Firmness was measured using a digital force gauge pressure
tester (model AD-4932-50N, ADTaiwan) fitted with a 5 mm cylinder
tip. Two measurements were performed on opposite equatorial
sides of each berry; 30 berries per each developmental stagewere analyzed. The mean was recorded and expressed as Newtons
(N) ± standard deviation (S.D.). After measurement of firmness, the
peduncle and calyx of each fruit were removed, and the fruit cut
longitudinally into two halves, frozen in liquid nitrogen and stored
at −80 ◦C until use.