Respiratory pathway metabolism and energy metabolism associated with senescence in postharvest Broccoli (Brassica oleracea L. var. italica) florets in response to O2/CO2 controlled atmospheres

• High O2/CO2 may be an ideal strategy for maintaining qualities of broccoli florets.
• To extend the broccoli storage time through studying its respiratory pathway and ATP.
• We found a negative correlation between the amounts of ATP extent and senescence of broccoli.
• 50% O2 + 50% CO2 treatment could enhance the stress resistance of broccoli.

Broccoli is a highly perishable vegetable with abundant nutritional and medical value. Recent studies indicated that O2/CO2 controlled atmospheres (CA) was an effective method for broccoli storage.In this study, ATP (adenosine triphosphate) content, energy charge level, respiratory pathway and their key enzymes of broccoli (Brassica oleracea L. var. italica) were investigated, employed CA treatments of 70% O2 + 30% CO2, 60% O2 + 40% CO2, 50% O2 + 50% CO2, 40% O2 + 60% CO2, 30% O2 + 70% CO2 at 10 °C. The 50% O2 + 50% CO2 treatment led to an obvious decrease in respiration rate of broccoli and it could inhibit the reduction of ATP level, energy charge level, SDH (succinic dehydrogenase), CCO (cytochrome oxidase), and boost the G-6-PDH (glucose-6-phosphate dehydrogenase) + 6-PGDH (6-phosphogluconate dehydrogenas) activity. Treatment of 50% O2 + 50% CO2 suppressed reduction of the TCA (tricarboxyfic-acid-cycle) and CCP (cytochrome oxidase pathway) rate, and increased the HMP (phosphopentose pathway), while had little impact on the EMP (embden-meyerhof-parnas) rate and PGI (phosphohexose isomerase) activity. Compared to 50% O2 + 50% CO2 treatment, treatment of 30% O2 + 70% CO2 had an opposite effect on broccoli. Results indicated that O2/CO2 controlled atmospheres could alter the proportion of respiratory pathway, and 50% O2 +  50% CO2 treatment could enhance the endurance capability of broccoli to high CO2 concentration according to the changes of respiratory pathway and delay in its senescence though relatively higher ATP.

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