Characterisation of volatile compounds associated with the flavour of flatbreads : effect of sorghum, cassava and whole or dehulled red and white cowpea flours

Abstract

This study characterised the volatile compounds in flatbreads prepared from red non-tannin sorghum flour, cassava starch, whole and dehulled red and white cowpea flours and composite flours (30% cowpea flour and varying combinations of cassava starch and sorghum flour). Compounds were extracted using solid-phase microextraction (SPME) and determined by GC-TOF-HRMS. A wheat flatbread was used as the standard. Compounds that were correlated with aroma and flavour attributes were identified. Volatile compound classes included hydrocarbons, aldehydes, alcohols, acids, esters, ketones, benzene derivatives, sulphur- and nitrogen-containing compounds, terpenes and terpenoids. Adding sorghum flour to the composite reduced the generation of aldehydes and contributed 2-methoxyphenol and 2-methoxy-4-vinylphenol to the flatbreads. The cassava starch presented acetic acid and aldehydes, which contributed to the fermented and green aroma of cassava-cowpea composite-flour flatbreads. The cowpea variety influenced the volatile profile of flatbread. The red cowpea flatbreads had more 1-octen-3-ol, phenylethyl alcohol and decane, different from the white cowpea flatbreads. Soaking and dehulling the cowpeas reduced flour hexanal levels while increasing 1-hexanol and 1-octen-3-ol in derived flatbreads. Cowpea flatbreads were characterised by pyrazines, with higher levels contributed by dehulled flour. The main compounds responsible for beany flavour were dimethyl trisulphide, hexanal, nonanal, 1-octen-3-ol, 2-pentylfuran, heptanal and 1-(2-furanyl)-2-butanone. Characterising the aroma compounds of flatbreads prepared from sorghum, cassava and cowpea flours offers valuable insights that manufacturers can apply to improve the sensory quality of bread products made from these flours to meet specific consumer demands and preferences and diversify bread flour options.