Acetification:

The formation of vinegar, usually caused contamination of the must, liquor or finished product with vinegar-producing bacteria and the presence of air. Fermentation bottles should be filled as high as the froth caused by fermentation will allow. Stored wine should have no more than one inch of air under the cork in the standing bottle (1/2 inch is preferred). Adding one Campden tablet per gallon may halt acetification in its early stages, when the wine emits a slight smell of vinegar and an acid taste.

Acetaldehyde is the second member of the aldehyde group. It is formed during fermentation from pyruvic acid by the enzyme carboxylase. It is an essential step in alcohol production, since no alcohol is produced unless acetaldehyde is reduced by the enzyme zymase. Large doses of sulphite will inhibit its reduction to alcohol so that glycerol will be the main product. If the fermentation temperature is too high, or infection occurs, an oxidation reaction takes place and acetic acid is produced rather than alcohol. This may also happen if a wine is over oxygenated during racking. However, bisulphite will combine with the acetaldehyde to prevent this oxidation reaction. Hence the need for bisulphite at racking

Acetals

Acetals are chemical compounds formed by the joining of an alcohol and an aldehyde, characterized by having a pleasant aromatic odor. They are formed during maturation, and play an important part in the bouquet of a wine.

Acetamide is a chemical substance which, if present in a wine, will cause an unpleasant off flavor usually referred to as mousey. It is produced by some of the spoilage bacteria and, once present, there is no cure. Prevention is by scrupulous hygiene at all stages of wine production.

Acetate, Ethyl The ester of acetaldehyde and ethyl alcohol, having a smell like that of pear drops. It is usually formed during the spoilage of a wine and its conversion to vinegar

Acetic Acid is a monobasic organic acid. It is formed in small amounts during fermentation and is the principal constituent of vinegar. Wine which is exposed to the air will become infected by bacteria which may cause the oxidation of alcohol to acetaldehyde and then to acetic acid. Wine which has become infected first shows an oily sheen on its surface and eventually smells vinegary and sour. It is interesting to note that during ageing small amounts of acetic acid are formed by oxidation of ethyl alcohol, without spoilage occurring. Indeed, its presence in small amounts adds to the final quality of the wine.

Acetification A term for the oxidation of alcohol to acetic acid. When this occurs it is best to allow the wine to go completely to vinegar. If this is not desired the wine must be thrown away lest it be the cause of further infection in the winery

Acetifying Bacteria are the species of bacteria responsible for the acetification of wine. They gain access to the wine by failure in hygiene. Commonly, this infection is carried by the fruit fly Drosophila

Acetobacteria One of two groups of bacteria responsible for the acetification of wine by oxidizing the alcohol to acetic acid. See Acetomonas.

Acetone is a substance produced by lactobacilli in addition to lactic acid. It produces its own characteristic off flavor. Prevention of this spoilage substance is by hygiene at all stages of production

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Acetomonas The second group of acetifying bacteria. The first (Acetobacteria) oxidize the alcohol to acetic acid which is then broken down to water and carbon dioxide by the action of Acetomonas.

Acid Chemical compounds characterized by the presence of a free hydrogen ion which in solution separates or dissociates from the other radicals to be available for reduction reactions. Acids are either strong or weak and form salts if they are mixed with alkalis.

Acid Blend:

Acid adjustment in fruit wines. Use in grape wines acceptable but not recommended due to difficulties manipulating malic acid and the possibility of malolactic activity.

Acid Reduction If after initial assay of the must the acidity is too high, there are three ways of reducing it: (a) Dilution The acidity of the must is assayed and expressed as acidity per gallon. If, for example, the acidity of 1 pint of juice is 64 parts per thousand (ppt), the acidity per gallon will be 8 ppt. If an acidity of 4 ppt is required, the juice is diluted by one volume. (b) Chalk can be added in the form of Precipitated Calcium Carbonate. + oz. per gallon will reduce the acidity by about 1.5 ppt. Care must be taken during this operation as foaming will occur. (c) Bentonite, used as a fining agent will reduce the acidity. This is because bentonite joins with tannin before clearing a wine and it is this conjoined tannin which is removed with a resultant reduction of acidity.

