WINE MAKING: The Beginning

Understanding the grape


Stalk and pipes: both there parts contain tannins, pipes also contain bitter oils, the stalk/stems are only available to the winemaker if the grapes are hand harvested 

Mesocarp (Pulp): water and sugar are the largest part of the pulp. The yeast will will use the sugar to make alcohol. As the sugar levels rise in the grape so does the density of the juice.

Exocarp(Skins): the skin, the immediate level underneath it contains high concentration of flavor compounds and gives wine some of the verital characters. they also have tannins and in black grapes, color compounds. The waxy surface of skin also contains yeast that can be used to ferment the wine.   

Tannins: gives red wine its texture and structure, they help age the wine. During fermentation they combine with color compounds and oxygen to create a more stable color. 

Grape prepossessing/making the juice(must)

• hand sorting away the unripe or rotten grapes
• Desteming and crushing(optional), a machine takes away the stem and crushes the skin of the grape with out damaging the bitter pipes. This creates free run juice. 
• Pressing, this separates the liquids and the solids, for white wines this happens before fermentation, for reds and rose wines they separate them a period after contact between skin and juice. Pipes are still avoided. 

A rough guide: 1kg of grapes=75cl wine

Adjustments

Sugar and alcohol: In cooler climates the grapes may not have the desired sugar content for the amount of alcohol. So the wine maker may carry out a must enrichment to increase the end result of alcohol, this is illegal in most places and controlled were its not. Sugar can also be increased by adding must from other grapes.

Acid: De-acidfaction happens mostly in colder climates. Acid can be neutralized by adding potassium bicarbonate or a mixture of calcium carbonate and calcium tartrate-malate, this can be done in conjunction with enrichment.

Tannin: If there are not enough tannins levels can be raised with tannin powder or wooden staves to the fermentation vat or by using some of the stems (Wines and Spirits).  

Fermentation 

This is a chemical reaction the is caused by the actions of yeast. The role of yeast is to create alcohol but they also create flavor. 

Alcohol fermentation: The conversion of sugar to alcohol. The byproducts of this processes is heat and flavor compounds. this fermentation will not start if the temp. is below 5° c or above 35°c-38°c.  This will normally continue until there is no sugar left or the alcohol gets so high the yeast dies normally around 15%. There are different ways to stop fermentation as well. Cooling, heating, raising alcohol content or filtering out the yeast. Controlling temp. is important, too hot yeast die, fermenting at aa lower temp. can avoid the loss of delicate volatile aromas and can encourage development of fruity esters in white wine. Fermenting at higher temp. is necessary for the extraction of color and tannins from black grapes.

Malolactic Fermentation(MLF): Takes place after alcohol fermentation has finished and is carried out by lactic bacteria. they convert malic acids( found in apples) into softer lactic acids(found in milk). All red wines go through MLK but is avoided in some white wines. This softens and reduces acid and creates flavor profiles like butter and hazelnut but can also reduce some pure fruit aromas. 

To learn more see Wines and Spirits (understanding style and quality)