Abstract
The adsorption of gallic acid (GA) and propyl gallate (PG) on activated carbon (AC) was studied as a function of the AC mass and temperature. Clean first order behavior was obtained for at least three half-lives and the equilibrium was reached after ∼4 h contact time. An increase in the temperature (T = 20–40 °C) increases their adsorption rate constant values (k1) by 2.5 fold but has a negligible effect on the amount of antioxidant adsorbed per mass of AC at equilibrium. We also analyzed the adsorption process of polyphenols from Bryophyllum extracts and ca 100% of the total amount of the polyphenols in the extract were adsorbed when using 7 mg of AC. Results can be explained on the basis of the Freundlich isotherm but do not fit the Langmuir model. Results suggest that the combination of emerging in vitro plant culture technologies with adsorption on activated carbon can be successfully employed to remove important amounts of bioactive compounds from plant extracts by employing effective, sustainable and environmental friendly procedures.
Highlights
The current trends in food consumption in developed countries reflect that naturalness is a crucial factor for the majority of consumers and it forces the development of novel strategies in the food processing industry
The adsorption profiles reveal that equilibrium is reached after 4 h and it is maintained for, at least, 24 h, which was the time set for subsequent studies
The temperature dependence of k1 values stands in marked contrast to that of the maximum antioxidant adsorption, qm values, which are nearly constant at the three temperatures with an average value of 0.284 ± 0.006 for gallic acid (GA) and 0.273 ± 0.009 for propyl gallate (PG)
Summary
The current trends in food consumption in developed countries reflect that naturalness is a crucial factor for the majority of consumers and it forces the development of novel strategies in the food processing industry. In order to satisfy consumers’ demands, plants have been extensively exploited as a major source of bioactive compounds, derived from their secondary metabolism as a result of their defense and adaptation mechanisms, in both food and pharmaceutical industries (among others) In this sense, polyphenols have gained much attention in such fields because of their ubiquitous presence in the plant kingdom and their organoleptic and health-enhancing properties[2]. (2) Polyphenols are, usually, extracted and purified with poor selectivity from plant sources These processes generally, use large amounts of organic solvents that generate a negative impact on health and environment, making the whole process expensive and time-consuming[10]. As their use should be limited in as much as possible, new approaches for the recovery of polyphenols from plant extracts need to be developed
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