Acidity : 

The amount of acid in the must, liquor, or finished wine. Insufficient acidity in the must will result in a poor fermentation, a slightly medicinal and flat taste. Too much acid will give the wine an unpleasant bite. Acid is necessary for fermentation, and one-fourth of the initial acid content will be consumed by the yeast during fermentation. Low-acid musts are usually corrected by adding citric acid, the juice of citric fruit, or acid blend. An acid testing kit is indispensable in measuring initial acidity. 

Acidity and Maturing A wine with an acid content at the upper limit for its type or style will take longer to mature, but once ready for drinking will have a better bouquet than a less acid wine (due to the greater amounts of esters formed during maturation). Citric does not readily esterify, but malic and, ever more so, succinic acids combine with alcohol to form bouquet producing esters. It must be emphasized that, for these changes to occur, time is essential, and that a wine drunk young will show no improvement in bouquet over the natural bouquet from the ingredients.

Acidity Determination

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Acidity Determination 10 mls of wine are diluted three or four fold with distilled water. Either phenolphthalein, or B.D.H. Universal Indicator, is added and decinormal Sodium Hydroxide run into the beaker until the end point is reached. The amount of alkali required to neutralize the acid in the wine is divided by 2 to give the free acid of the must in Parts per Thousand of Sulfuric acid. Sulfuric acid is not actually used in winemaking but is employed as the unit of measurement or standard for the purpose of assessing acidity; it is merely a convenient international method of expressing the quantity or weight of acid present as if it were Sulfuric acid itself.

Acidity of Fruits

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Acidity of Fruits various from year to year. Generally speaking, the acidity and sugar content of the fruit are in inverse proportion. A good summer will mean sweet fruit with a low acid content.

Acidity of Musts

Acidity of Musts is the free acidity present in the must after preparation. Its correct value is important to producing a well balanced, rounded wine. For usual ranges See Appendix II.

Acidity of Wine Types

Acidity of Wine Types depends on the wine style desired and suggested ranges are given in the table in Appendix II.

Acidity, Correction of

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Acidity, Correction of Most musts prepared by amateur wine makers are not of the right acidity unless corrected. Having decided on the required acidity of the wine the wine is titrated against Sodium Hydroxide and the weight of free acid determined. By subtracting the desired acidity from the actual acid present the amount of acid required for correction is obtained. If a negative result is obtained the must needs to be reduced in acid.

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Activating Yeast

Additives

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Additives Any chemical or compound added to the must, other than the basic recipe ingredients. They are essential for peace of mind for, if lacking, there is the possibility that the fermentation will stick. Basically, additives are necessary foodstuffs for yeast growth or yeast enzyme activity which will ensure a healthy ferment with minimum amounts of fusel oils being produced.

Adjuncts

Adjuncts are added to increase fermentable sugars, and hence alcoholic content. they include corn sugar, rice syrup, and honey.

Aeration is to stir a must in the presence of air to ensure the dissolving of oxygen in the mixture so that the first stage of fermentation, the establishment of a healthy yeast colony, can take place

Aerobic Fermentation Before alcoholic fermentation can commence, aerobic fermentation (or fermentation in the presence of air) takes place to establish a health yeast colony. During this phase little alcohol is formed. Aerobic fermentation, once an adequate yeast colony has been established, is not desirable for, apart from the lack of alcohol formed in the presence of air, there is always the possibility of infection

Aftertaste:

The taste, odor and tactile sensations that linger after the beer has been swallowed See Wine Tasting

Agar A special jelly for growing cultures which the amateur winemaker may come across if he buys his yeast in the form of agar slopes. Agar is placed in test tubes and yeast grown upon the agar under sterile conditions. When required, the yeast is activated in the usual manner. Agar is a polysaccharide derived from seaweed.

Air Lock:

See Vintner-s Starter Kit

Albumin

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Albumin A protein complex commonly found on the breakfast table as the white of your morning egg. In wine making this part of the egg is used for fining wine.

Alcohol:

A synonym for ethyl alcohol or ethanol.

Alcohol by Volume:

A measure of the amount of alcohol in wine; used as a primary measure in Canada. The measure of the amount of space the alcohol in a beer takes up as a percentage of total space.  See Determining Alcohol Content

Alcohol by Weight:

A measure of the amount of alcohol in wine; used as a primary measure in the U.S. The measure of the amount of weight the alcohol in a beer has as a percentage of total weight.  See Determining Alcohol Content

Aldehydes

A class of organic compounds that are important in the manufacture of plastics, dyes, food additives, and other chemical compounds

Aldose A portmanteau word to describe one of the main groups of sugars. They are characterized by having an aldehyde group (hence the Ald- part of their name); the "ose" is a suffix to denote a monosaccharide. Glucose is the Aldose of winemaking import.

