Process optimization and nutritional profiling of gluten-free quinoa-rice couscous: amino acid and polyphenol characterization.

INTRODUCTION

Quinoa (Chenopodium quinoa Willd.) is internationally recognized for its exceptional nutritional profile, yet its incorporation into traditional cereal-based foods remains limited.

METHODS

This study developed and optimized a gluten-free couscous from quinoa and rice using D-optimal response surface methodology, evaluating the effects of quinoa fortification level (0-100%), steaming time (10-30min), and water volume (350-450 ml/kg) on techno-functional properties, proximate composition, mineral profile, bioactive compounds, and color.

RESULTS

Quinoa fortification percentage was the dominant factor across the response set, while steaming time and water volume acted as secondary modulators. The nutritional optimum converged on 100% quinoa, with processing parameters of 20min steaming and 400 ml/kg water. Compared with commercial wheat couscous and rice-only couscous, quinoa couscous showed enhanced water-holding and oil-holding capacity, up to five-fold higher potassium, three-fold higher iron, and three-fold higher total phenolic content. LC-MS/MS amino acid putative profiling detected 18-19 of 20 amino acids in quinoa couscous versus 14 in wheat and 11 in rice couscous, with enrichment in branched-chain amino acids and detection of lysine, the limiting amino acid of cereal proteins, which was undetected in rice couscous and present only at trace levels in wheat couscous. Quinoa couscous exhibited around five-fold greater polyphenol diversity than wheat couscous, including flavan-3-ols, chalcones, and hydroxycinnamic acids exclusive to quinoa formulations. Higher quinoa levels darkened the product, with color stabilizing at fortification levels above 75%.

DISCUSSION: Unlike previous work on alternative-grain couscous, this study combines process optimization with LC-MS profiling of amino acid and polyphenol composition, providing an integrated framework for gluten-free quinoa-rice couscous development. The results demonstrate that quinoa-based couscous provides a nutritionally superior, gluten-free alternative to conventional wheat couscous, with processing conditions that preserve the raw material's nutritional attributes.