Technology of separation and purification and its efficiency of adzuki bean polyphenols with macroporous adsorption resins

Abstract: In the process of adzuki bean paste production, lots of wastewater isproduced. The cost of traditional anaerobic wastewater treatment is high, and the materials rich in adzuki bean water can't be fully used, such as polyphenols. It is also not good for enterprises to increase product added value. This paper focuses on the separation and purification technology of adzuki bean polyphenols. The adzuki bean polyphenols were purified using a macroporous adsorption resins method. By comparing the adzuki bean polyphenols separation effect of five different types (S-8，NKA-9、AB-8、D4020, and HPD 600) of macroporous resin, HPD 600 was selected as the ideal adsorbent as it had a strong adsorption ability and a high desorption rate. The adsorption isotherm of HPD 600 resin was studied, and the results showed that with the increase of polyphenols equilibrium concentration, the adsorptive amount of HPD 600 increased gradually. After the polyphenols concentration increased to a certain degree, the adsorption amount growth trend gradually smoothed. Through a nonlinear curve fitting with the Langmuir and Freundlich adsorption models, it was found that the fitting degree of adsorption isotherm and Langmuir and Freundlich function curve was very high, and the correlation coefficient R2 was greater than 0.99. The fitting effect of the Langmuir model (R2=0.9986) was slightly better than the Freundlich model (R2 = 0.9943). Static and dynamic adsorption, and desorption experiment results indicated that sample concentration, temperature, pH value, ethanol concentration, sample flow velocity, and desorption flow velocity had great influence on macroporous resin in the process of adsorbing and separating adzuki bean polyphenols. The ideal technological parameters were keeping the temperature for 30℃, the original concentration and pH value of hot water extracts of adzuki beans, sample volume 200 mL, flow velocity 1.0 mL/min until reaching adsorption balance, dynamically elute with 50 mL 60% ethanol, and the desorption flow velocity was 1.5 mL/min. After being separated and purified by HPD 600 resin, the total phenol content and total antioxidant capacity significantly was improved about 2.2 times. This showed that HPD 600 resin had better adsorption and enrichment impact for the polyphenols in adzuki bean, and was more suitable for the separation and purification of the polyphenols in adzuki bean wastewater.The materials in this experiment were water samples made from simulated industrial production of adzuki bean paste; the species and content of polyphenols in these samples were similar to the actual production. Therefore, the polyphenols adsorption condition optimized in this test can meet the requirement for wastewater treatment in adzuki bean paste production. The research provides a theoretical reference for the industrial production and further utilization of adzuki bean polyphenols. Extraction and purification of polyphenols from adzuki bean wastewater can not only ease the burden of wastewater treatment for a bean paste enterprise, but can also increase added economic value and benefit.