Anti-Pucker Chemical Sweet News for Citrus

A biochemist at the U.S. Department of Agriculture’s research center here 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 from the fruit, according to Hasegawa and industry officials.

If successful, Hasegawa’s process could save the California orange industry could save 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 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 on trees 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 that Hasegawa’s experiments are moving the industry “closer than we’ve ever been” to finding a way to prevent the bitterness.

“We are very much excited about this because it’s a very big problem in California,” he said. “We’re excited enough to bring him up here and see if it works.”

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

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, as has been the focus of other scientists.

Hormone Experiments

Hasegawa said that 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.

The next step is to try the chemical in the field.

One California orange grower, Fred LoBue of LoBue Brothers Inc. in Lindsay, said that 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 mask 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.

Unlike the laboratory experiments, in which the trees were injected, the orange trees in the grove will be sprayed to absorb the naphthaleneacetic acid through their leaves, Hasegawa said. Injecting each tree would be impractical, he said.

“Then, with a little luck, we’ll find out by the end of the year if it works,” Hasegawa said.

Although he will not be able to prevent the development of all limonin, Hasegawa said he is optimistic that as much as 80% can be halted.

Approval Needed

If Hasegawa’s process works, it would have to be approved by the federal Food and Drug Administration, said Emil Corwin of the FDA’s Center for Food Safety and Applied Nutrition in Washington.

Hasegawa said that since his discovery has been publicized, he has received inquiries from Florida, which produces primarily sweet-juice oranges but is interested in the possible benefits to other citrus fruit.

He has also heard from other citrus-producing countries, including Brazil, Japan, Israel, Italy, Australia, Spain and China, where bitterness has been even more of a problem.

For years, scientists in those countries have been trying with varying degrees of success to prevent bitterness.

In Japan and Italy, the citrus industry is using a process in which the juice is poured through absorbents, including activated charcoal, to remove the bitterness, Kimball said.

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