Ninety-nine percent of the sorghum grown in the U.S. is tannin-free. Different varieties of sorghum are valued for their grain, stalks, and leaves. Many people are familiar with sorghum syrup made from the sweet juice in the stalks of certain sorghum varieties or the use of sorghum in silage or pastures. However, this column will focus on grain sorghum. Several grain sorghum hybrids are considered food grade in the United States. Among them, Fontanelle 1000 is a very common source of wholegrain sorghum flour. (Note: Grain sorghum is milled like any other cereal, and if it is polished or debranned prior to milling it will produce refined flours suitable for applications in which refined flours are required. Consumers should check product labels to confirm that sorghum flour is whole grain or not.)
The carbohydrate, fat, and protein contents of the grain are about 75%, 3.3%, and 11%, respectively, with protein content ranging between 7% and 16%. While the protein content range is similar to other cereals, its lysine (limiting amino acid for all grains) content is lower. Sorghum protein digestibility is reduced upon cooking, but fermentation, decortication, and extrusion are reported to enhance its digestibility.
Fiber content of whole-grain sorghum flour is about 6.6%. The 2010 Dietary Guidelines for Americans pointed out that increasing consumption of total grains was not recommended, but increasing the proportion of whole grains to total grains was recommended. In particular, individuals with celiac disease or gluten intolerance may not consume adequate dietary fiber and may need more whole-grain gluten-free choices. Higher fiber intakes are associated with lower incidence of metabolic syndrome in adolescents (Carlson et al., 2011), and the recent EPIC (Chuang et al., 2012) study demonstrated that higher fiber intakes are associated with lower mortality, particularly from circulatory, digestive, and non-cardiovascular disease/non-cancer inflammatory disease. Sorghum grain is an excellent source of many vitamins and minerals. A comparison of 100 g of sorghum with the World Health Organization (WHO) Recommended Nutrient Intakes (RNI) for children aged 1–3 years shows the following: magnesium = 366%; iron (10% bioavailability) = 73%; zinc (moderate bioavailability) = 38%; thiamine = 47%; riboflavin = 28%; niacin = 49%; pantothenate = 63%; vitamin B-6 = 118%. WHO does not have established RNI for copper and manganese, but using the U.S. Recommended Dietary Allowance (RDA) criteria, 100 g sorghum meets the RDA for children aged 4–6 years thusly; copper = 245% and manganese = 92% (Sorghumcheckoff.com).
Specialty grain sorghums provide good to excellent sources of phytochemicals such as phenolic acids, anthocyanins, phytosterols, and policosanols, and various processing methods are used to concentrate the phenols in sorghum bran. These specialty sorghums are under study for health-promoting properties. Black sorghum bran (6%) diets (Richie et al., 2011) fed to rats with induced gut inflammation showed decreased colon carcinogenesis through anti-inflammation mechanisms. Awika and Rooney (2004) reviewed potential health benefits of sorghum phytochemicals and among other findings reported that antioxidant properties of several sorghum varieties significantly exceeded the antioxidant capability of several other grains and fruits such as blueberries, strawberries, or plums. Studies are under way examining sorghum bran as a natural antioxidant for food applications.
Sorghum is used worldwide in food applications including traditional breads (tortillas, chapatti, roti), fermented breads (kisra, dosa, injera), and beverages, especially beers. Whole sorghum is used in salads, and as cereals, side dishes, and pilafs. Sorghum flour is used in cookies, cakes, brownies, pizza dough, pastas, cereals, pancakes, and waffles. More research into sorghum grain food applications and education about sorghum nutritional characteristics are needed.
References cited in this column are available from the authors.
E. C. Henley, Ph.D., R.D.
Adjunct Professor, University of Georgia, Athens, Ga., and Principal, E.C. Henley Consulting
Jeff Dahlberg, Ph.D.
Director, University of California, Kearney Agricultural Research & Extension Center, Parlier, Calif.