E Kayitesi, A Minnaar, K G Duodu &  H L de Kock

Department of Food Science, University of Pretoria, Pretoria 0002, South Africa

Marama bean (Tylosema esculentum) is a wild underutilised legume in southern Africa.  It is potentially a valuable crop for semi-arid lands.  The edible seeds are good sources of protein and fat and can potentially enhance the nutritional quality of sorghum porridge, a staple in many African countries. Utilization of marama flour in composite porridge depends on sensory acceptance.  Heating of marama beans before milling is used to inactivate trypsin inhibitors.  Defatting of marama flour would improve shelf-life.  Six porridges (10% solids) were prepared.

• Full fat flour from heated and unheated marama beans composited with 70% sorghum,
• Defatted flour from heated and unheated marama beans composited with 70% sorghum,
• 100% sorghum flour
• Tsabotlhe (a commercial sorghum-soya composite)  used as a standard

These were subjected to descriptive sensory analysis and a consumer acceptance test (n=50). 

Compositing with marama flour reduced the cooked sorghum aroma/flavour intensities prominent in sorghum porridge.  A sweeter aromatic nutty aftertaste and overall aroma/flavour strength was more intense in composites than sorghum porridge.  Heating marama beans prior to milling resulted in roasted nutty flavour.  This was perceived in both full fat and defatted composite porridges. Porridges from full fat and defatted flour prepared from unheated marama bean and Tsabotlhe were characterised by a strong boiled nut aroma/flavour.  Porridges from full fat marama flours were described as buttery/creamy.  A slight bitter aftertaste was perceived in porridges from defatted flours.  The viscosity of marama-sorghum and Tsabotlhe composite porridges was lower than sorghum porridge.  The 100% sorghum and composite porridge with full fat flour from heated marama beans were more acceptable than the others. 

Compositing sorghum with marama flour provides for nutritionally-enhanced porridge.  In addition, compositing sorghum with full fat marama flour seems to provide a product with different but desirable sensory properties specifically a rich buttery/creamy flavour.

Keywords: Marama bean; sorghum; porridges; Descriptive sensory analysis; consumer acceptance test; heating; defatting