Ripening is a process in fruits that makes them acceptable for consumption by converting starch to sugar, changing color, and developing full flavor and aroma. Ripening is triggered by the plant hormone ethylene in climacteric fruits like bananas and tomatoes, causing a spike in respiration. In commercial operations, controlled ethylene exposure is used to induce ripening. Treatment with 1-methylcyclopropene binds ethylene receptors and inhibits ripening, allowing longer storage of climacteric fruits.

1. Fruit Ripening
V. Siva Shankar
12-541-009
TNAU

2. Ripening
• Ripening is a process in fruits that makes it acceptable for
consumption. The fruit becomes sweeter, and softer.
• During ripening starch is converted to sugar.
• The fruit is said to be ripe when it attains its full flavour and aroma
(watada et al., 1984).
• Ripening causes colour change in the fruit.
• Based on ripening behaviour, fruits are classified as:
– Climacteric
– Non Climacteric

3. Fruits show dramatic increase in the rate of respiration
during ripening and well respond to ethylene for ripening
Climacteric Fruits
Eg. Apple, Banana, Mango, Tomato

4. Fruits do not show dramatic increase in the rate of
Respiration during ripening and do not respond to
Ethylene for ripening
Non - Climacteric Fruits
Eg. Citrus, Grapes, Pineapple & Watermelon

5. produces
H2C=CH2
(ethylene)
induces/turns on
genesenzymes
(for enzyme synthesis)
producing
degrade
parts of fruit resulting in
increasing
(chlorophyll, acids, starches,
pectin, proteins, etc.)

6. BIO SYNTHESIS -- ETHYLENE
Methionine Adenosyl Methionine
ACC
Ethylene
ACC Synthase
ACC Oxidase
O2
Amino
Cyclopropane
Carboxylic acid
AdoMet Synthetase
ATP

7. Changes during ripening
• Cell wall
• Starch
• Organic acids
• Pigments
• Flavouring compounds
• Ascorbic acid
• Phenolics
• Amino acids and proteins
• Respiration
• Transpiration
• Ethylene evolution rate

8. Cell wall changes
• It is rich in polysaccharides are degraded and
solubilised during ripening (Jona and Foa, 1979).
• Loss of neutral sugars such as galactose and
arabinose (Tuker et al., 1987).
• Enzymes responsible for cell wall hydrolases
• Pectineasterase
• Polygalacturonase
• Cellulase
• β -galactosidase (Tuker, 1993)

9. Starch
• Amylase degrades starch to sugar, hence the
mealy quality to juiciness.
• Thus the starch is fully hydrolysed into sugars is
known as characteristic event for fruit ripening
(Hulme, 1978).
• Starch degrading enzymes in fruits are
• α-amylase
• β- amylase
• Phosphorylase
• α- 1, 6-glucosidase (Garcia et al., 1988)

10. Organic acids
• The total organic acids(malic + citric +quinic) is
decreased with ripening of fruits (Wang et al 1993).
• The decline in the content of organic acids during
ripening is the result of an increase in membrane
permeability (kliewer, 1971).
Pigments
• Degradation of chlorophyll pigment results in
anthocyanins or carotenoids.
• Phenylalanine ammonia lyase and flavone synthase
are the key enzymes for synthesis of anthocyanins
(Tucker, 1993).
• Biosynthesis of carotenoids lycopene acts as the
precursor of β- carotene.

11. Flavouring Compounds
• Interaction of sugars, organic acids, phenolics
and volatile compounds.
• Esters, alcohols, aldehydes and ketones.
Ascorbic acid
• Ascorbic acid is increase with fruit growth in
pome, pear etc
• Thereafter the levels declined with the
advancement of maturity and onset of fruit
ripening (Sharma, 1995).

13. Respiration
• Respiration is the process by which stored organic
materials (carbohydrates, proteins, fats) are broken
down into simple end products with a release of
energy.
• Respiration involves degradation of food reserves,
especially sugars, in order to produce chemical
energy (in the form of ATP and NADH) needed to
maintain cellular metabolic activity.

