Objectives This study aimed to assess the effects of different cooking methods and extraction solvents on the bioactive properties of sweet potatoes ( Ipomoea batatas L. Lam). Methods Sweet potato samples were processed using an air fryer (150 °C for 15, 20, or 25 min) or a microwave oven (720 W for 2, 3, or 4 min). The samples were cooled to room temperature, oven-dried, and extracts were prepared using either 100% ethanol or 50% ethanol–water. Subsequently, the extracts were analyzed for total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity, reducing power, and antimicrobial activity. Results Chlorogenic acid, 3,5-DNSA, and salicylic acid were detected in all samples, with chlorogenic acid being the predominant phenolic compound. The control SCW (extracted in 50% ethanol/water) showed the highest mean total polyphenol content (TPC, 7.53 mg GAE/g DW) and flavonoid content (TFC, 4.39 mg CE/g DW). Compared to microwave cooking, air-fried samples exhibited higher TPC (medium duration) and TFC (short duration). Control SCE (100% ethanol) exhibited higher radical scavenging activity (81.88%), however, the SCW demonstrated greater reducing power (0.92 for SCW vs. 0.89 for SCE). Ethanol/water extraction, significantly (p ≤ 0.05) enhanced antioxidant activity, with air frying showing greater radical scavenging at medium/high cooking and higher reducing power at low cooking times. Both aqueous and ethanol extracts of sweet potato possess notable antimicrobial properties, though the ethanol extract generally exhibited superior efficacy. Conclusions The results indicate that different extraction solvents and thermal processing treatments of sweet potatoes have varying effects on the content of bioactive compounds and these results might be beneficial for functional food processors.
Ahmad M. Salamatullah (Wed,) studied this question.