SO2 desired. For example, you can prepare a solution containing 100,000 ppm (10%) SO2 by weighing out 17.1 grams sodium bisulfite, 14.8 grams of sodium metabisulfite, or 17.4 grams of potassium metabisulfite and dissolve with enough water to make up a 100 milliliter solution. Thus, in order to obtain a 100 ppm concentration, either add 1 milliliter of the concentrate to 1 liter of juice or wine or 3.78 milliliters to a gallon.
|Stemmers and Crushers|
The sophistication of equipment used in winemaking depends largely on the volume and type of ingredients you wish to use.
To make high quality white grape wines, remove the stems before fermentation. The stems contain a large amount of tannic material which can lead to an overly astringent wine. With small amounts of grapes, you can remove the stems by hand. With certain red wines it may be desirable to leave some stems in the "must" (the juice before fermentation).
To prepare grapes for fermentation, the berries must be crushed. It is preferred they only be crushed enough to break the berry and force out the pulp and seeds. If you macerate the skins and seeds the wine may be highly astringent and difficult to press. A roller-type crusher is recommended. This tool, however, can be relatively expensive. For small amounts you can use a wooden plunger and a suitable container. If you wish to prepare a pulp from stone fruits, (peaches, apricots), any machine, such as a blender, can be used after you remove the pits. One of the simplest crushing devices is the conical sieve arrangement used in the homemaking of jellies and jams in which the material is crushed with a wooden roller and forced through the sieve.
The simplest type of press for home use can be improvised using a coarse cloth or gauze sack. Place the crushed fruit inside the sack, then close the sack by tying and suspending it overhead. If you let the sack hang for an hour or two, a considerable amount of juice will drain without applying pressure. Apply pressure by twisting the sack to produce higher yields.
A more sophisticated piece of pressing equipment is the basket or cider press. The choice of size depends on the size of the operation. Although the initial investment may seem high, a press is justified if you expect to make wine year after year. The operation is much faster, and a press yields more juice, particularly from such readily pressable fruits as grapes and apples.
|Primary Fermentation Vessels||Since fermentation produces carbon dioxide, you can use open containers during this process. This may be desirable in cases where the juice has not yet been separated from the solids, as in red wines. Use any food-grade, easily cleaned containers such as crocks or large plastic containers. Plastic containers are easily cleaned, virtually unbreakable, and if the proper plastics are selected, nontoxic. Loosely place some type of lid or cover on top to prevent exposure of the fermenting material to contamination from the environment.|
Once the vigorous stages of the fermentation are completed and the juice has been separated from the solids, transfer the juice to closed containers with some type of air trap to minimize exposure to air. The ideal container is the glass jug. You can usually find gallon jugs or smaller bottles at garage sales, second-hand stores, or even recycling centers. Keep several jugs on hand. More convenient are the 5-gallon carboys commonly used for distilled water readily available in most winemaking shops. Use glass containers, not plastic. Glass containers can be readily inspected for cleanliness. You can also easily observe the progress of the fermentation and clarification of the resultant wine.
All finishing vessels must be easy to clean, incapable of imparting off-flavors or odors. Select plastic containers carefully, since some contain toxic materials.
|Racking Materials||During the finishing of the wine, solid materials settle out of the wine. Thus, you must "rack" or siphon off the clear wine without disturbing the solids on the bottom (see Figures 2 and 3). Clear plastic hoses of Tygon or similar material are convenient for this operation. Attach the hose to a bent glass or plastic tubing placed in the container and hold it so that it does not disturb the solids on the bottom. With a transparent hose, you can observe the operation more easily and can determine when debris is being siphoned.|
After a number of rackings, the unfinished wine may not yet be crystal clear. Thus, you may need to fine to remove the remaining small suspended particles from the wine. The most common fining agents are bentonite and Sparkalloid. Bentonite is an aluminum silicate clay which will strongly bind proteins and form a floc (a light fluffy mass) that will absorb colloidal material on its surface and then settle out of the solution. To use bentonite effectively, moisten it well before use. Heating helps hydrate it. Prepare a bentonite solution at least one day in advance. Normally, winemakers prepare a 6% solution (about 2 ounces per quart, or 60 grams per liter). Directions for use of Sparkalloid (a proprietary agent) are usually supplied with the material.
