γ-Irradiation treatment decreased degradation of cell-wall polysaccharides in blueberry fruit during cold storage

The influence of irradiation treatment on the relevant indices of blueberry (Vaccinium spp.) softening during cold storage was studied by irradiating Bluecrop blueberries with 60Co source at a dose of 2.5 kGy. The effect of irradiation treatment on the firmness and ultrastructure of the cell walls of blueberries and the variations of the content and molecular weight of cell wall polysaccharides were investigated. γ-Irradiation postponed and delayed softening of fruit during cold storage. After 35 d of storage, the irradiated blueberry fruit 1.08 kg/cm2 firmer than that of control group. In addition, cells were more intact and were more tightly arranged. The content of water-soluble pectin (WSP) increased more slowly, while the contents of EDTA (ethylene diamine tetraacetic acid)-soluble pectin (ESP) and 24% KOH-soluble fraction (24KSF) decreased at a lower rate in irradiated fruit compared with untreated fruit. The content of the total cell wall materials (CWMs) remained unchanged. High-molecular weight polymers in the fruit were less likely to be degraded. However, no significant influences were shown on the sodium carbonate-soluble polysaccharide (SCSP) and 4% KOH-soluble fractions (4KSF). Therefore, γ-irradiation maintained the intactness of cell walls through regulating the solubility and adhesion of polysaccharides in cell walls of the fruit, thereby reducing softening of blueberry fruit during cold storage.