Effects of operating conditions on quality attributes of instant brown rice porridge prepared by microwave assisted foam-mat drying

Abstract

Foam-mat drying combined with microwave heating was applied to produce instant brown rice porridge. Concentration of egg albumin as a foaming agent and drying parameter, air temperature and microwave power were analyzed and optimized. Results showed that concentration of egg albumin of 18% (w/w) providing lowest foam density of 0.30 g mL-1, highest overrun of 223.54%, and an acceptably high value of foam stability (96.78%). Positive effects were observed with rehydration ratio and color change inversely related to drying time. Both drying parameters favorably affected textural properties including firmness, consistency, cohesiveness and viscosity index of the rehydrated samples. Response surface methodology showed good quadratic and linear correlations between input parameters for all responses, with R2 ranging 0.81-0.99, except for the response of viscosity index (0.56). Optimal drying air temperature of 72C and microwave power of 300 W were obtained and used for model validation. Small discrepancy errors for textural properties ranging 3.48%-24.73% showed a good basis for practical use in producing instant rice porridge.

Keywords

• foam-mat drying
• microwave heating
• response surface methodology
• foaming properties