Post-harvest loss is one of the biggest problems which affects economic growth globally. The FAO (Food and Agriculture Organization) estimates that 1/3rd of food products is lost every year. The loss depends upon the type of crop is grown. As the fruits and vegetables are perishable, so their chances are more to get spoiled or degraded. Post-harvest losses mainly occur in developed and developing countries.
Food losses occur naturally by the microbial attack, moisture, degradation etc. A major portion of the food is wasted at the stage of quality standards where a food item is tested based on shape, appearance and then either selected or rejected. And, as the increase in population has limited the food resources therefore to prevent food loss is of utmost concern.
Content: Post Harvest Loss
- Definition of Post-Harvest Loss
- The Objectives of Post-Harvest Losses
- Factors Affecting Post-Harvest Losses
- Types of Post-Harvest Losses
- Estimation and Causes of Post Harvest Loss
- Management of Post-Harvest Losses
Definition of Post-Harvest Loss
Post-harvest loss can define as the loss from the stage of harvesting to the stage of consumption which occurs as a result of qualitative loss, quantitative loss and the food waste (by the consumers) altogether.
What is food waste?
Food waste is the subcategory included in the post-harvest losses which occur after the stage of marketing to the consumers in the post-harvesting chain. It can define as the wastage of edible food that has been unutilized by the consumers. Food waste is strongly linked with the consumer’s behaviour, and it occurs by several ways like:
- Consumer’s refusal to the retailer for purchasing the product.
- Discarding of leftover food.
What is food loss?
Food loss is also a type which occurs from the stage of harvesting to the stage of marketing to the consumers in the post-harvesting chain. It occurs as a result of both qualitative and quantitative food loss.
- Quantitative loss can define as the food loss which occurs as the result of weight loss, spillage of crops, attack of moulds and pests etc.
- Qualitative loss can define as the food loss which occurs as a result of nutrient loss, undesirable change in taste, texture etc., presence of excreta of birds, rodents etc. and contamination by mycotoxin.
The Objectives of Post-Harvest Losses
There are certain objectives of post-harvest technology are:
- Maintenance of food quality: It is maintained by considering the following factors like appearance, texture, weight, flavour, nutritive value etc.
- Protection of food safety.
- Reduction in food loss: To reduce the food loss between the period of harvesting and consumption by improving harvesting, storage, transportation facilities and marketing policies.
- Reduction of food waste: To reduce the food wastage at the consumer’s level by improving marketing skills and by proper distribution of the product.
- Effective management of post-harvest losses.
- Promotion: It includes the promotion of both small and large scale production of crops.
Factors Affecting Post-Harvest Losses
There are some primary and secondary factors which affect the post-harvest loss of food products.
Mechanical loss: It is caused by poor handling from the stage of harvesting to storage.
Microbial action: It is caused by microorganisms like bacteria, fungi, yeasts which quickly affects the perishable food crops like fruits and vegetables.
Environmental factors: Temperature and humidity are the two important environmental factors which are mainly responsible for the post-harvest losses.
- Inadequate harvesting methods
- Incomplete drying before threshing
- Inadequate storage facilities
- Longer shipment
- Longer distribution period
- Lack of market access and policies
Types of Post-Harvest Losses
Based on the different stages of post harvesting, the losses are of the following types:
Direct and indirect loss
Direct loss is a food loss which occurs by spillage of crops from the bags and consumption by the pests. Whereas in an indirect loss there is a food waste which occurs at the consumer level like consumer’s refusal to purchase, infrequent visits to the market etc.
It is the observable loss which can be measured by the reduction in the moisture content of the food. An abnormal increase in weight of food through moisture absorption is also a cause of loss which can occur due to rainfall on the food items that have been kept in the open area.
Examples: Prolonged storage, shrinkage, consumption by insects, poor packaging are the reasons which can lead to weight loss.
It occurs as a result of loss in food crop both qualitatively and quantitatively.
Qualitative food loss: It is a type, which deteriorates the quality of the product by the degradation of nutrients, texture, taste, shape etc.
