Abstract
The contents of bitter substances and their seasonal changes in some varieties of citrus fruit in Japan were investigated with reference to bitterness of fruit juice. (1) Three methods for measuring naringin content were compared each other in the juice and the other parts of citrus fruit. The most accurate values were obtained by a high pressure liquid chromatography (HPLC) and the values close to those of HPLC by the potassium borohydride reduction method. However, a modified DAVIS' method gave misleading higher values. (2) The naringin content was 300-1200mg/100g in segment wall, central axis and albedo, and less than 100g/100g in flavedo and pulp (juice sacs). Each content of limonin was 1000-2000ppm in seed and less than 500ppm in peel and segment wall. In pulp, limonin content was less than 30ppm, and nomilin content was less than 10 ppm. The amount of these bitter substance decreased during ripening of fruit. (3) The content of the bitter substances was compared each other in various kinds of fruit juice prepared by using the four types of juice extractor. Its content varied in the range of 100-300%, according to procedures of the preparation. (4) In a sensory test, the minimum concentration of the above substances which was perceived bitterness by 50% of panel was 8mg/100g in naringin, 4ppm in limonin, and 3ppm in nomilin and by 100% of panel was 20mg/100g in naringin, 12ppm in limonin, and 8 ppm in nomilin.
