Ingredient Spotlight: Rice Protein

November 10, 2013

Emerging science on brown rice protein.

When life gives you rice, you make rice protein-brown rice protein to be exact. Rice has provided sustenance to the human race for thousands of years, and, not surprisingly, it is the third largest crop in planting acreage, after wheat and corn. Brown rice protein, however, has been commercialized for just over a decade, and it was initially produced for animal feed. Inspired by its prospective health benefits, advances in technology, and a surging global population with imminent food insecurity, food-grade rice protein was born. Considering all the gluten intolerance problems now occurring with wheat, and the GMO concerns of corn, rice in all its forms is becoming a massive contender in terms of providing sustenance to the world.

In spite of rice protein’s novelty, literature on rice protein as a nutritional and functional ingredient is vastly unexplored compared to other dietary proteins. But rice’s hypoallergenic nature, high nutritive quality among other grain proteins, and bland taste profile still make rice protein a viable candidate for today’s food ingredient market. And the health merits uncovered thus far suggest great potential,and warrant further investigation of this ancient grain–derived ingredient.

Much like with other protein concentrates, the process begins with raw material-in this case, raw brown rice grains that undergo one of several extraction processes. One natural extraction method begins with milling, followed by hydration, and finally biofermenting with enzymes until the desired protein concentration is achieved: 70–95%. Alternatively, manufacturers can extract the protein using hexane or other combinations of solvents. To enhance nutritive value, protein can be extracted from all layers of the rice grain-including bran and endosperm-though some manufacturers may only extract from the endosperm or white rice. The end result with brown rice protein should be a nutrient-dense, taupe-to-light brown powder with a mildly, granular mouthfeel and a soft taste of rice.

Nutritional Benefits

The nutritional benefits of rice protein do not fall far from its grain. As a popular hypoallergenic food source, it’s no wonder rice is recommended as a first food for babies. Rice protein holds nutritive value for anyone, but particularly for consumers with food allergies, and those following vegan or vegetarian diets. For years, animal-based whey protein has been the gold standard of protein in the fitness industry, but the technologies being created to obtain equally productive protein from rice are making this ingredient competitive.

Although it is possible to obtain all essential nutrients from plants, it takes careful planning and much variety. Protein is one of several nutrients that may be under-consumed without proper planning in plant-based diets-especially when daily requirements are high, such as in athletes, during pregnancy, or in hyper-metabolic conditions. Whether for convenience or necessity, supplements containing rice protein can help to fill nutritional gaps throughout the life cycle.

Protein Quality

The true digestibility and bioavailability of rice protein remains inconclusive due to both outdated and scarce data. Rice variety and protein concentration levels have also been factors in historical research. Nevertheless, all rice protein has undergone much criticism because of prior research on the inferior quality of plant-based proteins compared to animal proteins. But, in 1977, Bienvenido Juliano of the International Rice Research Institute determined the true digestibility and bioavailability of milled rice protein to be 94–100% and 68–75% in rats, and 79–85% and 59–67% in humans, using nitrogen balance trials.1 Since then, only one other study has explored these measures. In 1993, researchers from Hokkaido University in Japan found true digestibility and bioavailability of rice protein isolate in rats to be 87% and 51%, respectively.2

More research is needed to help define the true quality of rice protein, but true digestibility and bioavailability are suspected to be subpar due to rice’s plant-based origin.

Amino Acid Profile

Rice protein’s amino acid profile is considered highly nutritive compared to other cereal grains, despite rice’s common deficiency in the amino acid lysine. This is probably because about 38% of the amino acids in rice protein are essential and 19% are branched-chain amino acids. These measurements are slightly higher than those found in oats and wheat.3–4 Compared to dairy-based protein supplements, rice protein comes
closest to casein, which is typically made up of about 42% essential amino acids and 20% branched-chain amino acids.5

Lipid-Lowering Effects

While cardiovascular disease is the leading cause of death in the United States, lowering cholesterol levels is one measure that alleviates this health risk. The hypolipidemic effects of rice protein are promising, but so far they have only been shown in animal data.

In one study, Japanese researchers compared the effects of casein, soy protein isolate, and rice protein isolate on lipid metabolism in rats.6 Rats were divided into groups and fed diets with varying protein sources and protein levels for 18 days. Results indicated that, at a level of 400 g of protein/kg of body weight, rice protein diets produced significantly lower serum cholesterol concentrations than casein diets.

