Microbiology and Quality Attributes of ‘Pione’ Grapes Stored in Passive and Active MAP

Abstract

The quality of ‘Pione’ grapes was evaluated during passive and active modified atmosphere packaging (MAP) storage. In the passive MAP study, ‘Pione’ grapes were packaged in two types of films with an oxygen transmission rate (OTR) of either 440 mL/m2/d/atm (low OTR) or 1250 mL/m2/d/atm (high OTR) and stored at 25 °C or 10 °C. When the CO2 concentration in low and high-OTR films stored at 25 °C reached 10% and 3%, respectively, on day 2, grape berries showed lower bacterial counts in the low-OTR films than in the high-OTR films. At 10 °C, the packages approached an equilibrium of 12% CO2 in low-OTR films and 7% CO2 in high-OTR films during 8 days of storage, and no difference was observed in the bacterial counts between the two films. In an active MAP study, ‘Pione’ grapes were stored in low-OTR (440 mL/m2/d/atm) and high-OTR (1170 mL/m2/d/atm) films flushed with air or high CO2 (10%, 20%, and 30%) at 10 °C for 8 days. The CO2 concentration in active MAP with low-OTR films reached approximately 20% by the end of storage, while that with high-OTR films approached an equilibrium of 10% CO2 after 4 days of storage. The bacterial counts remained below the limit of detection until 4 days of storage in active MAP with high-OTR films. Although the fungal counts of berries were non-detectable or below the limit of detection in all active MAPs, Alternaria and Candida fungi and Chryseobacterium and Cutibacterium bacteria were found in the berries stored in active MAP. The firmness, soluble solid content, and surface color of the berries were not affected, regardless of the film type, in both passive and active MAP, and rachis browning due to high-CO2 injury was not observed in any samples in active MAP. These results indicate that passive MAP with low-OTR films or active MAP of 10–20% CO2 with high-OTR films at 10 °C were the optimum packing systems for ‘Pione’ grapes to control the physical and microbiological quality without high-CO2 injury, such as rachis browning.