Physical properties of Tylosemia esculentum and the effect of roasting on the functional properties of its flour

Abstract

The physical properties of two varieties of Morama beans and the effect of roasting on the functional properties of
their flours were studied. Majority (65, 92.5, 79%) of the seeds has medium dimensions (17.0 - 19.99, 14.0 - 19.99, 12.0
- 14.99 mm) of length, width and thickness respectively. The size of the Morama bean (MB) follows a normal
distribution, being much heavier than most other oil seeds and legumes with 1000-seed weight of 2.2 - 2.3 kg.
Significantly higher angle of repose was observed for the cement surface (9.76o
). MB sphericity (85.7-86.8%) and
aspect ratio (91.9 - 92.5%) indicates that the bean will roll rather than slide. Morama flour (MF) is rich in protein (31.7 -
33.1%), fat (36.4 - 39.0%) and ash (2.9%). Roasting significantly increased the protein and ash. Roasting increased the
water absorption capacity of MF significantly (P < 0.05) (211% increase). Roasting significantly increased the oil
absorption capacity (112% increases) . Emulsifying activity ranged from 37.90 - 38.20% respectively for light- and
dark-brown Morama flour. Emulsion stability ranged from 70.62% (light brown) to 72.18% (dark brown). The colour of
unroasted MF is light yellow (L = 82.71, Hue angle = 88.05, Chroma = 26.21), turning darker and less saturated on
roasting.