Use of D-optimal combined design methodology to describe the effect of extraction parameters on the production of quinoa-barley malt extract by superheated water extraction.

Superheated water extraction was applied to produce quinoa-barley malt extract. D-optimal combined design was used to optimize the extraction conditions (time (min), solid-water ratio and particle size to obtain maximum protein and carbohydrate content, and minimum turbidity and pH. Quinoa flour (10%-30%), barley malt flour (70%-90%), different particle sizes (F = 420 µm, G = 710 µm), time (15-45 min), and solid-water ratio (0.1-0.2) were selected as independent variable and protein, carbohydrate, turbidity, and pH as dependent factors. Polynomials models satisfactorily fitted the experimental data with the R 2 values of .9961, .9909, .9949, and .9987, respectively. The protein and carbohydrate value was affected by superheated water extraction parameters. Our results revealed that increasing quinoa/barley malt ratio has significant effect on the turbidity and pH. The optimum extraction conditions were quinoa flour (30%), barley malt flour (70%), solid-water ratio (0.2), time (45 min), and particle size (F = 420 µm).