As seen in the previous section, the absence of ability among farmers to harvest, thresh and dry the HYV crop caused huge field losses. Today, lack of experience with new equipment causes crop losses in the post-production system. The following examines losses that impact quality and payback of grain harvests.
Discoloured grain. Perhaps you have heard comments by farmers and millers that sun dried paddy produces whiter and glossier milled rice, than artificially paddy in dried mechanical dryers. Nothing can be further from the truth. Once it was a standard exercise in the UNDP/FAO/PHILIPPINES training programme to assign trainees to dry two samples of grain obtained from a uniformly mixed parent batch. One sample was dried under the sun, and the other sample in a heated air forced convection dryer. Both samples were milled in the laboratory under the same conditions. No colour or luster difference could be discerned from the controlled experiments.
It is true that the wet season harvest produced darker milled rice than the summer harvest. The darker colour of the wet season harvest happens because the metabolism is much more rapid in the high moisture grain, and the wet harvest under normal circumstances cannot be dried immediately. It usually takes two to three days for the high moisture grain to be dried; this delay may be longer if there is no drying facility available. In contrast, the summer harvest mature crop has a lower moisture at the start, and sun drying in the field starts immediately after reaping. The evidence supports immediate drying to prevent discoloured grain in the rainy season.
Yellow kernels. Another characteristic of the wet season harvest is the increased percentage of yellow kernels. At first, it was thought that the yellowing occurred in storage. Racquel Quitco (NAPHIRE, Philippines) and her research team found out that most of the yellowing happened in the field, while the freshly reaped high moisture harvest was piled in field stacks to await threshing. Overnight the temperature within the stacks rises to very high levels due to the heat released by metabolism. The yellowing advances with the time the grain is left in the stacks. Cereal chemists at IRRI state that the staining of the starchy endosperm comes from the bran or rice hull.
Darkening and contamination of the milled rice with yellow kernels severely diminishes its market value. Consumers, even in the rural areas, do not accept contaminants in their rice. Unfortunately, colour sorters cannot distinguish and remove the discoloured grains.
Varietal Mixtures and other Causes of Qualitative Losses
Kriankrai Mekanovich (Thailand, Dept of Extension) reports that in a survey they did to establish rice post-production constraints, 26% of Thai farmers use their own seeds which are primarily mixed varieties, which result in non-uniform paddy kernels and uneven cooking quality. This is also a common problem in the Philippines, where there has been a proliferation of new varieties. At one processing plant, 21 different varieties were received from the Filipino farmers during a harvest season. More confusing is the mislabeling of varieties through intention or error. Paddy with the same physical characteristics such as length and thickness, but of diverse varieties and amylose content cannot be differentiated by physical inspection. The cooking characteristics of rice with different amylose contents are not the same, affecting the quality.
The problem caused by varietal mixtures is the farmer's inability to obtain certified seeds. There is business in potential seed growing and processing. Simple technologies for seed drying, cleaning, grading, and storage should be developed for application at the village level. The government-sponsored seed processing plants are few and distantly located.
A serious problem exists in the trading of higher priced aromatic rice. Importers and retailers suspect that there is a certain amount of adulteration of the product, but no simple laboratory procedure exists to detect tampering. Importers of aromatic rice in Singapore and Malaysia have requested for help in training their technicians to find altered rice. What can be done?