POST-HARVEST HANDLING OF ORANGES
Olanrewaju Rukayat Ifedapo.
Do you have an orange grove or just a tree or a couple of trees in your home garden? This is a very blooming season for you. Your trees are heavy with those Vitamin C laden fruits ready to be picked. Typically, oranges have to be consumed between one to three weeks after harvest. Worried much? I believe the question running through your mind as an orchard owner is how am I going to harvest? Can oranges be stored? How can I store my oranges? How can I extend the shelf life of my fruit? How can I make the fruits available off-season? Be rest assured there are harvesting and post-harvest handling techniques and precautions one can do to reduce losses and spoilage and also store these sumptuous fruits for later days.
Source: Kauna Kitchen Ripe orange fruit.
Oranges (Citrus sinensis) is a member of the citrus family along with tangerine, lemons, limes, and grapefruit. It is a common fruit, when in season it can be found everywhere in the country. Orange is a choice fruit for roadside traders and hawkers in Nigeria. It is a very affordable source of Vitamin C and one of the cheapest fruits in Nigeria. Major products derived from this fruit include: Orange juice, orange concentrate, fresh squeezed juice, mixed fruit juice, smoothies and marmalades. Orange is an important source of Vitamin C and folate. It also provides significant number of antioxidants such as beta-carotene and flavonoid compounds.
Just like any other perishable fruit and vegetables in Nigeria, oranges are also affected by the food wastage problem plaguing our agricultural sector. Globally, post-harvest fruit and vegetable loss are as high as 30-40% and this is even higher in Nigeria. This is evident when you walk through orange distribution stands in a typical Nigerian market. A high percentage of oranges produced in the country annually isn’t consumed but wasted along the supply chain. Sometimes fruits get rotten in times of delivery from producer to consumers. This may be due to physical damage during harvesting, hauling and transport; physiological decay or sometimes glut in the market with no buyer.
Source: Yusha’u (2017) Typical orange distribution stand in Nigerian markets
(How do I harvest my oranges?)
Oranges can be picked manually or mechanically.
This involve the picking and collection of fruits by hand. For those of us with a few trees in our home gardens or farm and small-scale orange farmer with less than an acre of orange grove, hiring labour to pick the fruits is the best option. In Nigeria, most oranges are harvested manually with the aid of a sickle or harvesting knife attached to a long stick, or by shaking the branches, it is also harvested by climbers and in rural areas the fruits are hit continuously with the aid of a long stick to shake the fruits free. These methods of harvesting constitute a high percentage of orange losses resulting from the physical damages to the oranges (scarring and bruising of the orange peels and crushing of the oranges) during harvesting.
Preferably, harvesting should be done with the aid of a fruit picker. This tool has a hooked grip with an attached fabric bag or basket for receiving the oranges and a long handle for increased range. This will reduce scars, bruise and injury from hitting the ground. Fruit picking bags are recommended for the collection of harvested oranges. These bags are comfortable and it reduces occurrence of physical injury to the harvested oranges.
Source: Independent (2016) Fruit picker with handle source: eBay Fruit picker
Orange harvesting can be done mechanically through the canopy shake or the tractor shaken method. In the canopy shake method, a self-propelled machine is used to shake the oranges free from the tree. The oranges are fell and collected in a catch cloth (can be tarpaulin or large piece of any thick fabric) laid around the tree base. This is to reduce the fall impact on the fruit. This catch cloth is then dumped in the truck for transportation. The tractor-shaken method is a combination of both mechanical and manual picking. The tractor shakes the oranges free from the tree and workers pick them up and place them in picking bags.
Source: Agri Expo Harvesting bags
Dumping: After harvesting the picked oranges are dumped in a harvesting bin, field boxes or even directly into the truck. Ensure that the containers and the truck bed are clean and free from contamination. Layer the container with newspapers, paper bag, old sacks, or fabric. Harvested should be transported with care and try as much as possible to reduce fruit exposure to sunlight.
