Muscadet Cotes de Grandlieu is one of the four Muscadet appellations which dominate wine production in the Loire Valley's Pays Nantais district, on the central western coast of France. Introduced in 1994, the title covers exclusively white wines from vineyards around the Lac de Grand Lieu, one of France's larger natural lakes. The wines are made from Melon de Bourgogne, a grape variety brought to the western Loire Valley from Burgundy, as the name suggests. The similarity between the name Muscadet and that of the Muscat grape family is sometimes the cause of confusion. However, crisp, dry Muscadet is quite distinct from the sweet wines into which Muscat grapes are so often made.
The Grandlieu area from which the appellation takes its name lies just south-west of Nantes city. It is not as densely planted as neighboring Sevre-et-Maine, accounting for roughly 740 acres (300ha) of vineyards in 2008. They produced 277,500 gallons (10,500hL) of wine – about 10% of total Muscadet output.
The terroir here is well suited to the production of Muscadet wines. A combination of volcanic, metamorphic and alluvial soils has led to an abundance of potassium, magnesium and calcium, providing the vines with the minerals they require for optimal growth. Furthermore, in the wet maritime climate of the western Loire Valley it is vital for the vineyards to have efficient drainage; the limestone, granite and gravelly soils of the Grandlieu area provide that. The presence of clay, however – particularly in the soils close to the lake itself and the Boulogne river which flows into it – creates variability in the drainage speed, so site selection is important. The Lac de Grand Lieu is prone to dramatic flooding (it is very wide but only 13ft/4m deep), resulting in an expanse of marshland that is clearly unsuitable for viticulture and therefore not covered by the appellation.
Melon de Bourgogne is not a particularly flavorful grape variety, so without care in the vineyard and attentive winemaking Muscadet wines can risk being rather bland and featureless. This is particularly true in hotter vintages, when the intense heat robs the grapes of potential complexity and their characteristic acidity. On the flipside of that coin, the Loire has one of the wettest, coldest growing seasons in France, so the growers' goal is more often full ripeness than acid retention. To glean as much flavor and character from the grape must as possible, many Muscadet Cotes de Grandlieu wines are left sur lie ('on the lees') for a period of several weeks or even months. This extended contact with the lees imparts a richer, creamier mouthfeel to the wines and contributes to the general flavor profile. Each of the four Muscadet appellations is made in both standard and sur lie variants.
A good Muscadet Cotes de Grandlieu wine has subtle apple and citrus aromas, sometimes dressed with gentle hints of pepper and even a slight salinity evocative of the Nantais' maritime location. The best examples also have a certain underlying minerality, often thought to be a reflection of the chalky soils that characterize the best Muscadet vineyards.