The Cause of Occurrence of Pulp Hardening Syndrome in Pickled Japanese Apricot Cultivar ‘Nanko’

Abstract

Emergence of pulp hardening syndrome in the pickled ‘Nanko’ Japanese apricot is a serious problem of quality management. This study investigated the cause of this syndrome. The hardened pulp was estimated to include callose because the cell walls were stained with aniline blue. When the fresh fruit demonstrated a cavity adjacent the stone and the cell walls surrounding the cavity were stained with aniline blue, the fruit was found to develop pulp hardening when pickled. These findings suggest that wounding the pulp during removal of the stone causes the formation of pulp hardening by accumulation of callose in the cell walls. The pulp pulled away from the stone due to vigorous fruit thickening. In addition, decreased starch content in the bearing branch or drought stress during the early stage of fruit growth will decrease the cell numbers, which may also promote pulp removal.