Ripening is a process in fruits that causes them to become more palatable. In general, fruit becomes sweeter, less green, and softer as it ripens. Even though the acidity of fruit increases as it ripens, the higher acidity level does not make the fruit seem tarter. This effect is attributed to the Brix-Acid Ratio. Fruit ripening is a natural process in which a fruit goes through various physical and chemical changes and gradually becomes sweet, colored, soft, and palatable. Fruit ripening process can also be stimulated by applying artificial fruit ripening agents. Farmers and vendors often use artificial ripening agents to control the rate of fruit ripening. However, because of the potential health hazards related to the ripening agents, artificial fruit ripening process is highly debatable throughout the world.Different fruit ripening agents can be used to ripen fruits artificially and to provide fruits the desired color and taste within a short time. In recent years, the use of artificial fruit ripening agents is becoming much prevalent, the agents being mostly used for commercial purposes, i.e., to make the fruits available to customers during off-season. atural fruit ripening is a combination of physiological, biochemical, and molecular processes [21–24]. It involves coordination of different metabolisms with activation and deactivation of various genes, which leads to changes in color, sugar content, acidity, texture, and aroma volatiles [21, 22, 25]. The change in color during the fruit ripening process is a result of unmasking of pigments by degradation of chlorophyll, synthesis of different types of anthocyanins and their accumulation in vacuoles, and accumulation of carotenoids. Production of complex mixture of volatile compounds, such as ocimene and myrcene, and degradation of bitter principles (diverse groups of plant constituents such as alkaloid and sesquiterpene are linked only by their bitter taste), flavonoids, tannins, and other related compounds enhance the flavor and aroma of the fruit. Sweetness increases because of increased gluconeogenesis (metabolic pathway that generates glucose), hydrolysis of polysaccharides, decreased acidity, and accumulation of sugars and organic acids. Furthermore, textural changes resulting in the softening of fruits occur due to enzyme-mitigated alteration in structure and composition of the cell wall [23, 26, 27]. Through the above changes, fruit becomes ripe with distinctive characteristics: sweet, colored, soft, and palatable. Artificial fruit ripening and possible health hazards Ethylene, a hormone naturally produced within fruit, regulates fruit ripening by initiating and/or controlling a series of chemical and biochemical activities [28]; the compound does so by coordinating the genes responsible for activities including increase in the rate of respiration, autocatalytic ethylene production, chlorophyll degradation, carotenoid synthesis alongside conversion of starch to sugar, increased a

1. Ripening

2. Ripening
• Series of biochemical and physical
processes that cause an immature
fruit to develop all the desirable
aesthetic and edibility
characteristics
• The fruit become soft, sweet, less
acidic, aromatic, change color and
lose their astringency.
• Triggered by the hormone
ethylene

3. Role of
Ethylene
(C2H4)
Synchronizes different physiological
and respiratory events of ripening
Trigger production of more
ethylene
Exposed until autocatalytic
production of ethylene starts
Not harmful

4. Climacteric
Fruits
Fruits that can be picked green-mature
stage and subsequently ripen
Contain high starch that converted to
sugar
Color and flavor develop further after
harvest
Exhibit a respiratory climacteric
Produce ethylene autocatalytically

5. Climacteric
fruits
• Avocado, banana, bitter
gourd, bread fruit, canistel
(tiesa), durian, guava,
honeydew melon, jackfruit,
mango, muskmelon, papaya,
passion fruit, sapota (chico),
soursop (Guyabano), sugar
apple (atis), tomato

6. Non-climacteric
• Fruits that need to be picked ripe
• Not capable of ripening off the
plant since there is no further devt
of flavor after harvest
• No starch that can be converted to
sugar
• Little or no change in respiration
after harvest
• Only change in color – degreening
• Do not produce ethylene
autocatalytically

7. Non-climacteric fruits

8. Advantages of
Ripening
Regulation
Allows shipment of fruits at mature green stage
Better color development
Slower disease symptom expression
Less fruit shriveling
Faster means of getting cash
Takes advantage of transient price increases
Flexibility of selling
Efficient use of space

9. Ripening and Degreening Techniques
Introduce ethylene or other
sources in the environment of
the fruit
Ethephon (ethylene releasing compound)
Calcium carbide (acetylene)
Bioethylene (leaves or fruits)
Induce stress ethylene production

