CHAPTER XXXI - Barley: Post-Harvest Operations
Durable foodstuffs with low moisture content form the basis of most human diets precisely because these commodities can be stored for extended periods and are continuously available, provided that there is no insect infestation or spoilage. However, losses occur at every stage of grain handling, storage and processing. These losses may be either quantitative or qualitative. The magnitude of losses is highly variable and in certain cases they may even reach 100%. Qualitative losses are more difficult to evaluate then quantitative ones. Qualitative losses for example, may consist of changes in the physical appearance, nutritional degradation, loss of germination, presence of fragments and insect infestation, contamination by mould or development of mycotoxins. Some of them are difficult to detect visually (Navarro, 1997).
Overall losses of cereals including barley, wheat, maize and rice can be investigated under two important stages, pre and post harvest losses. The first stage consists of pre harvest losses resulting from weeds, insect pests and diseases and is estimated to be approximately 35% of total cereal harvest production (Schildbach, 1989). If appropriate techniques can be developed and applied to avoid such losses, world cereal production can be increased by 1/3 or higher.
The post harvest losses may result from inappropriate procedures during and after harvest and unsuitable storage conditions such as unbalanced humidity, temperature and O2 /CO2 levels which allow infestation of the stored grains by microorganisms, insect pests and rodents. Post harvest losses of cereals in the developing countries conservatively estimated by FAO's Special Action Program as %10-15 during 1980s (Navarro, 1997). In rural areas of developing countries, traditional storage systems are very common and due to very low socio-economic situation, new technologies cannot be easily introduced to these conditions. Navarro et al. (1998) clearly reported that, annual losses of 5-10% at village level mainly caused by rodents and insect pests are usually considered as inevitable. In Turkey, as in other developing countries, the cereals are stored in farmer granaries generally in unsuitable conditions and the storage loss varies from 5 to 10 % (TMO report, 1981).