Organic and Artificial fruit Ripening

Food Science and Technology

1. Fruit Ripening 1

2. contents Ripening Climacteric / Non climacteric  Processes associated with fruit ripening Factors effect fruit ripening Major factor for commercial ripening Mechanisms of ripening Fruit Abscission Respiration Changes during ripening Enzymes involved in ripening 2

3. Conti.. Regulations of ripening Role of ethylene in fruit ripening Use of ethylene gas Natural ripening/ artificial ripening 3

4.                 ripening 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 4

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6. Processes associated with fruit ripening Seed maturation Development of wax on peel Abscission of fruit Change in respiration rate Cell wall and membrane changes Formation of flavour volatiles 6

7. Factors effecting ripening 7

8. Major factors for commercial ripening  The four major factors for commercial ripening Temperature control.  RH control.  Ethylene gas.  Adequate air circulation  8

9. Mechanism of ripening The making of fruit is a developmental process unique to plant It require a complex network of interacting genes and signal pathway In fleshly fruits, it involves three distinct stages                      1.fruit set                      2.fruit development                      3.fruit ripening                                     Ripening has received more attention from geneticist and breeders  This important process activates a whole set of biochemical pathway that makes the fruit   More attractive , desirable and edible for consumer   Every fruit has a certain level of ethylene production throughout its lifecycle In some fruits,  ethylene levels shoot up when the fruit starts ripening 9

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11. Fruit abscission Abscission is a cell separation process by which plants can shed organs  Such as fruits, leaves, or flowers This process takes place in specific locations termed abscission zones In fruit crops like citrus, fruit abscission represents a high percentage of annual yield losses The process of fruit abscission is tightly linked with plant development  Through the function of specialized AZ cells where cell separation occur 11

12. respiration The start of ripening is accompanied by a rapid rise in respiration rate This is called the respiratory climacteric  After the climacteric, the respiration slows down as the fruit ripens and develops good eating quality During ripening the respiration rate increases or decreases, depending on the product This can also be linked with ethylene concentrations . In the process of respiration, the breakdown of sugar into carbon dioxide ,water   and heat also leads to mass load 12

13. Factors responsible for respiration Temperature Relative humidity Gas composition in the ambient and cell Moisture content of the tissue Wounding or injury Types of plant part Stage of development of tissue Pre harvest treatments and pH methods Chemical composition of tissue Size of produce 13

14. Changes during ripening Fruits typically ripen as they become softer, sweeter, and juicier.  The starches in the fruit break down into simple sugars, changing the flavour  As the fruit ripens, a dynamic colour change is   observed from green to yellow to red It is due to the biosynthesis of pigments like chlorophyll ,  carotenoids, and anthocyanins Climacteric fruits undergo a number of changes during fruit ripening The major changes include  fruit softening, sweetening, decreased bitterness, and color change These changes begin in an inner part of the fruit, the locule, which is the gel-like tissue surrounding the seeds. 14

15. Cell wall degradation The middle lamella present between cells is composed mainly of pectin It provide attachment to neighbouring cells Fruit softening involves alteration to various cell wall components such as cellulose, pectin and hemicellulose The cell wall swells and show an increased affinity for water Modification of cell wall determines the fruit texture and ripening characteristics Loss of galactose from pectin De-esterification of some pectin Depolymerisation of the hemicellulose polysaccharide xyloglucan, which is associated with a reduction in cell wall strength 15

16. Conversion of starch to simple sugar The conversion of starch to simple sugar is the most remarkable chemical change occurring in many fruits during ripening In bananas, starch content decreases from 20% in unripe fruits to about 2% in fully ripe fruit  The concentration of maltose , sucrose, fructose and galactose increases during ripening During early stage of ripening , sucrose predominates , but later glucose and fructose contents are higher Since sucrose is utilized for metabolic activity after degradation of starch, its concentration is decreases during the later stages of ripening process 16

