Degreening Difficult-to- Degreen Citrus Fruit: Cn it e done? Mrk Ritenour University of Florid Indin River Reserch nd Eduction Center
Why is Degreening Necessry? Consumers ssocite green citrus fruit with immturity (poor qulity) Fruit color is due to the interction of chlorophyll (green) nd crotenoid (red yellow) pigments Color chnge in the field is stimulted when nighttime tempertures drop elow 55F
Pre-hrvest Fctors Aginst Degreening Wrm wether prticulrly wrm nights Regreening in the Spring Fctors tht promote vigorous growth high rinfll high nutrient levels (esp. N & K) Field oil sprys Peel oil (e.g., from rushing) Some scle insects (e.g., chff & purple scle)
The Gol Remove chlorophyll (green pigment) Promote crotenoids (yellow-ornge pigments) Temperture optimums re different for chlorophyll & crotenoids Degreening does not ffect internl qulity of the fruit
Recommended Degreening Conditions Florid Temperture 28 to 29 o C (82 to 85 o F) Ethylene 5 ppm Humidity 90 to 96% Ventiltion (keep elow 0.1% CO 2 ) 1 ir chnge per hour Air Circultion 100 CFM per 900 l. in (CFM = cuic feet per minute)
Potentil Prolems The wrm nd humid conditions experienced during degreening promotes decy Ethylene stimultes growth of some decy pthogens, such s Diplodi nd Anthrcnose
Potentil Prolems Tempertures too high ove 85F, slows rte of chlorophyll degrdtion, nd increses fruit metolism, decy, nd rekdown
Grierson & Newhll, 1953 Temperture Hmlin ornge Mrsh GF
Potentil Prolems Ethylene nd wrm conditions promote tissue senescence. 32F 41F 50F 59F 68F 77F 86F 95F
Potentil Prolems Tempertures too high ove 85F, slows rte of chlorophyll degrdtion, ut increses fruit metolism, decy, nd rekdown Poor ventiltion & ir circultion = uneven temperture distriution nd locl uildups of CO 2 in the room Both = uneven color development
Ventiltion Removes wste gsses (e.g., CO 2 nd possily peel oil vpor) 1% CO 2 cn out stop degreening Continuous ventiltion is etter thn periodiclly opening the room Excessive ventiltion wstes ethylene nd (when used) heting
Potentil Prolems Poor ir circultion = uneven temperture distriution nd locl uildups of CO 2 in the room Both = uneven color development
Potentil Prolems Tempertures too high ove 85F, slows rte of chlorophyll degrdtion, ut increses fruit metolism, decy, nd rekdown Poor ventiltion & ir circultion = uneven temperture distriution nd locl uildups of CO 2 in the room Both = uneven color development Too much wter in the rooms fruit stys wet = slower degreening & incresed decy pressure Ethylene is not very solule in wter
Hue Hue */* rtio */* rtio 12.0 6.0 ge time (d) Use of LED Lights 4 6 4 6 rge time (d) 4 6 rge time (d) 8.0 2 3 5 7 storge time (d) Fruit first dipped for 1 min in 0.39 1,000 ppm ethephon (releses ethylene) 0.31 Blue LED 0.23 light significntly improved colortion (hue & 0.15 /) storge time (d) Yes: grpefruit, Nov-hrvested 0.55 0.47 30.0 N 24.0 No: Fllglo, Nvel, or grpefruit hrvest in Dec 18.0 R Red LED light hd no effect 12.0 Neither ffected internl qulity6.0 Dr. LiLi Deng 2 3 5 7 2 3 5 7 storge time (d) 2.0 0.4 0.33 0.26 0.19 0.12 0.05 22.0 18.0 14.0 10.0 6.0 2.0 O S 10h 2 4 6 8 storge time (d) Grpefruit (NOV) 10h 2 4 6 8 storge time (d) 10h 2 4 6 8 storge time (d)
Effect of cold shock on peel color Dr. Suming Di 32 cold shock 70 F degreening Cold shock resulted in etter peel color thn the commercil control fter 4 dys degreening no shock 85 F degreening
Cold Shock Effects Influenced y 3 Fctors Degreening temperture Cold shock ws not effective when the fruit were degreened t the norml 85F Degreened t 85F Degreened t 70F Dr. Suming Di
Cold Shock Effects Influenced y 3 Fctors Degreening temperture Cold Shock temperture Dr. Suming Di Degreened t 70F
Cold Shock Effects Influenced y 3 Fctors Degreening temperture Cold Shock temperture Prehrvest field tempertures Cold shock eventully enhnced fruit color development on Verni fruit hrvested in Dec No cold shock enefit in Jnury fter cold temps in the field
hrvest Fruit from second hrvest experienced cold shock in the field hrvest Dr. Suming Di
Conclusions Depending on citrus vriety, degreening t cooler tempertures cn improve finl color A 15 hr, pre-degreening cold shock (32F) could improve finl peel color of Verni Only worked when degreening t 70F, not t 85F No enefit fter nturl cold tempertures in the field Even fter 6 dys degreening, color ws still not gret
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