Effects of dynamic controlled atmosphere by respiratory quotient on some quality parameters and volatile profile of ‘Royal Gala’ apple after long-term storage

Abstract

The effects of dynamic controlled atmosphere (DCA) storage based on chlorophyll fluorescence (DCA-CF) and respiratory quotient (DCA-RQ) on the quality and volatile profile of 'Royal Gala' apple were evaluated. DCA storage reduces ACC (1-aminocyclopropane-1-carboxylate) oxidase activity, ethylene production and respiration rate of apples stored for 9months at 1.0°C plus 7days at 20°C, resulting in higher flesh firmness, titratable acidity and lesser physiological disorders, and provided a higher proportion of healthy fruit. Storage in a regular controlled atmosphere gave higher levels of key volatiles (butyl acetate, 2-methylbutyl acetate and hexyl acetate), as compared to fruit stored under DCA-CF, but fruit stored under DCA-RQ 1.5 and RQ 2.0 also showed higher amounts of key volatile compounds, with increment in ethanol and ethyl acetate, but far below the odour threshold. Storage in DCA-CF reduces fruit ester production, especially 2-methylbutyl acetate, which is the most important component of 'Royal Gala' apple flavour.

Extremely low oxygen partial pressures for the storage of ‘Royal Gala’ apple

“…Moreover, this enzyme is responsible for ethylene synthesis and is activated or inhibited depending on the concentration of the anaerobic metabolism products (Yang and Hoffman, 1984;Beaulieu and Saltveit 1997). A high concentration of acetaldehyde and ethanol can inhibit the activity of the ACC oxidase and reduce the ethylene production by fruit (Beaulieu and Saltveit 1997;Pesis 2005;Asoda et al 2009;Thewes et al 2015;Weber et al 2016;Both et al 2017), which helps to explain the low ACC oxidase activity in the fruits stored at 0.4 and 0.25 kPaO 2 . There was no significant difference for titratable acidity and soluble solids ( Fig.…”

“…This finding could be related to the damage due to accumulation of anaerobic metabolism compounds. However, when 'Galaxy' and 'Royal Gala' apples were in a DCA storage where the oxygen partial pressure was monitored by the respiratory quotient (DCA-RQ), and possessing an average O 2 near to 0.25 kPa, flesh firmness maintenance was observed (Thewes et al 2017;Both et al 2017). Figure 3.…”

“…The partial pressure of O 2 used during the storage is one of the most important factors in the CA storage. The reduction of O 2 to partial pressure that is too low (below 0.3 kPa O 2 ), may increase the production of volatile compounds such as alcohol, acetaldehyde and ethyl acetate, which in high concentrations can be harmful to the fruit, reducing the flesh firmness and increasing the occurrence of physiological disorders (Both et al 2017).…”

Model based leak correction of real-time RQ measurement for dynamic controlled atmosphere storage

“…During CA storage, fruit are exposed to a decreased O2 partial pressure, an increased CO2 partial pressure and a low temperature (Dilley, 2010;Ho et al, 2013). CA storage is intended to slow down respiration and other quality degradation processes that are associated with respiration (Saltveit, 2003;Verboven et al, 2006;Both et al, 2017). Optimal storage conditions are usually determined empirically as to deliver good quality after storage (Peppelenbos, 2003;Wright et al, 2012;Nock and Watkins, 2013).…”

“…This increase is therefore a good measure for low O2 stress (Gran and Beaudry, 1993;Jozwiak and Blanpied, 1993;Yearsley et al, 1997Yearsley et al, , 1996. RQ-DCA uses real-time estimates of the RQ of the stored fruit in the cool room to alter the CA setpoints continuously throughout the storage season based on measured changes of gas concentrations (Bessemans et al, 2015;Bessemans et al, 2016;Both et al, 2017, Thewes et al, 2017. Measured changes in CA composition of the cool room atmosphere are mainly caused by consumption of O2 and production of CO2 by fruit respiration (Hertog et al, 1998).…”