Effect of okra gum on pasting and rheological properties of cake-batter

Abstract

Alkaline-soluble okra gum was extracted from okra pods using 0.05 M NaOH solution (OE). The effect of OE on the density, pasting, rheological and textural properties of cake batter by replacing 2, 4, 6 and 8% of the flour weight. Rapid Viscosity Analyser (RVA) profiles illustrated significant increase in batter viscosity attributable to OE (p < 0.05). However, the maximum increase was observed at 8% replacement with a viscosity of 2607cP. Shearing effect on the cooked batters at 50 °C was determined using Brookfield rotational viscometer. Profiles indicated increase in shear stress (SS) as a function of shear rate (SR), confirming a pseudo-plastic behaviour of the blends (n < 1). Consistency index (K) and flow behaviour index (n) of the power law model were evaluated. The high K (3.6) was recorded at 8% OE corroborated the RVA viscosity data. However, the least n (0.24) reflected the highest pseudo-plasticity value of the batter. The Arrhenius activation energy (Ea) drop between the control and the 8% OE was 59 and 49% for ramping up and down, respectively. Overall, the reduction in Ea was linear for; ramping up; Y = −120x + 1697 (R2 = 0.99) and ramping dawn; Y = −132x + 2277 (R2 = 0.97). These results suggest that, higher OE levels reduced the thermal stability of the system. After overnight storage, the hardness of the cooked batter increased significantly (p < 0.05). In summary, the addition of OE negatively affected viscous and thermal stabilities of cake batters, but increased the soluble fibre of the final product.