Weakening of pummelo pulp in relation to their anatomy, Ca content, CO2 and C2H4 concentration, and activity of pectin methylesterase
1989
Rommanee Charoensub
Cross-sectioned structure of juice sac, Ca content, internal CO2 and C2H4 concentrations and pectin methylesterase (PE) activity in the pulp were studied in relation to pulp weakening of pummelos (Citrus maxima Merr.) cv. Khao Thongdi and cv. Khao Paen harvested at 7 months after full bloom. The pulp of Khao Paen was weakened less than that of Khao Thongdi. This characteristic was coincided with the cross-sectioned structure of the juice sac membrane. The number of layer of subepidermal cell in Khao Paen was higher than that in Khao Thongdi. After storing for one month, the integrity of the cell wall of these subepidermal cells was apparently decreased particularly in Khao Thongdi. The PE activity in Khao Thongdi was higher than that in Khao Paen, and might be responsible for the difference in weakening level of these two cultivars. The internal C2H4 concentration of Khao Thongdi was significantly higher while CO2 concentration was less than that in Khao Paen. The CO2 concentration measured was too low to give significant physiological response. The Ca content in Khao Thongdi was 3.66 mg./g. dry weight which was higher than that in Khao Paen (1.49 mg./g. dry weight). This study revealed that the difference in weakening between these two cultivars was affected by the difference in structure of the juice sac, internal C2H4 concentration and PE activity.
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