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Enzyme gets the guava juice out.

Enzyme Gets the Guava Juice Out

Juice from freshly picked guavas adds a light, clean taste to fruit beverages and carbonated drinks.

Food processors can extract a clear juice from guavas using natural enzymes, says ARS food technologist Harvey T. Chan at Hilo, Hawaii.

Chan and co-researchers reported recently that enzymes they've tested during the past few years yield more juice, in a shorter time, than those Chan tried more than a decade ago. What's more, today's guava juice is clearer and thinner, making it less likely to clog filters or narrow tubing used in producing sodas, sparkling water, and fruit juice blends. Blockages caused by bulky pulps, in contrast, can sometimes wreak havoc in bottling plants.

The thinner, clearer, amber-colored juice is also easier to make into a more highly concentrated product; that is, one that has very little water in it. "Because of the reduction in volume and weight," explains Chan, "it costs less to transport and store a concentrate than a full-strength juice. Later, at the bottling plant, you can add back as much water as you want."

Guava juice is high in vitamin C. It's also a good natural source of citric acid. That's an advantage for makers of all-natural beverages who need something besides synthetic citric acid to get the perfect balance of sweet and tart flavors in their product.

The hardworking enzymes Chan and colleagues used hasten the separation of juice from the thick pulp. The enzymes, called pectinases, speed the natural breakdown of pectin, a component of fruit cell walls.

In nature, fruits release their own pectinases as they ripen and soften. The scientists opted for pectinases derived from a fungus, Aspergillus niger.

Raised in indoor vats, A. niger is a prolific producer of the pectinases that are widely used to make wines or extract clear juice from apples, pears, pineapple, and about a dozen other fruits.

Chan worked with food technologists Aurora S. Hodgson and Catherine G. Cavaletto at the University of Hawaii and Conrad O. Perera at New Zealand's Department of Scientific and Industrial Research. They found that the enzymes work well on any kind of puree--fresh, thawed, or shelf-stable aseptic packs (the kind used for boxed juices).

Pectinases take about 2 hours to break down the pectins in guava puree that's heated to 122 [degrees] F.

Although some of the nation's largest beverage companies have inquired about the clarified guava juice, they have yet to add it to their products, Chan says. But he and co-workers are still confident of the potential of taday's clearer and thinner guava juice.

"When you list guava on a product label," Chan notes, "you're adding the appeal of both an exotic tropical fruit and an all-natural ingredient."

Harvey T. Chan, Jr., is with the USDA-ARS Tropical Fruit and Vegetable Research Laboratory, P.O. Box 4459, Hilo, HI96720. Phone (808) 959-9138
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Title Annotation:Agnotes
Author:Wood, Marcia
Publication:Agricultural Research
Date:Jan 1, 1992
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