14. Transpiration
• Water loss is a main cause for direct
quantitative loss, appearance, textural quality,
and nutritional quality.
• Transpiration is physical process that can be
controlled by applying some treatments to the
commodity. (like waxes and other surface
coating or wrapping with plastic films).

15. Current Ripening Methods
• Calcium Carbide is widely using chemical to hasten the ripening.
• It contain traces of arsenic and phosphorus, these are toxic and
may be hazardous to health.
• Calcium Carbide reacts with moisture in the air to produce
acetylene gas. Acetylene gas acts as a ripening agent, but is believed
to affect the nervous system by reducing supply of oxygen to the
brain.
• It is banned under Rule 44-AA of PFA (Prevention of Food
Adulteration) Rules, 1955.

16. Ripening with Artificial Ethylene
• Scientific and safe ripening method accepted worldwide.
• Ethylene is a natural plant hormone that the fruit itself emits
as it ripens.
• Ethrel or ethaphon (2-chloroethane phosphonic acid).
• Exposure of unripe fruit to a miniscule dose of ethylene is
sufficient to stimulate the natural ripening process until the
fruit itself starts producing ethylene in large quantities.
• The use ethylene to promote ripening is permitted under
FDA regulation 120,1016.

17. Ripe Fruit
chemical
cause
The hormone ethylene initiates the ripening response:
Unripe Fruit
physical
condition
Green
Hard
Sour
Mealy
chlorophyll
pectin
acid
starch
chemical
cause
red
soft
neutral
sweet + juicy
physical
condition
anthocyanin
less pectin
neutral
sugar
hydrolase
pectinase
kinase
amylase
Enzyme Produced
H2C=CH2

18. The four major factors for commercial
ripening
• Temperature control.
• RH control.
• Ethylene gas.
• Adequate air circulation.

19. Commercial Use of Ethylene
• Methods of application – cylinders of ethylene or
banana gas (C2H4 in CO2) with flow meters.
– ethylene generators (liquid ethanol plus catalyst
produces C2H4)
– ethylene-releasing chemicals
(e.g. Ethephon = 2-chloroethanephosphonic acid)

20. Commercial Use of Ethylene
• Ethylene concentration and duration of treatment:
– physiological responses saturated at 100 ppm.
– mature climacteric fruit should initiate endogenous
ethylene production within no more than 72 hours.
– degreening should continue for no more than 72
hours or risk increased peel senescence and decay.

21. Commercial Use of Ethylene
• Ripening of climacteric fruits:
– Banana
– Tomato
– Avocado
– Mango
– Papaya
– Persimmon
– Honeydew melon
Banana ripening

22. Commercial Use of Ethylene
Ripening of climacteric fruits:
• Recommended conditions (tomatoes):
– 20 to 21°C
– 90 to 95% RH
– 100 to 150 ppm C2H4
– Air circulation = 1 m3 per ton of product
– Ventilation = 1 air change per 6 hours or open room for 0.5 h
twice per day

23. Undesirable Ethylene Effects
• Undesired ripening and softening of fruits in
storage.
• Accelerated senescence and loss of green color in
immature fruit.
• Sprouting (stimulation or retardation)

24. Overcoming Ethylene’s undesirable effects
• Eliminating sources of ethylene
• Ventilation
• Chemical removal

25. Control of Ripening
Measure to control ripening helps to increase the shelf life of
fruits.
Temperature Regulation
• Rate of ripening increases with the increase in temperature.
• Storage at low temperature immediately after harvest
reduces the rate of respiration and ethylene production.
• Storing in low temperature below optimum level results in
cold injury and spoilage of fruit quality.

26. Regulation of storage atmosphere
The natural atmospheric air is conductive for the synthesis of
ethylene.
Lowering oxygen content or increasing carbon-di-oxide
concentration in the air within the storage cabinet retards
ethylene production.
Decreasing O2 concentration below 5 per cent and
increasing CO2 concentration between 3 to 10 per cent
delayed ripening by inhibiting ethylene. The shelf-life of
fruits can thus be increased.

