New packaging sweetens the taste of grapefruit juice

The bitter taste commonly associated with packaged grapefruit juice has long soured many potential consumers. But now Cornell University food scientists (Department of Food Science, Stocking Hall, Ithaca, NY 14853) have developed a container that significantly reduces the bitterness. Juices deteriorate over time, but with this active packaging the product's quality might actually improve.

Typically, fresh grapefruit juice found in the refrigerated sections of grocery stores is packaged either in polymer containers or paperboard containers lined with polymers. The shelflife of the grapefruit juice is about six weeks from the time it is processed. The causes of the bitter taste that leads many shoppers to reject grapefruit juice are two compounds: glycosidic flavanone naringin and triterpenoid lactone limonin.

Naringin is the bitter component found in most fresh citrus fruit and freshly-processed citrus juices. Limonin forms when fresh fruit juice is pasteurized. Fruit acids give an undesirable bitterness to the packaged juice. To counteract this, the researchers developed an active, thin cellulose-acetate film layer on the inside of the packaging, in place of the normal polymer lining. This layer of film contains the enzyme naringinase, which contains alpha-rhamnosidase and beta-glucosidase. When the juice comes into contact with the film, its bitter taste is reduced due to the activity of the enzymes.

Researchers found that the surface area of the film had a great bearing on how fast the juice lost its bitterness. They also found that as the film area increased inside the now-active package, the naringin was reduced more quickly. A panel of nonprofessional tasters reported that the grapefruit juice with a reduced level of naringin made the product taste sweeter, even though the sugar in the juice was not increased by the neutralization of the naringin.

This work demonstrates that an active packaging system may be feasible. Unlike the current situation where most foods deteriorate in quality during storage, products exposed to enzymes bound to packaging materials might improve during storage.

Further information. Joseph Hotchkiss; phone: [phone]; fax: [phone].