Contrary to popular belief, the rice we eat is the same as rough rice, just without the hull. The downside is that by removing the hull, which accounts for 10 percent of the grain, we eliminate 80 percent of the nutritional value, found in the bran and germ.
Rice bran is the most important rice by-product. It is an ingredient of great value in feed formulation, because it contains 15 to 18 percent protein, 14 to 18 percent oil, and 30 to 40 percent digestible carbohydrates. Non-defatted bran works as a binder in low inclusion levels, while defatted rice bran can be used at higher inclusion levels.
Rice manufacturing and rice products
Rough rice is processed to obtain white, or polished, rice through a series of procedures: cleaning, parboiling, hulling, pearling, polishing and grading. Parboiling or steeping of cleaned rice in hot water facilitates hull removal and improves the durability of the grain.
After hulling, the germ and outer bran layer are removed. To provide a finer appearance, rice from the pearling machine is passed through polishers to remove the starchy kernel or endosperm.
The percentage of by-products depends on production, the type of rice and other factors. To give a rough idea, rice hulls account for 20 percent; bran is 10 percent; middlings or polishings, 3 percent; broken rice, 1-17 percent; and polished rice, 50-66 percent.
Pollard is a mixture of bran and polishings. Rice mill feed is a mixture of all products obtained in the processing. It contains about 60 percent hulls, 35 percent bran and 5 percent polishings.
The drawback of rice processing, which includes hulling, is that lipase contained in rice bran is activated. This causes a rapid degradation of oil into free fatty acids and glycerine.
"Fatty acid degradation occurs in a matter of hours, and within two days it is oxidized," said Joon Park, vice president of food ingredients sales for RiceBran Technologies.
Rancidity "affects shelf life and stability of rice bran," said Mayette Ramos, sales manager for Insta-Pro International in the Philippines.
Lipase acts fast and, because bran has a high fat content, it is essential to keep it stable. Fat is very palatable.
"Rancid oils have unpleasant odors and tastes. It is very common that animals refuse rice bran that is not stabilized and that has been degraded. If consumed, unstabilized rice bran may reduce animal performance,” said Dave Albin, applied nutrition technologist for Insta-Pro.
The antioxidant oryzanol
In addition to the inherent energy value of fats, rice bran has a natural antioxidant that acts similarly to vitamin E. It has a ferulic esther structure of an unsaturated triterpene alcohol, which is called gamma oryzanol. This compound is believed to act on certain hormones, such as growth hormone and testosterone, which help regenerate muscle growth and recovery.
Stabilized rice bran oil can also be a source of omega-3 fatty acids, which can be used to enrich products such as eggs.
Stabilization of rice bran
This by-product of rice can be mixed into feed, but should be done quickly, so it will not oxidize. It will be necessary to stabilize the fat. The technology that has been developed must be applied as soon as rice bran leaves hulling. At 60 seconds of bran and germ coming off, a 66C (150F) heat and mechanical pressure are applied for a split second to stabilize rice bran, inactivating lipase, but without affecting micro-nutrients.
"It's a natural process, without chemicals or additives," Park said.
Stabilization by extrusion
Extrusion technology stabilizes rice bran and extends its shelf life.
"Rice bran must be extruded immediately after processing, at the right temperature," Ramos said.
It has been proven that high-shear dry extrusion process inactivates the enzymes, thus preventing rancidity.
But, can the extrusion do more to preserve and improve the feeding value of rice bran? Albin commented on experiments in which researchers have determined the effect of pelleting and extrusion on the digestibility of various parameters of rice bran fed to broilers.
"Extruded rice bran has a better digestibility," he said.
Formulating to include rice bran
"From our experience in the field, rice bran can be an extremely attractive ingredient for feed formulation, because of its low cost," Ramos said.
The price may, indeed, fluctuate during the year and formula will be adjusted accordingly. However, depending on availability and the area, there are times that rice bran can be obtained at very reasonable prices.
On the other hand, Darrel Ward, vice president of sales and animal nutrition at RiceBran, tells us: "Frankly speaking, in commercial production of chickens and laying hens, it is not necessarily a viable ingredient, because it is a value-added product. That is why, very small amounts of stabilized product is used in poultry production. Maybe in high-end, premium type poultry, with an added-value would allow to include it.”
Rice by-products are globally available, starting with the 70 million metric tons produced annually. It is a sustainable source of grains, which are non-GMO, and contains no gluten and no allergens. When it is stabilized, all pathogens are removed and it is a very healthy premium ingredient, without pesticides and with one-year shelf life.
Extrusion is a good choice, because it not only stabilizes rice bran, but it improves and preserves it for long-term storage.
Stabilized rice bran in chicken products
Stabilized rice bran can be used in poultry meat products. The inclusion of 1.5 to 2 percent rice bran in sausages made with chicken meat provides a good mouthfeel. In the case of chicken nuggets, it is an alternative to soy products.