QUANTIFICATION OF FLUX DECLINE AND DESIGN OF ULTRAFILTRATION SYSTEM FOR CLARIFICATION OF TENDER COCONUT WATER

Abstract

Clarification of tender coconut water was carried out in a continuous stirred ultrafiltration cell at transmembrane pressures of 276, 414, 552 and 690 kPa and at stirrer speeds of 800 (Reynolds number [Re] = 0.93 × 10 5), 1,000 (Re = 1.17 × 10 5), 1,400 (Re = 1.63 × 10 5) and 1,600 (Re = 1.87 × 10 5) rpm, for each pressure. Permeate flux decline was analyzed using a first‐order kinetic model for the development of the polarized layer resistance. Correlations were proposed for the steady‐state polarized layer resistance with the operating conditions, e.g., transmembrane pressure difference, Reynolds number and membrane resistance. Decrease in membrane permeability after subsequent experiments was also quantified. Average irreversible fouling resistance was estimated as 7.5 × 10 12 m−1. Using the developed design equations of the stirred continuous ultrafiltration system, finally, the performance of such system in terms of productivity as function of operating conditions, membrane area and number of cleaning cycles was also evaluated. PRACTICAL APPLICATIONS: The application of membrane technology is one of the emerging areas in the food industry. The major application includes fruit juice clarification and concentration. Because of the nonthermal nature of membrane separation, the juice can be clarified at room temperature and packed aseptically for longer shelf life without the loss of its initial quality parameters. The major problem during clarification is decline in permeate flux of fruit juice with time. Identification of the reasons for flux decline is essential for designing membrane modules to make the clarification process commercially viable. The quality of juice during storage is vital, so the determination of the variation of its physicochemical properties during storage is also important. The present study helps in designing membrane modules for the production of clarified tender coconut water.