Stabilization of antioxidant thyme-leaves extract (Thymus vulgaris) within biopolymers and its application in functional bread formulation

The aim of this study was to stabilize the antioxidant compounds of thyme (Thymus vulgaris) extract by spray-drying process and MD, WPC and MD-WPC carriers at different temperatures (120 and 150°С). Then, the optimal encapsulated sample was used in different ratios (1, 2, 3 and 5% w/w) to fortify pan-breads. The highest production yield (∼68%) was obtained in the extract encapsulated with MD-WPC at 150°С. The values of moisture (3.2-4.1%) and water activity (0.28-0.33) indicated the microbial stability of the powders. The functional characteristics of the particles (solubility and wettability) were affected by the composition and nature of the carriers. Also, the use of WPC led to an increase in physical stability, encapsulation efficiency (∼84%), TPC (4.4 mgGAE/g) and antioxidant activity (∼77%). The results of SEM and staining of the samples respectively indicated the effect of the process parameters on the morphology and the placement of the phenolic compounds within carrier's matrix. The physicochemical, textural characteristics, color indices (crumb and crust) and antioxidant activity of fortified breads were affected by the ratio of added free and spray-dried extract. The evaluation of sensory indices (color, texture, chewiness, taste and overall acceptance) indicated the ability to fortify bread with 3% spray-dried extract.