White wine the death knell of northern viticulture. The vine disappeared from northern Germany and Baden, and the maximum altitude for viticulture descended to 220 metres. Hans-Jürgen Otto noted that: "all the vineyards suffered and decreased in area". In England the vine also disappeared. The less early vineyards preferred to select white varieties of grapes because, even if unripe, white grapes allowed wine that was a little sour to still be consumable, while red grapes do not give enough colour and green tannins make the wine bitter. The interruption of the fermentation by a cold winter led to the discovery of the
Olmo grapes is a "teinturier" variety with pigmented, instead of clear, juice. Most red wine grapes have clear juice, the red color of wines coming from extraction of pigment from the grape skins. Rubired was originally intended for producing fortified port-style wines, and since the late 20th century, producers in Australia have included it in some port-style blends. Its intensely dark color is often useful in blending to intensify the color of other red wines, but it can also be used to create varietal wines. Emerald Riesling is a white wine grape crossing between the "vinifera" varieties Riesling and Muscadelle. Trials on