Considering the agro climatic suitability for fruit cultivation, richness of the soil and other related requirements one feels that horticulture in Ethiopia is a sleeping giant. The potential of this sector has not been taped. It can play wonders for boosting economy of the country, besides improving food and nutritional security. Though Government has taken many initiatives for boosting horticulture in the country, but there is a need to do something more for post-harvest and processing sectors. Sustainable development in horticulture sector is not possible without prioritizing these sectors. Reducing post-harvest losses needs lesser per unit resources for making additional food available than the increased production. Our farmers and other stakeholders need to understand that they can play a great role in reducing post-harvest losses, even without any Government intervention or any specialized infrastructures. Though Government support and interventions are always required for boosting this sector, but farmers and others associated with fruit handling also need to play their role in minimizing the post-harvest losses.
The term “postharvest loss” refers to measurable quantitative and qualitative food loss in the postharvest system. This system comprises interconnected activities from the time of harvest through crop processing, marketing and food preparation, to the final decision by the consumer to eat or discard the food. Thus Post-harvest losses of horticultural crops can be defined as losses of horticultural commodities in quality and quantity after harvesting till consumption. Let us first understand how the post-harvest losses take place. Harvested fruits and vegetables are living structures.
They continue to perform metabolic reactions & maintain the physiological systems which were present when it was attached to plant. An important feature of fruits & vegetables even after harvesting is that they respire by taking up oxygen and giving off carbon dioxide & heat. They also transpire, that is, lose water. The rate of deterioration is generally proportional to the respiration rate. We understand respiration and transpiration are among the basic contributors for postharvest changes. Any activity that promotes respiration, transpiration will lead to faster crop deterioration. All fresh fruits & vegetables contain high water content (above 80%) and the process of transpiration causes wilting and shriveling. Thus results in quality and quantity loss. Post-harvest deterioration is influenced by number of factors like rough handling from harvesting to consumption, high and low temperatures, low relative humidity, storage conditions etc.
Like most of the African countries the post-harvest losses of fruits & vegetables in Ethiopia are very high. During 201516 post-harvest losses ranging from 37.15 to 45.78 % for selected fruits have been reported in Ethiopia. Certain reports indicate losses even as high as 30 to 80% in some horticultural crops. Though lack of required infrastructures is one of the reasons for such post-harvest losses but lack of awareness about proper harvesting, handling, storage and other post-harvest operations significantly contributes for such losses. If post-harvest operations in Ethiopia are performed in a recommended manner there will be significant loss reduction even with the existing infrastructures.
Faulty post-harvest operations are very common in Ethiopia and such techniques are a normal routine with different stakeholders. These faulty operations are among the basic causes of post-harvest losses. The damages caused to the crops due to faulty post-harvest operations cannot be reversed and they cause the spoilage. In the present article some of the most common post–harvest operations and the faulty techniques being adopted for these operations have been identified by the author, so the effect of such faulty operations on post-harvest quality and shelf life are discussed here. The concepts discussed are very basic and can be easily understood by a common farmer. No high technological interventions have been suggested.
Harvesting is a hinge between pre and post-harvest operations. Though many pre-harvest factors influence post-harvest quality and shelf life, but in this article we will restrict discussions about post- harvest operations contributing for losses in Ethiopia.
Faulty Harvesting Techniques:- Harvesting is the starting phase of postharvest life of horticultural crops. Fruits and vegetables are very tender and are to be harvested & handled with great care. One must remember that fruits must be cared, the way we care small babies. They are delicate and are susceptible to injuries.
