New concepts for milling white rice

by Chrystal Shannon
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Japan faces changing consumption patterns, looks to redefine the role of rice processing plants

by Dr. S. Kanemoto, Satake Corporation

Rice is a staple food in Japan, where in 1999 approximately 10 million tonnes was produced. Nearly 8.8 million tonnes of rice was distributed into the rice market, of which 8 million tonnes was consumed as a principal food, 6.3 million tonnes of this for household use and the remaining 1.7 tonnes used in the food services industry. A further 0.8 million tonnes is used for value added products.

Although rice is now universally recognized as being a well-balanced nutritious food, in Japan, the per capita yearly consumption has declined from 118 kilograms in 1962 to 67 kg at the present time. Rice usage by the food service industry continues to increase, due to the westernization of food preferences and changes in employment patterns. The market for rice in convenience foods such as packed lunches, rice balls and takeout-boxed lunches, is about U.S.$23 million.

In Japan, rice is found in a diverse range of products from high quality gourmet type foods to simple cooked rice (non-washed). There are also natural and health food products (germ rice and organic rice). In addition, production and marketing of processed rice for the food service industry is flourishing. These comprise advanced secondary processed rice products such as frozen rice, retort rice, germ-free rice and dry rice that are very easy to cook.

A NEW PROCESS.

Traditionally, the manual washing of milled rice before cooking has been essential to cleanly remove the residual aleurone layer (bran part) in order to make a delicious cooked product. It has been said that the time and effort required for this manual washing is one of the principal reasons for the decline in the consumption of rice. The use of water for the traditional processing and preparation of the rice leads to its own problems too: increased water charges; the overloading of sewage treatment plant capacity and even the pollution of rivers due to the washed rice water drained by general households. For these reasons we have concluded that there is a need for a rice that requires no washing or a light washing just once or twice for easy cooking.

In the new non-washing rice processing system, low-pressure friction combined with an additional 5% of water on the surface of milled rice efficiently removes most of the aleurone layer. Complete removal of the remaining aleurone layer is then effected, without damage to the endosperm by the use of warm tapioca grains. This system is called the Neo Tasty White Process (NTWP), and the processed rice product from this system is called Tasty White Rice (TWR). Satake is launching this TWR as a new rice product for the 21st Century.

The NTWP is comprised of three principal stages. The first is a rice-polishing chamber with added water, which is used to loosen the aleurone layer remaining on the surface of the milled rice. Next, the mixing chamber allows the loosened aleurone layer to be removed from the rice by adhering to the surface of the tapioca, which is heated and at the lowest pressure. In the final chamber, the tapioca with its adhering aleurone, is separated from the milled rice and dried.

Figure 2 shows a series of microphotographs of the surface of milled rice taken by electron microscope at a 500x magnification. This shows that the aleurone layer has been uniformly removed from both the back and the belly regions of the rice kernel, whilst the remaining cellular layer remains intact.

RICE MILLING AS A FOOD PRODUCTION PLANT.

Since wholesalers started to enter the market in 1996, the number of large-scale rice milling plants in Japan has increased, reaching 758 by 1998, with a total power consumption of more than 104,000 horsepower. It is estimated that the annual rice milling capacity in Japan is 10.6 million tonnes of brown rice, which easily meets the market requirements.

It has often been said that there is rice milling equipment, but no rice milling industry in Japan. This is due to the unique production and distribution of brown rice and consumption patterns in Japan. By contrast, rice milling plants in other countries start from the paddy husking process, together with paddy drying and storage. In addition, these plants generate more ground rice, due to the use of long grain types and produce by-products, which are rare in Japan.

Outside Japan, by-products are generally more important, since the processing starts right from the paddy stage. The husk is used for power generation, ground rice is used for milling into rice flour and rice bran is used for extracting crude oil and animal feed. These facilities therefore operate more as food plants rather than simply concentrating on rice milling. In the future in Japan too, the trend for rice milling plants will be towards operating as a rice food manufacturing system. This is illustrated in Figure 3, which shows the production of non-washing rice and instant rice by the introduction of the Neo Tasty White Process (NTWP). Other aspects, such as quality management, health and safety controls, HACCP as well as the taste management of the rice (PACCP) and the fascinating quality control (TAQM), are necessary if a rice food manufacturing system is to operate totally automatically for 24 hours by means of the best control system.

FUNCTIONAL BROWN RICE.

Due to the increased longevity of society in Japan and the falling birth rate, cancer, cardiac disease, diabetes and dementia are increasingly prevalent diseases. In addition, there has been some westernization of the diet with its high preponderance of proteins and fat. Against this background, the merits of brown rice with its balanced protein, fat and carbohydrates, should be recognized.

Brown cooked rice, which retains its bran and germ, not only contains the three main nutrients (protein, fat and carbohydrates), but also an abundance of vitamins and minerals. The germ also contains an abundance of amino acids and high quality protein, which can be induced by using 6,000 atmospheric pressure. Brown rice flour is easily digestible. For these reasons, recent attention has concentrated on natural and healthy brown rice, rice bran and rice germ as materials for functional foods, both in Japan and in the rest of the world.

Brown rice comprises the endosperm together with its pericarp and aleurone layer. The endosperm and aleurone layer comprises 91% to 92%, germ 3% and the pericarp 5% to 6%. The pericarp protects the inner part of the rice kernel from penetration by moisture and disease causing germs. Beneath this pericarp layer, there is a cellular aleurone layer composed from a very hard protein structure. Usually the term rice milling describes the removal of the pericarp and partial removal of the aleurone layer.

The two types of brown rice are non-glutinous rice and glutinous rice, both of which are composed of 70% starch and 8% protein, the rest being fat, minerals, vitamins and water.

Figure 4 compares the typical ingredients in non-glutinous and glutinous rice. It can be seen that after milling, there is a loss of vitamins, ash (minerals), and fat. In fact, the rice bran formed by the pericarp and partial aleurone layer contains an abundance of vitamins and minerals.

Brown rice has a 1.3% mineral content. By contrast, milled rice contains only 0.6%. The pericarp and aleurone contain 5% to 6% minerals. Rice germ also contains a high level of minerals. Phosphorus, potassium and magnesium contents are high in brown rice. It is notable that there is a 50% reduction in mineral levels, except zinc, when brown rice is milled. Rice bran and rice germ contain an abundance of minerals, which are removed when milling rice to a 90% level.

The absorption of non-processed brown rice by the human body is very difficult, due to the fact that most of the minerals exist, although abundantly, in combination with phytic acid IP6 in a hard granular form. Germ-containing brown rice that is presently marketed in Japan, dissolves the hard bond, thus making the minerals more easily absorbed by the human body.

USEFUL BY-PRODUCTS FOR A NEW TYPE OF PLANT.

Rice bran and germ contain an abundance of anti-oxidant substances, such as ferulic acid, inositol and phytic acid, with well established health benefits.

The bran of non-washed rice processes contains an abundance of vitamin B, vitamin E, amino acids and minerals, which are together considered to be an effective healthy supplement. Healthy food and drinks can be produced with enzymes from bran from the non-washing rice processing system.

With the introduction of NTWP in future rice milling plants, the bran derived will have the effect of increasing the milling yield, increasing the whiteness of and improving the taste of the milled rice.

More effective use of the high-value by-products derived from the non-washing rice process (rice husk, rice bran, rice germ and bran) can be used to develop new rice products. In addition, brown rice (long grain, medium grain and short grain) should be considered as a source of functional foods.

By upgrading the working activities in phases and by careful study, it is likely thatthe rice milling plant of the future will be more integrated and added-value rice products will be developed from the resulting products and co-products.

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