Rice (Oryza sativa) bran is the main commercial by-product of rice grain milling. It is a multilayer fraction composed by the most external tissues of the rice caryopsis. It is produced in large quantities worldwide and its composition is mainly related to insoluble dietary fibres, lipids and other nutrients and bioactive compounds with significant health-related properties.
1. Introduction, rice bran composition and application
Food processing is a set of operations that permit to transform raw materials into valuable food ingredients. Cereal crops, for example, are rarely consumed as whole grains and during their transformation process a large amount of residue is produced. Rice bran (RB) is a by-product that derives from the milling of rice grain, the third most consumed cereal overworld . It represents around 12% of the total kernel weight and it is composed by the external layer of the seed (i.e., pericarp, tegmen, and aleurone layer (Figure 1)), translatable in almost 68 million tons of hardly unmanageable material per year, worldwide .
Figure 1. Schematic representation of rice grain, highlighting the multilayer bran fraction.
Similarly to other cereal species, the kernel surrounding layers are richer in bioactive compounds, minerals, vitamins, dietary fibers, proteins and lipids than the core endosperm, which is characterized by simple carbohydrates and starch granules  (Table 1). In particular, rice bran has a not-negligible amount of lipids (15–20 g/100 g of RB), where some of the most important bioactive compounds, such as γ-oryzanol, ferulic acid, tocopherol and polyunsaturated fatty acids could be found; thus, for this reason, RB has been used for oil extraction . Despite that, RB is highly sensitive to lipid oxidation due to the rapid activity of lipolytic endogenous enzymes, which means that a thermal stabilization step usually required . However, the first fate of rice bran is the feed formulation industry, losing the opportunity for the recovery of its potential and to building of a strong circular economy based on agri-food waste reintegration.
Table 1. Mean proximate composition of rice bran and the content of its main bioactive compounds.
|Dietary fibres (DF)||15–30|
|Phenolic acids *||800–1243|
* as total ferulic acid, the most abundant phenolic acid found in cereal grains (soluble and insoluble forms).
Despite the poor organoleptic quality of rice bran, its treatment and manipulation through fermentation, extrusion and air classification seems to be emerging technologies for obtaining a valuable food ingredient with a pleasant sensory profile, good nutritional properties and excellent functionalities, for the further development of new food products and the concomitant exploitation of cereal industry side-streams.
The entry is from 10.3390/foods10010085
- Food and Agriculture Organization of the United Nations: Statistical Databases (FAOSTAT) Production/Crops. Environ. Sci. Technol. 2019, 53, 11302–11312.
- Kahlon, T. Rice Bran. In Fiber Ingredients; Informa UK Limited: London, UK, 2009; pp. 305–321.
- Fritsch, C.; Stäbler, A.; Happel, A.; Márquez, M.A.C.; Aguiló-Aguayo, I.; Abadias, M.; Gallur, M.; Cigognini, I.M.; Montanari, A.; López, M.; et al. Processing, Valorization and Application of Bio-Waste Derived Compounds from Potato, Tomato, Olive and Cereals: A Review. Sustainability 2017, 9, 1492, doi:10.3390/su9081492.
- Schieber, A. Side Streams of Plant Food Processing as a Source of Valuable Compounds: Selected Examples. Annu. Rev. Food Sci. Technol. 2017, 8, 97–112, doi:10.1146/annurev-food-030216-030135.
- Gul, K.; Yousuf, B.; Singh, A.K.; Singh, P.; Wani, A.A. Rice bran: Nutritional values and its emerging potential for develop-ment of functional food—A review. Bioact. Carbohydr. Diet. Fibre 2015, 6, 24–30, doi:10.1016/j.bcdf.2015.06.002.
- Gopinger, E.; Ziegler, V.; Catalan, A.A.D.S.; Krabbe, E.L.; Elias, M.C.; Xavier, E.G. Whole rice bran stabilization using a short chain organic acid mixture. J. Stored Prod. Res. 2015, 61, 108–113, doi:10.1016/j.jspr.2015.01.003.
- Ti, H.; Li, Q.; Zhang, R.; Zhang, M.-W.; Deng, Y.; Wei, Z.; Chi, J.; Zhang, Y. Free and bound phenolic profiles and antioxi-dant activity of milled fractions of different indica rice varieties cultivated in southern China. Food Chem. 2014, 159, 166–174, doi:10.1016/j.foodchem.2014.03.029.
- Elleuch, M.; Bedigian, D.; Roiseux, O.; Besbes, S.; Blecker, C.; Attia, H. Dietary fibre and fibre-rich by-products of food pro-cessing: Characterisation, technological functionality and commercial applications: A review. Food Chem. 2011, 124, 411–421, doi:10.1016/j.foodchem.2010.06.077.
- Huang, Y.-P.; Lai, H.-M. Bioactive compounds and antioxidative activity of colored rice bran. J. Food Drug Anal. 2016, 24, 564–574, doi:10.1016/j.jfda.2016.01.004.
- Chinma, C.E.; Ramakrishnan, Y.; Ilowefah, M.; Hanis-Syazwani, M.; Muhammad, K. REVIEW: Properties of Cereal Brans: A Review. Cereal Chem. J. 2015, 92, 1–7, doi:10.1094/cchem-10-13-0221-rw.
- Ferreira, S.C.; Fernandez, A.M.; de Castillo-Bilbao, M.D. New functional ingredients from agroindustrial by-products for the development of healthy foods. In Encyclopedia of Food Security and Sustainability; Elsevier: Amsterdam, The Netherlands, 2018. ISBN 9780128126882.
- Razak, D.L.A.; Rashid, N.Y.A.; Jamaluddin, A.; Sharifudin, S.A.; Long, K. Enhancement of phenolic acid content and anti-oxidant activity of rice bran fermented with Rhizopus oligosporus and Monascus purpureus. Biocatal. Agric. Biotechnol. 2015, 4, 33–38, doi:10.1016/j.bcab.2014.11.003.