(WSJ) - WHEN MICHEL ROLLAND was named the winemaking consultant to France's Château Figeac two months ago, a great protest was registered in certain wine-drinking circles. The St. Émilion grand cru would be ruined; the wine would be "Rolland-ized," opined drinkers posting on a popular discussion board. One reader even declared that the move was "a disaster for all fans of Figeac." The impassioned discussion ran to seven pages and lasted two weeks. Who would guess that a winemaking consultant—even the world's most famous one—had the power to provoke such an outpouring of passion, not to mention a purported ability to destroy a Bordeaux estate?

Winemaking consultants range from professionals who might offer a word of advice on the final blend to those who are involved in every phase of the winemaking—from the vineyard to the bottling line. While consultants have been employed for decades, the profession has lately been the subject of much debate: Do consultants actually help elevate the wines of an individual estate, or do they simply stamp out the same wine over and over again?