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Making food go further

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- where saving cracked rice could help by Dr Ye Aung, rice technician and consultant

e face urgent challenges as we move ever closer to 2050, when it is predicted that the world’s population will reach more than 9 billion and our growing global population will face food shortages if we cannot double food production. An important contribution to this effort can come from reducing food waste. Improved food production processes and innovations in technology must play a part in ensuring that from field to fork, food wastage is significantly reduced. In terms of meeting this growing demand, the outlook does not look promising in light of prevailing circumstances around the world. Drought areas are expanding rapidly, while natural resources are drying up faster than expected. Further still, the denial of global warming by some means that we do not have a clear picture as to how urgently we need to act. However, organisations such as the International Rice Research Institute are playing a pivotal part in the development of high yielding, drought resistant rice varieties. Under these circumstances the only sensible response is to work to save food throughout the production process. Food saving is not only a matter for the future, but a thing we must turn our attention to now. If we consider today’s post-harvest handling, at every step there are tremendous losses involved in turning crops into food. In the rice milling industry alone, the yield of finished rice can be as low as 40 percent, with 30 percent broken rice resulting as a by-product. However, broken rice can still be processed into usable rice, with specific characteristics, with the help of state of the art technology. Bühler is just one company at the forefront of producing top quality reconstituted rice that is indistinguishable from the natural product. In terms of the overall process about 15 percent of rice is lost, as a raw material, when it makes its way to the milling facility. A further 20 percent is lost due to moisture problems giving a

40 | Milling and Grain

total loss amounting to about 35 percent just in raw material form. Therefore broken rice production in the milling process should be regarded as a serious issue. Milling machines are generally blamed for breaking rice but, with the right technology, the cracking of rice can be minimised. Rice is a delicate natural material and should be treated as such. Cracked grains are the product of excessive breaks, which are formed in the grains by the drying operation and during storage. Grain is often cracked under the influence of stresses, namely 1) moisture stress, 2) thermal stress, and 3) mechanical stress. Mechanical stress is easily understandable and happens during milling. Moisture stress is created by the accumulation of moisture on the grain surface or retained within the grain itself. Thermal stress is generated by heat - either by internal heating (the respiration process) or by external heat (during drying). Grains are still alive even after they have been cut from the plant and they will continue to breathe. Like other living things they produce heat, carbon dioxide and moisture. If this heat and water are not taken away immediately they create stresses in the grains, which lead to cracking. Freshly harvested paddies contain a lot of external moisture that must be removed immediately. In storage paddy rice can accumulate heat by the respiration of grains. This is harmful - not only in terms of the grain cracking but for other qualities too. Thus effective removal of heat during storage is essential. If the cracking of rice cannot be avoided, cracks that form during the drying process should be minimised at the very least. There is a balance between the damage that might be done by the heating involved in drying the grain and the damage done by too much moisture. The two extremes are demanding and the drying work should be carried out with extra care, particularly when drying the grain’s interior. Removing moisture from the peripheral parts of the grain is relatively quick and carried out using a higher temperature. However, heating the inner parts of the grain requires more heat, which risks burning the surface and therefore the temperature should not be too high. This temperature control will mean that the rice is exposed to heat for longer, during which time the moisture is able to expand within the rice grain.

Mar 15 - Milling and Grain magazine  

The March edition of Milling and Grain magazine

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