L8 - Chilling Injury Flashcards

1
Q

What is Chilling Injury (CI)?

A

Chilling injury is a disorder caused by exposure to low temperatures.

Not freezing temperatures!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Are all cultivars of a species sensitive?

A

No, some cultivars are less sensitive than others, even within a species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Typical CI symptoms

A
  1. Developmental disorders

-Incomplete or inhibited ripening:
Excessive softening
Deficient aroma and flavour
Unable to colour

  1. Physiological symptoms
  • Pitting
  • Skin yellowing
  • Tissue decomposition / internal or surface browning
  • Fungal or bacterial rot
  • Mealy texture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

CI may occur in

A

-(long distance) transit: Often sea transport is cheaper
Tropical fruit
Flower transport

-market distribution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Difficulty with CI is that symptoms are often

A
  • Not visible during cold storage
  • Only visible during shelf-life
  • Often economic losses due to CI are not recognised!
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

CI for tomatoes (low temperature storage)

A
  • for green harvested tomatoes -> increased softening (effects on firmness: sunken areas,pitting)
  • for red harvested tomatoes -> decrease of lycopene (antioxidant) -> tomato turns orange (effects colour + fungal decay and water soaking)
  • volatiles break down
  • hexanal (grassy green odour) -> decreases
  • mouldy off flavour -> increases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Physiology of Chilling Injury

A

Chilling injury is caused by membrane ruptures:
Membranes start to leak: electrolyte leakage

Membranes create pockets inside the cell with conditions optimized for:

  • Photosynthesis
  • Respiration
  • Protein synthesis
  • Gene transcription, etc
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why do membranes rupture?

A

-Low temperature makes membranes less fluidic

  • Respiration is the source of energy for plant products
  • consists of many steps, in different (membrane) compartments
  • Less membrane fluidity means that respiration becomes less efficient…as transport is hindered

-ROS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

ROS (Reactive Oxygen Species). How do they work? what is the resutl?

A

ROS oxidize the membrane lipids,

resulting in membrane rupture and cell death

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q
A

Fruits & vegetables are generally able to cope with short amounts of low temperatures…and will recover

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What natural defences do plant products have?

A
  • Presence of unsaturated fatty acids in the bilayer

- Presence of antioxidants in the bilayer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

unsaturated fatty acids

A

Ratio of unsaturated fatty acids higher in chilling resistant cultivars

-ROS will react with the double bonds.
But also makes the bilayer less fluidic.
So this is only a temporary defense

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Presence of antioxidants

A
  • Antioxidants have a high affinity to react with ROS
  • Are in the membrane and protect the membrane
  • 1 molecule of vitamin E (fat soluble) can protect about 200 fatty acids
  • Vitamin E is recycled (E and C work together) by vitamin C (water soluble)
  • Chilling resistant tomato cultivars have higher vitamin C levels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How to measure Chilling injury?

A
  1. Breakdown products of lipid peroxidation: malondialdehyde
  2. Electrolyte leakage (conductivity measurements)
  3. Chlorophyll Fluorescence
  4. Weight loss
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do WE deal with Chilling Injury? (1/4)

A

A. Pre storage dips (1-3 mM) with:

  1. Jasmonic acid (tomato)
  2. Salicylic acid (peach/pomegranate)
  3. Glycine betaine (green peppers)
  4. Gibberellins (tomato)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How do WE deal with Chilling Injury? (2/4)

A

B. Induces plant defences:

  1. Production of ascorbic acid
  2. Production of antioxidant enzymes
  3. Induces Heat Shock Proteins: help partially unfolded proteins in the bilayer to refold
17
Q

How do WE deal with Chilling Injury? (3/4)

A

Pre storage hot water dips

Typically a 2-5 minutes at 40-50 °C
Induces also plant defences

Increase chilling tolerance for: 
citrus fruit
Kiwifruit
Tomato
papaya
18
Q

How do we deal with chilling injury ? (4/4)

A
Intermittent warming : warming every 7 days to 20oC
-two cycles optimal
-cultivar/growing conditions dependent 
(far-red treatment)
-workds for bell peppers
19
Q

Sensitive to CI

A
  • tropical/subtropical fruits
  • tomato <15
  • banana <10
  • culinary herbs (basil) <10
  • anthurium, gerbera <15
  • peaches,nectarines
  • avocado, mango
  • chrysanthemum
20
Q

Non-sensitive to Cl

A
  • lettuce (high quality at 0oC)
  • brussels sprouts (high quality at 0oC)
  • some apples
  • broccoli, cauliflower
20
Q

LOOK at summary conclusions

A