For highly tannic wines, which include highly pigmented red wines, use a protein fining agent. The protein combines with tannins and forms a floc. This can reduce the astringent character of a wine. The most commonly used protein fining agents are gelatin, casein, and egg white.
With bentonite, casein, or gelatin, the quantity commonly used is 0.08 to 0.64 ounce (2.27 to 18.2 grams) per 10 gallons (37.8 liters) of wine. Bentonite is usually used with white wines and 0.32 ounce (9.1 grams) per 10 gallons of wine is usually sufficient to obtain adequate stabilization and clarification. About 0.16 ounce (4.55 grams) of protein fining agent per 10 gallons of red wine is usually adequate.
|Laboratory Materials and Methods|
You should have a hydrometer for measuring the soluble solids (sugar content) of the juice and fermenting wine (Fig. 4). A hydrometer is a cylindrical glass device with a bulb on one end containing a dense material. The slender end is divided into a scale usually in degrees of Brix or Balling. The hydrometer is floated bulb down in the juice or wine, and a reading is taken from the Brix scale at the meniscus (where the liquid's surface meets the scale). The reading for all practical purposes equals the percentage of sugar in the liquid. The hydrometer must be clean and dry before use.
You also need to measure titratable acidity (TA). Equipment required includes a 10-milliliter burette (a graduated glass tube), a 1% phenolphthalein solution, a 0.1 N (normal) sodium hydroxide solution, a 100-milliliter beaker, a glass rod, and a 5-milliliter pipette. Perform the titration as follows:
1. Fill the burette (a 10-milliliter pipette can be used instead) with the sodium hydroxide solution and allow a small amount to run through. Record the sodium hydroxide level in the burette.
2. Place about 50 milliliters of hot distilled water in the beaker.
3. Add 5 milliliters of juice to be tested to the hot water using the pipette.
4. Add 5 drops of the phenolphthalein solution to the water-juice mixture.
5. Slowly add the sodium hydroxide from the burette to the mixture, stirring with the glass rod. Stop the sodium hydroxide addition when the mixture turns pink.
6. Record the sodium hydroxide level in the burette, and calculate the number of milliliters used. Multiply the volume of sodium hydroxide used by 0.15. The product is the percentage of titratable acidity of the sample expressed as tartaric acid.
Since you must weigh the preparation of the proper concentrations of several materials (fining agents, sulfur dioxide, etc.), acquire a single or double beam balance capable of weighing up to 200 grams. (Table 3.)
|Steps in Winemaking|
Crush white grapes as soon after harvest as possible. While crushing, add enough sulfur dioxide to produce about 100 ppm (0.01%) in the juice. At this time, add pectin enzymes, if they are to be used, to help clarify the juice and aid in pressing. Allow the resultant juice, "must," to stand for 4 to 18 hours on the skins in order to extract "character" from the skins. Drain the must and press the solids (pomace) to extract the remaining juice. Put the combined juices in closed containers, and store at cool temperatures overnight to allow the solids to settle. At this time, take a sample and check it for TA and soluble solids. Then siphon the clear juice into clean containers that will be used for the primary fermentation and adjust the sugar and acid levels if necessary.
You can combine the remaining solids and repeat the settling procedure to increase yield. Eventually, the solids can be fermented separately to maximize yield. Carefully watch the juice resulting from the solids, since it is in this material that you may most often encounter problems with hydrogen sulfide production through the action of the yeast. The settling operation as a whole is optional. The procedure, however, does produce a cleaner, fruitier wine than if the juice is fermented with the solids in it.
The most convenient way to start the fermentation is to add dry yeast directly to the must. The safest, most sure method, however, is to prepare a small amount of must ahead of time and add dry yeast, generating an actively fermenting starter which is added to the bulk of the must. (Do this while settling is underway.)
