Ultrafiltration of synthetic juice (mixture of sucrose and pectin with varying composition) as well as enzymatically treated mosambi [Citrus sinensis (L.) Osbeck] juice is performed in a batch, unstirred membrane cell. Thin-film composite polyamide membrane of molecular weight cutoff 50000 was used. The flux decline mechanism is found to be controlled by the growth of a gel layer of pectin over the membrane surface. Using standard cake filtration theory, the flux decline and the growth of gel layer is quantified. The gel layer is characterized in terms of specific gel layer resistance, gel porosity, and gel density. A transient model is proposed and solved numerically to quantify the transport of sucrose through the pectin gel for the synthetic juice and enzymatically treated juice. The hindered diffusion coefficient of sucrose through the gel is calculated by comparing the results with the experimentally obtained permeate concentration profile of sucrose. The calculated permeate concentration profile agrees well with the experimental data.