Relationships among volatile metabolites, quality and sensory parameters of 'Italia' table grapes assessed during cold storage in low or high CO2 modified atmospheres

Table grapes (cv. Italia) were stored at 5 degrees C in air or in modified atmosphere with low O-2 (1%) and low (0.03-10%) or high (> 20%) CO2. Volatile organic compounds (VOCs) associated with quality (respiration rate, acetaldehyde and ethanol, water status of rachis) and sensory parameters (visual quality, rachis browning, characteristic odour and flavour, off-odour and off-flavour) were evaluated. Low CO2 preserved the quality and sensory parameters, whereas high CO2 caused a fermentative metabolism. A total of 126 VOCs were identified by HS-SPME/GC-MS analysis. Principal component analysis (PCA) identified (Z)-2-hexenal and (E,Z)-2,4-hexadienal as potential marker of freshness; whereas, acetaldehyde, ethanol, 1-butanol, 3-methyl-1-butanol, 1-octanol and 1-nonanol were correlated to fermentation processes. Partial least-square regression analysis (PLSR) was used to identify (R-2 = 0.95) the main predictors of off-odour as ethanol and ethyl acetate (+) and hexanal and beta-linalool (-).