Drying Rate of Selected Varieties of Cassava at Different Times of Harvest- A Response Surface Study

Aims: To process cassava varieties-TME 419, TMS 30572 and TMS 98/0505 at different harvesting regimes by shredding with three shredding apertures-3 mm, 6 mm and 10 mm of a motorized cassava shredding machine and determine their drying rate.

Study Design: Cassava varieties were harvested at three months interval- 10, 13 and 16 months. They were shredded at each harvesting regime. A faced central composite design (k=4) was employed to study the linear, interactive and quadratic effects of the independent experimental variables- temperature, shred diameter, time of drying and time of harvesting on drying rate.

Place and Duration of Study: Cassava tubers were obtained from National Research Institute, Umudike, Abia State. Shredding was done at the Engineering workshop of National Research Institute, Umudike.

Methodology: Sixty nine (69) experimental runs were generated. Center points were replicated nine times, corner and star points were not replicated, data obtained were subjected to response surface analysis and Analysis of variance.

Results: Drying rate of the cassava shreds ranged from 0.000248 g/sec (TMS 30572,5400sec, 3 mm,100ºC) to 0.001063 g/sec (TMS 30572,5400 sec,10 mm,100ºC) at the 10th month; 0.000173 g/sec (TMS 30572,3600sec,6 mm,80ºC) to 0.000958 g/sec (TMS 98/0505,1800 sec, 3 mm,100ºC) at the 13th month and 0.00004 g/sec (TME 419,3600 sec, 6 mm, 80ºC) to 0.000336 g/sec (TMS 30572,1800 sec,10 mm,100ºC) at the 16th month. Linear and quadratic effects of time of drying had significant effect on the drying rate of TME 419; interaction between shred diameter and time of drying had significant effect on the drying rate of TMS 30572. Linear and quadratic effects of time of drying and interaction between shred diameter and time of drying had significant effect on the drying rate of TMS 98/0505.

Conclusion: Drying rate increased with shred diameter and temperature and reduced with reduction in shredding aperture.