Washing: the harvested oranges are washed and dried to remove dirt and reduce contaminations. Endeavor to use clean water for washing and a clean dry cloth for drying. Washing can be done mechanically in a washing drum and dried by blowing hot air on the fruits.
Sorting and grading: Sorting involves the separation of damaged, bruised, or crushed oranges from the intact ones. It is recommended to remove damaged fruits from the healthy ones to prevent spread of microbes. It will also prevent the infection of healthy fruits by the damaged ones. Oranges are graded by size. It can be done both manually and mechanically. When grading manually it is best not to judge the size by sight only. A simple way to check orange sizes is to cut a series of round holes in a thin wood board or cardboard according to standard market sizes. Grading can also be done with the aid of grading machines.
Source: fftc (2003) Wood board for manual sizing grading machine
Packaging and transportation: In Nigeria, many oranges are lost in transit. Oranges are usually packed in nylon sacks, bags or baskets and loaded in trucks to the market. The oranges are exposed to the sun and heated in the sacks, they are also crushed and sometimes they are transported with other ethylene-producing fruits, this results in crushing and bruising of the oranges. It may also create an enabling environment for the spread of microbes.
Source: FAO (2003) Typical plastic crate holding fresh oranges
It is advisable to use wooden crates and plastic crates for packaging and transporting oranges to the market. This well-ventilated crates are stackable thus it will reduce damaging of the peel and crushing of the fruits. These crates should be stacked neatly in well-ventilated truck for transportation to the market. Oranges are best transported in the morning or evening to reduce exposure to sunlight and heat. Oranges may be packaged in fruit nets before being arranged in crates, or they may be arranged directly into crates.
Source: fftc (2003) Oranges packed in boxes ready for the market
(How can I extend the shelf life of my oranges?)
Treatment and Curing
Only fruits that are not damaged can be stored. Although it is difficult to harvest fruits without minor injury but endeavor to reduce such to the barest minimum. Sometimes a chemical treatment is applied to the fruits prior to storage to reduce incidence of post-harvest diseases. Spraying thiabendazole (40% diluted at 500X) on fruits one or two weeks before harvest or soaking the fruits for three minutes immediately after harvest can reduce incidence of rot during storage. Also, Iminoctadine 25% (diluted at 2000X) can be sprayed on the fruits four days before harvest or alternatively it can be used to soak the fruit before they are packed to reduce fruit rot. After chemical treatment, the fruits are cured. They are kept in the shade for a few days reducing the water content of the peel before they are packed in Polyethylene (PE) plastic bags (0.02-0.03mm thick). This reduces cell activities in the peel which otherwise would soften the fruit. On average it takes about 3-7days to reduce fruit weight by 3%. The length of curing depends on the temperature, the length of time the fruit would be stored and the peel thickness. For long time storage, the cured fruits are wrapped in plastic to reduce water loss.
Source: fftc (2003) Stacked crates of oranges wrapped in plastic bags ready for storage
(Can oranges be stored?)
Oranges are stored after treatment and curing. The cured oranges are packed in polyethylene plastic bags. These bags are arranged carefully in plastic crates or boxes for storing the fruit. Avoid putting too much layers in one box, it may cause bruising of the fruits. The fruit crates are arranged in storage rooms. They should be stacked in a way that would allow good ventilation.
During the first few weeks of storage, ventilation windows should be left open. At night or cold weather windows should be left open in order to cool the fruit. During the day, ventilation windows should be closed to prevent sunlight penetration inside the storage room.
A good storage room is key to increasing shelf life of oranges. Storage room should be constructed in places where cold air can flow into the room at night. It must have a high roof to allow better cold air circulation at night. The ventilation windows should be small but many to allow air circulation. The roof and walls should have good heat insulation to keep temperature as cool as possible. The room should be insect-proof and rat-proof. It is recommended to bury some ventilation pipes underground to bring cool air through the floor of the room.
Source: fftc (2003) Well ventilated storage house
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