Postharvest Physiology and Quality of Gai-Lan (Brassica Oleracea var. Alboglabra) and Choi-Sum (Brassica Rapa subsp. Parachinensis)
Postharvest quality changes of gai-lan (Brassica oleracea var. alboglabra) and choisum (Brassica rapa subsp. parachinensis) are similar to those observed in other cool-season Brassica vegetables. For gai-lan, average respiration rates were 8, 10 and 29 μl CO2/g-h at 0°, 5° and 10°C, respectively; for choi-sum the corresponding rates were 5, 8, and 17 μl CO2/g-h. Ethylene production by both products was <0.1 and <0.3 nl/g-h at 0° and 10°C, respectively. Fresh leaves, tender and fresh stalks, and developed but closed flower buds are important quality criteria for gai-lan and choi-sum. Common postharvest defects included flower bud deterioration, leaf dehydration and yellowing, and stem pithiness. Pithiness and flower bud deterioration usually occurred more rapidly in choisum than in gai-lan. Visual quality attributes of gai-lan and choi-sum were best maintained at 0°C and a shelf-life >21 days was achieved at that temperature. Products stored at 5°C maintained marketable quality for 7 to 14 days; shelf-life was reduced to 3 to 4 days at 10°C. Ethylene (1 ppm) exposure at 5°C decreased shelf-life of both products approximately 30%.