The influence of solid and sugar contents on rheological characteristics of akamu, a semi-liquid maize food

Abstract

An investigation was carried out on the effects of solid (5–13%) and sugar (0–54%) contents on the viscosity of akamu. A rotational viscometer was used at speeds between 10 and 100 rev/min. The viscosity was measured at 30 °C, 40 °C, 50 °C, 60 °C, and 70 °C. An empirical power-law equation fitted the rheological behaviour with correlation coefficients between − 0.9932 and −1.0000. Akamu exhibited a pseudoplastic behaviour and a value of 0.32 was proposed as its power-law index. Neither temperature, solid content nor sugar content affected the pseudoplastic response. Consistency indices decreased with temperature and sugar content but increased with solid content. Exponential equations were used to describe these dependencies. Solid content affected the viscosity more than the sugar content. Sweetened akamu was more sensitive to temperature changes. Consistency index (K) was related to solid content (S) and absolute temperature (T) using an equation of the form: K = 3.03 × 10 −4 exp(0.41S + 1965.56/T) (r = 0.9796) and to sugar content (G) and temperature by an equation: K = 2.35 × 10 −3 exp(−1.55 × 10 −2G + 2924.62/T) (r = 0.9410)