Grape sugar content

For the new wine to contain the desired 15-16 vol % alcohol, it is necessary to add some sugar to the juice or the partially fermented wine except in cases of unusually high sugar content in the grapes. In any event, it is necessary to have an accurate estimate of the sugar concentration in the juice before more sugar is added and before fermentation starts. It is better not to add the calculated amount of sucrose to the juice immediately but to make two or three smaller additions after the fermentation is actively under way. This technique is known as syruped fermentation and can yield wines of as much as 17 vol % alcohol under favorable conditions of yeast nutrients and temperature control. 

Once the grapes arrive at the winery, a sample of the juice is assessed chemically for parameters such as probable alcohol and sugar content. Grapes must have fall within the range of 12-14 Baurne. Wines can be made separately by variety or mixed together. 

The classification of port wines according to sugar content is presented in Table 5.5. The sweetness level depends on when grape spirits were added to stop fermentation. The probable alcoholic degree of the juice... 

Another style of botrytized sweet wine from France involves the category of "Selection de Grains Nobles" (SGN). This legal definition was introduced in 1984 in Alsace, but similar wines are produced also in the Loire valley from grapes of different varieties and sugar contents (Table 6.2). 

The other appellations of SGN wines are Coteaux du Layon, and Coteaux de l Aubance in the Loire valley, Anjou. Coteaux du Layon produces sweet wine only, and the single variety here is Chenin blanc, a neutral, acidic grape cultivar. It is extremely prone to noble rot. The required initial sugar content of the must is 294 g/1 for SGN wines (INAO, 2007). Two individual AOCs within this region are Bonnezeaux and Chaume. Most of these SGN wines are very sweet, in comparison with the other French styles. 

Germany are produced from similar quality grapes the highest sugar content ever measured in a TBA must was 327 °Oe, corresponding to more than 65°Brix (Dittrich and Grossmann, 2011). 

To make juice extraction easier, a cold pressing (cryoextraction) technology has been developed (Chauvet et ah, 1986). Cooling the grapes below 0 °C (potentially as low as —16 °C) freezes berries with lower sugar contents, while the juice of berries with the highest sugar content... 

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