Harvesting is basically a simple operation involving the removal of the produce from the parent plant and placing it in containers for removal from the field to the market, or to the packing shed in the farm itself or to the packing – house. Most roots and tubers that live beneath the soil are likely to suffer mechanical damage at harvest because of digging tools, which may be wooden sticks, hoes or forks. Faulty harvesting techniques are one of the basic causes for spoilage of the crops. Any injury or pressure applied at any part of the produce causes damage and results in post-harvest deterioration. Some fruits in Ethiopia are harvested by beating fruit plants with long hard sticks. This causes injury to the fruit either by the stick or by falling on the ground or by both. Most of the times these injuries may not be visible on the skin of the fruit but the impact of these injuries exists on fruit flesh beneath the skin and the injured part starts deteriorating. It expands to other portion of the fruit and also damages the healthy fruits packed or placed adjacent to these bruised fruits. Farmers must understand that any type of injury or pressure on the produce will cause quality and quantity deterioration, so harvest with care. Digging of root crops must also be given proper attention and injuries during their harvesting must be avoided.
Mechanical Damages:- Mechanical damage can take place at any postharvest operation due to various factors like faulty handling/ containers/carriers / transportation etc. The initial damage is small, but it expands and damages the entire fruit and the other adjacent fruits also. Suitable packaging materials and handling techniques can minimize the damage. Any injury on the fruit provides entry point for the microorganisms and as such spoilage is further accelerated.
Handling:- Improper procedure for collection and handling during harvesting is another cause of post-harvest losses. Once the fruit/vegetable is harvested the collection process is very damaging. Fruits & vegetables are dumped at collection spot by emptying the basket from a height of few feet. This causes injury to the produce and thus faster deterioration. Many of the times even the produce is thrown on the collection heap from few meters, thus causing bruises. Rough handling of fruit from harvest to loading/unloading, over packing or under packing of containers, use of rough handling containers or very weak packing material, harsh technique of emptying containers, and improper handling during transportation contribute for huge post-harvest losses.
Pictorial depiction in the Figure below shows how a farmer empties his basket of harvested papaya from a ground height of about one meter. The damage caused to fruits can easily be observed.
Heaping of produce in the field:- During collection of produce, the fruits & vegetables are heaped in the field. Dumping /heaping in Ethiopia is generally taking place in open sunshine, that raises the temperature and thus results in faster rate of respiration and evaporation which in turn causes faster deterioration. The produce also generates heat by normal respiration that further increases the temperature and causes much faster deterioration. Collection of produce under shade is recommended. Produce in the sun are 3 to 10°C higher in temperature than ambient air temperature. Weight losses under traditional conditions of heaping under sunshine have been observed to be 2.5% in 4 hours, compared to 0.5% in 4 hours under shade. Tomatoes and eggplant in the sun for 1 hour after harvest have been found 15°C hotter than produce in the shade. Any activity that raises temperature of the produce increases rate of respiration and thus causes faster deterioration. Therefore, heaping produce in the open sun is one of the causes for post-harvest losses in the country. Farmers must ensure to collect the fruit under shade.
Grading and Packing under Open Sunshine:- The produce is exposed to open sun light even during grading and packing. This promotes fast deterioration due to the effects of high temperatures on rate of respiration. Such exposure to high temperatures also results in higher transpiration losses thus causing weight loss of the fruit. Lack of shade contributes to high pulp temperatures and high water losses. Thus the temperature in the horticultural produce during handling, transport and marketing is much higher than that recommended for quality maintenance of the produce. High temperatures contribute to high rate of respiration and other related biochemical reactions of the produce, which in turn results in faster deterioration.
Containers/Boxes used for handling and packing:- Rough containers, baskets and crates that may have splintered wood, sharp edges, poor nailing or stapling, damages the fruit and cause post-harvest losses. In general the containers being used for collection, handling or packing have a very rough surface, splintered wood, sharp edges, outward projecting nails and such other defects. These rough surfaces cause scratches / bruises on the produce and ultimately an irreversible deterioration of the produce starts. The field containers for harvesting must be of a size that can be conveniently carried by the harvest workers while moving through the field. Locally made containers/ baskets could be used but their inner surface must be smooth. If required the liners could be used. Liners could be even a locally available soft grass growing in the farmers’ field or any other material available with the farmer.
