TROPICAL FRUIT QUALITY AFTER QUARANTINE TREATMENT USING IRRADIATION Peter Follett & Marisa Wall U.S. Pacific Basin Agricultural Research Center Hilo, Hawaii
Regulations key to the adoption of irradiation as a quarantine treatment US FDA approved irradiation doses up to 1000 Gy for preservation and disinfestation i ti of fresh fruits and vegetables (1986). USDA APHIS approved generic irradiation doses for quarantine disinfestation of fresh commodities (2006). 150 Gy tephritid fruit flies 400 Gy all insects except Lepidoptera
Hawaii two commercial irradiators Hawaii Pride E-beam/X-ray source Started 2000 Designed for fresh produce Low dose uniformity ratio Pa ina Hawaii Genesis irradiator (2012) Cobalt source Designed for fresh produce Low dose uniformity ratio
Hawaii: Irradiation treatments approved for export to U.S. Fruits Abiu Atemoya Banana Breadfruit Cherimoya Dragon fruit Guava Jackfruit Longan Lychee Mango Mangosteen Melon Papaya Pineapple Rambutan Sapodilla Star fruit Vegetables Bell pepper pp Eggplant Long bean Moringa Squash Sweet potato Tomato
Irradiation tolerance of fresh commodities Approved dose for Thai fruits is 400 Gy Dose uniformity ratio is 2.0-2.5, so 800-1000 Gy May be very close to the phytotoxic t limit it
Research objectives: Determine postharvest quality and composition at potential maximum irradiation doses to ensure fruit quality while providing quarantine security. Experimental design Multiple cultivars Varying harvest seasons Range of doses Uniform maturity & quality at start of expt. Adequate sample size and replication.
Dosimetry For fruit quality research, extensiv e dose mapping provides low dose uniformity ratios (1.05 to 1.15). 15) Commercial Max/Min Ratio Tropical fruit = 1.5 Sweet potato = 2.0
Tropical fruit irradiated, stored, ripened, and evaluated Irradiation 0, 400, & 800 Gy Storage 1 week at 10 C Ripening 22 C Quality analyses: days to ripe, weight loss, color, firmness, y y y p, g,,, disease, scald, soluble solids, acidity
Possible adverse effects of irradiation on fruit quality Altered ripening Pitting, darkening, discoloration, scalding Softening Loss of flavor or aroma Higher disease incidence Lower vitamin C and organic acids
Irradiation research: Multiple variables measured to determine postharvest quality at a range of irradiation doses. Initial maturity CO 2 & C 2 H 4 rates Firmness (peel and flesh) Weight loss Color (peel and flesh) Disease incidence Injury rating Days to ripe; shelf life Composition Sensory
Thailand: Fruits approved for export to U.S. using irradiation i (400 Gy) Fruit Dragon fruit Longan Lychee Mango Mangosteen Pineapple Rambutan (Guava) Cold storage 10 o C 2-4 o C 2-3 o C 8-13 o C 9-12 o C 7-13 o C 10 o C
Dragon fruit Doses : 0 to 800 Gy Three clones (white flesh & purple flesh) Two growing regions (dry, wet) Quality, composition, disease, shelf-life, & injury evaluated
Dragon fruit sugar concentrations decline slightly with 800 Gy treatment. Internal color and firmness not affected by irradiation. (mg. g -1 ) Sugar co oncentration 65 60 55 35 30 Fructose Glucose ncentration (mg. 100 g -1 ) Sucrose co 3.0 25 2.5 2.0 1.5 0 200 400 600 800 Irradiation Dose (Gy) 0 200 400 600 800 Irradiation Dose (Gy)
Dragon fruit tolerate irradiation at 800 Gy
Longan Doses : 0 to 800 Gy Biew Kiew Quality composition disease shelf life & Quality, composition, disease, shelf-life, & injury evaluated
Longan: some peel darkening after irradiation 0 Gy vs. 400 Gy 0 Gy vs. 800 Gy * Darkening may vary with harvest maturity.
Lychee Kaimana variety Irradiated d at 400 Gy Stored at 2 o C or 5 o C for 8 days Color, weight loss, % soluble solids, ph, acidity, external appearance, firmness, sensory Tolerant of irradiation Postharvest problems: peel darkening
Lychee Effect of time post-harvest on color
Rambutan 2 varieties Irradiated d at 400-800 Gy Stored for 1-3 weeks Color, weight loss, % soluble solids, ph, acidity, external appearance, firmness, sensory Tolerant of irradiation Postharvest problems: spinturn and peel darkening
Pineapple: variable response to dose Bract damage at 800 Gy Less mature fruit may have improper ripening after 800 Gy treatment.
Mangosteen: postharvest concerns l Probably tolerant of y irradiation at 800 Gy. Yellow latex and translucent flesh disorder
Mango cultivar and maturity important Negative: Peel injury 4 (scald, pitting, poor 3 ripening) 2 Positive: Delayed ripening (1 week after 300 Gy) Scald rating 1 0 0 Gy 400 Gy 800 Gy M BML PML BPM Fruit mixture 5 Haden Mango 0 Gy Mango 800 Gy
Mango combination treatment (Dr. Monique Lacroix, Canada, 1991) 20 days storage at 18 o C Control HW + Irradiated Irradiated
Considerations for irradiation treatment: Dose uniformity Cultivar Fruit maturity or stage of ripeness Fruit condition at harvest Postharvest and storage conditions (e.g. cold chain) Mode of transport
Future research topics What can you do to reduce phytotoxicity? Lower the radiation dose (mango and longan) Lower dose for pests below 400 Gy** Cold plus irradiation (e.g. melon fly) Reduce the dose uniformity ratio Pre-conditioning i treatmentt t Modified atmosphere packaging** Hypobaric storage**
Hawaii irradiation research: Lowering the dose for pests Pest Fruit flies (3) Sweet potato pests (3) Mango seed weevil Litchi fruit moths (2) Armored scales (2) Banana moth Ants (2) Light brown applemoth Spotted wing drosoph. Papaya mealybug Dose (Gy) 150 150 300 250 150 150 100 150 80 In progress
Thailand - Longan Lowering the dose below 400 Gy Quarantine pests Fruit flies (2) Maconellicoccus Scales (4) Conopomorpha Cryptophlebia Deudorix Radiation Dose (Gy) 150 250 (200?) 250 250 Deudorix (250?)
Modified atmosphere packaging Lower O 2 concentration and respiration Before treatment After treatment 19.8% 5.6% Mango, pineapple, rambutan: 3-5% O 2 + 5-10% CO 2
Hypobaric storage container Low pressure conditions: -15 mm Hg -Low oxygen - Refrigerate at 13 o C Fruit in a suspended state for 1-2 months
Thank you! Questions?