Membrane deterioration during postharvest senescence of broccoli florets: modulation by temperature and controlled atmosphere storage

Abstract

Abstract When freshly cut heads of broccoli ( Brassica oleracea L.) are stored in air at 23°C or 10°C, the florets rapidly senesce. Chlorophyll levels decline by 80–90% within 4 days at 23°C and within 10 days at 10°C, and under the same storage conditions microsomal phospholipid phosphate and fatty acids in the florets decline by 70–90%. The breakdown of membrane phospholipids is accompanied by a large decrease (… 35%) in bulk lipid fluidity of the membranes. These changes are temperature-dependent inasmuch as they are completely inhibited during storage for comparable periods in air at 5°C. Also, the potential of microsomal membranes isolated from florets to degrade exogenous, radiolabelled phosphatidylcholine increases during storage in air at 23°C or 10°C, but not at 5°C. Storage at 5°C or 10°C in a controlled atmosphere (5% CO 2 , 3% O 2 , 92% N 2 ) at … 80% relative humidity strongly inhibits loss of chlorophyll and the change in microsomal bulk lipid fluidity reflecting phospholipid breakdown. Thus reduced integrity of thylakoids and membrane phospholipid degradation appear to be inherent features of broccoli floret senescence that are sensitive, directly or indirectly, to ambient CO 2 and O 2 concentrations. These observations confirm the potential of using controlled atmospheres to enhance the storability of broccoli and identify physiological and biochemical parameters of floret senescence that can be used to establish optimum controlled atmosphere conditions.