10. Ripening/Degreening
Requirements
Fruits should be mature
Uniformly low temperature
Uniformly high humidity
Good air circulation and ventilation
Air-tight

11. Recommended
Temp. and RH
Commodity T (⁰C) RH (%)
Banana 18-25 90-95 →75-80
Papaya 20-27.5 85-95
Mango 20-25 90-95
Durian 25-30 70
Tomato 15-20 90
Oranges 15-25 90-96

12. Ethylene
Application
Introduced
from
pressurized
cylinders
Ethylene
generators
Balloon
method
Canisters or
cartridges
Ethylene
sieves
Use of
polyethylene
tent
Danger:
explosive at
30,000 ppm
or 3% of air

13. Ethylene
Treatment
Commodity Level (ppm) Time (h) T (⁰C)
Avocado 10-100 10-48 6-18
Banana 100-100 24 18-20
Durian 100 24 28
Mango 100 24 25
Pummelo 250-500 24 25
Tomato 100-1000 24-48 20-25

14. Quality
problems due
to improper
ripening
method
• Dull skin color
• Poor flavor and rapid
deterioration of ripe fruits
• Appearance good but pulp fails
to ripen completely
• Fingers shedding or skin
splitting

15. Improper Ripening vs. Proper ripening
VS.

17. Treatment with
Ethephon
• A liquid formulation less
expensive than ethylene gas
• Known as 2-chloroethyl
phosphonic acid
• Marketed as ethrel with 480 g
L⁻¹ ethepon
– Has pH of 1 and release
ethylene gas above pH of
4.6 (cell sap has pH 5)
• Spraying, dipping (5 min) and
use of NaOH in confined place
(24-36 hrs)

18. Ethephon level for ripening/degreening
Commodity Cultivar Level (ppm)
Banana Latundan 500-1,000
Lakatan 1,000-2,000
Papaya Cavite 500-2,000
Mango Carabao 1,000
Orange Valencia 5,000
Tomato Improved Pope 1,000

19. Treatment with Acetylene
A gas generated from
calcium carbide (CaC2)
when reacts with water
(transpiring fruits)
Mimics the ripening
effects of ethylene gas
100x less effective than
ethylene
Explosive at 2.5-8%
volume in air
Cheap, readily available
and easy application
Health risks when fruits
are in contact with
CaC2 (phosphorus
hydride , arsenic
hydride)

20. Acetylene application
Traditional method – CaC2 chunks are wrapped
with newspaper and inserted at the bottom or
within layers of piles of fruits in a confined place
Tent method – wrapped CaC2 is inserted among
large heaps of bananas (6m high) and covered
completely with a burlap or thick cloth
Modified method – CaC2 is inserted in the hole
bored in stalk of a bunch of banana

21. Amount of CaC2 for ripening of fruits
Fruits Amount of CaC2
Mango 1 g kg¯¹ (20 g per 20 kg basket of fruits, 15-25 g
per 15 fruits for 4 days
Banana 5 g per 10 bunches in a closed container, 60 g
per 208 L container for 24-48 h, 0.25 kg per 20
bunches for 12-48 h
Chico 3 g per 60 kg in basket for 12-18 h

22. Bioethylene from Leaves
Newly expanded leaves have higher ethylene
Mature of leaves of acacia have more ethylene
Using 25 g of kakawati per 100 fruits of ‘Saba’ banana, ripening is
delayed by one day compared with ethylene and CaC2
Acacia (13.44 nL g¯¹h¯¹), anonang (12.5), katuray (9.43), Malunggay
(3.28), balimbing (3), peanut (1.75), Gliricidia (1.66), Ipil-ipil (< 1)

24. Guidelines in using Bio-ethylene from leaves
Use the most suitable and available
leaves
High levels of ethylene
Low CO2 producer
Readily available
Not better economic use
Use the right amount of leaves
Acacia (5% of fruit weight of tomato) for 2-4 d
Gliricidia (10% of fruit weight of tomato) for 4 d
70-100 g of Gliricidia for 1 kg of banana

25. Bioethylene from Fruits
Commodity nL g¯¹h¯¹ Duration (d)
Purple passion fruit 464.61 12
‘Java T2’ Chico 18.31 5
‘Cardaba’ banana 7.17 10
‘Improved Pope’ Tomato 3.16 6
Green avocado 1.18 5
‘Maquiling’ Amplaya 0.85 4

