Malva nut mucilage prepared by alkaline-aided extraction: Application as a co-structuring agent to enhance stability and encapsulation efficiency of alginate-based composite hydrogel

The alginate (Alg) hydrogel with health promoting effect was fabricated using malva nut mucilage (MNM) as co-structuring agent and Reishi extract (RE) as encapsulated compound. Firstly, effect of MNMs extracted by alkaline solutions at varying concentrations (i.e., 0, 0.05, and 0.1 M) as co-structuring agent for preparation of composite Alg based hydrogel was observed. Alkaline condition could elevate MNM extractable yield along with increased solubility of the derived mucilage. Incorporation of the alkaline extracted MNMs led to enhanced microstructure of the hydrogels expected since preferably interaction between Alg and the alkaline treated MNMs with more exposed functional groups. The MNMs extracted by 0.05 M NaOH (MNM 0.05M ) was selected for mixing with Alg at different ratios (i.e., Alg:MNM 0.05M of 3:1, 2:1, and 1:1) to fabricate the composite hydrogels. The mucilage promoted formability and improved microstructure of the hydrogels. Using Alg:MNM 0.05M at 2:1 could prepare the composite hydrogel with enhanced stability without disturbing effect on thermal property of the hydrogels. Then, the composite hydrogels were loaded with RE at varying contents (i.e., 1, 2.5, and 5% to produce RE-1, RE-2.5, and RE-5 hydrogels, respectively). Encapsulation efficiency (EE) of the hydrogels was improved with the added RE content: The EE of ca. 55.6, 60.3, and 61.3% for RE-1, RE-2.5, and RE-5 hydrogels, respectively. The RE loaded hydrogels showed heat tolerance and improved stability under varying pH conditions. Additionally, the beads exhibited competent phenolic retainability even in a harsh acidic condition of simulated stomach and effective phenolic compound releasing in a simulated intestinal condition.