Labo VinGlossary
Acids (mixture of)
[ Using an acid mixture for the sap correction leads to more harmonious wines than a unique acid, because each acid acts on the yeast metabolism in a special way.
We recommend this mixture:
- tartaric acid: 551 g
- malic acid: 248 g
- citric acid: 152 g
- succinic acid: 49 g
1 g of this mixture is equivalent to 1 g tartaric, which is our acid unit. ]
Acidometer
[ An acidometer is a test-tube graduated directly in g/L equivalent tartaric acid, provided one use a special coloured NaOH solution whose concentration fits to the graduations of the test-tube (very practical system). ]
Airlock
[ Water valve allowing the outflow of CO2 , but avoiding any air-intake. It is preferable to fill it with a mixture of water and glycerol. ]
Bromothymol blue
[ Dissolve a knife tip of bromothymol blue in 25 mL alcohol 50%. ]
Champenoise (method)
[ Called today "traditional method". This is a method of yeast extraction after fermentation in bottle (at least 3 month). At the end of fermentation, the bottles are inclined, neck downward, put on a device called "pupitre". They are regularly revolved (once a day) so as to let slip the yeast into the hollow plastic stopper. When the whole yeast is in the stopper, the bottles are cooled (0-4° C) and their neck is plunged in a mixture of ice and salt. The wine in the stopper freezes. The stopper is removed, taking the frozen wine and the yeast. This removed wine is replaced by wine eau-de-vie, and the final cork is placed. Nowadays, more and more immobilized yeast in alginate beads are used. They are much more easily removed. ]
Clarification (test of)
[ - One or two days before racking, fill with wine 5 100 mL bottles numbered 0, 1, 2, 3 and 4.
- Whip up an egg white with a little water and bring it to 1 litre, integrating the foam.
- Add to the bottles from this solution as many times 1 mL than the number the bottle bears. Close, shake the bottles and place them in a fridge without shaking any more. The racking day, pick out the clearer bottle that is suitably astringent and note its number (the bottle 0 must be the less clear).
If several bottles are clear, choose the bottle being rightly astringent; the egg white has indeed reduced the tannin content.
- Rack the wine, adding to it, for 1 litre, an egg white solution volume matching up to 10 times the chosen bottle number. ]
Fruit wine
[ Beverage obtained by alcoholic fermentation of various fruit juices. ]
Fusel oil
[ The fusel oil is a mixture of several superior alcohols (amyl, isoamyl...) produced by the yeasts metabolism. In large amount, the fusel oil is toxic and negatively modifies the wine savour. The amount of produced fusel oil essentially depends on the used yeast strain and its culture conditions. Thereby the wild yeasts (apiculate yeasts) produce large amounts of fusel oil, as well as yeasts cultivated in bad conditions (yeasts suffering due to lack of nutritive salts, excessive temperature...). ]
MetaK
[ Solution 0.25 M of potassium metabisulfite (K2S2O5, Mr=222), prepared by dissolving in water 55.5 g potassium metabisulfite (failing which, 47.5 g sodium metabisulfite - Na2S2O5, Mr=190) for 1 L solution.
10 mL of this solution equals 320 mg SO2 (5 millimoles).
This solution can be kept for a long time in a tightly sealed bottle. ]
Methanol
[ Methanol, a very toxic alcohol, is always present, in small amount in a wine. Contrary to what is generally thought, it is not formed during the fermentation, but in the must, well before the fermentation starts, by hydrolysis of the fruits pectin by dint of an enzyme: pectin methylesterase present in the fruits. Very ripe fruits contain already some methanol (as well as ethanol). ]
Must
[ Juice before or during alcoholic fermentation. ]
Ouiller
[ Ouiller (French verb): to compensate wine evaporation through a cask in order to keep it full. Use a wine excess got in small containers during a preceding racking, or, failing which, an alcohol solution at 15 % vol. ]
Pectinase
[ The pectinase is an enzyme (protein, biological catalyst) that destroys the pectin. It follows a better flavours extraction, a better sap yield, along with a good ulterior clarification. The pectinase is sold as a liquid or a powder. Conform to the manufacturers instructions. Too much pectinase is not damaging, but it is wasting. ]
Pectin
[ Mixture of methylated polygalacturonic acids. By enzymatic hydrolysis, the pectin releases toxic methanol. It forms a net that traps the juice, rendering it viscous, so decreasing the yield at the pressing stage. ]
pHmetre
[ Device allowing the pH measurement of a solution by dipping in it an electrode. Small pHmeters can be found moderately priced and accurate enough. ]
Refining
[ Refining a wine is reducing its tannin content to a right level. ]
Siphonage
[ Rack the wine carefully, attending to withdraw as less as possible dregs (a rigid tube is more convenient than a flexible hose directly plunged in the wine). Possibly pinch the hose to avoid a too violent aspiration. Bring in the wine as less air as possible (hold the hose extremity in the bottom of the receiving container. ]
SorK
[ Potassium sorbate at 50 g/L. This solution cannot be stored. ]
Tannin
[ The word tannin applies to various badly defined compounds, often polyphenolic acids esterified by a sugar. The tannins are very widespread in a lot of plants, mostly barks, fruits, tree leaves, oak wood...
The oenological trade tannin is mostly extracted from oak apple, sometimes also from grape skin.
The tannin has a typical astringent savour and a characteristic subtle odour. It is an amorphous pale yellow to brown powder. The tannin is essential in a wine: it is necessary for the wine clarification (min. 3 g/10 L juice). It forms insoluble compounds with proteins and metallic ions, starch and a lot of alcaloids. It also contributes much to the wine keeping. The tannin content of wines varies from 350 mg/L in white wines up to more than de 3 g/L in red wines. Ageing wines in oak casks increases their tannin content. ]
Unsaturated fatty acids
[ In a Pyrex receptacle (never aluminium!), prepare a solution of 100 mL water containing 20 g potassium hydroxide (KOH). Bring to a light boil and add bit by bit, while stirring 100 mL (90 g) soy oil. Continue the heating for half an hour while stirring. Add 15 mL alcohol, mix well and, when the mass is homogeneous, add water up to 430 mL (= 86 g acids, 0.2 g/mL).
Add 1 mL of that solution in 10 litres juice. ]
Wine
[ Beverage obtained by alcoholic fermentation of grape juice. ]