Alkaline extraction of phenolic compounds from intact sorghum kernels

Sorghum (Sorghum bicolor L. Moench) is a major drought-resistant food crop in Africa and Asia. In Western countries, sorghum is utilised as animal feed but is a viable ingredient alternative in gluten-free foods and biofuels (O’Kennedy et al., 2006). The high level of phytochemicals in sorghum kernels is found in the bran and germ (Dykes & Rooney, 2006). A range of phenolic compounds in sorghum offering antioxidant capacity (AOC) includes phenolic acids, flavonoids, anthocyanins and tannins (Awika & Rooney, 2004). Phenolic compounds have been extracted from cereal grains using various techniques such as aqueous alcohol (Medina, 2011; Cuevas Montilla et al., 2011) and enzymes (Cuevas Montilla et al., 2011). However, these methods require grain kernels to be processed into meal or flour prior to analysis. Decortication, a mechanical method, is often cited as a means to isolate the phytochemicalrich bran from the grain (Awika et al., 2005). Yet, decortication is an abrasive method of bran removal and may be less efficient for grains with a softer pericarp (Mwansaru et al., 1988). Researchers have reported success in using alkali solutions to remove bran and improve milling yields in corn (Blessin et al., 1970; Mistry & Eckhoff, 1992), but in the literature, there are no available data concerning the evaluation of the waste streams obtained by a chemical debranning process for phenolic compounds. The objective of this study is to explore the application of NaOH extraction for sorghum bran removal and phenolic compounds recovered from the waste stream.