27. Chemical Regulators
Potassium permanganate is a good ethylene absorbent.
Using KMnO4 coated newspaper as packing materials in
the bottom delays ripening.
Ethylene synthesis inhibitors
(block synthesis of SAM→ ACC)
AVG - Aminoethoxy Vinyl Glycine
MVG - Methoxy Vinyl Glycine
AOA - Amino Oxyacetic Acid

28. Avoiding Exposure to Ethylene
• Removal of ethylene from storage rooms:
– use of adequate ventilation (air exchange)
– use of ethylene absorbers
• potassium permanganate (alkaline KMnO4 on
inert pellets “Ethysorb,” etc.)
• Activated and brominated charcoal +/- KMnO4 =
“Stayfresh” absorbers

29. Avoiding Exposure to Ethylene
• Removal of ethylene from storage rooms:
– use of ozone or UV radiation to oxidize ethylene:
1. O2 + UV → O3
2. C2H4 + [O] → → CO2 + H2O
– must remove excess O3 to avoid injury to fruits & vegetables

30. Inhibiting Ethylene Biosynthesis & Action
Biosynthesis inhibition:
• AVG - Aminoethoxy Vinyl Glycine
• MVG - Methoxy Vinyl Glycine
• AOA - Amino Oxyacetic Acid
Inhibits ACS (i.e., SAM → ACC)
• Action inhibition
– 1-MCP (1-methylcyclopropene)
• Irreversibly binds to ethylene receptors
• “EthylBloc” and “SmartFresh”

31. 1-MCP (1-Methylcyclopropene)
Cyclopropane derivative (Cyclodextrin
powder)
Gaseous ethylene action inhibitor
Non- toxic
Odourless gas
Binds irreversibly to ethylene receptor
Simple organic compound(C4H6)
(Sisler and Serek, 1999)
Ethylene Action Blocker (ethylene→ block action)

32. 1-MCP Mode of Action
32
• Works by tightly binding to the ethylene receptor site in fruit
tissues, thereby blocking the effects of ethylene.
• Once ethylene production is prevented, It no longer promotes
ripening and senescence .
• Blocking of ethylene receptor by 1-MCP gas causes fruits to be
ripen and soften more slowly.

33. Application of 1-MCP
• EthylBloc®(0.14%), SmartFresh™(3.3%), SmartTabs™(0.63%).
When the product is mixed with water or a buffer solution, it releases
the gas 1-MCP.
• Formulation Type: Powder
• Timing: Immediately after harvest.

34. Commercial products of 1-MCP
EthyBloc® – for use with ornamentals
SmartFresh® – for use with fruit and vegetables
34

35. • Chemical :1-MCP (0.6 µl l−1 )
• Cultivars :‘Cortland’ and ‘Empire’ apple
• Duration of exposure to of 1-MCP :0, 3, 6, 9, 12, 16,
24, or 48 h
• Temperature :3, 13, or 23 °C

36. Fruit firmness of ‘Cortland’ (A) and ‘Empire’ (B) apples exposed to 0.6
µl l−1 1-MCP for 0, 3, 6, 9, 12, 16, 24, or 48 h at 3, 13, or 23 °C, and
stored 120 days in air at 0–1 °C.

37. Incidence of severe superficial scald development in ‘Cortland’ apples
exposed to µl l−1 1-MCP for 0, 3, 6, 9,12, 16, 24, or 48 h at 3, 13, or 23
°C, and stored 120 days in air at 0–1 °C plus 7 days at 20 °C.

38. Conclusion
• The treatment temperature and duration are important
factors that affect the effectiveness of 1-MCP on apple
quality and different cultivars respond differently to 1-
MCP treatment
• 1-MCP has tremendous potential for maintaining
apple quality during storage, but its efficacy can be
affected by treatment temperature and duration as well
as by apple cultivar

39. • Ethylene induced ionic leakage and water loss
and peroxidase activity.

40. References