Adsorption of Phenolic Compounds from an Aqueous By-product of Sunflower Protein Extraction/Purification by Macroporous Resins

Abstract

In this study, adsorption of phenolic compounds from an aqueous by-product of sunflower protein isolate production was investigated. Phenolic compounds in this by-product (ultrafiltration permeate of protein purification step) were almost exclusively CGA (mainly 5-CQA isomer). Five different macroporous resins including XAD4, XAD7, XAD16, XAD1180, and HP20 were screened for CGA capture. XAD16 had the best massic adsorption capacities (15.32 ± 0.04 mg/g), while XAD7 had a better surface adsorption capacity (0.027 ± 0.00146 mg/m²). CGA adsorption on both resins followed the pseudo-second-order kinetic model with a similar intra diffusional pattern. Adsorption isotherms of the two resins better fitted the Langmuir model with Qmax for XAD7 and XAD16 of 0.054 and 0.040 (mg/m²), respectively. The adsorption process of phenolic compounds revealed to be exothermic, physical adsorption, and spontaneous. Better adsorption results were observed at 25°C. Maximal CGA desorption ratio was observed from 70% (v/v) ethanol. The high values were reached with both the resins (88.09 ± 0.13 and 86.16 ± 0.32% for XAD7 and XAD16, respectively). The CGA purity in the desorption phase was surprisingly high (77.56 ± 0.99% and 74.59 ± 0.12% for XAD7 and XAD16, respectively).