By Antonio Acedo Jr; Warwick Easdown

Introduction 
Post-harvest losses negatively impact the economic benefit derived from vegetable production (Weinberger and Acedo, 2011). Vegetables are essential parts of human diets, but they are perishable by nature. Losses between farms and consumers are highest in developing countries where there is a lack of knowledge, skills, technologies, techniques, and facilities for produce handling and processing. This loss of nutritious food and economic opportunities contributes to poverty, unemployment, and malnutrition. This paper analyses the status of post-harvest losses in South Asia, a region with high levels of poverty, malnutrition and food insecurity, and assesses approaches to reducing these losses.

Post-harvest losses 
Post-harvest losses vary with crop, location, growing season and the value chain actors involved. The causes of post-harvest losses can start well before harvest in the choice of variety, pest or disease attacks or how the crop was grown. Therefore measures to reduce post-harvest losses should start before harvest. Crops and varieties vary in their degree of perishability, and the growing and harvesting environment and methods used have an impact on losses while the supply and demand situation at harvest time affects the time and distance the produce needs to travel. The social, cultural and economic conditions in a country and those of the main actors in the vegetable value chains also have an impact on their abilities to address losses. In many developing countries, the necessary data is not available to credibly estimate the extent of post-harvest losses (USDS, 2013). In general, loss figures are derived from a single measure (e.g. outright volume loss) or combined with other quantitative measures (weight loss and equivalent volume loss based on price reduction due to reduced quality of still marketable produce). From these figures, global, regional, national and local loss estimates (percentages, volume and monetary value) are derived. Credible loss data at different stages of the value chain is the essential requirement for designing effective interventions to reduce those losses.

Global situation 
In 2011, a study commissioned by the Food and Agriculture Organization of the United Nations (FAO) reported that roughly one-third of global food produced for human consumption is lost or wasted, which amounts to about 1.3 billion tons per year worth nearly one trillion US dollars (Gustavsson et al., 2011; CGIAR, 2013). Food losses amount to US$ 310 billion annually in developing countries, where nearly 65 per cent of food losses occur at the production and post-harvest stages. In the Asia-Pacific region, between 15-50 per cent of food crop output is lost between the production and marketing stages (FAO, 2014).

Vegetable post-harvest losses vary considerably, with maximum average losses of up to 50 per cent or higher occurring in developing countries (Weinberger and Acedo, 2011). They are a standard feature of supply chains in these countries often typified by hot and humid tropical climates, where there is a lack of knowledge, techniques and facilities in produce handling and processing. Adverse climates and poor management combined with the perishable nature of vegetables have a large impact on reducing the profitability and efficiency of supply chains.

South Asia situation 
South Asia comprises of Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan and Sri Lanka, and has severe problems of post-harvest losses across many crops that contribute to a high incidence of poverty and food insecurity in the region. The highest losses are in perishable vegetables and fruit, but there is also a lack of reliable data in many situations, with the highest losses often being reported where there is least data available.

Within the region, India is the most advanced in addressing the problem of post-harvest losses and estimating actual losses, and this is a key focus in the country's 12th Five Year Plan (USDS, 2013). India is the world's second largest vegetable producer with an annual production of over 150 million tons growing at a compounded annual rate of 5-6 per cent. (ASSOCHAM, 2013). The All India Coordinated Research Project on Post-harvest Technology conducted a national study to obtain reliable loss estimates for all phases of production and distribution for major crops (Nanda et al., 2012). For vegetables, the total average post-harvest losses were estimated at 7-8 per cent for cabbage, cauliflower and onion, and 13 per cent for tomato. The Associated Chambers of Commerce and Industry of India reported that about 30 per cent of vegetables and fruit are lost after harvest, worth a total of over 2 trillion INR per year (over 33 billion USD) due to lack of storage and processing facilities and indifferent attitudes towards tackling the problem (ASSOCHAM, 2013). Among the states, post-harvest losses are highest in West Bengal (over 136.6 billion INR), followed by Gujarat (114 billion INR), Bihar (107 billion INR) and Uttar Pradesh (103 billion INR). Other authors have also recently estimated loss data (Narayana et al., 2014; www.assocham.org; www.crosstree.info/Pages/Links.aspx).