17. Changes in pigment During the ripening process the amount of chlorophyll decreases as it is broken down by the enzymes chlorophyllase Other pigments such as carotenes , xanthophylls are anthocyanins   are synthesized which gives  specific colour to fruits during ripening In yellow ripe fruit banana alpha carotene, beta carotene and lutein is present The green to red colour changes in tomatoes is due to transition of chloroplast to      Chromoplast with degradation of  chlorophyll  And  result in accumulation of lycopene, carotenes and xanthophylls Apples and plum- cyanidin( anthocyanin): grapes (malvidin) strawberries         pelargonidin   17

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19.   Changes in flavour and aroma 19

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21. Enzymes involved in ripening This ethylene signal causes developmental changes that result in fruit ripening  New enzymes are made These include hydrolases to help break down chemicals inside the fruits,   Amylase to accelerate hydrolysis of starch into sugar  Pectinase to catalysis digestion of pectin (the glue between cells) The major enzymes involved in softening of fruits are  cellulase , lipase, acid phosphatase , kinase 21

22. Regulations of ripening The ripening process is  regulated by thousands of genes  That control progressive softening and lignification of pericarp layer,  Accumulation of sugars, acids, pigments, and release of volatiles  Key to crop improvement is a deeper understanding of the processes underlying fruit ripening Ripening is a highly regulated by developmental process aiming to maximize fruit organoleptic traits to attract herbivores The timing of tomato fruit ripening is tightly regulated and  dependent upon the plant hormone ethylene Ethylene   serve as core  regulator for climacteric fruit ripening.  22

23. Role of ethylene in fruit ripening Promote its own biosynthesis Ethylene production is largely pre- determined in both time and amount by the genetics of the fruit During ripening both carbon dioxide and ethylene increase significantly  An unripe fruit generally has low levels of ethylene  As fruit mature, ethylene is produced as a signal to induce fruit ripening Play important role in abscission of fruit, suppress stem and root elongation, stimulate flower, leaf abscission 23

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25. Use of ethylene gas for ripening  Used for De-greening of citrus fruits External application of ethylene gas generated from various sources such as                1.Ethylene gas cylinder                2.Compressed ethylene gas                3.Ethanol                4. Ethephon These are used to trigger the ripening process in fruits It can be used at a concentration up to 100ppm Mature climacteric fruits can initiate endogenous ethylene production  within no more than 74 hour 25

26. Natural ripening   Once fruit attains maturity, the ripening process beginning  Ethylene gas formation starts at the central core of fruit  like Banana or near the stone  like  Mango The gas flows inside  out, which triggers on the sugar formation by softening the internal tissue Natural ripening of fruits is a physiological process, which makes them edible, tasty and nutritious The ripening process  makes the fruit soft, increases sweetness, decreases bitterness and there are changes in colour and appearance  The natural ripening of fruits takes place only after proper mature 26

27. Artificial ripening Artificial ripening is the process by which ripening is controlled to achieve desired characteristics  Intended for better consumer acceptance and improving sales  It is generally carried out on climacteric fruits so there is uniform ripening Calcium carbide is used in some countries for artificial ripening of  fruit When calcium carbide come in contact with moisture, it produces acetylene gas,     which is similar in its effects to natural ripening agents Ethylene and acetylene play important role in ripening process Ethephon  are some of the commercial ripening agents  27

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29. An artificially ripened fruit will be Not have the natural fresh aroma of ripe fruit Have a smooth , wrinkle free and shining skin Have yellow skin but the insides will be green in colour Have patches of green on the yellow skin Be very dry and not juicy as rip e fruits 29

30. Delayed ripening Ethylene signals the onset of fruit ripening  D elayed ripening on some plants can be achieved by modifying their ethylene receptors  The gene ETR1 is one example  And it has been shown to encode an ethylene binding protein Plants with modified ETR1 lack the ability to respond to Ethylene stimulations of color development were prevented by treatment with gibberellic acid    Gibberellin can delay the progress of some components of the ripening of fruit, preventing some of the changes triggered by ethylene 30

31. Advantages of delayed ripening Assurance of top quality Allowing the fruits to exude fruit quality Consumers will get value for their money Widening of market opportunities Reduction in postharvest losses 31