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.