Post Harvest Techniques and Process
Today, we are learning “Post Harvest Techniques” of agriculture crops.
Factors of Pre-harvest which are responsible for ripening, maturity, deterioration:
The losses occurred in the post-harvest of fruits and vegetables are high starting from 3% to 40%. Up to 15% of fresh vegetables and fruits become stale and decrease their value in the market along with the acceptability of the consumer. Reducing these losses which occur will rise their supply without any land to the cultivation process. This will also be a major help in controlling pollution. Mechanical losses are cracking, bruising, cuts, damage caused by fungi and bacteria. Physiological losses will be the change in the rate of respiration, pigments., flavor and organic acids. Up to 40% of the vegetables get decayed because of the bacteria which is soft-rot and 32% of the fruits get decayed because of the Penicillium species. These losses can be decreased by choosing the correct pre-harvest and post-harvest treatments.
The varieties which give maximum yield, very good quality, which gets ripened slowly and has a very long shelf-life under the conditions which are ambient and also good quality of processing need to be developed and grown in a commercial way.
These operations will be a major help in increasing the shelf-life of fruits and vegetables. Pruning or Thinning will rise the size of the fruit and minimize the Acidity and TSS. The quality of the post-harvest of the citrus fruits will rise in a significant way when tangelo, trifoliate orange are utilized as a rootstock. Fruit quality can be raised by applying Potassium, Magnesium, and Zinc whereas Higher nitrogen and Phosphorus will decrease the quality. Too much irrigation prior to harvesting will reduce the shelf-life and the quality whereas less irrigation will improve the crop maturity.
For root crop types, the soil must be prepared to a tilth of porous nature for the avoidance of root forking. Irrigation which is not done on a regular basis will cause cracks in the carrots and radish and there would be splits in the external scales of onions. In garlic and onion, irrigation should never be stopped prior to three weeks of harvesting to make sure that there is better quality. Too much application of fertilizers containing nitrogen will cause deterioration in the tissues in a faster way whereas controlled supply will improve the quality of vegetables.
Treatments in Pre-harvest:
The shelf-life in post-harvest of vegetables and fruits will be increased by the application of chemicals in the pre-harvest. Topsin-M at a percentage of 0.1% or Bavistin at a percentage of 0.1% should be sprayed three times with an interval of 15 days prior to harvesting. This will control the anthracnose and rots at the end of the stem in mangoes. In the same way, decay caused at the time of post-harvest can be regulated by spraying Ben late at a percentage of 0.1 or Topsin-M at a percentage of 0.1 three times at the time of pre-harvest at an interval of 15 days. Application of Maleic hydrazide at the time of pre-harvest will decrease the onion and potato sprouting at the time of storage. In Kharif and rabi types of onions, applying maleic hydrazide of 2000 ppm after 3 months of transplantation will decrease the sprouting at the time of 5 months of storage in the structures which are ventilated. The diseases caused in the post-harvest of onion and tomato can be regulated by 3 sprays of 0.2 Difolatan at the time of pre-harvest at an interval of 10 days. In the same way, applying promoters of growth like N-benzyladenine at 20 ppm at the time of pre-harvest will increase the shelf-life of leafy vegetables.
The quality at the time of postharvest and the life of storage of fruits will be completely controlled by the maturity. If the harvest of fruits is done at the correct stage of maturity, there would be an excellent quality of fruits. Harvest of vegetables is done when they grow to a maximum size and are still tender. Too much maturity in the root crops will cause pithiness and sponginess. The harvesting of the root crops should not get delayed. This delay in garlic and onion will decrease the quality of storage.
Harvest should be done in the day when the temperature is cool, preferably the morning would be better. The produce should be transferred to the shade at the early times. If the harvest is done in the hot periods, it will increase the heat of the produce which in turn causes shrivelling and wilting. Harvesting which is done at the time of rains or immediately after rains will cause a severe increase in the microorganisms by creating favorable conditions for them to get multiplied. Citrus fruits will become sustainable to any damage if their harvest is done at the time of rains as their rind will become turgid and can survive to easy brushing. Proper care at the time of harvest is very much important as any injuries which occur at the time of harvesting will later become brown or black patches which make them look unattractive. The latex which comes out of the stem mainly in the mangoes should not be fell on fruits as it will lead to the creation of black spot. An injury caused to the peel might also become a point of entry to the microorganisms which in turn cause rotting.
