Market Watch: The peak of flavor for San Joaquin Valley oranges

January is peak season for oranges from the San Joaquin Valley, the state’s leading growing area. It takes a little more care to obtain top-quality citrus from this district, where each variety has a relatively defined season, than fruit from Southern California, where citrus can hang on the tree much longer. Some of the best choices right now are Page, Washington navel and Moro blood oranges.

Page hybrid

Page is not a purebred orange, or even a mandarin, as it’s sometimes called, but a hybrid of Minneola tangelo and clementine made by the U.S. Department of Agriculture in 1942.

Great parents don’t always make a great fruit, but they did in this case. Minneola (itself a cross of the best-flavored grapefruit, Duncan, and the classic tangerine, Dancy) combined with old-fashioned clementine to yield a round fruit with a distinctive circular scar at the blossom end and an intense, very pleasant mandarin aroma.

Page never became a major commercial variety, however, probably because it is not all that easy to peel, is moderately seedy and is variable in size, with many small fruits. Size doesn’t matter to flavor, but the larger fruits tend to have more seeds. The best way to enjoy a Page’s tender, juicy flesh is to slice it into sixths or eighths.

The San Joaquin Valley Page season started a week ago and runs for a month. Southern California Pages will be available from February through April.

Washington navel

Navel oranges are tricky to time because, in addition to the original, the Washington navel, there are dozens of varieties, many of them earlier or later, grown in several districts. The exact variety is not often identified, even at farmers markets, but farmers will usually know if you ask.

The most dependable, never bettered for flavor, is the Washington navel, which became a sensation soon after arriving in Riverside from Brazil via Washington, D.C., in the 1870s. It is still the most-grown citrus variety in California.

Peak season for San Joaquin Valley Washington navels is January and February. As with other citrus, the Southern California season starts and peaks about a month later.

Many commercial growers, and some growers who sell at farmers markets, store fruit longer on the tree and delay the harvest by applying gibberellic acid, a natural plant growth regulator.

“Gibbed” fruit is paler in color, firmer in texture and harder to peel, but on balance the technology represents a plus for orange lovers, because it extends the season.

You can slice or peel navels, of course, but don’t turn them into juice unless you will drink it promptly, because after a day or so the flavor is degraded by a bitter compound called limonin, formed during juicing.

Moro blood orange

The Moro is California’s leading blood orange because its flesh is dramatically dark purplish, almost black in some specimens from the San Joaquin Valley. The flavor is distinctive as well, although I fail to detect the raspberry component alleged by many.

The variety’s main drawback is that it tends to be tart, so much so that in Italy, where it originated in the 1930s, it is primarily used for juicing rather than for eating fresh.

San Joaquin Valley Moros are sold commercially as early as Thanksgiving but don’t become acceptably sweet in a normal year until Christmas. They are even better from mid-January through February.

By the end of March, the anthocyanin pigments responsible for their red coloration break down into compounds that cause bitterness and off-flavors, so that over-mature specimens reek like old tennis sneakers.

Such overmaturity is not usually a problem with late-season Southern California Moros, which start in a few weeks at farmers markets and will be at their peak next month through April. They rarely get as dark as San Joaquin Moros but at their best develop a richer, more complex flavor.

The relationship between rind and flesh pigmentation is mysterious and undependable in blood oranges: Fruits with scarlet-streaked peels can be plain orange inside, or vice versa. Moros usually have at least some color inside, however.

A deep greenish-chocolate color that looks like it’s almost seeping out of the rind is a good indication that the flesh inside will be dark.

food@latimes.com