UC Davis

Raspberry (Rubus ideaeus L.) fruit are high value but have a short shelf life due to fungal decay, leakiness, off-flavor, and loss of firmness. High CO2 in combination with low O2 can increase raspberry storage time and quality. In fall 2020 and 2021, we examined raspberry shelf life and sensory quality periodically during storage at 5℃ for two weeks in four different CO2 atmospheres; 15 kPa CO2, 6 kPa O2 (15 kPa); 8 kPa CO2, 13 kPa O2 (8 kPa); 5 kPa CO2, 16 kPa O2 (5 kPa); or 0.03 kPa CO2, 21 kPa O2 (0.03 kPa) to identify an ideal postharvest atmosphere that will increase raspberry shelf life without degrading the sensory quality. Raspberry visual attributes, color, glossiness, decay incidence and leakiness deteriorated over time in all atmospheres, but high CO2 atmospheres reduced fruit discoloration and decay, and slowed the rate of deterioration and leakiness. After 5 days, the quality of air stored raspberries was significantly degraded, while raspberries stored in elevated CO2 maintained firmness with bright red color up to 10 days. In 2021, a trained sensory panel conducted a descriptive sensory evaluation of the raspberry fruit periodically during storage and found that raspberries stored in 8 or 15 kPa atmospheres had significantly lower off-flavor and higher tartness scores. Raspberries stored in 8 kPa atmosphere scored highest in raspberry flavor with substantial juiciness and sweetness scores. The fermentative volatiles; acetaldehyde and ethanol were higher in raspberries stored in 15 kPa atmosphere, while most other raspberry volatiles decreased with increasing CO2 concentration, including flavor-related volatiles α-ionone, α-terpineol, limonene and linalool. While raspberries stored in 15 kPa atmosphere had longer shelf life, the decrease in flavor-related volatiles was most pronounced in this fruit. However, fruit stored in 8 kPa atmosphere had better sensory quality and 10 days of shelf life and was the optimal atmosphere for raspberry in our study. Raspberries should not be stored in air beyond 5 days without modified or controlled atmospheres.