Ferment white wines at cool temperatures (preferably below 60°F/15.5°C) since this best retains desirable aromas. If you do the active primary fermentation in an open container, transfer the fermenting juice to a container to which an air trap can be attached in the latter stages of fermentation when CO2 evolution slows. This will minimize danger of the fermentation stopping ("sticking") and avoid oxidized wine.
There are two major differences between red and white wine production. First, most of the color and tannins are contained in the skins, particularly in red grapes. Thus, in order to extract these components you must carry out the fermentation in the presence of the skins. Second, since we usually wish to emphasize factors other than a fresh, fruity character in red wines, fermentation is done at relatively high temperatures (80°F to 85°F/26.7°C to 29.4°C).
You may remove stems either before or after crushing. Add about 75 ppm (0.0075%) sulfur dioxide. After crushing, allow the must to stand overnight so the SO2 can work. (During this period, measure and adjust the soluble solids and acidity of the must.) Add an actively fermenting yeast starter. Do not fill the containers more than about 2/3 full in order to avoid overflowing.
After fermentation starts, the skins will rise to the top of the container. Punch them down at least twice daily to aid in color and tannin extraction. If you look at the juice and skins, you can normally determine when color extraction is nearly complete (normally 3 to 5 days of active fermentation). The extent of color extraction you allow depends on the type of final product desired. If a rosé wine is the objective, remove the skins sooner than if you want a robust, deeply colored, highly tannic product, which normally requires more aging. For a rosé, use a lower fermentation temperature, since that will emphasize the fruity character of the grape.
After color has been extracted, remove the skins and solids, and press to extract the juice. You can skim most of the skins off the top of the actively fermenting juice. Screen the rest of the juice or run it through a coarse cloth to remove the larger solid materials. Combine the press and screen juices and put them in closed containers with air traps to prevent entrance of oxygen.
Normally, red wines are allowed to undergo malolactic fermentation (the conversion of malic acid to lactic acid and carbon dioxide by lactic acid bacteria). This fermentation results in a reduction in the total acidity of the wine because lactic acid has one acid group while malic acid has two. This process is needed because the tannins in red wines accentuate the acid character resulting in harsh tasting wines.
Dry preparations of Leuconostoc oenos are available with directions for rehydration. The culture should be added to the fermenting must after extraction of the solids. After adding the culture the wine should be stored in closed containers with an air trap at room temperatures (68°F, 20°C) until the malolactic fermentation is complete (usually 2 weeks to 2 months; carbon dioxide evolution should stop and titratable acidity reduced).
|Fruit and Berry Wines|
You can make other fruit and berry wines by procedures similar to those for grape wines. One of the major differences is that you will have to macerate the fruit into thick pulp that is not easily pressed. In this case, it is wise to ferment the whole pulp, and, as the pulp rises to the surface during active fermentation, scoop it off and drain it through a fine-meshed cloth. If you do this during the active fermentation, the danger of oxidation will be small, since the yeast is still producing large amounts of CO2. Colored fruits often have most of their color in the skins, so treat them like red grapes.
A major problem with many fruit wines made from peaches, apples, apricots, and pears is oxidation. Always use sound fruit and cut out discolored pieces prior to maceration. Also add sulfur dioxide at the time of maceration (crushing). Using pectic enzymes may aid in clarification and increase yield.
Most of these fruits, as well as berries and rhubarb, require amelioration (adjusting the sugar-acid content) . Therefore, once the juice is obtained, add enough sugar to adjust the sugar content to 21% to 23%. At this time test and adjust acidity if necessary. For most berries and rhubarb the juice must be diluted with a 21% to 23% sugar solution in order to reduce the acidity. For some of the low acid fruits such as pears, peaches, and certain apple varieties, you may need to add acid. After fermentation, acid can be added to taste much more readily, since the sugar will not be present to interfere with the perception of acidity.