A team of Chinese researchers reached similar findings with rats fed rice protein versus casein, but it also concluded that the cholesterol-lowering capabilities of rice protein could be related to its lower digestibility and method of extraction.7 Here, total cholesterol and LDL cholesterol were significantly lower in rice protein isolate diets compared to casein diets.

Anti-Hypertensive Effects

As many as 67 million Americans have high blood pressure, and health care providers might one day prescribe rice protein to remedy it. Though this area of research is still emerging, scientists at Jiangxi Agricultural University in China investigated the in vitro and in vivo anti-hypertensive effects of rice protein hydrolysates.8 Results showed a significant decrease in systolic blood pressure following a single oral dose of rice protein hydrolysates at 600mg/kg of body weight in spontaneously hypertensive rats. From the rice protein hydrolysate, the researchers isolated a compound with angiotensin converting enzyme (ACE)–inhibitor activity, which also yielded significant decreases in blood pressure after a single oral dose.

Muscle Building and Repair

Although whey has long since reigned as the go-to sports protein, new sources of protein and protein blends are gaining steam on the market. Greater awareness of environmental issues and a desire to revert back to more “natural” ingredients have strengthened the platform for more plant-based products rather than animal-based ones. Yet, little was known about the ability of rice protein as a sports nutrition supplement until recently. Results of a study published in Nutrition Journal in June 2013, found that trained athletes experienced similar increases in acute recovery and obtained significant gains in muscle, power, and strength whether they were taking a rice protein or whey protein supplement following resistance training for eight weeks.9

Future of Rice Protein

Considering its novelty and plant-based origin, rice protein has much to offer for consumers and formulators. But not all rice proteins are created equal. Differences in rice variety, extraction method, protein concentration level, GMO status, growing conditions, and country of origin are a few ways to distinguish quality and nutritional benefit. Fortunately, the U.S. Pharmacopeial Convention is currently developing a monograph standard for rice protein, which will help manufacturers avoid misbranding and adulteration.

Rice protein’s forthcoming is nothing short of astonishing. Emerging technologies have already allowed for the development of rice protein with improvements in suspension, thereby alleviating previous challenges with miscibility for beverage and nutrition applications. And extrusions and meat analogs are among other impressive advances.

Protein is undoubtedly a hot topic in the food industry, and demand for natural food products underscores this increasingly valuable ingredient. Whether for nutritional benefit, medical necessity, or functionality, rice protein may continue in rice’s legacy to provide sustenance for many years to come. 

References

1. BO Juliano, “Metabolic evaluation of rice protein,” Food Chemistry, vol. 3, no. 4 (October 1978): 251–263.
2. T Morita et al., “Mass production method for rice protein isolate and nutritional evaluation,” Journal of Food Science, vol. 58, no. 6 (November 1993): 1393–1396.
3. Food and Agriculture Organization. Agriculture and Consumer Protection. Amino Acid Content of Foods, 1970. Accessed at: http://www.fao.org/docrep/005/AC854T/AC854T04.htm
4. Food and Agriculture Organization. Agriculture and Consumer Protection. Amino Acid Content of Foods, 1970. Accessed at: http://www.fao.org/docrep/005/AC854T/AC854T07.htm
5. Food and Agriculture Organization. Agriculture and Consumer Protection. Amino Acid Content of Foods, 1970. Accessed at: http://www.fao.org/docrep/005/AC854T/AC854T52.htm
6. T Morita et al., “Rice protein isolates produced by the two different methods lower serum cholesterol concentration in rats compared with casein,” Journal of the Science of Food and Agriculture, vol. 71, no. 4 (August 1996): 415–424.
7. L Yang et al., “Rice protein extracted by different methods affects cholesterol metabolism in rats due to its lower digestibility,” International Journal of Molecular Sciences, vol. 12, no. 11 (2011): 7594–7608.
8. GH Li et al., “Antihypertensive effect of rice protein hydrolysate with in vitro angiotensin I-converting enzyme inhibitory activity in spontaneously hypertensive rats,” Asia Pacific Journal of Clinical Nutrition, Supplement 16 (2007): 275–280.
9. JM Joy et al., “The effects of 8 weeks of whey or rice protein supplementation on body composition and exercise performance,” Nutrition Journal, vol. 12, no. 1 (June 20, 2013): 86.