Seasonal changes in organic acid concentration were determined for ‘Eureka’ lemon (Citrus limon Burm. f. Eureka), an acid citrus species, Natsudaidai (C. natsudaidai Hayata) and Hyuganatsu (C. tamurana Hort. ex Tanaka), two table citrus species.
Citrate was the major organic acid throughout the season in all three species, amounting to 63.7 to 96.7% of the sum of recovered acids. Malate was the next abundant organic acid. Its concentration was less than 10% of citrate. The sum of citrate and malate amounted to 71.0 to 99.9% of the sum of recovered acids.
Harvest season of Natsudaidai and Hyuganatsu was when the concentration of both citrate and malate had decreased, while that of ‘Eureka’ lemon was when citrate showed its maximum concentration and malate was relatively high.
The highest value of the ratio of citrate to malate in ‘Eureka’ lemon was in May, well after the harvest season, while that of Natsudaidai and Hyuganatsu was prior to the harvest season.
Concerning the ratio of citrate to malate, the harvest season was similor for acid citrus species and table citrus species, i.e. the harvest season was fairly close to the season when the ratio decreased from a higher value.