Postharvest losses represent a challenge to global food systems. These losses refer to the measurable reduction in both the quantity and quality of agricultural products after they are harvested but before they reach the consumer. Addressing this issue is important for ensuring food availability and minimizing wasted resources.
Understanding Postharvest Losses
Postharvest losses occur once crops are removed from the field. These losses can happen at numerous stages within the food supply chain, including initial harvesting, subsequent handling, during storage, throughout processing activities, and during transportation to markets or consumers. The degradation can be quantitative, meaning a reduction in the physical amount of produce, or qualitative, affecting aspects like nutritional content, taste, texture, or appearance. This phenomenon applies to diverse agricultural products, not solely grains. Fruits, vegetables, roots, tubers, and even livestock products are susceptible to losses after harvest. For instance, highly perishable items such as fresh fruits and vegetables can experience losses ranging from 20% to 50% globally, sometimes exceeding 50% in developing regions, while cereals and grains might see losses between 10% and 30%.
Primary Causes of Losses
Losses after harvest stem from a combination of interconnected factors.
Biological and Physiological Factors
Biological and physiological factors are inherent to the produce, as items continue to respire and undergo metabolic changes. This includes natural aging processes like senescence, sprouting in crops like onions or potatoes, and rooting. Pathogens such as fungi and bacteria, along with pests like insects and rodents, also cause deterioration by consuming or contaminating produce.
Mechanical Damage
Mechanical damage occurs during various postharvest operations. Bruising, cuts, and crushing can result from rough handling during harvesting, sorting, or packing. For example, mechanical shelling of maize can damage kernels, making them more susceptible to insect penetration, while improper threshing can lead to grain breakage. Such physical injuries compromise the protective skin barrier, accelerating water loss and creating entry points for spoilage microorganisms.
Environmental Factors
Environmental factors, including temperature and humidity, affect postharvest quality. High temperatures accelerate respiration rates and the growth of spoilage organisms, significantly shortening shelf life. Conversely, low temperatures can cause chilling injury in sensitive produce, while excessive moisture promotes mold growth and too little moisture leads to wilting and shrinkage. Exposure to unfavorable light conditions or atmospheric composition can also negatively impact produce quality.
Logistical and Infrastructural Issues
Logistical and infrastructural issues exacerbate losses, particularly in developing regions. Inadequate or non-existent storage facilities, such as the lack of cold storage or proper silos, lead to rapid spoilage. Inefficient transportation networks, characterized by poor roads, limited access to refrigerated vehicles, or prolonged transit times, expose produce to adverse conditions and increased damage. Additionally, a lack of processing capabilities means that surplus or lower-grade produce cannot be converted into value-added products with extended shelf lives.
Human Factors
Human factors, such as improper handling techniques and lack of training, contribute to postharvest losses. Workers may not be aware of optimal harvesting times, gentle handling methods, or the correct sorting and packing procedures. These deficiencies can lead to avoidable damage and spoilage, underscoring the need for education on best practices across the supply chain.
Widespread Consequences
The impacts of postharvest losses affect food security, economic stability, and environmental sustainability.
Food Security
These losses directly reduce the amount of food available for consumption, exacerbating hunger and malnutrition, particularly in regions already facing food shortages. This diminishes the effectiveness of efforts to feed a growing global population.
Economic Stability
Economically, postharvest losses result in financial setbacks for all stakeholders in the agricultural supply chain. Farmers face reduced incomes due to diminished yields and lower market prices for damaged or spoiled produce. For instance, in Sub-Saharan Africa, these grain losses alone are estimated to cost around $4 billion annually. Consumers also experience higher food prices when supply decreases, impacting the affordability of nutritious food, especially for vulnerable populations.
Environmental Sustainability
Environmentally, food waste squanders valuable resources used in its production. This includes water, land, energy, and fertilizers, all of which are consumed without yielding any nutritional benefit. Decomposing organic matter from spoiled produce releases greenhouse gases, such as methane and carbon dioxide, contributing to climate change and increasing the ecological footprint of agriculture.
Reducing Postharvest Losses
Minimizing postharvest losses requires improved techniques, better infrastructure, and enhanced knowledge.
Improved Harvesting and Handling
Improved harvesting and handling techniques are a primary step. This involves training workers to handle produce gently, using appropriate harvesting tools to minimize physical damage, and harvesting at optimal maturity to ensure product quality. Rapid cooling immediately after harvest can also slow deterioration by removing field heat and reducing respiration rates.
Better Storage Solutions
Better storage solutions are also important for extending the shelf life of agricultural products. This includes investing in modern facilities that offer controlled temperature and humidity, such as cold storage units for perishable goods or airtight silos for grains. Technologies like modified atmosphere packaging, which alters the gas composition around produce, and edible coatings can further slow spoilage and maintain freshness during storage.
Efficient Transportation
Efficient transportation networks reduce losses from farm to market. This involves minimizing transit times, using appropriate packaging to protect produce from mechanical damage and vibration, and utilizing refrigerated transport for perishable items. Proper loading and unloading procedures, along with route optimization, can also prevent damage and delays.
Value Addition and Processing
Value addition and processing offer another avenue for loss reduction. Converting raw produce into processed goods, such as dried fruits, juices, or canned vegetables, extends shelf life and creates new market opportunities for produce that might otherwise spoil. This approach can transform lower-grade produce into economically viable products.
Education and Policy
Education and training for farmers and supply chain workers are important for adopting these improvements. Providing knowledge on best practices for harvesting, handling, storage, and pest management empowers individuals to make informed decisions that reduce losses. Policy and infrastructure development, including government support for research, investment in rural infrastructure like roads and cold chains, and the establishment of quality standards, are also needed to create an environment conducive to reducing postharvest losses.