On a small island known for olives and wild monkeys, Rika Onishi spends her days tasting and sniffing sesame oil. She's one of a small group of Kadoya Sesame Mills Inc. employees who make sure the oil always has the same taste and aroma.

"We're getting customers to eat this, so we need to take it seriously," she says.

Founded in 1858, Kadoya imports sesame seeds from Africa and turns them into the edible oil commonly used in Japanese and other Asian cuisines. Generations of families have worked at Kadoya's sole plant on Shodoshima Island off Shikoku, meticulously producing thousands of tons of oil a year.