Perishable food crops, by definition, refer to agricultural food produce which have short life-span and must be consumed or processed within a short-time after harvest. Examples of perishable crops include tomato (Lycopasicum esculentum), pepper (Capsicum spp), banana (Musa spp), leafy vegetables amongst others. These crops are very sensitive to extreme conditions such as high temperature, pest attack, improper handling, improper storage conditions and so on. Consequently, such crops require proper handling right from the point they are harvested on the farm till they reach consumer’s table or the processing plant.
The most important goals of postharvest handling are to keep the product cool, thereby avoiding moisture loss and slowing down undesirable chemical changes and to avoid physical damage such as bruising in order to delay spoilage. This in turn will help ensure increased food security, as food security goes beyond food production to include distribution and marketing, adequate and stable supply, and accessibility to food. Research has shown that large proportions of perishable farm produce are spoilt after harvest especially during transit to the market or while being stored. This has serious implication on food security as it is bound to affect the affordability and availability of the fresh produce to consumers.
In Nigeria, where most of the fruit vegetables, like tomatoes are grown commercially in the Northern parts, loss during transportation occurs especially en route southern markets. In the face of recent economic recession therefore, where the prices of food crops have skyrocketed, AgroNigeria has therefore taken it upon herself to sensitize the public on some low-cost strategies of reducing post-harvest losses of perishable food crops. In order to take an in-depth analysis of the strategies, the consideration will be done on a crop-specific basis. Therefore, in this week, we will observe the simple strategies that could be employed in curbing post-harvest losses of tomato. The choice of tomato is premised on the fact that Nigeria has just recovered from the outbreak of ‘Tomato ebola’- Tuta absoluta; a disease that ravaged tomato and made it become ‘precious stone’ in Nigerian markets.
Tomato is a vegetable crop commonly grown by peasant and some commercial farmers in Nigeria. The fruit which is known as berry is commonly eaten raw, used to make stew or soup or in preparing vegetable salad and other food. Tomato contains higher amounts of lycopene- a type of carotenoid with antioxidant properties which is beneficial in reducing the incidence of some chronic diseases like cancer and many other cardiovascular disorders. Despite its nutritive value and dietary importance, tomato is one of the most susceptible crops to post-harvest losses; no thanks to its physiological nature- high moisture content, high respiration rate and soft pericarp, which subjects it to microbial, mechanical and physiological damages among other factors. Certain practices are however necessary in order to prevent rupture of tomato fruits after harvest. Some of these strategies are highlighted below:
Use of paper to cover the produce instead of polythene bags: t his is the most effective overnight storage mechanism for tomatoes. It is commonly observed that some market women use polythene bags cover tomatoes at nights. Often times, this hastens rottening of tomatoes and within few days can reduce the once succulent tomato fruits to a caricature of themselves. Such rotten tomato fruits, popularly referred to as ‘esa’ amongst the Yorubas, are sold cheaply in order to prevent total damage. What happens is that polythene bags contain certain chemical constituents which react with tomato fruits thus facilitating rottening of tomatoes. Furthermore, the black colour of polythene bags naturally aids ripening of fruits; in fact, one of the artificial methods of inducing ripening of fruits is to cover unripe fruits with black polythene bags. Therefore, instead of utilizing polythene bags for covering tomato fruits over the night, paper is more appropriate.
Cleaning and Disinfecting of Tomatoes is another simple post-harvest technique for increasing the shelf life. Unfortunately, cleaning or disinfecting tomatoes after harvest is not a common practice for most tomatoes handlers in developing countries especially those from Africa. One of the reasons adduced to this negligence is the unavailability of portable water at the production sites or the sheer ignorance of the practice. However, in places where water is not a constraint, the use of disinfectants in water either for washing or for cooling can reduce both postharvest and food-borne diseases in tomatoes. The use of various disinfectants during postharvest treatment of tomatoes is well documented. For instance, sodium hypochlorite (NaOCl) solution can be used to sterilise tomato fruits in order to reduce the incidence of fungal infection before any postharvest treatment was applied. Dipping of tomato fruits in thiabendazole (C10H7N3S) solution also reduces microbial load on the fruits.
Postharvest heat treatment of fruits and vegetables is receiving more attention as a way of reducing the incidence of chilling injuries in temperature sensitive fruits of tropical origin. Postharvest heat treatments involve the use of hot air and heated water in order to reduce chilling injuries in tomatoes. This is also applicable to some fruits such as oranges and mangoes. Heat treating of tomato fruit at temperatures of about 37–42°C prior to cold storage can slow down ripening while increasing pathogenic resistance when in storage. Research has shown that heat treatment prior to storage enhances or causes no change in some quality traits of stored tomatoes.
Another strategy of reducing post-harvest losses of tomatoes, especially for large scale producers is to reduce the tomato fruits to pellets or puree. This could be done by grinding or milling as the case may be. However, this strategy might require the use of some grinding machines as well as preservatives in order to increase the shelve life of tomato puree.
Drying of tomato fruits is another low-cost strategy of preventing losses at the post-harvest stage of tomato value chain. Sun drying is one of the cheapest preservation techniques for most perishable produce. There are other means of drying such as oven-drying, but more sophisticated equipment might be needed when these techniques are employed. Dried tomato fruits can be packaged and exported as it is highly demanded outside Nigeria…… Other strategies such as refrigeration, use of Modified Atmosphere Packaging, grading and sorting as well as the use of calcium chloride can be deployed to preserve tomatoes.
In order to get more of these techniques for reducing post-harvest losses of perishable food crops, please keep an eye on our website as we continue to dish them out in subsequent publications.