Sorting and Grading:- The produce is generally kept in heaps for sale without proper sorting and grading. Even few infected or damaged fruits are sufficient to multiply infection or cause damage to other healthy fruits. Thus the entire lot is vulnerable. Sorting and grading practices are not being followed and as such even healthy fruit gets damaged. Absence of sorting and grading of damaged produce at the selling and collection centers also cause losses. Farmers must ensure to sort out the decayed, bruised and infected fruits.
Transportation:- Transporting fruit openly in carts having rough surfaces, sharp edges, poor nailing or stapling , unhygienic surfaces is very common in production areas. Improper handling during transportation, such as walking on produce and packed containers during the process of transport causes injuries to the fruit. The damage to the fruit results to loss of quality and shelf life. Without any consideration, a cart puller, a labor, a driver or the farmer stands on the fruit causing damages to the produce.
Storage of fruits and Vegetables: – Fruit/ vegetable traders in markets and small street level vendors cover the produce with polyethylene or tarpaulin sheets when they close their trading in the evening. Covering under such sheets accumulates the heat and ethylene generated by normal respiration. This in turn accelerates the process of deterioration.
Damage caused due to such defective storage technique is very common and the losses are of higher magnitude when the produce remains covered for longer hours (like from Saturday evening to Monday morning), especially when the atmospheric temperatures are high. Even the individual farmers also adopt such faulty storage techniques of covering the produce with tarpaulin, placing in open sunshine etc. It has to be kept in mind that any storage condition that raises temperature and/ or stops ventilation will accelerate deterioration. Thus such situations need to be avoided while storing any horticultural produce.
Marketing:- Display of fruits and vegetables on the open ground during selling at “wholesale & retail markets is very unhygienic. This causes contamination’s, bruises on fruit, accelerates deterioration and results in losses.
Many times farmers make delay in marketing of the harvested produce. Delay in marketing and storing under inappropriate temperatures and humidity during such periods further aggravates the deterioration of the crop.
Post-harvest Infections:- Postharvest diseases destroy 10 to 30% of the total yield of crops, and in some perishable crops, especially in developing countries, they destroy more than 30% of the crop yields. Fresh fruits and vegetables are highly perishable products; and their quality is affected by postharvest handling, transportation, storage and marketing. The improper handling, packaging, storage and transportation may result in decay and multiplication of microorganisms, which become activated because of the changing physiological state of the fruits and vegetables. Fungi are the most important and prevalent pathogens infecting a wide range of host plants and causing destructive and economic losses of most fresh fruits and vegetables during storage and transportation. Post-harvest diseases can also be spread by field boxes (contaminated by soil or decaying produce or both), contaminated water used to wash produce before packing, decaying rejected produce left lying around packing houses, contaminating healthy produce in packages etc. Decayed fruits are generally lying around the fruit collection sheds, containers, carrier vehicles and at other such locations. It is advisable to use properly cleaned containers, storage chambers, carts, and other carriers for handling, transportation and storage of any horticultural crop.
Conclusion
High post-harvest losses of horticultural crops in Ethiopia are mostly due to faulty handling during harvesting, transportation, storage and during other post-harvest operations. Exposures to high temperatures or creating conditions leading to increase of storage temperatures are very common at farm level, stores and fruit markets. Unhygienic conditions of handling containers, carrier vehicles, stores, packing sheds etc. also contribute for infection/decay and ultimately for post-harvest losses.
Though appropriate infrastructures are required for maintaining quality of produce, but we must manage to reduce losses within our available infrastructures. Proper handling and care can significantly reduce huge postharvest losses. Awareness, education and training to the stakeholders can create great difference, even with existing infrastructures. There is an urgent need to create awareness among farmers and other stakeholders about the basic operations. This will provide quick results without creating any additional infrastructures.
The Ethiopian Herald May 31,2020
DR. GHULAM HASSAN SHAH
E-mail:- drshahgh7@yahoo.co.in
