Adsorption of polyphenols from ginger rhizomes on an anion exchange resin Amberlite IR-400 – Study on effect of pH and temperature

Abstract

Adsorption of ginger (Zingiber officinale) polyphenol on an anion exchange resin, Amberlite IR-400 was studied for purification of polyphenols from the crude extract. The work was carried out to understand how the processing parameters can be manipulated to optimize the purification of ginger phenolics for its further use in nutraceuticals and functional foods. In this work the effect of pH and temperature on ginger polyphenol adsorption on anion exchange resin was studied. Adsorption was studied by mixing 10 gm (dry weight basis) of pretreated resin (Amberlite IR-400) with dilute hydro alcoholic (50:50) ginger extract at temperature varying from 25-40°C and pH values ranging from 4.0 to 6.5. The total polyphenol content was determined by Folin-Ciocalteau method. Within the pH range studied, pH 4.5 and 5.5 gave the best results reaching 91% and 92% adsorption of total polyphenol. At 25°C highest adsorption was obtained (92%). With the increase of temperature, adsorption percentage showed a gradual decrease, with only 70% adsorption of total polyphenols at 40°C. Statistical analysis of pH and temperature variation was done to obtain their influence on the efficiency of adsorption. For pH, we found that the calculated value of F at 5% level of significance at degrees of freedom (2, 15) [Fcalculated=13.738] is much greater than the given value of F=3.68. In case of temperature as a variable, the calculated value of F at 5% level of significance at degrees of freedom (2,9) [FCalculated=28.66] is also much greater than the given value of F=4.26. The Null hypothesis at 5% level was rejected and it was concluded that the difference in adsorption percentage of total polyphenols under different pH and temperature range is significant. This result will help in designing experiments for optimization of physical parameters for purification of polyphenols from ginger.