Saint-Emilion Grand Cru wines are produced under slightly tighter production restrictions than regular Saint-Emilion wines. As with other Grand Cru appellations, the intention behind this is to improve the quality, and to distinguish the area's finer wines from the more everyday wines.
There are four key differences between the production restrictions for Saint-Emilion wines, and those for Saint-Emilion Grand Cru wines. First, the vineyard yield is restricted to 8,000kg per hectare rather than 9,000 (which translates to 55 hL per hectare rather than 65). Second, the grapes (with the significant exception of Merlot) must be harvested with a must weight of at least 189 grams of sugar per liter rather than 180. Third, the finished wine must reach a minimum alcohol level of 11.5% ABV rather than 11%. Fourth, and finally the wine must be stored by the producer for an extra 14 months before being released for sale.
Since the introduction of the Saint-Emilion Grand Cru appellation in 1954, many have suggested that these conditions are too relaxed to warrant the term Grand Cru. The yield restriction is the same as that in force in Bordeaux's other red-wine appellations (e.g. Pauillac and Graves), and the exception of Merlot from the second condition instantly excludes more than 65% of the total Saint-Emilion vineyard area. Further, the increase of the minimum alcohol level by 0.5% is effectively meaningless, as very few, if any, wines from Saint-Emilion are ever contain less than 12% alcohol. The only condition which escapes this criticism is the extended elevage - the period which the wine spends (in tank, barrel or bottle) before general release.
All French wines undergo official panel tastings before being granted AOC status, which provides some guarantee of quality. But the panels test for typicity and consistency (they do not compare one Grand Cru appellation with another) and the quality expected of Saint-Emilion Grand Cru wines has been firmly established over the preceding 60-or-so vintages.
The top-tier wines from Saint-Emilion, then, are not marked out by their Grand Cru status, but by their appearance in the Saint-Emilion Wine Classification. This works in much the same as the classifications of the Medoc, Graves and Sauternes, but with one significant difference: it is periodically reviewed to keep it up-to-date and relevant. It was first drawn up in 1955, and (after a controversial review in 2006) was most recently updated in 2012. For more information see: Saint-Emilion Wine Classification.