Citrus Researchers Put the Squeeze on Bitter Juices

A biochemist at the U.S. Department of Agriculture’s research center in Pasadena may have solved a multimillion-dollar problem that has plagued the world’s citrus industry for years.

After 2 1/2 years of study, Shin Hasegawa thinks he has found a chemical that prevents newly squeezed fruit juice from becoming bitter.

Some juice, especially that from California navel oranges, develops a bitter taste within hours after being squeezed, Hasegawa and industry officials said.

If successful, Hasegawa’s process could save the California orange industry between $3 million and $8 million a year, officials said. California accounted for 32.8% of U.S. orange production in 1985, according to the most recent state Food and Agriculture Department figures available. The state’s orange crop was valued at $524 million.

Tests Near

Hasegawa and his team of researchers are about to take their discovery out of the laboratory and test it in an orange grove in the San Joaquin Valley community of Lindsay. But it has already won praise from growers and fruit processors.

Dan Kimball, director of research and development for California Citrus Producers Inc. in Lindsay, said Hasegawa’s experiments are moving the industry “closer than we’ve ever been” to finding a way to prevent the bitterness.

For years, scientists in the United States, Israel, Japan, Italy and Australia have been trying to solve the bitterness problem.

In Japan and Italy, juice is poured through absorbents, including activated charcoal, to remove the bitterness, Kimball said.

That process is not popular among American processors because it is expensive and neutralizes Vitamin C, he said.

Although it is most pronounced in the juice of navel oranges, the bitterness is present in the seeds and peels of all citrus fruits, including Valencia oranges, lemons and grapefruit. But it is more noticeable in the seedless navels, which account for about half the orange production in California.

The bitterness comes from the chemical limonin, which develops during the growth cycle. After the fruit is squeezed, the bitter limonin taste grows stronger.

To counteract the bitterness, Hasegawa and his researchers have been concentrating on preventing the bitterness from occurring rather than removing it from the juice after it has been squeezed.

Hormone Experiments

Hasegawa said he and Edward D. Orme, Peter Ou, Zareb Herman and Chi H. Fong began experimenting two years ago with plant hormones that had been used on grapes and apple and pear trees to prevent premature ripening. They hoped that the hormones, called auxins, would retard the development of limonin.

After injecting about 2,000 different auxins into citrus trees at their Pasadena laboratory, the scientists found one that worked, Hasegawa said.

The discovery that naphthaleneacetic acid worked to prevent the formation of limonin “was just a matter of luck,” he said.

One California orange grower, Fred LoBue of LoBue Brothers Inc. in Lindsay, said if bitterness can be prevented, it could make the difference between “surviving or not surviving” for some farmers during lean years.

“It sounds good to me. We can draw a little better return for our products,” said LoBue, whose farm includes 500 acres of navel oranges and 200 acres of Valencias.

The “better return” would come from selling more pure fruit juice, rather than losing money by having to sell so much as a juice ingredient.

Bitter Juice Rejected

Juice processing companies, such as California Citrus Producers and Sunkist, squeeze the oranges and sell the juice or concentrate to other companies for packaging and marketing. Juice packaging companies buy the sweet juice from Valencias, for example, for about $1 a gallon, but do not want the bitter juice, Kimball said.

Bitter juice must be sold at a reduced price, about 80 cents a gallon, to soda and fruit drink companies, which use it in products they market as containing “5% real juice,” he said. The high sugar content of those drinks masks the bitterness, Kimball said.

Hasegawa said an experiment is scheduled to begin in May on about 10 to 15 navel orange trees in a California Citrus Producers grove in Lindsay.

If the process works, it would need approval from the federal Food and Drug Administration.