26. Bioethylene from Fruits
To ripen tomato, put 40% of ‘Cardaba’ on polyethylene bag with tomatoes
for 6 days. Put 8 pin pricks per bag for gas diffusion.
800 g of purple passion fruit is needed for 2 kg of tomatoes (40% of fruit
weight) enclosed in polyethylene bags with 8-16 diffusion holes for 6 d
‘Saba’ banana (10% of fruit weight of tomato)
100 g Squash peel / kg banana

27. Stress Ethylene
• Wounding the fruit
–Inserting pointed stick (15 cm) at the stem
end of jackfruit, soursop
–Scouring (rubbing) in sapota (chico)
–Pinching in papaya, avocado
–Pricking with pin the tip of banana finger
–Twisting banana crown

28. Stress Ethylene
• Plasmolysis
– Putting salt on stem scar of
tiesa and chico
– Immersion of banana fruits
salted or sea water for a day
• Moisture loss
– 1.2% per day reduce time of
ripening by 43%

29. Use of increased temperature
Bury among rice hull
or grains
Enclose in a container
or put in a warm
room
Place fruits in a big
pot (100 L) with small
pot of burning leaves
or straw at the top
Place bananas in a pit
covered with rice
straw
Exposure to direct
sunlight for a short
time
Dip in hot water – 52-
55⁰C, 10 min dip in
mango

30. Use of Smoke
• Smoke contains ethylene and acetylene
• Rice straw, gliricidia, mango and banana
leaves
• Methods“:
– Pit with bamboo pipe at the side (2
days)
– Use of joss sticks (3-4 days)
– Use of dried cakes of cow dung
– Smoke from slow burning materials
• Heat injury risks, carbon deposition

31. Slowing down Ripening
• Avoiding production or
introduction of ethylene
• Removal of ethylene
• Inhibition of ethylene
action

32. Avoiding production or
introduction of ethylene
1. Careful handling to minimize stress
ethylene
2. Low temperature to suppress ethylene
3. Avoid storing and transporting with high
ethylene producing materials
4. Keep away from exhaust of engines,
rubber, fluorescent lights
5. Follow strict sanitation practices
6. Remove ripening fruits
7. Modified or controlled atmosphere
packaging

33. Removal of ethylene
1. Ventilation with fresh air
2. Use of ethylene scrubbers
3. Potassium permanganate (KMnO4)
4. Heated catalyst ethylene scrubbers
5. Brominated or activated carbon
6. Use of UV light for 4 hrs/day for 4 days
7. Use of biological systems – mycobacterium

34. Ethylene Inhibitors
• Low temperature, Modified and controlled
atmosphere, irradiation and hypobaric storage
• Silver ions, AVG, AOA
• 2,5-norbornadiene (2,5-NBD) and
diazocyclopentadiene (DACP)
• 1-methylcyclopropene (1-MCP), 3-MCP, 1-
ethylcyclopropene (1-ECP), cyclopropene
• Calcium infiltration, waxing

35. Color adding
• Application of dye to pale-colored
fruits to improve color
• Mature quality fruits, dye approved
by FDA
• Fruits should be treated not more
than 4 min at 49⁰C
• Constant treatment temperature
• Fruits should be blemish-free
• Water quality should be low in sulfur
or iron

36. Color adding
Water and equipments should be clean
Optimum concentration must be established (1 gallon dye per
300 gallon water)
Coloring is done after grading and degreening
Treated fruits are thoroughly rinsed after color-adding to
remove excess dye, then air-dried and/or waxed.

37. Tinting
Application of dye to white
cutflowers
Contact tinting
– dipping for 4-8 sec.
- acidic pH, reduce wax, positively charged dyes
(textile dyes)
- roses, calla lilies, orchids

38. Tinting
• Systemic tinting
– stem ends are placed in 2.5
cm deep solution and allowed
to be taken up
- high transpiration, warm
temp. (20-25%), low RH (80-
85%), negatively charged dyes
(food dyes)
- gladiolus, carnation, tuberose

39. Tips for
successful
Systemic
Dyeing
Leave stems out of water for
some time before placing in
the solution
Recut stems while
submerged in dye solution
Remove in the solution after
tinting, keep stems in water
and store in dark room.

40. THANK
YOU
FOR
LISTENING
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