Extraction of refined carrageenan from Kappaphycus alvarezii and evaluation for a sheet face mask gel

A sheet face mask is a type of facial skincare cosmetic applied to the entire face to provide hydration, a refreshing sensation and skin tightening. A paradigm shift is now underway, fuelled by consumer concerns over the long-term safety of synthetic chemicals used in these products and the broader ecological footprint of cosmetic production. Consequently, κ-carrageenan is an alternative to these synthetic chemicals due to its natural origin, being free of harmful chemicals, gelling and hydration properties. The red seaweed, Kappaphycus alvarezii, the only seaweed species commercially cultivated in Sri Lanka is a rich source of κ-carrageenan, however, it has not yet been used locally to extract carrageenan and test its application in skincare cosmetics. Precipitation of κ-carrageenan using KCl is a critical step in carrageenan extraction process as it imparts strength to carrageenan gels. In this study, carrageenan was extracted using three concentrations of KCl and its suitability for a sheet face mask gel was tested across three carrageenan concentrations. The results showed that comparatively higher yields of 31.89±0.05 and 33.52±2.50 were obtained at 2.50% and 3.50% KCl concentrations, respectively. All tested characteristics for a leave-on sheet face mask gel were achieved at 1.00% carrageenan concentration prepared using carrageenan extracted at 3.50% KCl concentration. Notably, prepared carrageenan gels were able to moisturise the skin without altering skin oiliness.