Multi-response optimization of alginate bleaching technology extracted from brown seaweeds by an eco-friendly agent

Alginate only finds industrial applicability after undergoing a bleaching process to improve its visual appearance. Box-Behnken Design was used to optimize bleaching parameters (time, oxygen flow and temperature) for sodium alginate (SA) extracted from seaweeds using ozone as the bleaching agent. The optimal conditions (oxygen flow 2 L/min for 35 min at 25 °C) resulted in an ozone-bleached SA with a mannuronic/guluronic acids ratio of 0.70, viscosity-average molecular weight of 66.30 kDa and dynamic viscosity of 1.39 mPa.s, aligned to strong and brittle gels formation, which are potentially suitable for hydrogels and bioink application. Results indicated that ozonation caused depolymerization of the SA chain. Colorimetric parameters showed that ozone has a great bleaching efficacy. The bleached sample presented high antioxidant capacity, highlighting that discoloration by ozone might have minimal effects on the bioactive compounds which are valuable ingredients for food-based products.