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).