Phytochemical Value and Bioactive Properties of Sweet Potato Peel Across Varieties and Drying Techniques
Gordana Ćetković, Anja Saveljić, Teodora Cvanić, Olja Šovljanski, Aleksandra Ranitović, Biljana Lončar, Vladimir Filipović, Vanja Šeregelj
Abstract
The aim of the present study was to investigate how different drying techniques (lyophilization, convective drying, and osmotic dehydration) affect the phytochemical profile, biological activities, color parameters, and antimicrobial potential of sweet potato peel from four varieties (white, pink, orange, and purple). Lyophilized orange peel showed the highest carotenoid content (21.31 mg β-carotene/100 g), while osmotic dehydration resulted in the highest retention of anthocyanins in purple peel (229.58 mg cyanidin-3-glucoside/100 g). Among phenolic compounds, the most abundant were caffeic and cinnamic acids, reaching up to 434.57 mg/100 g and 430.91 mg/100 g, respectively, in white peel. Antioxidant activity was strongest in purple peel, particularly in lyophilized samples. Convective drying enhanced anti-inflammatory activity in orange peel (68.25% inhibition), and all samples demonstrated significant α-glucosidase inhibition, with values up to 96.93%. Antimicrobial effects were observed only in purple peel extracts, which showed strong antifungal activity, especially against Saccharomyces cerevisiae (inhibition zone >50 mm). These results confirm that sweet potato peel holds considerable potential as a functional ingredient and that its bioactive value can be significantly influenced by the drying method applied.