WELCOMEPostharvest HorticultureB.Sc. Ag 6th Semester

Institute of Agriculture and Animal ScienceLamjung Campus

Lamjung

Amit KhanalAssistant Professor

Department of Horticulture and Plant Protection

POST-HARVEST DETERIORATION

Postharvest DeteriorationAll the crops after harvest is also living entity, so should be carefully handled

Once they are detached from the parent plant, they are deprived of the supply of hormones, nutrients, water etc.

These perishables are highly prone to damagePostharvest deterioration refers to the sets of undesirable biochemical, physiological, physical changes that shortens the shelf life and quality of the commodities and make it unsuitable for the consumption.

Postharvest deterioration is following types

PhysicalPhysiologicalPathologicalEntomological

Physical deteriorationOne of the most common and severe defects of horticultural products

Physical deterioration of fruits and vegetables occur due to inappropriate harvesting and postharvest handling (lesions and browning)

It not only directly affects appearance attributes (skin and flesh ) but also creates sites for pathogen infection and water loss

Physical injury stimulates ethylene production and respiration in plant tissues

That leads to acceleration of senescence

Refers to injuries in the outer surface or inner part of the produce which shorten shelf life of produce and make unsuited for consumption

Injuries occurs during harvesting, cleaning, packaging, loading, unloading, transport etc.

Freezing injury is a type of physical injury

Freezing point of fruit and vegetable and fruits is usually higher than 0°C

Freezing injury occurs when ice crystals form in the tissues

• Cultivars, locations, and growing conditions may affect the freezing point

• To be safe side, the highest temperature at which freezing of a specific commodity may occur should be used as the guide for recommending the optimum storage temperature

physiological deteriorationPhysiological deteriorations are the abiotic non-transferable problem arising from the interaction between the commodity and climate

A number of physiological processes occur in the harvested, non processed horticultural product that contributes to deterioration of fruits and vegetables

What are the physiological process that leads to deterioration of produce?The physiological process which leads to the deterioration of the produce are given below:

Transpiration:Respiration:Suffocation:Growth (Sprouting):Maturity:Ripening and Senescence:Abscission:Biochemical transformation:Greening:

What are the factors affecting physiological deterioration?

Physiological deterioration may develop due to various pre-harvest factors or postharvest factors.

Pre-harvest factors and their role in physiological deteriorationTemperature: Fruits exposed to sun results in blotchy ripening.

Larger fruits are more susceptible because of lower heat transfer coefficient resulting from their relatively smaller surface to volume ratio.

Blotchy ripening Sunburn

Preharvest factors contd…Moisture stress: Imbalance in moisture status of soil and outside environment causes cracking of fruits

Cracking of fruits is severe when water stress is followed by rainfall

Cracking of litchi, mango and tomato after a long draught followed by rain is a common physiological problem

Preharvest factors contd…Mineral nutrition: Deficiency or excess of some mineral nutrient causes physiological disorder in some fruits and vegetables.

Calcium deficiency: Blossom end rot in tomato, capsicum, eggplant, squash: symptoms:Blossom-end rot usually begins as a small water-soaked area at the blossom end of the fruit.

As the lesion develops, it enlarges, becomes sunken and turns black and leathery.

Secondary molds often colonize the affected area, resulting in a dark brown or black appearance.

Causes of blossom end rot:It is a physiologic disorder associated with a low concentration of calcium in the fruit.

Control:Maintain the soil pH around 6.5.Use nitrate nitrogen as the fertilizer nitrogen source. Ammonical nitrogen may increase blossom-end rot as excess ammonium ions reduce calcium uptake.

Foliar applications of calcium.

Cracking:Cracking of tomato can be either radial or concentric. 

Radial cracking are often the result of rain or excessive watering after a prolonged dry period.

Concentric cracking is due to calcium deficiency.

Radial cracking concentric cracking

Spongy tissue of mangoSymptoms: Fruits look normal from outside. But inside, a patch of flesh becomes spongy, yellowish and sour. It is characterized by unripe, acidic, pale yellow to brown corky tissue with or without air pockets.Causes: Ca deficiency was a factor of inducing spongy tissue disorder.

When Ca content was normal, the level of K content was the main factor of inducing disease.

Control: harvest at ¾ matured rather than fully matured.

Preharvest spray or postharvest spray of calcium.

Internal breakdown of mango The disorder, also known as flesh breakdown or internal flesh breakdown, is referred to as jelly seed, soft nose, or stem-end cavity (SEC).

Symptoms: characterized by premature and uneven ripening of the mesocarp. It results in watery, translucent tissue around the seed giving an over-ripe appearance. Causes: Ca deficiency Control: pre harvest or postharvest spray of calcium.

Bitter pit in appleSymptoms: development of discrete pitting of the cortical flesh, the pits being brown and becoming desiccated with time.The pits may occur predominantly near the surface or deep in the cortical tissue. Causes: calcium deficiency.Control: Rapid cooling, CA storage, and application of postharvest calcium drenches may be able to reduce its occurrence.

