Purification of Purple Sweet Potato Extract by Dead-End Filtration and Investigation of Membrane Fouling Mechanism

Pulsed ultrasound-assisted extraction with water was carried out to extract valuable compounds from purple sweet potato (PSP). Quality properties and dead-end filtration of PSP extract were investigated. Solutes concentration in PSP extract were 118.60 +/- 2.83, 599.8 +/- 8.28, and 0.72 +/- 0.03 mu g mL(-1) for total protein, total polyphenol, and total anthocyanin, respectively. Filtration with PES 50 kDa membrane-augmented polyphenol purity from 83.4 % in extract to 99.6 %. A protein removal coefficient of 99 % was achieved. Resistance in series model and Hermia's model was applied to quantify filtration resistance and investigate fouling mechanism during filtration. Gel layer resistance was the most important for all three used membranes (PES 0.1 mu m, PES 100 kDa, and PES 50 kDa). Fitting of experimental data by Hermia's model revealed that the most suitable fouling mechanism varied, cake layer model for PES 0.1 mu m and PES 100 kDa membrane and intermediate blocking model for PES 50 kDa membrane. For the purpose of more efficient polyphenol production, advanced filtration modules, such as cross-flow and rotating disk filtration module, are expected.