Postharvest Handling of Fruits and Vegetables
Fruits and Vegetables are the gifts of nature to human beings. In addition to meeting the nutritional needs of us they are also beneficial in other ways. They are helpful in preventing diseases. Many of the fruits and vegetables are very low in calories and fats and are helpful for controlling the weight. Eating a healthy diet consisting of lots of fruits and vegetables can reduce the risk of several diseases such as type 2 Diabetes, heart disease, stroke, high blood pressure and perhaps some forms of cancer. According to World Health Organization (WHO) recommendation an adult should consume 400 g of fruits and vegetables per day. According to WHO eating at least 400 g of fruits and vegetables daily can reduce the risk of non-communicable diseases . In order to get benefits of such amazing fruits and vegetables there should be proper post-harvest handling and care of these commodities. But unfortunately most of our Horticultural produce suffers from post-harvest losses. 20-40 % of the total Horticultural produce (Fruits and Vegetables) of Pakistan is lost due to improper post-harvest handling of these commodities. Much of the commodity produced by the grower is spoiled and lost before reaching the consumer which is the ultimate goal of the grower, wholesaler and retailer.
Causes of Losses: The postharvest losses are associated with the interaction of metabolic and environmental factors which bring about undesirable changes in our fresh produce. The main causes of spoilage are as follows:
*Insect pests and Diseases
*Loss of water
*Mechanical injury (physical damage)
*Chilling injury due to low temperature
*Other causes Losses are also caused during transportation of the produce. These damages and losses are mainly caused due to mechanical damage and overheating.
Mechanical damage is caused by many factors such as careless handling of the produce by workers during loading and unloading, vibration or shaking of the vehicle while transporting the produce, over speeding and bad condition of the vehicle, poor packing which may cause the packages to move back and forth or sideways causing collision due to which the produce inside gets damaged, packages piled too high which will result in more vibration and more bruising.
Overheating can occur not only by the external sources but also from the heat generated by the produce itself in the package. Overheating elevates natural breakdown and decay and increases the water loss from the fresh produce .When water is lost from the produce, it causes shriveling and shrinkage.
Overheating of commodity is caused due to use of closed vehicles having no ventilation, close -stow stacking of crates which will cause hindrance in the movement of air between the packages, absence of proper ventilation in the packages themselves and exposure of the packages to the sun while waiting for transport or waiting for unloading.
But these losses can be minimized and we can increase the shelf life of fruits and vegetables using the proper preharvest and postharvest handling techniques. We can use the modern postharvest handling technologies for maximizing the shelf life of our Horticultural produce which can increase to our benefits and also give more returns to the farmers. Following operations should be carried out to increase the shelf life of our produce.
Sorting: A preliminary sorting should be carried out to remove unwanted foreign matters such as debris of plants, nails, soil particles and stones. These substances may cause physical damage to the produce. Also the damaged and diseased fruits and vegetables should be discarded because they may cause the transfer of diseases to healthy portion.
Cleaning and Washing: Cleaning of unwanted foreign matters may be done by hand picking or sieving. Some type of produce can be washed and brushed. Washing is required to remove the latex stains which are developed by injuries from poor harvesting and handling.
Treatment with Fungicide: One of the major reasons of the loss of fresh produce during storage and marketing is due to the decay caused by molds or bacteria. Attack may occur before or after harvest, through injuries or direct penetration through the skin. Therefore in order to avoid such damage the produce should be treated with proper fungicide. Fungicide may be applied by two methods i-e dipping and spraying.
Waxing: Waxes are applied to improve the look and reduce the loss of water from the produce such as citrus. Waxing is normally done before fungicide treatment.
Storage: For storing fresh produce for longer time following techniques are used.
Refrigeration and Cold Storage: Fresh produce can be kept for longer time if they are kept at low temperature. Temperature requirements are different for different fruits and vegetables. According to U.S. Department of Agriculture (USDA) following fruits and vegetables can be kept in refrigerator for the following number of days:
Apple: For 3 days
Apricot: For 5 days
Artichoke: 1 week
Asparagus: 3 days
Avocado: 3 days
Banana: 5 days (banana is sensitive to chilling injury; its skin will become black but flesh will be good for eating)
Controlled Atmosphere Storage (CA) : Controlled Atmosphere is a storage technique in which the level of oxygen (O2) is reduced and CO2 is enhanced .
Fruits and vegetable respire like humans; they take in oxygen (O2) and give out carbon dioxide (CO2).When fruits and vegetables are stored in a gas tight environment, then the level of oxygen in the air is reduced and level of CO2 is enhanced. This will cause the long term storage of fruits and vegetables inhibiting the ripening and aging processes. In this method of storage ripening is delayed. Due to the changes in gas conditions of the cool cell, respiration of fruits and vegetables is reduced. Thus the quality and freshness of the produce can be maintained for longer time. By using CA storage many products can be stored for 2 to 4 times longer than usual.
Modified Atmosphere Storage (MAS): In modified atmosphere storage the composition of internal of a package is changed to increase the shelf life of our commodity. This technique involves reducing the amount of Oxygen (O2) changing it from 20.9 % to 0 % in order to reduce the growth of aerobic organisms and oxidation reactions which will cause the food to spoil. The removed oxygen is replaced with Nitrogen (N2) or Carbon dioxide (CO2) which lowers the pH and suppresses the growth of bacteria.
Manzoor ul Hassan
B.Sc. (Hons) Agricultural Sciences
Institute of Horticultural Sciences,
University of Agriculture Faisalabad, Pakistan
Cell #: 03413275596
Manzoor ul Hassan*, Mubashir Abbas1, Syed Ikram Ali Shah2
Author * Institute of Horticultural Sciences, University of Agriculture Faisalabad
1 &2 Co- Author, Center of Agricultural Biochemistry and Biotechnology (CABB), University of Agriculture Faisalabad.