Performance of asymmetric spinel hollow fiber membranes for hibiscus (Hibiscus sabdariffaL.) extract clarification: Flux modeling and extract stability

Abstract

This work evaluates a filtration process with and without centrifugation through asymmetric spinel hollow membranes for clarification of hibiscus extract. The centrifugation step increased the steady state flux through the membrane in 23.4%. Complete pore blockage was the main fouling mechanism and polysaccharides, proteins and phenolic compounds were mostly responsible for fouling. After sequential membrane filtration, total soluble solids, total solids and L* color coordinate (luminosity) were reduced from 5.53 to 4.03 °Brix, 47,120 to 37,780 mg/L, and 15.69 to 22.03, respectively. Seven individual bioactive compounds were identified in both extract and permeate by ultra performance liquid chromatography - mass spectrometer. The filtrated extract showed greater stability than the feed extract after 20 storage days (reduction of 43.1% in tea cream formation). The sequential centrifugation and filtration through asymmetric spinel hollow membranes can be potentially applied to produce hibiscus ready-to-drink tea with high antioxidant content. Practical applications Membrane separation process is a filtration technique based on the permeation of solute molecules through a semipermeable membrane. The ceramic membrane is widely used for the purification and clarification of food products, but the cost of material is a disadvantage for the use of filtration processes. This work demonstrated the possibility of exploring the use of asymmetric spinel hollow membrane in clarification and increased stability of teas ready for consumption. This membrane presents composition of 25 wt% of dolomite and 75 wt% of alumina, thus presenting high stability, high permeate flows and low-cost ceramic material. This filtration technology membrane can also be combined as a pre-treatment, such as centrifugation, thus improving filtration efficiency and product stability. Finally, the new membrane used was feasible to produce a hibiscus tea ready-to-drink rich in antioxidants.