ナス果実の低温障害発生並びに表皮構造の変化に及ぼすコンディショニングの影響

Abstract

In this paper, the influence of pre-storage conditioning (at 10°C or 20°C for 5 days, 10 days or 15 days, respectively) on the occurrence of chilling injury and the change of surface structures in eggplant fruits stored at 1°C was examined. The surface structures were examined by scanning electron microscopy.Pre-storage conditioning extended the shelf life of eggplant fruits stored at 1°C by retarding chilling injury. The occurrence of pitting, the first symptom of chilling injury, was delayed by 2-3 days. In fruits stored at 1°C after conditioning, two types of pitting were observed; in one the pits were larger in size (100μm-1500μm) and fewer in number (referred to as type I pitting), while in the other the pits were smaller in size (100μm-300μm) and larger in number (reffered to type II pitting). In fruits stored directly after harvest, only type I pitting was observed.When stored after conditioning, type II pitting occured more frequently in fruits packaged in perforated polyethylene bags than in those packaged in sealed ones, while the occurrence of type I pitting was the reverse. Pasteurization, by dipping in ethanol after conditioning, reduced the occurrence of type II pitting.Circular protuberances were observed on the surface of fruit stored at 20°C. A fungus (Alternaria sp) was frequently observed on and near the protuberances, through which it frequently penetrated into the eggplant fruits.Sectioning of fruit showed first in type I pitting there was no destruction of epidermal cells that the destruction of parenchyma cells was the main cause of the pitting. In type II pitting, penetration of fungus was observed, indicating that destruction of epidermal as well as parenchyma cell seemed to be the cause of the pitting.