While serving as an army pharmacist for France in the Seven Years' War, he was captured by the Prussians, and in prison in Prussia was faced with eating potatoes, known to the French only as hog feed. The potato had been introduced from South America to Europe by the Spaniards at the beginning of the 16th century. It was introduced to the rest of Europe by 1640, but (outside Spain and Ireland) was usually used only for animal feed. King Frederick II of Prussia had required peasants to cultivate the plants under severe penalties and had provided them cuttings. In 1748 the French Parliament had actually forbidden the cultivation of the potato (on the grounds that it was thought to cause leprosy among other things), and this law remained on the books in Parmentier's time.
From his return to Paris in 1763 he pursued his pioneering studies in nutritional chemistry. His prison experience came to mind in 1772 when he proposed (in a contest sponsored by the Academy of Besançon) use of the potato as a source of nourishment for dysenteric patients. He won the prize on behalf of the potato in 1773.
Thanks largely to Parmentier's efforts, the Paris Faculty of Medicine declared potatoes edible in 1772. Still, resistance continued, and Parmentier was prevented from using his test garden at the Invalides hospital, where he was pharmacist, by the religious community that owned the land, whose complaints resulted in the suppression of Parmentier's post at the Invalides.
In 1779 Parmentier was appointed to teach at the Free School of Bakery in order help stabilize Paris' food supply by making bread in a more cost-effiicient fashion. In that same year he published “Manière de faire le pain de pommes de terre, sans mélange de farine”, in which he described how one can make potato bread that still has all the characteristics of wheat bread.
Parmentier therefore began a series of publicity stunts for which he remains notable today, hosting dinners at which potato dishes featured prominently and guests included luminaries such as Benjamin Franklin and Antoine Lavoisier, giving bouquets of potato blossoms to the King and Queen, and surrounding his potato patch at Sablons with armed guards to suggest valuable goods — then instructing them to accept any and all bribes from civilians and withdrawing them at night so the greedy crowd could "steal" the potatoes. These 54 arpents of impoverished ground near Neuilly, west of Paris, had been allotted him by order of Louis XVI in 1787.
In 1771 Parmentier won an essay contest in which all the judges voted the potato as the best substitute for regular flour. This was before a time France needed a replacement for wheat, so Parmentier continued to face criticism and lack of acknowledgment for his work. The first step in the acceptance of the potato in French society was a year of bad harvests, 1785, when the scorned potatoes staved off famine in the north of France. In 1789 Parmentier published Treatise on the Culture and Use of the Potato, Sweet Potato, and Jerusalem Artichoke (Traité sur la culture et les usages des Pommes de terre, de la Patate, et du Topinambour), "printed by order of the king", giving royal backing to potato eating, albeit on the eve of the French Revolution, leaving it up to the Republicans to accept it. In 1794 Madame Mérigot published La Cuisinière Républicaine (The [Female] Republican Cook), the first potato cookbook, promoting potatoes as food for the common people. The final step may have been the siege of the first Paris Commune in 1795, during which potatoes were grown on a large scale, even in the Tuileries Gardens, to reduce the famine caused by the siege.
Parmentier's agronomic interests covered a wide range of opportunities to ameliorate the human lot through technical improvements: he published his observations touching on bread-baking, cheese-making, grain storage, the use of cornmeal (maize) and chestnut flour, mushroom culture, mineral waters, wine-making, improved sea biscuits and a host of other topics of interest to the Physiocrats.
Any dish whose name includes the description "Parmentier" will contain potatoes (especially mashed or boiled) as a major ingredient (e.g., potage Parmentier, brandade de morue Parmentier). The popular dish hachis Parmentier is very similar to cottage or shepherd's pie, consisting typically of a mixture of skinless mashed potato with finely ground meat which has been cooked before grinding. The ground meat can be mixed throughout the mashed potato or kept as a distinct layer in the middle or bottom. Common additional ingredients and seasonings include salt, pepper, chopped onions, chopped garlic, and a generous helping of butter or meat fat. The whole dish is baked briefly at high temperature to form a golden brown crust on the top.
Another dish named after the man who heightened culinary interest in potatoes is potage Parmentier, a leek and potato soup, puréed. Unpuréed, the soup is referred to as potage parisien. Pommes Parmentier is diced cubed potatoes fried in butter (bacon, onions, garlic or herbs can be added).
Some historians claim that any dish containing potatoes can be named "Parmentier" but even classic French potato dishes do not (pommes Anna, gratin dauphinois and the aforementioned potage parisien being examples).
Parmentier died on 13 December 1813, aged 76. He is buried in Père Lachaise Cemetery in Paris, in a plot ringed by potato plants, and his name is given to a long avenue in the 10th and 11th arrondissements (and a station on line 3 of the Paris Métro). At Montdidier, his bronze statue surveys Place Parmentier from its high socle, while below in full marble relief, seed potatoes are distributed to a grateful peasant. Another monumental statue of Parmentier, by French sculptor Adrien Étienne Gaudez, is erected in the square of the town hall of Neuilly-sur-Seine.