Studies on the Postharvest Physiology and Storage of Citrus Fruit

Citric acid metabolism in Satsuma mandarin fruit was investigated during storage for 90 days after harvest by injecting with citric acid-1, 5-14C into the fruit segment. The cumulative radioactivity of respired 14CO2 continued to increase after injection with the substrate and the curve nearly leveled off after 10 days. The substrate was metabolized rapidly to cationic and neutral fractions and proteins in both peel and segment of the fruit. The content of titratable acid in the peel and pulp of the fruit continued to decrease gradually during storage. The specific activity of citric acid in the pulp, therefore, decreased to one tenth within 10 days after injection, and retained a constant specific activity for the subsequent 50 days. It is concluded that the rate of turnover of citric acid in the fruit may be considerably high during storage period.