Journal of Food Engineering, Vol.78, No.2, 546-550, 2007
Soaking behaviour and milky extraction performance of tiger nut (Cyperus esculentus) tubers
Three diameter sizes (D < 0.5 cm, 0.5 cm < D < 1 cm and D > I cm) of tiger nut (Cyperus esculentus) tubers growing in Cameroon (Central Africa) were soaked between 20 degrees C and 100 degrees C until water content equilibrium, and pressed for extraction of milky beverage ("horchata"). Application of Peleg model was investigated for predicting water absorption of tubers during soaking. The model showed to predict kinetics of the tiger nut soaking. The Peleg absorption rate constant (k(1)) decreased as temperature increased, indicating increase in absorption rate with temperature, with a discontinuity at 60 degrees C. The water absorption capacity (k(2)) was relatively stable, but displayed the same discontinuity at 60 degrees C. The extraction yield and the insoluble extract content of the milky beverage increased with temperature, while its soluble extract content decreased in the same conditions. These trends were attributed to the weakening of cell walls of the tubers at higher soaking temperature, generating high level of material transfer, as justified by the very low values of k(1) at high soaking temperature. (c) 2005 Elsevier Ltd. All rights reserved.