Few gadgets of harvesting are developed. For examples harvesters developed for mangoes in Lucknow, Ratnagiri and Bangalore and there need to get popular.
Several vegetables and fruits are being harvested without ripening to handle them safely. Marketing and transportation must be done when they are matured so that they will have time to get ripened later on in a normal way and grow with good quality for eating.
Read: Vegetative Propagation Types.
Factors of Post-harvest which are responsible for ripening, maturity, deterioration:
This should be conducted as soon as harvesting is done. This will make the skin of the produce strong. The curing process is done at a very high temperature and humidity which include suberization of the external tissues which in turn develop the wound which acts as a barrier against the loss of water and infection. This would be favored by the temperature and humidity which are high. Sweet potato, potato, garlic, onion, and colocasia will be cured before storage. This condition will be quicker in sweet potato when the temperature is at 35°C and relative humidity is at 96%. The tubers of potato will be held at a temperature of 18°C for a time span of 48 hours and then the temperature can be decreased to 10°C for 1 week to 10 days at a relative humidity of 92%. The curing will decrease the content of moisture mainly in garlic and onion. The leaves which are present on the onion bulbs get dried and this will help them in getting protected from the infections caused by microbes in storage. The safest temperature for the curing of onion is 38°C for about five days.
This is the process in which the green pigments present in the fruits get decomposed. This is done by the application of ethylene or few metabolic inducers in order to provide the fruit of its natural color which is mostly preferred by the consumers in the market. This can be applied for fruits like banana, tomato, citrus, mango. The time which is needed to a degree of fruits will be completely based on the degree of the natural color and the maturity. The more the green color and more the maturity of the fruit, the lesser time would be needed to decrease the chlorophyll to a required level.
Degreening will be done in special rooms with temperature and humidity controlled where there would be an application of fewer concentrations of ethylene. The supply of ethylene will be done from gas cylinders. These special rooms are ventilated in a thorough way in order to keep the level of carbon dioxide less than 1% which will not allow high coloring. If the fumes of kerosene are kept outside the room where the degreening is done, they will enter the room from the ducts by the ventilation which is forced. Irrespective of the hazard of fire which is present, the fumes of kerosene will produce fruits with better color than the fruits which are produced by ethylene. This is because of good ventilation. The temperature which is best for degreening is 27°C. The temperatures which are high will delay the process of degreening. In this process, the relative humidity should be to the maximum of 90% starting from 85%. The humidity levels which are high will give rise to condensation at the time of degreening and there are closely associated with gradual degreening and raise in decay. Though the humidity which is low will check the decay, it will cause an excess level of shrinkage and break down of the peel.
In other method, frits present in the containers will be sealed by using two plastic sheets of film and water. Polyvinyl chloride which has a thickness of 0.2mm can also be used. The ethylene is taken from a can which has the capacity of 4 liters in the film which will cover up to 1 tonne of fruits, the concentration of ethylene will become almost 900 ppm which would result in the coloring which is satisfactory. After 16 hours of time, the film will be taken off by the enforcement of fruit into the air. The process of degreening will take a time span of 3 days. Ethylene will accelerate the chlorophyll decomposition without affecting the process of carotenoid pigments significantly.
Temperatures which are high tend to cause harm to the quality of fruits and vegetables, mainly when the harvest is done at the time of hot climates. Pre-cooling is a method of taking off all the heat in the field. This process will slow down the respiration rate of the produce, decreases the chances of getting attacked by the microorganisms, decreases the loss of water and reduces the load on the system of cooling of storage. Okra and peas are the ones which deteriorate rapidly and need cooling very promptly. In a few situations, the ripening stage and the level of heat of produce will determine the requirement of pre-cooling. In the process of air-cooling, we get to attain cool air from the cold storage. The temperature should not go down from -10°C in order to prevent freezing. If the temperatures at nights are low, the doors of the storage rooms can be left open for the purpose of cooling at night times. In the process of water cooling, the heat present in the field can be removed rapidly. This method will be used for leafy vegetables to maintain their freshness and texture. You can also add ice in order to decrease the temperature. Controlling the temperature is mandatory in order to prevent injuries in the fruits and vegetables which are sensitive to cold.
