Chemical Compositions and Internal Anatomy of the Gelated and Granulated Juice Sacs of Sanbokan (Citrus sulcata hort. ex Takahashi) Fruit

Abstract

In Sanbokan fruit, chemical compositions of the granulated juice sacs in the stem-end region of segment and the gelated and granulated sacs in the middle region of segment were investigated. Some microscopical observations were also made on these juice sacs.
By the microscopical observations, we found that the epidermis of the granulated juice sacs were extremely thicker than that of the healthy sacs in the stem-end region of segment, but, in the middle region of segment, it was slightly thicker than that of the healthy sacs. Cell wall polysaccharide contents of the epidermis and inner parenchyma were suggested to be higher in the granulated sacs than the healthy sacs by staining with PAS.
Pulp and alcohol-insoluble solid (AIS) contents were higher in the granulated juice sacs than the healthy sacs. Cell wall polysaccharide content was also higher in the gelated and granulated sacs, and it was especially true for hot water, hemicellulose and cellulose fractions.
In the stem-end region of segment, free acids, flavonoids, carotenoids and RNA were lower, while bound acids, vitamin C, total-N, AIS-N and amino-N were higher in the granulated sacs than the healthy sacs. Total sugars differed little between them. In the middle region of segment, all the chemical components measured were lower in the gelated sacs than the healthy sacs. In the granulated sacs, however, AIS-N and amino-N were higher than in the gelated and healthy sacs, and total sugars, bound acids, flavonoids, carotenoids, vitamin C and total-N were higher than in the gelated sacs but lower than in the healthy sacs. RNA was almost the same as, and free acids were lower than in the gelated sacs.
In the stem-end region of segment, mineral components (crude ash, Ca, Mg, K, Na) were all higher in the granulated juice sacs than the healthy sacs. In the middle region of segment, they tended to be slightly lower in the gelated sacs than the healthy sacs. In the granulated sacs, Ca was higher, while K was lower than in the gelated sacs.
On the basis of these results, we discussed the development of gelation and granulation in juice sacs of Sanbokan fruit.