Synthesis and characterisation of porous polyvinylpyrrolidone-co-poly(divinylbenzene) (PVP-co-PDVB) copolymer resins for the isolation of betalains from red beetroot

Betalain is a natural pigment with serious antioxidant and biological activities currently used as a food colourant, however; the isolation of this compound is difficult because of its instability. The research was aimed to synthesise and characterise the copolymeric adsorbents for the recovery of betalains by means of the solid-phase extraction (SPE) technique. For this purpose, divinylbenzene (crosslinker) was polymerised with polyvinylpyrrolidone containing vinyl groups by using free radical polymerisation, and toluene was used as a porogene. Polymeric resins in different polyvinylpyrrolidone/divinylbenzene (PVP/DVB) and toluene/divinylbenzene (Tol/DVB) rates were synthesised. The effects of these parameters on the polymerisation efficiency, size distribution, morphology, swelling properties and adsorption capacities of adsorbents were investigated in the later characterization stage. Adsorption tests were conducted by analyzing phenol adsorption in batch model systems. The KOD-4 coded adsorbent exhibited the best performance in adsorption tests with PVP/DVB and Tol/DVB ratios of 0.5 and 1.5, respectively. The betalains were recovered strongly from the red beet juice via the packed bed adsorption column system filled with KOD-4. Then, column reusability and regeneration were studied. In total, the prepared column system was used five times. Ultimately, the results of this study can lead to wide-scale application of betalain-enriched beetroot extracts in the food, pharmaceutical, and cosmetic industries due to their antioxidant and colourant properties as well as their biological activities