Drying and washing:
Many of the vegetables and fruits will be washed after completion of harvest in order to increase the appearance, avoid wilting and also for the purpose of removing the inoculum load of microorganisms. Therefore, a fungicide must be kept in washing water. Washing will increase the shelf-life of bananas by postponing their ripening. After washing is done, anything excess should be taken off which you would feel that will encourage the spoilage of microbes. Tuber and root crops are washed more often in order to remove the soil which adheres to these.
Grading and Sorting:
The fruits and vegetables which are bruised, immature, diseased will be sorted. Most of the countries will have their own standards of international and domestic trade and they have specific definitions for their standards too. Grades are completely dependent on the color, weight, shape, and size of the fruits which are close to the temperature of freezing in a particular period.
Mango, Papaya, watermelon and few other fruits are prone to attacks caused by fruit flies. Disinfestations will be done by the treatment with the heat caused by vapor at 45°C by the saturation of air with vapor for approximately 8 hours by fumigation of ethylene dibromide. Any residues left by bromide which is inorganic should not go beyond 11 vg/g.
Treatment at the time of post-harvest:
Applying Bavistin of 0.1% and Topsin at 0.1% at the time of post-harvest will regulate the diseases caused to mangoes at the time of storage. At the mandarins of Nagpur, hot water will be treated with Imazalil at 0.1%, benlate at 0.1% and Bavistin at 0.1% as this would have great effects.
There would be a natural waxy layer for fruits and vegetables on their external layer which would be partially removed at the time of washing. An extra layer of wax which is discontinuous will be applied in an artificial way with enough consistency and thickness for the prevention of anaerobic conditions in fruits which would also provide good protection from the decay organisms. Waxing is mainly necessary if there are any minute injuries and scratches present on the surface of fruits and vegetables. These will be sealed by using wax. Waxing will also improve the glossy shine on fruits and vegetables. Hence, there would be an improvement in appearance which makes them more acceptable.
If there is no availability of storage facilities using refrigerator, skin coating with wax which causes protection will improve the life of storage of fruits and vegetables at temperatures which are ambient. There are two kinds of emulsions of wax called wax W and Wax O.
The wax W composition will not impart any sort of gloss to vegetables and fruits and hence wherever there is a requirement of gloss for the improvement of marketing ability of the produce, the wax O is suggested. Both of these wax emulsions will consist of 12% of solids.
Applying emulsions to the produce which is harvested recently and is healthy will protect them from excess loss of moisture, higher respiration rates, building up of heat or thermal decomposition. Quality and texture of the produce which is fresh can be maintained closer to the fresh condition for as much long duration as possible. The emulsions of wax without the use of fungicides will not give any kind of protection to the fruits and vegetables from damage caused by microbes. Hence, you need to choose fungicides which are suitable to add them to wax emulsions.
The ripening will transform the plant organs which are mature physically into the ones which are attractive visually and also by taste and smell. It will complete the development and starts the deterioration caused by age of the fruit and is basically an event which is irreversible. The achievement of fruit ripening can be done through the ethylene application.
Usage of a perfect quantity of ethylene should be done in the ripening room at regular time periods. A carbon dioxide concentration of about 1% will help in the delay of the ripening process.
Using plastic film for pre-packaging:
Pre-packaging will improve the shelf-life of the fruits and vegetables by creating a varied atmosphere with a rise in the concentration of carbon dioxide in the package. The material which is used for packaging should be used to provide access to the content of oxygen. To make this happen, polystyrene and cellulose acetate will be put into use. But, LDPE films which consist of high oxygen content and transpiration of carbon dioxide rates live for long durations. The pouches need to have perforation for the transmission of oxygen and carbon dioxide quickly sufficient for the respiration of the produce which is fresh. The pouch which is used for decreasing the bruises will facilitate the inspection, decreases the loss of moisture and helps in the prevention of dehydration. This will also help in the creation of modified atmosphere.
At the time of pre-packaging, stalk, leaves, stem etc are cut, cleaned and washed. The quantities are weighed and are kept in pouches. The absorbent of ethylene should be added to the package wherever necessary to delay the process of ripening. Insertion of hydrated lime will also be advantageous in the carbon dioxide control within the package of the film.
Read: Fruit Farming Information.