Effect of relative humidity under various packaging treatments on quality of grape fruits during cold storage

The influence of relative humidity (RH) under various packaging treatments on weight loss and quality of 'Kyoho', 'Campbell Early', and 'Muscat Bailey A (MBA)' grape fruits was investigated. Fruits were stored at -1 similar to 0 degrees C tinder various RE conditions for 50 days. Low-density polyethylene (LDPE) film (0.03 mm) with and without pores (5 mm diameter) was used to generate various RH conditions under packaging treatments. Two clusters (400-450 g fresh weight per cluster) were put into a white plastic tray (25 X 20 cm) and covered with LDPE film and then sealed. Control fruits were stored without packaging treatment. RH resulted from various packaging treatments were obtained as following; sealed bag without pores (RH 100%), 10 pores (RH 90-98%), 20 pores (RH 80-90%), 30 pores (RH 70-80%), open-coverage without sealing (RH 63-70%), and as control non-packaging (RH 48-65%). RH conditions greatly affect the weight loss in all grape fruits during cold storage. Cultivars with good storability, such as 'Kyoho' and 'Campbell Early', were less sensitive to lower RH conditions than 'MBA' and showed lower weight loss. However, storage Under RH 100%, sealed bag without pores, gave poor quality owing to decay induced by pathogens. Fruits stored at low RH (48-65%) had higher ethylene production, pH, and soluble solid contents but lower anthocyanin content than those at high RH (100%). Based on weight loss data observed through the study, we also could suggest a functional formular to predict weight loss (%) according to storage duration of grape fruits under various RH conditions resulted from packaging treatments of cold storage chamber.