2018-06-24 15:45:00 (UTC+08:00)
Rice Today, International Rice Research Institute, January 2004
Emil Q. Javier, Chair, Asia Rice Foundation
Agricultural advances in the past 3 decades have made remarkable progress in providing affordable cereals to most of the poor in the developing world. As a result – and despite the continuing plight of 800 million desperately poor – we hear less these days about famine and severe calorie and protein deficiency in sub-Saharan Africa and South Asia, the two most vulnerable regions.
Now we must overcome the "hidden hunger" of the poor for essential vitamins and minerals. As cereals constitute the bulk of the diet of those who can't afford micronutrient-rich foods such as meat, milk, fruits and vegetables, any increase in the vitamin and mineral content of staple grains helps combat this insidious form of malnutrition. High-quality protein maize, developed by the International Maize and Wheat Improvement Center in Mexico, is now being popularized in many developing countries. Rice cultivars high in beta carotene (provitamin A), iron and zinc are in the pipeline at IRRI and some of its national partners in Asia.
There is, however, another strategy that has not received the attention it deserves: encouraging the consumption of whole grains.
Whole rice and wheat offer significant levels of protein and essential vitamins and minerals, but most of these nutrients are removed in the polishing stage of the milling process. In rice, polishing removes 15% of the protein, 85% of the fat, 90% of the calcium, 75% of the phosphorus, 80% of the thiamine, 70% of the riboflavin and 68% of the niacin. Additionally, whole-grain rice – popularly called brown rice – is rich in dietary fiber, which protects against hypercholesterolemia, diabetes and colorectal cancer. And, of course, bran functions as a gentle laxative.
Brown rice also has high levels of phytic acid, which diminishes the availability of essential minerals such as iron, phosphorus and calcium but protects people prone to kidney stones by reducing urinary calcium. (A mutant rice line low in phytic acid has been identified, and the character has been bred into a popular rice variety in the United States, having its phytic acid content).
Besides the nutritional benefits of consuming brown rice, there are two economic ones. First, foregoing polishing and whitening reduces the power demands of milling by as much as 65%. Second, with the bran and the nutrient-rich embryo intact, and with fewer broken grains, whole-grain milling recovery is as mush as 10% higher than for white rice. So, if all the rice grown in the Philippines, for example, were consumed as brown rice, there would be no need for rice imports, which in 2002 cost US$200 million.
Here's the rub. Promoting brown rice is a formidable challenge because most Asian rice consumers have acquired a taste for polished white rice. Before the advent of machine mills, people dehulled rice manually by mortar and pestle. For most, brown rice was the only rice. Today, Asians associate white rice with modernization and affluence, and brown rice with backwardness and poverty.
If brown rice were marketed in Asia as a fashionable health food, as in Europe and North America, people would become accustomed once more to its grittier texture and nutty flavor. At the household level, people would learn that cooking brown rice requires a little more water and cooking time (or else 30 minutes of soaking). Rice millers would adjust their machines to produce brown rice – an easy procedure if demand makes the extra effort worthwhile.
A significant drawback is shorter shelf like because the lipid-rich layer left on the whole grain is susceptible to microbial and insect damage. The hulling process – particularly using metal rollers – breaks up the bran cells, releasing their lipase enzyme, which breaks down the oil in the bran, producing free fatty acids that cause rancidity and spoilage.
The obvious solution is just-in-time hulling, but this isn't always practical. Experiments in the Philippines have shown, however, that brown rice dehulled with rubber rollers, which are now commonplace, can be kept for 90-150 days at room temperature (23 to 34ºC) without vacuum packing, if the grain is dried to 14% moisture content. Brown rice with a higher moisture content can be packed in custom-sized polyethylene bags (2-5kg) and then sealed, which is good for 2 to 3 weeks' storage – or longer in a refrigerator.