The present invention provides a sugar content-improving material that can prevent oxidative damage of fruits and vegetables after harvesting as well as can improve the sugar content, a method for improving the sugar content of fruits or vegetables, fruits or vegetables having an improved sugar content, a sugar component-adjusting material, a method for adjusting a sugar component of fruits and vegetables, fruits or vegetables having an adjusted sugar component, a taste-adjusting material, a method for adjusting the taste of fruits or vegetables, and fruits or vegetables having adjusted taste. The sugar content-improving material includes a breathable, permeable and flexible sheet containing proanthocyanidin and trehalose. The proanthocyanidin is contained in the sheet in a proportion of 250 to 300 mg/m2. The trehalose is contained in the sheet in a proportion of 5 g/m2.
