Optimizing Antinutrient Removal and Structural, Morphological, and Techno-Functional Modifications in Five-Leaf Yam (<i>Dioscorea pentaphylla</i>): A Comparative Study of Processing Methods

Pretreatment processing is essential for removing or reducing antinutrients in Dioscorea pentaphylla. This study evaluated the efficacy of various pretreatment processes in reducing antinutrients in Dioscorea pentaphylla, specifically soaking for 4, 8, and 12 h; boiling for 5, 15, and 25 min; and steaming at 121 °C for 5, 15, and 25 min. The reduction rates were observed as follows: phytate (53–65%), oxalate (18–55%), tannin (74–91%), saponin (78–85%), trypsin inhibitors (52–91%), and α-amylase inhibitors (40–70%). Additionally, pretreatments significantly diminished the levels of total phenolics (33.50–70.87%), flavonoids (44.92–67.41%), and antioxidant activities (49.20–64.95%). Structural characterization via XRD, FTIR, and SEM revealed notable alterations in flour morphology, particularly under boiling conditions. Boiling for 25 min emerged as the most effective pretreatment for antinutrient reduction, substantially impacting the size and shape of starch granules, as evidenced by SEM analysis.