Natural Compound Improves Apples' Red Coloring
Methyl jasmonate helps
deepen the blush on
the cheeks of Fuji apples.
Methyl jasmonate (MJ) has many functions. This natural
compound derived from plant oilsespecially jasmine and honeysuckle
oilshelps plants muster pest-defense proteins. Incorporated into
cosmetic products, it produces a sweet, flowery aroma. Now, spraying
MJ onto apples before harvest may improve uniformity and depth of red
coloring in the fruit's peel, new research suggests.
"Applying MJ increases the total percentage of the
crop having uniform red color, an important grading issue for domestic
and export markets," says ARS
plant physiologist James Mattheis.
The approach draws on published research showing that
when apples are exposed to natural or artificial light, MJ activates
processes in the peel that produce anthocyanin pigments. MJ also breaks
down the peel's green chlorophyll, though light isn't required.
"Application timing is important; treat too early
in the season, and the color can fade by harvest," says Mattheis,
who heads ARS' Tree Fruit Research Laboratory in Wenatchee, Washington,
a state forecast to produce 88.8 million boxes of fresh-market apples
Though research is ongoing, ARS in May 2002 applied for
patent protection (10/146,687) on the treatment, since no similar products
are currently marketed, notes Mattheis, whose research team includes
graduate student Dave Rudell and food technologist Xuetong Fan.
One particular use for MJ may be ensuring a more uniform
red color on Fuji apples that have spent much of the growing season
enclosed within opaque bags. In the United States and Japan, where Fujis
originated, bagging is practiced to enhance the apple's red color close
to harvest. Starting in late June, more than a month after a Fuji's
flowers have bloomed, two overlapping bags are placed around the immature
fruit by hand and kept in place until a few weeks before harvest (late
September to early October in Washington). Even after the bags are removed,
the red color continues to develop, albeit unevenly. Spraying MJ helps
correct for this by promoting red color development on all sides of
the apple, Mattheis notes.
MJ also works on such popular varieties as Red Delicious
and Gala. "We didn't see any significant change in eating quality
compared to untreated fruit," says Mattheis of lab and orchard
studies in which apples were treated with a water-based emulsion containing
a surfactant and 2 percent or less MJ.
Other positives: MJ also works on harvested fruit for
degreening, and is already classified by the Food and Drug Administration
as a Generally Recognized As Safe substance. Despite its promise, MJ
needs further evaluation. Too much can harm the fruit, and at about
$43 an ounce, the economics of orchard-scale treatments are uncertain.
"We're still not totally there in terms of minimizing
the variability," Mattheis says. "We're still trying to improve
MJ formulation and timing and better understand the factors that influence
success with this treatment."
But if the approach bears fruit in terms of consistency
and cost, apple growers could get a head-start on improving their crop's
Suszkiw, Agricultural Research Service Information Staff.
This research is part of Crop Production, Product Value,
and Safety, an ARS National Program (#303) described on the World Wide
Web at www.nps.ars.usda.gov.
"Natural Compound Improves Apples' Red Coloring" was published in the May 2003 issue of Agricultural Research magazine.