Effect of some process variables on flowability and thermal properties of sprouted tigernut (Cyperus esculentus) flour.

Abstract

The effect of drying temperature, drying time and post sprouting sampling time on flowability and thermal properties of tigernut flour was investigated using response surface methodology. Fresh and cleaned tigernut seeds were subjected to different post sprouting time (PSTm), drying temperature (DTp) and drying time (DTm) based on the experimental design, and thereafter milled into flour. The flowability and thermal properties of the flour samples were determined using standard analytical methods. The result showed that increasing drying temperature (from 46.59 oC to 56.00 oC) and drying time (from 11.5 h to 13.0 h) increased flow rate from 1.5×10- 3 kg/s to 2.1×10-3 kg/s. Similarly, increasing the post sprouting sampling time (from 35 h to 43.5 h) and drying temperature (from 46.59 oC to 56.44 oC) increased the flow rate from 1.75×10-3 kg/s to 2.5×10-3 kg/s. An increase in drying temperature and post sprouting sampling time caused significant (p≤0.05) reduction in the onset, peak and conclusion temperatures as well as enthalpy value of the tigernut flour. Optimized process conditions of 56.44 oC drying temperature, 12.03 h drying time and 43.53 h post sprouting sampling time produced flour of 2.75 % moisture content with flow rate of 2.5×10-3 kg/s and better thermal properties (60.58 oC onset temperature, 65.43 oC peak temperature, 68.03 oC conclusion temperature and enthalpy of 12.06 J/g indicating less heat energy for processing or cooking).