Protein-rich expanded snack from red quinoa (Chenopodium quinoa Willd. INIA 415 Pasankalla) optimization of processing conditions and product quality

This study optimized the expansion parameters of gluten-free snacks produced from quinoa (Chenopodium quinoa Willd.) variety INIA 415 Pasankalla using Response Surface Methodology (RSM). A face-centered Central Composite Design was applied to evaluate the combined effects of expansion pressure (120–170 psi) and initial grain moisture content (13–20%) on 17 physicochemical, functional, structural, and textural responses. Quinoa samples of 80 g were processed using a Chinese-manufactured popcorn expansion cannon (QOXVYN-RPC, 304 stainless steel), in which whole unexpanded grains were placed inside a hermetically sealed chamber heated with a 96% ethanol burner until the target pressures of 120, 145, and 170 psi were reached. The equipment directly measures only chamber pressure, while grain expansion occurs as a result of rapid chamber opening and sudden decompression, producing expanded, puffed, or popped quinoa grains. Proximate composition, bulk density, expansion index, water absorption index (WAI), water activity (aw), degree of starch gelatinization, CIELab color parameters, texture profile analysis, and microstructure by scanning electron microscopy (SEM) were evaluated. The fitted quadratic models showed high predictive capacity, with coefficients of determination ranging from R² = 0.8885 to 0.9984 and statistical significance at p < 0.05. Pressure–moisture interactions significantly affected protein retention, expansion behavior, starch gelatinization, density reduction, and textural development. Higher pressure combined with intermediate moisture enhanced expansion, reaching an expansion index of up to 8.18, reduced bulk density values of 0.460–0.807 g/cm³, and increased starch gelatinization up to 0.88, while maintaining moderate aw values between 0.20 and 0.44. Multi-response optimization achieved an overall desirability of 0.846, identifying 170 psi and 17% moisture as the optimal processing conditions. Under these conditions, the expanded quinoa exhibited improved structural porosity, a protein content of 14.17%, low bulk density of 0.460 g/cm³, and desirable crispness, confirming the suitability of RSM for optimizing quinoa-based expanded products.