DEBBIE ELLIOTT, host:

As we turn to this week's food moment, let us consider poor Lady Macbeth as she roamed in sleep, crying, Out, damned spot. She could never scrub her hands of the bloody stain of her crime. Lady Macbeth may have been better off had she merely juiced a blood orange. The vibrant pigments in blood oranges do stain, but according to exotic fruit connoisseur David Karp, they're water soluble and should wash off easily in the sink.

David Karp joins us now for an appreciation of this dramatic and yet perfectly legal winter fruit that's making its appearance now in some markets. Karp recently wrote about blood oranges for the publication "Fruit Gardener."

Welcome.

Mr. DAVID KARP (Fruit Connoisseur): Hi, Debbie.

ELLIOTT: Blood oranges do have this dramatic air. You even tell the story of a woman who notices the fruit on one of her trees and suspects her neighbors of foul play.

Mr. KARP: That's right. There was a Mrs. Smith. She lived in Moorpark, California in the 1980s. She suspected her neighbor of injecting blood or some kind of poison into her beloved Valencia orange tree. She called the police. The police were flummoxed. They brought the fruit to the University of California at Riverside's Citrus Variety Collection, where the authorities eventually told them this woman's tree has recapitulated the birth of the blood orange in China some thousands of years earlier. It developed a mutation.

ELLIOTT: Recapitulation? Explain this.

Mr. KARP: It re-enacted the birth of the blood orange. The presence of the red pigment in blood oranges, which is their distinctive characteristic, is due to anthocyanins, which are also responsible for the red coloration in cherries and apple skins and numerous fruits and vegetables.

Most oranges, common oranges, only have one of the two genes necessary to create red pigments, but blood oranges have both of them.

ELLIOTT: How does the taste of the blood orange differ from the oranges, say, that we have everyday in our orange juice?

Mr. KARP: Well, you know what, there is no one blood orange, curiously enough. There's the Moro, the most darkly pigmented one, which can be almost purple black on the inside, and almost chocolaty greenish on the outside. And that tends to be tart, tarter than a navel or Valencia orange that we're most familiar with.

In Italy they looked down their nose at the Moro and they consider the supreme orange de tabla, the table orange, the Tarocco. And those are sweeter. They're tenderer, more rag-free; that is, there's less chewy stuff in your mouth after you've eaten a segment. And those are considered absolutely the finest eating oranges that there are in the Mediterranean.

ELLIOTT: Now, what do those varieties share? What is it about their taste that's different from the blonder varieties?

Mr. KARP: You know, the first mention of blood oranges in Western literature, Ferrari's "Hesperides" from 1646, a book in Latin published in Italy, described them as having a grape-like flavor. Now, that's one of many attempts that been made over the years to describe the unique flavor of blood oranges, which is different, but I don't know if anybody could actually describe precisely was it is.

ELLIOTT: Now, we have noticed that blood oranges tend to be a favorite on Valentine's Day menus. We've seen dishes like grilled snapper with (unintelligible) and beet blood orange chutney, or Mire lemon pistachio tort with rose water syrup and blood oranges. It all sounds very nice. What is your favorite way to eat a blood orange, David Karp?

Mr. KARP: I'll just slice it usually because that way the flesh is actually next to my lips and next to my palate. I can taste the juice that way best. Or I juice it. Third favorite would be to peel it and to eat the segments like you would a navel orange.

However, I wouldn't recommend wearing a white cashmere sweater as you set out to messily eat a blood orange and spatter juice all over the place because who knows whether they will ever come out or not.

ELLIOTT: David Karp writes about fruit for the New York Times and other publications. And he's working on a new book about fruit connoisseurship.

Thank you for talking with us.

Mr. KARP: Thank you. Transcript provided by NPR, Copyright NPR.