Analysis of Histological and Chemical Factors Related to the Ease of Pellicle Removal in Japanese Chestnut

Abstract

Histological and chemical factors related to the separation between the pellicle and ker-nel of Japanese and Chinese chestnut cultivars were analyzed. Peeling time and weight of each tissue of nut of Japanese chestnut (Castanea crenata Sieb. et Zucc.) and Chinese chest-nut (C. mollissima Blume) were measured.1. A negative correlation exists between the peeling time and the moisture content of the pellicle (r= -0.616**), whereas it was positive between the peeling time and the alcohol in-soluble solid (AIS) content in the pellicle (r=0.551**).2. The pellicle of Japanese chestnut, which is difficult to peel, was thick in comparison with that of Chinese chestnut, which is easy to peel. There was a negative correlation be-tween peeling ratio and thickness of pellicle in the cultivar and selections (r= - 0.836*).However, there was no relation between the surface area of the pellicle in contact with the kernel and the peeling character of individual nuts.3. When the nut of the Japanese chestnut was still immature, it was easy to peel; and tan-nin like cells were not yet recognizable in the pellicle. Before pellicle was difficult to peel from kernel, tannin like cells, which contained phenolic compounds, were formed in pellicle. As the tannin like cells in the pellicle increased, the pellicle became increasingly more difficult to peel. After the nut fell down from tree, phenolic compounds accumulated in all of pelli-cle tissue and surface of kernel.4. The degree of adhesion between the pellicle and kernel is not based on a physical bind-ing, but we attribute the adhesion to a chemical process involving the formation and action of polyphenolic compounds in the pellicle.