Does a sorghum–cowpea composite porridge hold promise for contributing to alleviating oxidative stress?

• Compositing sorghum with cowpea increases total free phenolic content.
• Cooking has varying effects on cereal–legume phenolics depending on type and source.
• Sorghum–cowpea composite flour retains some radical scavenging activity on cooking.

The effect of compositing red non-tannin sorghum with cream-coloured cowpea and porridge preparation on phenolic profile and radical scavenging activity was studied. A maize–soybean composite porridge representing a similar product on the South African market was used as reference sample. UPLC–QToF-MS-ESI was used to determine phenolic composition of the grain flours, their composites and porridges. Total phenolic content was determined using Folin–Ciocalteu method while radical scavenging activity was determined using the ABTS, DPPH and NO radical scavenging assays. Four benzoic acid derivatives and five cinnamic acid derivatives were identified in the samples. The predominant flavonoid subclasses identified in sorghum were flavan-3-ols, flavanones and flavones while cowpea had mainly flavan-3-ols and flavonols with soybean having mainly isoflavones. Compositing the cereals with legumes significantly (p < 0.01) increased their total flavonoid content and radical scavenging activities. Sorghum–cowpea composite porridge showed better promise in contributing to alleviating radical induced oxidative stress than maize–soybean composite porridge.