What is rice flour?
Rice flour is made by grinding whole kernels and or broken rice kernels recovered from the milling process into a powder. Rice flour varies widely based on:
- The type of rice
- How it was milled
- The starch content
White Rice flour or brown rice flour is commonly used in gluten-free baking. It has a neutral flavor and white color, can be digested easily, and is considered hypoallergenic.1 Gluten-free dough made with rice flour will resemble a batter more than a dough.
Rice genotypes show variations in amylose content. Amylose is a starch that characterizes the gelatinization temperature, pasting behavior, and viscoelastic properties of dough made with rice flours.1
Rice flour is very common in parts of the world where rice is a staple ingredient. China, India, Indonesia, and Bangladesh have the highest levels of rice consumption and use of its flour. In the 1980’s, it was introduced to the Western world, where it became a primary ingredient in many processed foods in the baking industry. Of the world’s total rice production, 90% is grown and consumed in Asia.3
Rice flour is used as an alternative to wheat flour in gluten-free baked goods. Bread produced from it may have lower loaf volume, harder texture, and shorter shelf life.1 It is important to use it in combination with other flours, starches, gums, and enzymes to help mimic the gluten matrix.
Using rice flour with these ingredients will improve water absorption. It has a water absorption of 42.9–60.7% based on dough weight.1 Higher water absorption levels indicate a dough that is more elastic. Adding hydrocolloids at 2% to a rice flour formulation has shown an increase in water absorption to the 63.4–67% range.1
Rice flour is high in fiber, gluten-free, and low in saturated fat, cholesterol, and sodium. It has less nutritional value than whole-grain rice or whole grain brown rice flour) but is a significant source of manganese.4 It has around 7–10% protein, 75–82% carbohydrates, and .7–1% fat.4 Rice flour is enriched with vitamins and minerals to meet nutrient requirements.
Rice is first dehulled, after which it is tempered and milled to remove its bran, then enriched for table rice, but not for rice flour production unless required by the customer. There are several milling options available, yielding different particle sizes, textures, and starch content. A process of partial boiling (parboiling) is used to produce more nutritious varieties. The process entails soaking the rice, then heating and drying it after or before it is dehulled. During the parboiling process, thiamin migrates from the rice pericarp into the endosperm.5
Different grinding methods can be used:2
- Wet grinding is the most traditional – and the most expensive – process for obtaining rice flour. Wet grinding results in significantly smaller average particle size and a lower percentage of starch damaged starch than alternative grinding methods.
- Semi-dry grinding is simpler than the wet grinding method. Rice kernels are soaked and dried before they are grinded into flour. The method is expensive and time-consuming.
- Dry grinding is done without any prior soaking of the rice kernels. The kernels are ground using varying tools (e.g., hammer mill, roller mill, impact mill, pin mill, disk mill) until the particle size of the rice flour is consistent.
- Freeze grinding is a newer method that uses less energy and produces less waste from processing. Rice kernels are frozen using liquid nitrogen and then dry-ground into flour. Freeze-grinding temperatures have been shown to damage starch content in the rice flour.
Rice flour is used in food for gluten-intolerant consumers. It’s use in bread-making is still limited because rice proteins are unable to retain the gas produced during the fermentation process.
Here are several methods to enhance the quality of gluten-free products made with rice flour:
- Add transglutaminase: Rice proteins are polymerized through the transglutaminase reaction, providing a protein network necessary for holding the gas produced in fermentation. With the addition of 1% transglutaminase in the presence of 2% hydroxypropyl methylcellulose (HPMC), rice bread’s specific volume increases and its crumb becomes softer.6
- Add hydrocolloids: Hydroxypropyl methyl cellulose (HPMC) has been found to be the most suitable hydrocolloid, and yields rice bread with a specific volume comparable to that of wheat bread. HPMC can provide rice flour dough with film-forming and CO2-entrapping properties. Other hydrocolloids like CMC and xanthan gum can’t replace HPMC because they cannot deliver similar gas-retaining and film-forming properties. HPMC has been used at levels of 3.5–5.3%.6 Its usage level can be lowered by adding glucose oxidase.7
- Use modified rice flour: Bread prepared with phosphorylated rice flour showed a reduction in hardness at both 21oC and −24oC storage temperatures. Phosphorylation also shows an effect on rice bread volume and crumb appearance and color.8
Glutinous rice flour is not the same as rice flour. It can be used in combination with rice flour in gluten-free baking but not as a substitute.
Rice flour is GRAS regulated by FDA in article 21CFR170.30 of the Code of Federal Regulations.9
- Gallagher, E. Gluten-Free Food Science and Technology. Wiley-Blackwell, 2009, p. 79.
- Zhou, W., and Y. Huri. “5 Rice.” Bakery Products Science and Technology, 2nd ed., Wiley Blackwell, 2014, pp. 103–116.
- Steiger, G., et al. “Fortification of Rice: Technologies and Nutrients.” Annals of the New York Academy of Sciences, 2014, pp. 29–39, doi:10.1111/NYAS.12418.
- “Rice Flour, White Nutrition Facts & Calories.” Nutrition Data Know What You Eat., nutritiondata.self.com/facts/cereal-grains-and-pasta/5726/2 Accessed on 26 March 2018.
- Delcour, J.A., and R.C. Hoseney. “Chapter 10 Rice and Oat Processing.” Principles of Cereal Science and Technology, 3rd ed., AACC International Inc., 2010, pp. 156–157.
- Gujral, H.S., and M.R. Cristina. “Functionality of Rice Flour Modified with a Microbial Transglutaminase.” Journal of Cereal Science, vol. 39, no. 2, 2004, pp. 225–230, doi:10.1016/j.jcs.2003.10.004.
- Gujral, H.S., and M.R. Cristina. “Improvement of the Breadmaking Quality of Rice Flour by Glucose Oxidase.” Food Research International, vol. 37, no. 1, 2004, pp. 75–81, doi:10.1016/j.foodres.2003.08.001.
- Kringel, D.H., et al. “Influence of Phosphorylated Rice Flour on the Quality of Gluten-free Bread.” International Journal of Food Science & Technology, vol. 52, no. 5, 2017, pp. 1291–1298, doi:10.1111/ijfs.13376.
- U.S. Food and Drug Administration. “CFR – Code of Federal Regulations Title 21.” Accessdata.fda.gov, www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=137.Accessed on 26 March 2018