Quality and Volatile Emission Changes of `Mondial Gala' Apples during On-tree Maturation and Postharvest Storage in Air or Controlled Atmosphere

Starch index (SI), color, firmness, titratable acidity (TA), soluble solids content (SSC), ethylene production, and aroma volatile emission were recorded weekly during on-tree maturation of `Mondial Gala' apples. Fruit were harvested on commercial date and held for 3.5 and 6.5 months in regular atmosphere (RA) or in three controlled atmospheres (CA) (2% O₂ :2% CO₂, 1% O₂ : 1 % CO₂ and 1% O₂ :3% CO₂). After each storage period plus 0 and 7 days at 20 °C, color, firmness, TA, SSC, aroma volatile emission, acetaldehyde and ethanol concentrations, and sensory acceptability were evaluated. At orchard, changes in SI, SSC, background color, and aroma volatile emission were almost concomitant or slightly previous to the increase in ethylene production. During storage, all three CA conditions, regardless of storage period, led to better preservation of standard quality. CA-stored fruit also received higher acceptability scores, although aroma volatile emission was decreased in response to these storage conditions. At the end of long storage (plus shelf life period), fruit stored in 1 :1 atmosphere showed a good retention of firmness and TA in comparison to the rest of CA-fruit. Fruit stored under all considered CA conditions showed similar aroma volatile emission after 3.5 or 6.5 months of storage. Storage period had no apparent influence on the aroma volatile emission of CA-stored apples, with the exception of fruit stored in 2:2 atmosphere immediately upon removal from storage. No significant differences in sensory acceptability were found either for fruit stored under different CA conditions during 3.5 months immediately after transfer to 20 °C. In contrast, fruit stored in either 1 : 1 or 2: 2 atmospheres during 6.5 months were better accepted by consumers than those stored in 1 : 3 atmosphere upon removal from cold storage. However, these differences disappeared after 7 days of shelf-life at 20 °C.