Effect of different drying methods on the physicochemical characteristics of cassava flour (“pupuru”)

Abstract

The effects of smoking, toasting and oven drying methods on the physical and chemical characteristics of “pupuru”, a fermented cassava product, were studied. Cassava tubers were manually peeled, washed and steeped in water for four days after which the water was decanted; the soft wet mash was packed into Hessian sack and pressed. One portion was moulded into small-sized (500 g) ball shape and smoked on wood fire for 72 hours (Traditional method). The second portion was moulded into 500 g size ball and dried in the hot air oven at 60 °C for 14 hours. The two products were pulverized and sieved with 60 mesh size into fine pupuru flour. The third wet meal was sifted and toasted on an aluminum pan over fire and then milled into fine toasted pupuru flour. The flours were subjected to physicochemical evaluations. There was reduction in drying time when pupuru was toasted compared to the tradition smoking method. The range of final moisture content achieved was 7.14- 8.40% (db). Despite the shortness in the drying time, the toasted samples had the lowest moisture content. Irrespective of the drying methods, there were significant differences (p < 0.05) in the proximate composition. The crude fibre content was highest in smoked dried with 3.17% compared to the toasted and oven dried samples with 2.12% and 2.53% respectively. The titratable acidity increased by about 78% from 0.09 to 0.16 with corresponding decrease in pH from 5.34 to 4.18. The toasted product had the lowest pH value of 4.18 while smoked and oven dried had 4.67 and 4.63 respectively. The bulk densities for both loosed and packed \ were higher for toasted product with values of 0.54 and 0.62 g/ml respectively,  while smoked dried had the least value of 0.21 and 0.40 g/ml. The swelling power was highest in the toasted pupuru with value 0.38 ml/g and water holding capacity was 259.42 ml/g. The cyanide content of the smoked, oven dried and toasted product were 0.42, 0.48 and 0.47 mg/100g respectively. The toasting method gave the best sample in terms of drying time, moisture content, physical properties and sensory qualities. It can be concluded that toasting drying method is a better alternative method of producing pupuru.

Keywords: Cassava, pupuru, physicochemical, sensory, processing.