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Optimising degreening conditions
to reduce lemon chilling injury
Andrew Macnish, Hung Duong, Lawrence Smith, Andrew Mead, Peter Hofman
Supply Chain Innovations, DAF Queensland
Serviced
Supply
Chains
Monitoring fruit quality during export
• Lemon shipments occasionally arrive in Asian markets with an unacceptably high incidence of skin defects
• Variation in fruit source, harvest time, degreening and pre-cooling practices and shipment temperatures could contribute to these defects
When things don’t go to plan
Monitoring from farm to retail
• Variation in degreening room temperature and ethylene
concentrations were observed in central Qld facilities
Time (day)
0 2 4 6 8 10 12 14 16
Eth
yle
ne c
on
cen
tratio
n (
ppm
)
0
10
20
30
40
Time (day)
0 2 4 6 8 10 12 14 16
Tem
pera
ture
(oC
)
20
25
30
35
Farm 1Farm 2
When things don’t go to plan
Monitoring from farm to retail
• Shipment temperatures varied between 2-3oC
When things don’t go to plan
Trial 1. Temperature x ethylene
Aim: Identify effect of temperature and ethylene concentration
on skin colour and defects
Materials and method:
• Late season 2017 ‘Eureka’ seedless lemons were harvested
from three blocks at a Qld farm
• Fruit were degreened at 3 temperatures (24, 29, 34oC) and
3 ethylene concentrations (0, 5 and 29 ppm) for 3 days
• After degreening, fruit were stored at 1oC for 21days then
held at 20oC for 6 days to assess skin defects
Identifying contributing factors…
Fruit assessment:
• Minolta colour meter was used to measure skin colour (hue angle)
• Chilling injury (CI) was assessed using a 0-3 rating scale .
113o 106o 99o 96o
0; nil 2; 1-3 cm2 3; >3 cm21; <1cm2
Defined CIDiffuse CI
Trial 1 Results
Ethylene concentration (ppm)
0 5 10 15 20 25 30
Skin
co
lou
r (H
o)
92
93
94
95
96
97
98
99
100
242934
LSD
Degreening temperature (oC)
Effect of temperature and ethylene on colour development
96o
After 3 days of degreening
Effect of temperature and ethylene on CI incidence
Degreening at 24oC plus 5 ppm ethylene gave the best
outcome in terms of colour and minimising skin defects
Ethylene concentration (ppm)
0 5 10 15 20 25 30
Ch
illin
g in
jury
in
cid
en
ce
(%
)
0
10
20
30
40
5024 29 34
Degreening temperature (oC)
LSD
Ethylene concentration (ppm)
0 5 10 15 20 25 30
Rots
(%
of
fruit a
ffecte
d)
0
10
20
30
40
5024
29
34
Degreening temperature (oC)
Lsd
Trial 1 Results
Diffuse browning
Trial 2. Temperature x time
Aim: Identify the optimal time and temperature to degreen
lemons without increasing skin defects
Materials and method:
• Early season 2018 ‘Eureka’ seeded lemons were harvested
from three blocks at a Qld farm
• Fruit were degreened with 5 ppm ethylene at 20, 23, 26, and
29oC for 0, 1, 2, 3 and 5 days
• They were consolidated at 7oC for 2 days
• Fruit were stored at 1oC for 21days then held at 20oC
Identifying contributing factors…
90
95
100
105
110
115
2023
2629
01
23
4
5
Skin
colo
ur
(Ho)
Temperature (o C)
Degreening duration (day)
95.5 95.0
94.894.9
95.2
95.1
95.9
95.496.9 96.4
Cold removal/Sea freight
Trial 2 Results
90
95
100
105
110
115
2023
2629
01
23
4
5
Skin
colo
ur
(Ho)
Temperature (o C)
Degreening duration (day)
96.596.3
94.4
95.2
96.5
94.7
After degreening
Effect of duration and temperature on skin colour change
Trial 2 ResultsEffect of duration and temperature on skin defects
Removal
time (day)
% of fruit with any diffuse chilling
injury at retail assessment
% of fruit with any rot at retail
assessment
Temperature (oC) Temperature (oC)
20 23 26 29 20 23 26 29
0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
1 3.3 0.0 0.0 6.7 0.0 0.0 0.0 0.0
2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.3
3 0.0 0.0 6.7 3.3 3.3 6.7 10.0 0.0
5 0.0 6.7 6.7 0.0 3.3 3.3 0.0 13.3
• Chilling and rots tended to occur on fruit that were degreened at higher
temperatures (26 and 29°C) and for the longest time (5 days).
Ensuring good fruit quality in-market
• Be aware that fruit robustness varies
• Don’t degreen above 26°C with ethylene
• Don’t treat with more than 5 ppm ethylene
• Do degreen lemons at 20-24°C for 3 days
• Do condition fruit for 1-3 days prior to cooling
• Ensure shipment temperatures are maintained
just below the maximum protocol limit
Wouldn’t it be great if we could predict
the robustness of lemons for export?
The Serviced Supply Chains project is funded by the Hort Frontiers Asian Markets Fund, part of the Hort Frontiers strategic partnership
initiative developed by Hort Innovation, with co-investment from the Department of Agriculture and Fisheries, Queensland, Department of
Jobs, Precincts & Regions (Victoria), Manbulloo (mangoes), Montague Fresh (summerfruit), Glen Grove (citrus), the Australian
Government plus in-kind support from The University of Queensland and the Chinese Academy of Sciences.
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