Influence of microwave‐assisted roasting on the proximate, techno‐functional, thermal, structural and storage properties of African walnut ( Tetracarpidium conophorum ) flour

Abstract BACKGROUND Physical modification, compared to untreated flour, through microwave treatment as a means of increasing food application potential in tree nuts has been well hypothesised in recent times. The objective of this study was to investigate the effect of microwave‐assisted roasting (450, 600 and 900 W each at 5 and 10 min) on the proximate, functional, bioactive, thermal, microstructural and microbiological storage of African walnut flour, with the aim of enhancing its functional food applications. RESULTS Results obtained on the flour samples showed that treatment significantly ( P < 0.05) reduced moisture content (41.19–4.75%), but improved protein (20.57–39.85%) and fat contents (8.07–18.24%). Similarly, the treatment improved water absorption capacity (1.27–2.90 g g −1 ) and oil absorption capacity (1.30–2.57 g g −1 ), while the L * values (42.30–36.21) and pasting properties decreased with increasing treatment conditions. Furthermore, treatment increased the total phenolic compound (16.30–31.00 mg GAE 100 g −1 ), antioxidant capacity (69.10–95.40%) and thermal properties at onset (58.33–63.38°C) and conclusion temperature (70.23–74.18°C), respectively. Treated samples also displayed agglomerated morphological clusters, functional hydroxyl (OH), amine (NH) and (CO) carbonyl stretching and X‐ray diffraction crystalline structure of the ‘A' type. Moreover, the bacterial and fungal populations were significantly reduced to a non‐detectable level after 8 weeks of storage. CONCLUSION This study shows that the physical modification of African walnut flour through microwave roasting serves as a potential and promising technique to improve its food application across various food industries for novel product development. © 2025 Society of Chemical Industry.