The finishing operations described here are common to all types of table wines. The first racking (siphoning) may occur in the latter stages of fermentation when a considerable amount of the yeast has settled out. At this time, siphon the wine above the lees (residue in the bottom of the container) into a clean container, taking care to minimize aeration of the wine (unless hydrogen sulfide is detected; see Oxidation section). An early racking is particularly desirable if you want to "stick" (stop) the fermentation before all the sugar is consumed. This can result in a small amount of residual sugar. If a totally dry wine is desired, delay the first racking until the sugar is completely gone (less than 0.5% sugar). With some white wines you may need to resuspend the yeast by agitation in order to ferment the last remaining sugar. Carefully mix with a clean rod, minimizing the amount of air incorporated into the wine.
After the fermentation is complete, store the wine in a cool area. The lower the temperature at this point, the better. When you see that most of the solids have settled out, rack the wine again. Add approximately 25 ppm SO2 to protect against oxidation. Fill the containers to the neck to minimize air space between the stopper and wine. This space should only be large enough to allow for changes in volume due to temperature fluctuations.
Repeat the racking operation until very few solids continue to settle. Generally, two to four rackings over a period of 6 months will be adequate. However, you may need to store red wines in large containers for a year or more before the final finishing and bottling.
Commercial wineries often fine their wines prior to cold stabilization. You may find it more convenient to expose the wines to low temperatures (24°F to 32°F/-4.4°C to 0°C) shortly after fermentation. This will aid both in precipitating potassium bitartrate and in settling out the solids. If you live in a cool region, you can get the desirable temperature range by placing the wine outside in the early winter. After the rackings, the wine should be reasonably clear, although if you shine a light through the wine you may see suspended matter at a point perpendicular to the light beam (Fig. 5).
The fining operation is an attempt to remove this fine colloidal material from the wine. With white wines a treatment of 0.32 to 0.64 ounce (9.1 to 18.2 grams) of bentonite per 10 gallons (37.8 liters) should be adequate to settle out the suspended matter. It may be worthwhile to test, on a small scale, different amounts of bentonite in order to determine the minimum amount required for clarification. Avoid excessive bentonite since it may impart a musty flavor to the wine.
For most red wines, use a protein material for fining. Use a 1% gelatin solution (prepared by heating 10 grams per 1000 milliliters0.33 ounce per quartof water). The treatment rate should be in the range of 0.16 to 0.65 ounce (4.5 to 18.4 grams) per 10 gallons of wine. Add the fining agent during racking while the wine is being siphoned into a new container. Once the floculated material has settled out, immediately rack the wine into a clean container. Siphon the residue containing the settled material into a common container and resettle it to increase the yield.
The wine is now ready for aging or bottling. Age red wines either in the original container or in oak wood. The length of time wine is held in the oak wood will depend upon condition of the barrel, its age, and size. Obviously, in a small oak container (less than 50 or 55 gallons) the amount of surface area to liquid is relatively large and, therefore, it takes a short time to extract oak materials into the wine. Also, the wine absorbs oxygen faster. A new barrel contains much more oak extractives than an old barrel. Therefore, carefully taste the wine periodically to determine the rate of pickup of oak extractives. You don't want to obtain so much of the oak that it detracts from the character of the wine. If the wine is placed in oak barrels, keep the container full and sealed so the wine does not become oxidized or turn into vinegar.
Aging of red wines is hastened considerably by storing at slightly higher temperatures (60°F to 65°F/15.5°C to 18.3°C). After the wine is held in the oak barrel as long as necessary, bottle it immediately. The red wine will continue to age in the bottle at a rate that depends on the temperature at which it is stored. In no case should the temperature exceed 65°F/18°C.
Clarify white wines and bottle them as soon as possible. Store the wine at a relatively cool temperature (preferably below 55°F/ 12.7°C) and allow it to age in the bottle. Generally, white wines are short-lived and should be consumed within the first year or so after bottling. Store the bottles on their sides or inverted to prevent drying of the cork.
