Abstract:

The optimum extraction conditions of polyphenols from quinoa grains were investigated in this study. On the
basis of single factor experiments, alcohol concentration, solid/liquid ratio and extraction temperature were selected for
a three-factor, three-level Box-Behnken experimental design. In addition, Design-Expect 8.0 software was employed to
analyze the experimental data and the response surface methodology was applied to optimize the extraction conditions. The
results suggested that optimal extraction conditions were determined as 56% ethanol as the extraction solvent, an extraction
temperature of 84 ℃ (water-based heating) and a solid/liquid ratio of 1:40 (g/mL). Under these optimized conditions, the
extraction yield of polyphenols from quinoa grains of the variety “PI634920” was 2.273 mg/g. The sequence of factors
affecting the extraction yield of polyphenols was as follows: alcohol concentration > extraction temperature > solid/liquid
ratio. Meanwhile, great variation in polyphenol content of quinoa grains was found among 20 different varieties, of which
the variety “PI596293” had the highest polyphenol content (2.72 mg/g).

Key words: quinoa, polyphenol extraction, response surface methodology, process optimization, varietal differences