Cassava (Manihot esculenta Crantz) is a woody perennial shrub of the Euphorbiaceae family. In view of its favourable agronomic traits, tolerance to abiotic stresses and adverse environments, the crop is produced by small farmers in marginal agricultural areas in the Caribbean as well as other parts of the world. In recent years in African, the Caribbean and Latin American countries, cassava production has grown and is projected to increase further because of its demand as food and its value as raw material for industrial use. In Guyana, cassava production has increased by a modest 11 percent from 2007 to 2012. Cassava cultivars are classified into two groups based on the amounts of hydrogen cyanide (HCN) present. Sweet types contain less than 50 mg kg-1 (fresh weight) and are generally sold as fresh roots, whereas bitter types have a larger amount of HCN, but have higher yields and starch content. Fresh cassava roots are highly perishable under ambient conditions, becoming unmarketable in 3 days or less. With proper post-harvest handling and management practices fresh roots can be stored up to 30 days. In recognition of the importance of cassava as a source of carbohydrates and the potential for further development of a diverse range of value-added products, FAO in collaboration with CARICOM initiated a project entitled ‘Reduction of post-harvest losses along the food chain in the CARICOM subregion 'Reduction of post-harvest losses along the food chain in the CARISOM sub-region' and identified cassava as one of the three commodities for post-harvest loss measurement.
The main objectives of the investigation included: an in-depth analysis of post-harvest handling
practices of cassava producers, retailers (roadside and mobile market vendors, municipal markets, supermarkets), wholesalers, exporters, processors for development of value-added products and consumers, to obtain a more complete understanding of the system-wide nature of quality deterioration and subsequent losses in order to formulate appropriate solutions for quality management and loss reduction strategies; analysis of the cassava value chain as items for food consumption, with quality attributes, which must be protected and enhanced in various marketing channels; the examination of the significance of losses of both technological and socio-economic origins; examination of links between growers and provisions for transferring relevant research information on identified problems to producers, traders and processors; the design and evaluation of improved operations throughout the system and alternative post-harvest handling systems; and the description of key factors affecting the logistics performance in the CARICOM Region with particular emphasis on logistics that affect produce losses in the supply chain.
Post-harvest losses of cassava were measured at three critical loss points (CLPs) after screening the value chains in both countries. The critical loss points were at harvest (CLP#1), packinghouse operations (CLP#2) and at retail markets (CLP#3).
At CLP#1 total losses averaged 6.5 percent mainly because of physical damage and pathological and entomological damage being 3 and 3.5 percent respectively. No physiological losses were measured at CLP#1 and 2 and total losses at CLP#1 were at least three times more than CLP#2. Losses were cumulative and injuries to roots at CLP#1 created avenues for further quality degradation as the commodity was moved along the value chain to CLP#3. Nevertheless, while the nature of all types of damage was almost the same (3.5 percent) after 6 days of retail marketing, the limit to marketability based on qualitative ratings was only up to day 2.
Strategies to reduce post-harvest losses include the use of appropriate harvesting tools such as the hand lifter to minimize breakage; removal of roots within 2-4 hours after harvest and providing protection against sunlight to minimize the desiccation of roots; washing of roots to remove dirt and dipping in a fungicide such as immazalil to limit microbial contamination; storing treated roots in polyethylene bags at a safe low temperature and high relative humidity 85-90 percent; inducing curing treatment to heal superficial wounds by keeping roots at 28-30 °C and 85-90 percent relative humidity; and application of wax treatment at 55-65 °C for a few seconds after treatment with a fungicide.