The type of bottle you use can vary considerably (Fig. 6). Screw-cap bottles are convenient and inexpensive, since a corker and corks are not required. Clean the bottles by scrubbing with a detergent, rinsing with hot water, and rinsing with a 200 ppm solution of SO2 prior to use. Used corks can be utilized only if they have not been torn up by using a screw-type cork puller. Corks in good condition are those removed with the two-pronged cork puller (Fig. 7). If you use corks, heat them in boiling water. Boiling has several functions. First, it moistens and expands the corks so they are no longer brittle. Second, it washes the corks and extracts "corky" flavor. Third, it sterilizes them. Inspect new corks for cork dust or other debris. If sanitizing with SO2, give the corks a preliminary washing to remove debris.
With both white and red wines at the time of bottling, add approximately 25 ppm to 40 ppm SO2 to scavenge the oxygen picked up in the bottling operation.
|You can make good, palatable wines if you take the necessary precautions. Keep sanitation uppermost in mind. Liberal use of scrubbing brushes, detergents, and hot water along with dilute bleach solutions or sulfur dioxide solutions for sanitizing is required to produce consistently good wines. Pay close attention to the quality of the fruit that goes into the production of the wine, adjust the sugar content, and ameliorate or adjust the acid so it is within an acceptable range for consumption. You must exclude air from your wine. Oxidation can rapidly destroy the varietal characteristics of the wine and produce flavors reminiscent of certain sherries. Finally, keep records so you can repeat any successful procedure and minimize mistakes.|
Amerine, M. A., and Marsh, G. L. 1962.
Fessler, J. H. 1968.
Taylor, Walter S., and Vine, Richard P. 1968.
Wagner, P. M. 1976. Grapes into Wine. New York: Alfred A. Knopf.
|Winemaking Supply Sources|
Liberty Malt Supply Co.
Jim's Home Beverage Supplies
The Wine Cellar
Stan's Merry Mart
Evergreen Brewing Supply
Acidity - the quantity of acid, i.e., the amount of the natural acids which give a tart or sour taste to wine or fruit.
Air trap - device which allows carbon dioxide to escape during fermentation and at the same time excludes air from the container.
Amelioration - adjusting sugar and/or acid content to improve quality of finished wine.
Citric acid - a fruit acid commonly found in citrus or berries.
Colloidal material - small particles that remain suspended in a fluid medium without settling.
Fining - process of adding a component to clear up cloudy wines.
Floc - a light fluffy mass formed by the aggregation of a number of fine suspended particles.
Hydrometer - a sealed glass tube that floats in liquids and is used for measuring specific gravity or density of the liquid. Often has graduated scales which read as percent sugar.
Lees - the sediment at the bottom of a vessel.
Malic acid - a fruit acid commonly found in apples and other tree fruits.
Must - unclarified juice.
Oxidation - chemical process in which wine reacts with oxygen. Process browns wines, and when slow is partially responsible for aging red wines.
Pomace - solid residue of fruit after the juice has been expressed.
Ppm - parts per million.
Primary fermentation vessel - container in which juice (or must) is held during initial fermentation.
Racking - the removal of wine from sediment (i.e., lees) by siphoning or pumping.
Sticking - process in which a wine stops fermenting before all the sugar has been converted to alcohol and carbon dioxide.
Sulfur dioxide (SO2) - a gas formed when elemental sulfur is burned. SO2 is a selective antiseptic and an antioxidant.
Tannin - a general term for the components in wines that impart an astringent and/or bitter taste. In most fruits, tannin is found in the skins, stems, and seeds.
Issued by Washington State University Cooperative Extension and the U.S. Department of Agriculture in furtherance of the Acts of May 8 and June 30, 1914. Cooperative Extension programs and policies are consistent with federal and state laws and regulations on nondiscrimination regarding race, color, gender, national origin, religion, age, disability, and sexual orientation. Evidence of noncompliance may be reported through your local Cooperative Extension office. Revised July 1998. Subject code 660. B.