fruit ripening

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fruit ripening

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1. Fruit Ripening Increase in membrane permeability which releases compartmentalized enzymes Increase in protein (enzyme) synthesis Changes in color, flavor, and texture that give rise to the best eating quality of the fruit

3. Fruit Classification Climacteric fruits Fruits that will ripen in response to ethylene Non-Climacteric fruits Fruits that do not ripen in response to ethylene

4. Climacteric Fruits Avocado Banana Biriba Blueberry Breadfruit Cherimoya Durian

6. Ethylene Ethylene is gaseous plant growth substance which is involved in the regulation of many aspects of: Growth and development Fruit ripening Senescence It is physiologically active at levels as low as less than 0.1 ppm. Therefore, the regulation of ethylene biosynthesis and action is very important in agriculture today.

7. Synthesis of Ethylene Ethylene is synthesized from methionine with ACC synthase as the rate limiting enzyme Met ? SAM ? ACC ? H2C = CH2

8. Effects of Ethylene in Ripening Conversion of starch to sugars via hydrolysis Cell wall degradation and tissue softening Synthesis of pigments Synthesis of flavors

9. Respiration The process by which stored organic materials (carbohydrates, proteins, fats) are broken down into simple end products with a release of energy. Oxygen is used in this process and carbon dioxide is liberated.

10. Ethylene and Climacteric Ethylene that is released by many fruit species that is coincident with the increase in respiration rate Respiration rate is coincident with ripening and senescence Released ethylene by one fruit can stimulate climacteric in immature fruit located nearby

11. Climacteric

12. Pigment Changes Chlorophyll (Green color) - a loss of chlorophyll in tomatoes is good but a loss in chlorophyll in broccoli is bad Carotinoids (Yellow, Orange and Red colors) - Carotinoids are desirable in fruits such as apricots, peaches and citrus giving them their yellow and orange color. In tomatoes and pink grapefruit a specific carotinoid called lycopene gives them their red color Anthocyanins (Red and Blue colors) - Anthocyanins give red and blue color to apples, berries, cherries etc. Phenolic compounds - Are responsible for tissue browning.

13. Carbohydrate Changes Conversion of starch to sugar - Not desirable in potato but very desirable in apples, bananas Conversion of sugar to starch - Not desirable in sweet corn but very desirable in potato Conversion of starch and sugars to CO2 and water during respiration - Not desirable because it leads to a reduction in quality

14. Other Changes Organic acids (affects sweetness) Proteins (affects texture) Amino acids (affects flavor) Lipids (affects flavor)

15. Factors that Increase Ethylene Maturity at harvest Physical injuries Disease High or low temperature Water stress

16. Consequences of Respiration Speeding up the ripening process Speeding up the senescence process Reduced food value for the consumer Loss of flavor, especially sweetness Loss of salable dry weight

17. Control of Ethylene Production Reducing the storage temperature Reducing O2 levels to less than 8% Treating with enzyme inhibitors of ACC synthase and ACC oxidase Genetic engineering (using antisense technology to prevent enzyme expression).

18. Ethylene Blockage Treating with silver thiosulphate (commonly used in flowers); Hypobaric storage - keeping the commodity under vacuum; Elevating CO2 to more than 2% Genetic engineering (blocking the ethylene receptor)

19. Tomato Ripening

20. Exposure to Undesirable Temperatures Freezing injury - causes a collapse in tissues Chilling injury - occurs in tropical and subtropical crops, common symptoms are browning, pitting, water soaked areas, uneven ripening, off-flavors and molds and decay Heat injury - causes bleaching, surface burning, uneven ripening, desiccation and other problems

21. Physical and Pathological Damage Mechanical injuries causing bruising lead to water loss, fungal infection and stimulate respiration and ethylene production leading to a loss in quality

22. Environmental Factors Influencing Deterioration Temperature Relative Humidity Atmospheric Composition amounts of O2 or CO2 Ethylene Light

23. Temperature Management Hydrocooling In package icing Evaporative cooling Refrigeration Vacuum cooling Hydro-vacuum cooling

24. Relative Humidity Relative humidity can influence water loss, decay development, incidence of some physiological disorders and uniformity of fruit ripening. Proper relative humidity is typically 85 to 95% RH for fruits and 90 to 98% RH for vegetables

25. Control of Relative Humidity Adding moisture (water mist or spray) to the air with humidifiers Sprinkling produce with water Wetting floors in storage rooms

26. Supplements to Temperature and Humidity Management Use of controlled or modified atmospheres (CA or MA), which is the regulation of CO2 and O2 levels Curing root, bulb and tuber crops Remove damaged fruits (remember on rotten apple spoils the whole bushel) Waxing and other surface coatings Heat treatment Treatment with fungicides and insecticides Treatment with sprout inhibitors Treatment with calcium, growth regulators or anti-ethylene compounds Ethylene treatment (degreening or ripening) Sanitation

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