Peter Mondavi, shown in 2005, began his winemaking career in 1943. (Eric Risberg/AP)

Peter Mondavi, who steered his family’s Charles Krug Winery for more than half a century in California’s Napa Valley and used cold fermentation to produce crisper, fruitier white wines, died Feb. 20 at his home in St. Helena, Calif., on the Charles Krug estate. He was 101.

The wine company announced the death but did not disclose a cause.

Mr. Mondavi began his career in Napa in 1943 when his parents paid $75,000 to buy the winery, which was founded in 1861 by Prussian emigrant Charles Krug, making it the oldest operating winery in the region today. Peter Mondavi assumed the role of chief executive after his mother’s death in 1976 and retired last year, turning over the operations to his two sons, Marc and Peter Jr.

When the Mondavi family got into the winemaking business, Napa had a lackluster reputation for quality. It was mostly jug wine, sold on the cheap. “Vin ordinaire,” Peter Mondavi later quipped. Peter and his older brother Robert operated the winery for 22 years, and they made notable advancements in quality.

Charles Krug became the first winery in Napa to import French oak barrels for aging and was among the pioneering vintners who planted pinot noir and chardonnay grape plants where dairy cows had previously dominated the Carneros region of the valley.

Moreover, Peter Mondavi had “studied the effects of cold fermentation on white and rosé wines, which were then being fermented at higher temperatures and losing their distinct characteristics through oxidation. His revolutionary research and practical methods resulted in the production of exceptionally crisp, fruity white wines.”

The brothers had markedly different personalities that eventually caused a breach in family relations for years. “I’m conservative,” Peter Mondavi told Time magazine. “Bob is an extravert, a promoter.”

Their feuds about the business’s future reached a low point in November 1965, when they got into a fistfight. “When it was all over, there were no apologies and no handshake,” Robert Mondavi wrote in his 1998 memoir, “Harvests of Joy.”

He soon left Krug to start Robert Mondavi Winery in Oakville, Calif., but legal entanglements between the two family branches persisted until the case was settled in 1978. Robert Mondavi Winery was acquired by Constellation Brands in 2004.

Peter Mondavi was born in the northern Minnesota town of Virginia, a once-thriving home to iron-ore mining, on Nov. 8, 1914. He was the youngest of four children.

His mother, Rosa, ran a boardinghouse for Italian iron miners while his father, Cesare, opened a saloon. Prodded by other Italians, Cesare began making and selling wine. He would travel to California to buy grapes and, in 1922, the family moved to Lodi in San Joaquin County.

Peter Mondavi, who got his start as a boy nailing boxes for his father’s business, received an economics degree from Stanford University in the late 1930s. He conducted wine-making research at the University of California at Berkeley before serving in the Army Air Forces in Europe during World War II. After his discharge, he was named production manager at his family’s winery.

His wife, the former Blanche Hurtzig, died in 2010. Survivors include three children; and many grandchildren and great-grandchildren. Robert Mondavi died in 2008.

Asked late in life to note his proudest accomplishment, Peter Mondavi replied: “Never losing control of our family winery. If I could, I would tell my father: I did the best I could during the difficult years. I was determined and we held on.”