Res. Agr. Eng., 2025, 71(4):224-234 | DOI: 10.17221/84/2025-RAE

Effect of foam-mat drying conditions on drying rate and anthocyanin content in purple sweet potato powderOriginal Paper

Chi Dung Nguyen ORCID...1, Van Hao Hong ORCID...1, Ngoc Giau Tran ORCID...1, Minh Thuy Nguyen ORCID...1, Van Tai Ngo ORCID...2
1 PhD Student, Institute of Food and Biotechnology, Can Tho University, Can Tho city, Vietnam
2 Institute of Food and Biotechnology, Can Tho University, Can Tho city, Vietnam
3 School of Food Industry, King Mongkut's Institute of Technology Ladkrabang, Bangkok, Thailand

The study aimed to optimise foam-mat drying parameters for producing purple-fleshed sweet potato (PFSP) powder. Egg albumin (EA) (5–15%), xanthan gum (XG) (0.1–0.5%), and drying temperature (50–70 °C) were used as independent variables for optimisation via Response Surface Methodology with a Box-Behnken design. The response variables (drying rate and anthocyanin content) were assessed by 18 treatments, which included 6 central points. The analysis of variance showed a high coefficient of determination (> 88%) between predicted and experimental values across all models. Optimal foam-mat drying conditions were 11.02% EA, 0.34% XG, and 65.1 °C to achieve the highest drying rate (2.49 g water.g dry matter–1.min–1) and anthocyanin content (1.01 mg.g–1). After 3.5 h of drying at 65.1 °C, the foam-mat dried PFSP showed a low moisture content (4.35%) and water activity (0.29). Its water solubility index, water absorption index, rehydration ratio, total polyphenols, and antioxidant activity were determined to be 56.49%, 3.55%, 3.82, 3.66 ± 0.06 mg GAE.g–1, and 58.49 ± 0.88%, respectively. Under these conditions, the powder maintained its natural beautiful and characteristic purple colour. The microstructure of the foam-mat dried PFSP powder (via SEM images) was also observed.

Keywords: foam-mat drying; microstructure; nutritional quality; optimisation; purple sweet potato

Received: June 5, 2025; Accepted: October 1, 2025; Prepublished online: December 9, 2025; Published: December 16, 2025  Show citation

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Nguyen CD, Hao HV, Tran NG, Nguyen MT, Van Tai N. Effect of foam-mat drying conditions on drying rate and anthocyanin content in purple sweet potato powder. Res. Agr. Eng. 2025;71(4):224-234. doi: 10.17221/84/2025-RAE.
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