Preharvest applications of calcium may be far more effective than postharvest drenching.

Jonathan spotSymptoms : Sharply sunken area at the lenticel that is very dark brown or black and

about 1/8 of an inch in diameter. These spots penetrate the flesh somewhat below the surface of the skin.

Causes: cause of this disorder is calcium deficiency.

Control: Harvesting fruits at optimum maturity, prompt cooling, and sharp control of storage temperatures.

Preharvest or postharvest spray of calcium also reduces this disorder.

Low temperature breakdownSymptoms: the affected tissues are more likely to be firmer, more moist, and darker in color.Causes: calcium deficiency.Control: preharvest or postharvest spray of calcium.

Senescent breakdown Causes: harvest of overmature fruitwith low calcium content.Control: drenched with calcium before storage.harvesting fruit at a less mature stagerapid cooling and reducing storage duration.

Water coresSymptoms: Intercellular air spaces in the core and cortical tissues become filled with liquid, predominantly sorbitol.Causes: It is associated with advancing fruit maturity and low night temperatures prior to harvest.

Low calcium level also associated with this malady.

Control: preharvest or postharvest spray of calcium.

Boron deficiencyLumpiness in papaya:Symptoms: fruits become deformed And lumpy, and they do not grow to full size.Causes: boron deficiencyControl: boron sprayCork spot in pear: characterized chiefly by a bumpy, uneven appearance of the pear surfaceAffected areas usually have a more yellow color than the rest of the surface. When diseased fruits are peeled or cut, large masses of brown or grayish necrotic tissues are seen to underlie the spots

Boron deficiency contd…Black head in cauliflower:

Excess nitrogenStem end rind breakdown of citrus:symptoms: It is characterized by the irregular collapse and darkening of rind tissue around the stem end of citrus fruit. A narrow ring of unaffected tissue immediately around the stem (button) is a distinctive symptom of SERB.

Causes: pre-harvest imbalance in nitrogen and potassium.

control: Postharvest practice that minimizes water loss .

coat of wax are currently the best means of reducing SERB.

Use of optimum quantity of nitrogenous fertilizer.

Exanthema:Symptoms: Exanthema is characterized by dark brown, glossy, gum soaked eruptions occurring as irregular blotches that turn black as the fruit matures.

Causes: This disorder caused by copper deficiency and is aggravated by high nitrogen and phosphrous fertilization.

Control: foliar spray of copper and using appropriate dose of nitrogen.

Cultural practicesOleocellosisSymptoms: It appears as irregularly shaped green, yellow or brown spots that darken over time and make the glands more prominent.

Causes: It arises when mechanical damage releases oil from the oil glands. The oil is toxic to surrounding tissue and will inhibit degreening of that tissue.

Control: do not harvest turgid fruit early in the morning, when dew is present, during foggy conditions or immediately after rain or irrigation

Rotting of potato, sweet potato, onion etc are very high if irrigated close to the harvest period.

Post harvest factorsTemperature

High temperature: Very high temperature (90-95°F) during ripening of banana causes weak neck.

In this case banana easily separate from the bunch, weak neck is usually followed by neck rotting.

Low temperature:Black heart in pineapple: If pineapple is stored below 10°C they showed the water soaked spot near the core.

At later stage some fruitlets turn brown and this is termed as endogenous brown spot or black heart of pineapple.

Chilling injury:Chilling injury is the major problem in low temperature storage of the susceptible commodities.

The symptoms of chilling injury vary with the type of tissue involved.

The symptoms of chilling injury normally occur while the produce is at low temperature.

Sometimes the symptoms appear only after produced is held at high temperature, at which the rate of deterioration is very fast.

The injured tissue are more prone to pathological attract which results faster deterioration of the commodity.

Mechanism of chilling injuryAbnormal respiration rateAccording to this hypothesis chilling injury results from disruption of the synchronization of the various stages in the complex respiratory sequence

Not all the reactions are reduced by lower temperature

As some of the reactions are reduced at differential rates than other, there is accumulation of intermediate metabolites, which cause abnormal metabolism, production of off flavor, undesirable volatiles etc.

Changes in membrane permeability:Membranes of cellular and sub cellular organelle are composed of lipid and protein molecules

Depending on the types of fatty acid involve and nature of combination, the viscosity of membrane is influenced by temperature

At low temperature the change of some lipids from liquid to solid state changes the permeability of membrane and streaming of the substrates is restricted

Cessation of streaming may results metabolic abnormalities such as anaerobic respiration, accumulation of intermediary substrate and undesirable reactions, which ultimately cause chilling injury, and death of the tissue

Plants of tropical and sub tropical origin contain fatty acids than are highly saturated thus they are most susceptible to chilling injury

Imbalance of tissue distribution of chemical compounds

Within the fruits also the nature of tissue and chemical composition varies in different portion, thus chilling injury appears in weak and sensitive tissue.

