What are the causes of food loss?

In 1981 the FAO defined ‘food’ as weight of whole some edible material that would normally be consumed by humans. ‘Loss’ was defined as any change in the availability, edibility, wholesomeness or quality of the food that prevents it from consumed by people.

Postharvest losses can arose from a number of causes. These fall into three main categories, each of which has economic implications.
*Physical loss that can be measured by weight
*Loss of quality (including presence of contaminants), with changes in appearance, taste or texture that may cause the food to be rejected by potential buyers
*Loss of nutritional value

There are number of causes for food loss generation from retail shops and the wholesale sector. The main reason observed is that the food turns ‘un-saleable’. When the product has turned ‘un-saleable’ it is rejected by the customers.

However a product turning ‘un-saleable’ is more a symptom on real problems, and it is more interesting to focus on reasons for why the food has turned ‘un-saleable’ (e.g. ‘best before dates’ expire due to the fact customers pick the products with the longest ‘best before dates’).

Food losses due to mechanical damage such as spillage, abrasion, excessive milling or trimming of food in processing, perishable are more susceptible to mechanical damage. Food loss due to bruising (animals being transported) is of most significance in slaughter animals, particularly cattle and is due to whole or partial carcass condemnation and trimming of bruised tissue.

In addition, there may be considerable loss of value of the carcass, epically if it is downgraded.

Biological and microbiological loss and damage to food by insects, mites, rodents, birds, molds and bacteria: not only the direct loss through consumption of food fall this category, but also the quality loss through contamination by excreta, hair, etc which is sometimes so high that the food becomes unfit for human consumption.
What are the causes of food loss?