Analysis of flux decline during ultrafiltration of apple juice in a batch cell

• Response surface methodology is used to get optimum condition of enzyme treatment.
• A model is proposed to analyze the flux decline in apple juice ultrafiltration.
• Intermediate pore blocking and cake filtration coefficients are estimated.

In the present work, ultrafiltration of enzyme pre-treated apple juice is studied under batch concentration mode in a stirred batch cell. Response surface methodology (RSM) is used to study the effects of incubation temperature, incubation time and enzyme concentration and their mutual interaction effects on the physical characteristics of apple juice such as alcohol insoluble solid (AIS), viscosity, clarity, total polyphenol, flavonoid and protein during enzyme treatment of apple juice. A central composite design (CCD) is employed to develop the quadratic model and optimizing the operating conditions of the enzyme treatment process for obtaining the desired characteristics of juice. During ultrafiltration enzyme pre-treated apple juice, the flux decline behavior is modeled using Hermia's approach for constant pressure dead-end filtration laws. Two model parameters, namely intermediate pore blocking coefficient and cake filtration coefficient are obtained by minimizing the error involved between calculated and experimental flux data. These parameters along with known operating conditions, membrane permeability and physical properties of feed enable one to predict the transient permeate flux decline. The effect of various operating conditions, such as feed temperature, stirrer speed and transmembrane pressure on the flux decline is demonstrated. Experimental results show that operating conditions have significant effect on the onset of cake formation as well as on the flux decline behavior. The model predictions are in good agreement with the experimental data.