Naringin and limonin are the principle bitterness components of citrus juices. Our objective was to determine if the perceived bitterness in grapefruit juice could be reduced during storage through interaction with active packaging ®lm. Storage of 10°Brix grapefruit juice at 7°C in contact with fungal-derived naringinase immobilized on cellulose acetate ®lm reduced bitterness as perceived by a sensory panel. The ®lms reduced naringin and limonin concentration by hydrolysis and adsorption respectively. Reduction in the naringin and limonin content of grapefruit juice by cellulose acetate ®lms containing immobilized enzyme from 600±400 mg/l and 8.0±6.7 mg/l respectively could be detected as a reduction in bitterness by a sensory panel (p `0.10). As the area of ®lm (cm 2 )/volume of juice (ml) ratio increased from 1.1 to 3.6, the time to decrease the naringin level decreased. The reduction in naringin was not affected by agitation or holding the samples quiescently. The amount of enzyme desorbed from the ®lm represented only 2% of the amount of enzyme immobilized in the ®lm. The reduction in bitterness comes from direct interaction with the active packaging ®lms.