Use of Ethylene Gas for Degreening of Sweet Orange (<i>Citrus sinensis</i> Osbeck) ev. Mosambi

Abstract

Ethylene gas was applied by trickle method to ‘Mosambi’ sweet orange (<i>Citrus sinensis</i> Osbeck) fruits in a specially designed chamber (170 cm length × 170 cm width × 227 cm height, internal dimensions) for degreening. Three sprays of carbendazim (500 ppm) were applied to fruits on tree at 15 d interval prior to harvesting. Complete degreening of green but mature Mosambi fruits (TSS 9-10 per cent and titratable acidity nearly 0.30 per cent) was achieved within 48 h with 5-10 ppm ethylene at 27-29^oC and 90-95 per cent RH with four air changes/h and air circulation of 0.5-0.6 L/s/kg fruit. Ethylene-exposed fruit developed bright

yellow colour with hue angle less than 90^o while non-exposed fruit remained green with hue angle of 100°. The 48 h treatment resulted in 1.95-2.15 per cent mass loss in ethylene-exposed and control fruits. Respiration rate increased from initial 35 to 80 mg CO₂/kg/h in ethylene-exposed fruits in 48 h and slowly declined after removal from ethylene atmosphere. Fruit firmness, juice content and total soluble solids and ascorbic acid remained unchanged with ethylene treatment but titratable acidity declined significantly (p < 0.05). Fruit rind degreening continued in treated and untreated fruits during storage at 24±4^oC. The hue

angle was almost similar at the end of 30 d in degreened and non-degreened fruits but intensity and brightness were lower in the latter. Polyethyelene liner minimized mass loss during storage with no difference due to ethylene treatment (p > 0.05) but cumulative decay losses due to <i>Geotrichum candidum</i> were higher in non-degreened<span style="font-size:7.5pt;font-family:Fd470610-Identity-H; mso-bidi-font-family:Fd470610-Identity-H"> fruits (p < 0.05 ).

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