ATLANTA -- The bitter taste commonly associated with packaged grapefruit juice has long soured many potential consumers. But now Cornell University food scientists say they have developed a special type of "active" container that significantly reduces the bitterness.
"Juices deteriorate over time now, but with active packaging the juice product might actually improve," says Joseph Hotchkiss, Cornell professor of food science.
Research into the new packaging was the work of Nelda de Fatima Ferreira Soares, as part of her Cornell doctorate, which was awarded this year. Hotchkiss was her adviser. Soares is a food scientist with the Departamento de Tecnologia de Alimentos, Universidade de Federal de Viaosa, in Viaosa, Brazil.
Hotchkiss will discuss the packaging breakthrough at the Institute of Food Technology (IFT) conference in Atlanta June 24.
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 shelf life 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, says Hotchkiss, are two compounds, glycosidic flavanone naringin and triterpenoid lactone limonin. Naringin is the bitter component found in most fresh citrus fruit and, therefore, freshly processed citrus juices. Limonin forms when the 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 an enzyme called naringinase (which contains alpha-rhamnosidase and beta-glucosidase); when the juice comes into contact with the food-safe film, its bitter taste is reduced due to the activity of the enzymes.
Soares and Hotchkiss found that the surface area of the film had a great bearing on how fast the juice loses its bitterness. The researchers also found that as the film area increases inside the now-active package, the naringin was reduced more quickly. Indeed, a panel of nonprofessional tasters reported that the grapefruit juice with a reduced level of naringin made the grapefruit juice taste sweeter, even though the sugar in the juice was not increased by the neutralization of the naringin.
Says Soares: "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 might improve during storage."
Hotchkiss' talk at the IFT conference, titled "Improving Citrus Juice Quality Through Active Packaging," will begin at 9 a.m.