Example: The nutritional factors like carbohydrates, proteins, vitamins act as prey for different parasites like:
- Weevils feed inside the seed, which contains high carbohydrate content.
- Some insects attack the cereal cover which is rich in vitamins.
- Moulds and bacteria attack on perishable foods as they have a high moisture content that is favourable for their growth.
- Loss due to the soluble excreta of pests, pesticides, pathogenic organisms.
Quantitative food loss: It is a type which reduces the quantity of a product by the weight loss that occurs by factors like an attack of insects, birds, rodents, moulds etc.
Example: Staple foods (like rice, maize, wheat etc.) are the target of rodents and insects.
Seed viability loss
It occurs due to poor storage conditions or preservation methods. By certain pests, atmospheric conditions (temperature, moisture, light etc.) are the reasons for the seed viability loss which leads to the excessive respiration of the food product.
It is a type of loss which ultimately leads to economic and monetary loss. It occurs by the following reasons like:
- Customer refusal to the retailer to buy a product
- Rejection by the quality standard team
- Both qualitative and quantitative loss
- And, all the above factors which are mentioned above can be the reason for the commercial loss.
It occurs by the excessive respiration of the product, mechanical rubbing of the grains, shrinkage in the food product, mechanical injuries etc. The extra production should compensate for the loss. In simple words, we can say the production rate must be higher than that of losses.
Estimation and Causes of Post Harvest Loss
The post-harvest chain comprises of several stages where a crop is harvested from the field to the final stage where a product is transported to the retailer market. Post-harvesting is done as a small as well as large scale production.
During the whole phase of the post-harvesting chain, there is about 10-30% food loss occurs in small scale production as well as large scale production.
Causes: There are some causes which lead to food loss from the stage of harvesting to the consumers.
In the stage of harvesting: Poor production processes and climatic conditions are the two main causes that affect the crop at the stage of harvesting.
At the stage of food storage: Attack of insects, birds, rodents etc., improper handling, humidity, temperature etc. are some causes that affect the crop at the stage of storage.
In the stage of food processing: Discarding of mechanical injured food, substandard food product, visual-based rejection of product etc. are the main causes that contribute the food loss.
At the stage of packaging: Packaging failures and lack of packaging services are the two main causes.
In the stage of marketing: Improper portioning, supersizing, dented cans are the reason which contributes to poor marketing and ultimately to the food loss.
At the stage of consumption: The leftovers, impulse buying, infrequent market visits etc. are the causes which lead to the food waste that is related to the consumer’s level.
Management of Post-Harvest Losses
There are specific control measures by which, the post-harvest losses can be controlled by the following steps:
- The harvesting of the crop should be done at the correct maturity state.
- For fruits and vegetables, the water should be sanitized with sodium hypochlorite, bleach etc. before dunking into the tank.
- Water which is used for the irrigation purpose must not be too cold, as for the seed germination there should be milder temperature otherwise, there may occur spoilage like soft rot and other crop diseases.
- If there is any mechanical injury in the food product, it should be discarded early as it can favour the entry of pathogenic microorganisms.
- Harvesting should be done in cooler temperature for the perishable products which are then directly transferred to the storage areas.
- Threshing of grains should be handled properly.
- The grains should be dried completely before transportation to the storage areas.
- The storage areas should be highly sanitized and there should be proper ventilation and cleaning.
- The packaging of the product must obey the quality standards in accordance to the shape, weight, nutritional value etc.
- The transportation to the market retailers should not be at long distance as there may occur a chance of food spillage, decay of the food product etc.
Therefore, the term post-harvesting is the second stage after pre harvesting process. In the post-harvesting of grains, there is a chain of several stages which are given in the diagram below.
For the post-harvesting of fruits and vegetables, there is a chain of several stages which are given in the diagram below.
During the stages of post harvesting, many kinds of losses may occur which we have discussed above. So to prevent the post-harvest losses, there should be correct measures to avoid qualitative loss, quantitative loss and also food waste by the consumers.