Advanced Postharvest Physiology

Hort-MSc

A. A. Ramin

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Chapter 1: Introduction(Def: Postharvest)

• The handling, storage and marketing of perishable plants or plant parts in the living state (Kays, 1997)

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What is postharvest Physiology?

• Postharvest physiology deals with the time period from harvest or removal of the plant from its normal growing environment to the time of ultimate utilization, deterioration, or death.

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Utilization

• Ultimate utilization varies with the type of product:

• -Seeds and cutting=planting• -Cut flowers=display• -Food=processing or consumption• -Medicinal plant parts=active substances

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Detrioration and Death

• Approximately 33% of all harvested products worldwide are discarded prior to utilization, due to:

• -Senescence• -Stress responses• -Pathogen activity• -Insect attack• -Mechanical damage

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Role of a Postharvest Physiologist

• To minimize the postharvest loss of horticultural products

• and maintain market, nutritional value and safety of the product by using postharvest technology that mitigate the postharvest deterioration of the product

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Characteristics of Harvest Plant ProductsProducts are alive

• However, they no longer have access to:• -Water• -Light• -Nutrition-

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Characteristics of Harvest Plant Products

• Furthermore they are subjected to numerous stress, including:

• -Wounding• -Mechanical damage• -Physical pressure• -Low temperatures• -Altered atmosphere• -Pathological and physiological stress

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Control of Postharvest loss

• Almost all postharvest technologies manipulate metabolism of the harvested product by inhibiting respiration rate of the product,

• and ethylene action

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Respiration and energy

• Ripening requires the synthesis of novel protein, pigments and flavour compounds.

• These anabolic processes require both energy and a supply of carbon skeleton. These are supplied in fruits, just as in other tissues by respiration.

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Respiration and Ripening

– While all fruits carry out respiration, there are marked differences in both the rate and patterns of change of this respiration between fruits. Fruits can be classified as either climacteric or non-climacteric.

– In general fruits such as banana and avocado with highest respiratory rate, tend to ripen most rapidly are most perishable.

– For non-climacteric fruit the general correlation exists between high respiratory rate and short shelf life.

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Aerobic Respiration cycles

• Glycolysis

• Kerbs (TCA)

• Pentose Phosphate Pathway (PPP)

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Respiration and N2o : Benkeblia, and Varoquaux, Postharvest Biology and Technology, 30: 161-168, 2003

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1-MCP and Respiration: Ramin, 2006, Amer-Eurasian J. & Environ. Sci., 1(2): in press

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Superatmospheric O2 and Respiration: Kader et al, 2000, Postharvest Biology and Technology, 20: 1-13

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Fruit ripening

• Fresh fruits are important part of our diet (flavour, colour,texture, vitamin, sugar, fiber..).

• Fruit contain a very high percentage of their fresh weight as water, in tomato 95% and may even be as high as 98%.

• Fruit has high metabolic activity, compared to other plant such as seed. Therefore they have short shelf life, transportation problem and long time storage.

• Two major respiratory substrates in fruit are sugar and acid and are available for respiration

• Ref: • Biochemistry of Fruit Ripening, Chapman & Hall• By: Seymour, Taylor and Tucker, 1996

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Ethylene synthesis in grape(1)

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Ethylene synthesis in grape

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