In Bangladesh, post-harvest losses of vegetables were reported to range from 18-44 per cent, equivalent to an average yearly loss of over 2 million tons of produce worth about 3,392 million BDT (45 million USD) (Halim, 2013; Hassan, 2010). In Mymensingh, the highest post-harvest loss was recorded for tomato (37 per cent) followed by okra (34 per cent) and the lowest loss was for pepper (14 per cent) (Hassan, 2010). The causes of losses were improper handling and transportation, poor technologies for storage, processing, and packaging, the involvement of too many market actors, and poor infrastructure including a lack of transport. A recent study in three districts (Barisal, Jessore and Faridpur) found post-harvest losses ranged from 11-33 per cent depending on the crop and value chain actor, with the highest losses found in tomato and by farmers (AVRDC, 2014). The key factors contributing to losses were inappropriate post-harvest technology and insufficient product development services, complex and fragmented marketing systems, lack of appropriate supply chain organization and management, lack of infrastructure such as grading, packing and cool chain facilities, and lack of finance for farmers, traders, wholesalers and retailers for commercial production and marketing.

Nepal produces about 3 million tons of vegetables from an area of 235,100 hectares and post-harvest losses generally range between 25 to 30 per cent (HVAP, 2011). Tomato had the highest losses (33 per cent) followed by cauliflower (14 per cent), cabbage (13 per cent), green peas (10 per cent) and beans (7 per cent). Losses were measured at different stages in the supply chain. For tomato, losses are 10 per cent at the farm gate, 5 per cent at the collection centre, 8 per cent at the wholesale market, and 10 per cent at the retail markets. Losses were due to a lack of proper handling, storage and transportation and in most cases, there is no grading. In the Terai districts of Kapilvastu and Banke, post-harvest losses of tomato and cauliflower were estimated at 25 per cent and 21 per cent, respectively (AVRDC, 2015). Losses borne by tomato farmers, collectors, wholesalers and retailers differed only slightly from each other and were in the range 5-7 per cent, while cauliflower collectors and wholesalers had higher losses than farmers and retailers. Losses borne by farmers were mainly due to pre-harvest insect and disease damage while those borne by collectors, wholesalers and retailers were due to deficiencies in packaging, storage and transportation.

Pakistan produces over 8 million metric tons of vegetables from 611,700 hectares but between 15-40 per cent is lost after harvest (Khokhar, 2014; Pakistan Horticulture Development and Export Board, 2007). The three leading vegetables - potato, onion and tomato - have post-harvest losses of 15 per cent, 20 per cent and 40 per cent, valued at about 582, 579, and 341 million PKR or 58, 58 and 34 million USD, respectively. Post-harvest losses for other vegetables averaged 30 per cent, worth 2,161 million PKR (216 million USD). The causes of loss include a lack of roads for linking farmers to markets, a lack of packing and grading facilities in the production areas, poor grading and packing procedures to meet market requirements, and a lack of refrigerated transport.

In Afghanistan, post-harvest losses of vegetables and fruit were reported at 50-60 per cent of total production (Soofizada, 2014; USDS, 2013). The main causes of the losses include a lack of farmers' knowledge of good post-harvest practices (proper handling, packing, sorting, grading, cooling, observing quality standards and food safety, processing, and marketing), poor extension services, communication and coordination, inadequate cold storage, refrigerated truck and packing house facilities, inadequate processing facilities, poor transportation, and high transportation cost.

In Bhutan, post-harvest losses of the major vegetables were reported to range from 16-22 per cent for potato, 15-20 per cent for cabbage, 22-25 per cent for tomato, 20-22 per cent for beans, 30-35 per cent for peas and 15-18 per cent for cauliflower and broccoli (Thinley, 2014). These losses were mainly due to inadequate handling, packaging, transport and storage practices resulting in physical damage and spoilage of the produce.

In Sri Lanka, about 16-40 per cent of the total production of vegetables (565,250 metric tons from an area of 110,960 ha) is wasted after harvest (Bamunuarachchi et al., undated; Warushamana, 2011). Poor packaging and transportation were the leading causes along with a lack of proper storage.

Losses in nutritional quality 
Unseen losses relating to loss of nutritional value (e.g. loss of vitamins) are not reflected in the loss figures above. Vegetables are essential to balanced diets, being rich in vitamins, minerals, dietary fiber and phytochemicals whose retention from farm to table should be maximized (Acedo et al., 2014; Terry, 2011). Some losses are inevitable, but better understanding of the possible causes can help to find measures to diminish such losses. Some nutrients begin to decrease after harvest and continue to decline until the produce is eaten, and so the sooner fresh produce is eaten, the less the nutrient loss.