Alkali A chemical compound which, when mixed with an acid, forms water and salts. If hydrochloric acid and sodium hydroxide are mixed, then sodium chloride and water are obtained. When determining the free acidity of a wine an alkali, sodium hydroxide, is added and titrated against the free acid. In this case the products are water and the sodium salts of the acids present in the wine.

Alpha Acids

Alpha acids are the chemicals found in hops that are responsible for their Bittering characteristics

Amines A group of chemicals produced by some of the spoilage organisms. They are characterized by having a fishy smell

Amylase

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Amylase The enzyme which breaks down starch to maltose and short chain dextrins. The short chain dextrins are broken down by maltase to glucose. If amylase is not added to starch containing must the finished wine will have a haze due to the starch and dextrins, since wine yeasts do not secrete this enzyme.

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Anaerobic Fermentation:

A fermentation conducted in the absence of fresh air, as in a fermentation bottle, jug or carboy fitted with a fermentation trap.

Anti Oxidant Tablets:

Anti-Oxidant A term for any chemical used to prevent oxidation in wine, usually at racking time.

Anthocyanins are a group of related plant pigments (either red, blue or purple) which combine with glucose to form glycosides. In the plant, depending on soil pH, neighbors may vary widely in color such is the effect of pH on color production. Glycosides are often bitter to taste and some of them, such as the foxglove glycoside digitalis, can be toxic. If released, usually by alcoholic extraction, they will add color to a must.

Anthoxanthins

Anthoxanthins A class of plant pigments which are yellow in color

Anti-Oxidant

Anti-Oxidant A term for any chemical used to prevent oxidation in wine, usually at racking time. See Ascorbic Acid ; See Sulphite , See Ethyl pyrocarbonate.

Apiculate Yeasts are so called because of their shape; they are pointed at both ends. They are found in profusion on most fruits. They are undesirable in winemaking because they are not wine yeasts and, like all yeasts, they are capable of fermentation, but will only produce 3 to 4 percent alcohol before being inhibited by the alcohol they have produced. They tend to ferment rapidly to their end point, and will produce a sweet cordial rather than a wine. If a must is not sterilized, apiculate, or wild yeasts, may commence fermentation but, with the other organisms present on the fruit, spoilage will almost inevitably occur.

Apo-Ferment

Apo-Ferment This is a complex protein substance present in all living cells which select the type of compound to be metabolized by the co-ferment

Argols

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Argols Tartaric acid tends to form potassium tartrate. As it is not very soluble it tends to produce a haze in a wine. Cooling the wine decreases its solubility so that is precipitates out. The precipitate may then crystallize to form crystals often referred to as Argols. The free acidity of the wine may be lowered considerably if excess potassium salts are present in the must, either as potassium bisulphite or as potassium phosphate.

Ascomycetes

Ascomycetes One of the four classes into which the true fungi are divided. In addition to exotics like the Truffle, this class also includes bear and wine yeasts.

Ascorbic Acid:

Ascorbic Acid is a strong anti-oxidant and can be used instead of bisulphite at racking time to prevent over-oxidation. If it is used, it must be remembered that it will raise the acidity of the wine. Some commercial vignerons use it in the production of wines which are high in malic acid. It is not bacteriocidal, so that after racking, a malo-lactic fermentation can be encouraged to change the malic acid to lactic and thereby smooth the wine. 

Aspergillus A mould sometimes encountered in winemaking when a prepared must not start immediately and becomes infected by aerobic spores. Aspergillus may be recognized by its characteristic black color. If infection does occur it is possible to save the wine by straining the must and restarting. In Japan, however, it is required to make Saki.

Astringency A wine-tasting term to describe dryness of the mouth on tasting a wine. If pronounced and unpleasant, it may be due to excess tannin

Autolysis

Autolysis When yeast cells die, the cell, no longer protected by the electrical charge on the cell membrane is metabolized and broken down by the enzyme system of the yeast itself. The whole series of complex reactions is known as autolysis (or self destruction).