Is the physiological maturity at harvest influencing nectarine flavour after cold storage?

Peach and nectarine are often harvested immature to withstand the postharvest handling without considering the consequence on fruit quality and therefore consumer’s satisfaction and their likelihood of repurchase. Indeed, the inaccurate determination of the optimal harvest time leads to a considerable reduction in fruit quality at consumption. Despite fruit volatile organic compounds (VOCs) being positively associated with the consumer acceptance, VOCs are not well-considered in the optimization of pre- and postharvest fruit management. The aim of this research was to investigate the effect of fruit physiological maturity at harvest on the development of VOCs during a simulated postharvest chain. Fruits of ‘Stark Red Gold’ nectarine, harvested at different maturity stages, determined by the “index of absorbance difference” (IAD), were stored at 1°C (90-95% RH) for 20 days then maintained 6 days in shelf-life at 20°C. The evolution in aroma production was monitored in each day of shelf life by proton transfer reaction – time of flight – mass spectrometry (PTR-ToF-MS). Besides the VOC measurement, fruit were assessed for the main quality traits: soluble solids content, flesh firmness and titratable acidity. Results of this research shows that the concentration of the main aroma compounds such as lactones (mainly γ- and δ-decalactones) and esters (mainly methyl acetate) increased during the progression of ripening while aldehydes (mainly pentanal) and C6-aldehydes (predominantly hexanal and 3-hexenal) decreased. However the concentration of these compounds, irrespective of the harvest maturity stages, was significantly reduced after cold storage, indicating a negative effect of low temperature in the development of aroma compounds. In addition fruit senescence was clearly marked by an enhanced emission of off-flavour compounds, such as ethanol, acetaldehyde and methanol.