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Effect of drying methods
on the rheological characteristics and colour of yam flours
K. O. Jimoh1,
T. O. Olurin2* and J. O. Aina3
1Department
of Food Science and Technology, The Polytechnic Ibadan,
Saki, Nigeria.
2Department
of Food Technology, Bells University of Technology, Ota,
Nigeria.
3Department
of Food Technology, University of Ibadan, Ibadan, Nigeria.
*Corresponding author. E-mail:
taye_olurin@yahoo.com.
Accepted
26 June, 2007 |
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The effect of drying methods (sun and oven-drying) on the
rheological properties and colour of amala, a thick
paste from yam flour, was investigated using two varieties
of yam (Dioscorea rotundata and Dioscorea alata).
The yam flour produced was later reconstituted to produce
amala of different pasting characteristics, textural
qualities and colour. D. rotundata produced amala
of higher paste viscosities, and firmer gels were produced
from D. rotundata than yam flour paste produced from
D. alata. A higher water binding capacity (156.7%)
was observed in yam flour paste produced from D. alata
as compared with that of D. rotundata, while no
significant difference was observed in the solubility index
and swelling power of the two varieties. Blanching, a unit
operation in yam flour processing, has a significant effect
on the pasting characteristics of the reconstituted flour.
It reduces the peak viscosity, holding strength, final
viscosity, set back and elasticity but it has little or no
significant effect on the adhesiveness, smoothness and
cohesiveness of the paste. Sun and oven drying had no effect
on the pasting characteristics or physicochemical
properties. However, yam flour produced using sun drying
method had a more elastic paste and a higher brown-index.
Key
words:
Dioscorea alata, Dioscorea rotundata, drying,
rheological properties, brown index. |
