Polygonum cognatum Powder as a Functional Ingredient: Improving Nutritional Quality and Reducing Glycemic Index of Gluten-free and Wheat-based Crackers

Polygonum cognatum is an underutilized edible plant rich in dietary fiber, minerals, and bioactive compounds with potential applications in functional foods. This study evaluated the effects of Polygonum cognatum powder (PCP) incorporation (0-15%) on the nutritional, bioactive, technological, sensory, and glycemic properties of gluten-free and wheat-based crackers. PCP addition significantly (p < 0.05) increased protein, total dietary fiber, phenolic content, antioxidant capacity, and mineral composition (Ca, Fe, Mg, K, and P), while reducing phytic acid levels in both formulations. Antioxidant activity (DPPH, FRAP, and CUPRAC) and total phenolic content increased markedly in a dose-dependent manner, indicating the high bioactive potential of PCP. In vitro starch digestion analysis showed that PCP incorporation effectively reduced the estimated glycemic index (eGI), with values decreasing from 92.45 to 57.98 in wheat-based crackers and from 96.57 to 60.12 in gluten-free crackers. Gluten-free samples consistently exhibited slightly higher eGI values, likely due to the higher digestibility of starch-based matrices. PCP addition increased spread ratio and hardness, Spread ratio and hardness increased above 3% PCP substitution level. Sensory evaluation indicated that 3-6% substitution provided optimal acceptability, whereas higher levels (≥ 12%) negatively affected color, taste, and crispness. Overall, PCP is a promising functional ingredient for developing nutritionally enhanced and lower-glycemic bakery products.