Impairment of enzyme activityThe kinetics of enzyme action and synthesis are temperature dependent

Each enzyme has its own temperature optimum for maximum activity

At a given temperature some enzymes are more activate while others are inactivated as a result there is accumulation of intermediary metabolites and development of chilling injury

Accumulation of toxic metabolitesAs a result of abnormal metabolism there may be accumulation of toxic metabolites which causes damage to the tissue (chilling injury).

Factors affecting chilling injuryMaturity:Variety:Growing conditions:Mineral nutrition:Abrupt change in temperature:Humidity in storage:Controlled atmosphere storage:

Light Greening in potato Presence of light during storage causes greening of potato, which is a physiological problem.

Greening is associated with the production of alkaloid named as solanine.

Greening occurs in eye, peel and sprouts.

Gases Oxygen and carbon dioxideSelf modification of environment in storage and inside packages sometimes causes physiological disorder.

Polybag storage is common way of packaging fruits and vegetables.

If ventilation is not provided there will be continous increase in carbon dioxide and decrease in oxygen.

Lack of oxygen and increased carbon dioxide in storage causes various kinds of physiological disorders.

e.g. striking odor in broccoli, black heart of potato etc.

Black heart of potatoBlackheart is storage or transportation induced

disorder caused by low O2. Typically, blackheart is induced at > 30 °C (86 °F), which increases respiration. If air exchange around tubers is sufficient, low O2 conditions develop in the interior of the tuber and the cells suffocate and turn black.

Carbon dioxide blocks the pathway of aerobic respiration from pyruvate to Acetyl Co A. accumulation of pyruvate causes anerobic fermentation and produce acetaldehyde (CH3CHO) and alcohol (CH3CH2OH).

Ethylene In some commodities ethylene causes abnormalities and deterioration of quality.

Leafy vegetables: chlorophyll breakdown and yellowingCarrot: production of isocoumarin causes bitterness.Asparagus: toughening of tissue and textural modification

Capsicum: color changeAmmonia•It is commonly used in refrigerator and cold storage.• In some cases leakage of ammonia causes discoloration of stored commodities.

•If red onion is exposed to ammonia they will turn greenish black, while white onion will turn gray to brownish black.

Chilling injury of orange:Symptoms: Chilling injury include pitting, brown staining, increased decay, internal discoloration, red blotch and loss of juice off-flavors, and watery breakdown.

Causes: develop at 5 °C (41 °F) or become evident 1 to 2 days after moving to room temperature (about 72 °F).

Control: The best means of preventing chilling injury is by storing fruit at non-chilling temperatures.

Creasing (albedo breakdown)Symptoms: Irregular deterioration of albedo cells (white spongy tissue) and the collapse of the overlaying flavedo (colored portion of the rind) into irregular grooves over the fruit surface.

Such areas are weaker and often split, providing entry for pathogenic fungi and subsequent decay. Common in thin skinned fruits.Causes: potassium deficiency and is associated with advanced fruit maturity.

Control: earlier fruit harvesting and proper fertilization of potassium fertilizer.

Asparagus Chilling injury: Asparagus is subject to chilling injury after about 10 days at 0 °C (32 °F).

Symptoms include loss of sheen and glossiness and graying of tips.

A limp, wilted appearance may be observed. Severe chilling injury may result in darkened spots or streaks near the tips.

Elongation and tip bending: Asparagus continues to grow and elongate after harvest if not cooled immediately and stored at low temperatures < 5 °C (41 °F).

Contacting water at the base will also promote spear growth and elongation.

Tip bending occurs as the result of upward growth of the tips when the spears are horizontal.

Chilling injuryElongation and tip bending

Watery scales of onion: symptoms include thick leathery skin, which when peeled away, reveals watery, glassy, fleshy scales below.

Late harvesting and prolonged field drying produce the highest occurrence of leathery skin.

Scale greening of onionExposure to light after curing causes green coloration of outer scales.

Feathering or skining of potato: common disorder in early-crop or “new” potatoes (harvested

immature). Soil drying and vine death enhance skin set,and thus decrease skinning.

Hollow heart of potato: it is related to irregular growth, inadequate water availability and/or widely fluctuating temperatures.

Blotchy ripening of tomato: characterized by the randomized development of green or green-yellowish areas on the surface of red tomato fruit. Apparently, the development of this disorder is related to the availability of low potassium and inorganic nitrogen in the soil system.

Irregular ripening of tomato: characterized by the appearance of non-uniform ripening

and white internal tissue. It has been associated with the feeding of sweetpotato whitefly on tomato fruit.

Pathological deterioration30% loss by postharvest pathology only

Fungi, bacteria, are major MODisease are high where temp and RH is higher

Pathogens not only produce diseases but also produce ethylene gas and lead to deterioration of commodity at faster rate

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