The distribution of bitter principles, and its processing properties, in grapefruit

Naringin and limonin are some of major bitter principles in grapefruit (Citrus paradisi). In order to clarify the distribution of naringin and limonin in grapefruit, their concentrations in each part of the grapefruit were measured. Fruits imported from the USA and South Africa were used. Domestic fruits were also used for comparison. The fruits were separated into four parts and each part was analyzed by HPLC. The distribution of naringin and limonin in the four grapefruit was not very different among all the fruits. Naringin was significantly contained in the albedo, and limonin was significantly contained in the segment membrane. The juice vesicles contained both naringin and limonin, at an average of 178mg/100g and 9.05mg/1,000g, respectively. This showed that naringin and limonin were the primary cause of the bitterness in grapefruit and its juice. Also, in the juice vesicles, the naringin concentration in the solution was very low. This suggested that naringin was significantly present in the membranes of the juice vesicles. Furthermore, it was determined that the limonin concentration of the fresh grapefruit juice using a household mixer was significantly increased within a few hours after juicing.