Impact of drum drying conditions on functional properties and flow behavior of gluten-free instant fermented mung bean-rice soup.

The effect of drum drying conditions on functional properties of a nutritious, gluten-free instant fermented (tarhana) soup which was developed for celiac people by a partial substitution of rice flour with mung bean flour (1:1, w/w) was investigated. Response surface method was used to optimize drum drying process conditions for development of mung bean fortified soup. Impacts of independent variables; feed moisture (45-55-65%), drum rotating speed (0.6-1.4-2.2 rpm) and steam pressure (75-85-95 psi) on water and oil absorption capacities, foam capacity, foam stability, protein solubility and flow behavior were investigated. Responses were significantly affected by process variables. Feed moisture was the main factor affecting water and oil absorption capacity and viscosity, while drum rotating speed primarily affected protein solubility, foam capacity and stability. Maximum foaming abilities were obtained at high drum speeds and low feed moistures. Optimum process conditions were determined as 62.22% feed moisture, 2.20 rpm rotating speed, 75 psi pressure, with a desirability value of 0.693. The best achievable response values predicted by numerical optimization for these combinations were water absorption capacity: 3.25 mL/g, oil absorption capacity: 0.51 mL/g, protein solubility: 2.68 mg/mL, foam capacity: 0.07 mL/mL, foam stability: 14.59 min, and consistency coefficient: 2.04. Gluten-free mung bean-rice soup with increased protein content (20.52-22.62%) and functional properties along with higher dietary fiber (2.63-3.94%) will contribute to life quality of celiac patients.