Abstract/Summary

Polyphenols from grape pomace are of high interest because of their great sources of natural antioxidants, their potential benefits to human health and other functionalities related to their antioxidant capacity. However, the extraction process with organic solvents can lead to toxicity, so there is a need to remove the solvents before inclusion to food or non-food applications. Therefore, an integrated, cost-effective and environmental friendly separation process is necessary. In the present study, the recovery of polyphenols from grape pomace extracts was investigated using Colloidal Gas Aphrons (CGA). CGAs are defined as stabilised surfactant micro-bubbles generated by intense stirring of a surfactant solution with unique properties; making them an attractive alternative bioseparation process. Hydro-alcoholic (EE) and hot water (HWE) extracts of grape pomace was applied to the CGA generated from TWEEN20 (non-ionic). Similar trend of recovery was obtained with both extracts, with some selectivity in relation to sugar, particularly in EE at lower volumetric ratio (volume of CGA to the volume of extract). An increase in volumetric ratio led to an increase in the polyphenols recovery but a decrease after ratio 16. The opposite trend was noted with drainage time; anincrease in drainage time led to a decrease in the polyphenols recovery. The EE and HWE along with their CGA fractions were tested for inhibitory activity against skin relevant enzymes (collagenase and elastase) which were responsible for skin aging. The highest inhibition was found in the HWE. Further separation with CGA from both EE and HWE led to more potent fractions, particularly against collagenase. This effect might be related to the ability of TWEEN20 to solubilise the polyphenols and in this way facilitated the interaction of these polyphenols with the enzymes. When individual polyphenols permeability was tested across pig skin,a higher penetration and diffusion was obtained with the polyphenols in TWEEN20 than in water. Moreover, the highest stability of anthocyanins was obtained in CGA fractions that contained 8.58mM TWEEN20 when compared against crude extract and extract with sorbic acid. This suggested the role of surfactant at a given concentration in protecting the anthocyanins from oxidation. As a final conclusion, CGA is an interesting, novel and promising recoveryformulation technique especially with TWEEN20 as the surfactant since its removal is no longer needed. CGA can contribute to the development of “greener” processes by reducing the use of solvents and hence addressing the environmental concerns, making the CGA very attractive to be applied in cosmetics and food applications/formulations.