Ascorbic acid (vitamin C) is often used as an index of nutritional quality loss because it is susceptible to loss after harvest and during storage, processing and cooking as it is water soluble and sensitive to heat, light, and oxygen (Barrett, 2007). Vitamin C losses depend on the crop and the conditions before and after harvest, and can range from 27-100 per cent after 7 days at 20oC (Rickman et al., 2007a). Losses in B vitamins also occur during transportation and storage of fresh vegetables. In particular, thiamin and vitamin B6 are quite sensitive to heat and light and losses in various vegetables may range from 7-70 per cent with canning and 20-60 per cent with blanching and freezing. Polyphenolics generally decline with the storage of fresh vegetables and as a result of canning and blanching, while mineral and fiber contents, being relatively inert and not sensitive to the thermal processes used in food preservation and preparation, have been found to be at similar levels in fresh, canned, and frozen vegetable products. Fat-soluble nutrients such as vitamins A and E and the carotenoids (including lycopene) are sensitive to heat, light, oxygen, and pH. However, because these compounds are fat-soluble, there is little leaching into cooking water or the canning medium (Rickman et al., 2007b). Compared to the water-soluble vitamins, the carotenoids are relatively stable during processing, storage, and cooking. Traditional sun-drying, although the cheapest and most accessible means of food preservation in developing countries, causes considerable destruction of nutrients and bioactive compounds, particularly during storage of the dried product because of the greater surface area of the dried product exposed to oxygen and light compared to the fresh produce. Drying in even a simple and inexpensive solar dryer can appreciably reduce nutrient losses. Protecting the food from direct sunlight during storage also has a positive effect. In the last two decades, non-thermal processing technologies (e.g. high pressure processing, high-intensity pulsed electric field processing) have been introduced to inactivate microorganisms and enzymes, without adverse effects on sensory and nutritional properties. These technologies can be adapted to South Asia.

Table 1 shows the typical nutrient losses from different processing operations. However, this information is only intended to serve as a guide because several factors can influence nutrient losses, such as type of produce, location, and growing and processing conditions.

 

 

 
Source: http://nutritiondata.self.com/topics/processing#ixzz3aaSAgR6R

 

Reducing post-harvest losses 
The 'Save Food: Global Initiative on Food Loss and Waste Reduction' launched by FAO and its partners in 2011 ignited renewed interest in food loss reduction (FAO, 2012). A similar FAO initiative was pursued in 1975 but over the next three decades over 95 per cent of donor support to increase food availability went in increasing crop production rather than in reducing post-harvest losses (Kader and Rolle, 2004).

The global loss reduction initiative was backed by various development groups including the World Bank (2014), CGIAR (2013) and USAID and provided the impetus for regional initiatives such as the Save Food Asia-Pacific (FAO, 2014). Today, two thirds of the world's 870 million hungry and malnourished people are in South and South-East Asia (FAO, 2010). There is a need to feed an additional two billion people by 2050 (FAO, 2011), and governments are well aware of the social unrest associated with food price increases. It has been estimated that half of the current post-harvest losses can be prevented with a more efficient supply chain and the saved food can feed about one billion extra people.

Many targeted approaches can be used to reduce food loss and waste. Practical and cost-effective approaches that could be implemented quickly, and that could achieve quick gains include using evaporative coolers in places where refrigeration is unavailable, introducing hermetically sealed plastic storage bags, using plastic crates instead of bags, changing food date labels to reduce consumer confusion about when food is unsafe, conducting consumer awareness campaigns and facilitating food redistribution (Lipinski et al., 2013). Several cross-cutting strategies such as the ones below are needed and require action from multilateral and bilateral donors, intergovernmental agencies, national governments, and the private sector:

  1. Developing a food loss and waste measurement protocol.
  2. Setting food loss and waste reduction targets.
  3. Increasing investment for reducing post-harvest losses in developing countries.
  4. Creating entities devoted to reducing food waste in developed countries.
  5. Accelerating and supporting collaborative initiatives to reduce food loss and waste.

Reducing post-harvest losses through appropriate post-harvest technologies has far-reaching benefits. As developing countries integrate into the world economy, the implementation of post-harvest technologies can enable these countries to improve the quality of their agricultural produce in domestic and international markets at competitive price.

Conclusion 
The benefits of adopting post-harvest technologies to reduce losses are high. Addressing the post-harvest problems that characterize the vegetable sector in developing countries, including South Asia, provides significant scope to increase food supplies and to improve the well-being of millions of poor farm households, and it is a key aspect of the work of AVRDC -- The World Vegetable Center.

(List of references can be made available upon request)